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LITHIUM NICKEL MANGANATE POSITIVE ELECTRODE MATERIAL, PREPARATION METHOD THEREFOR AND APPLICATION THEREOF

20250070139 ยท 2025-02-27

    Inventors

    Cpc classification

    International classification

    Abstract

    The present application discloses a lithium nickel manganate positive electrode material, a preparation method therefor and an application thereof. The lithium nickel manganate positive electrode material has a molecular formula of Li.sub.Ni.sub.Mn.sub.2-M.sub.O.sub.4-/N, where 0.951.1, 0.40.6, 0.00050.02, 00.2, M is a single-crystal dispersing element, and M is at least one of V, Nb, Ta, Mo or W; N represents a coating layer, and the coating layer includes a P compound and/or an Al compound, and a coating amount of N is 500-10000 ppm. By means of adding a small amount of a single-crystal dispersing element (V, Nb, Ta, Mo or W), a high-voltage nickel manganese material having good dispersity of single crystals is prepared. By means of uniformly coating the P compound and/or the Al compound to the lithium nickel manganate positive electrode material, the direct contact between the positive electrode material and an electrolyte, is avoided.

    Claims

    1. A lithium nickel manganate positive electrode material, having a molecular formula of Li.sub.Ni.sub.Mn.sub.2-M.sub.O.sub.4-/N, wherein 0.951.1, 0.40.6, 0.00050.02, 00.2, M is a single-crystal dispersing element, and M is at least one of V, Nb, Ta, Mo or W; N represents a coating layer, and the coating layer comprises at least one of a P compound and an Al compound; a coating amount of N is 500-10000 ppm.

    2. The lithium nickel manganate positive electrode material according to claim 1, wherein when the coating layer is the P compound and the Al compound, a mass ratio of Al to P is (0.2-3):1.

    3. The lithium nickel manganate positive electrode material according to claim 1, wherein a coating rate S1/(S1+S2) of at least one of P and Al is 20%-80%; wherein S1 is a peak area corresponding to a content m.sub.1 of at least one of P and Al, and S2 is a peak area corresponding to a content m2 of Ni and Mn elements.

    4. The lithium nickel manganate positive electrode material according to claim 1, wherein when the coating layer is the P compound, the lithium nickel manganate positive electrode material has a BET of 0.4-0.7 m.sup.2/g; or when the coating layer is the Al compound, the lithium nickel manganate positive electrode material has a BET of 0.6-0.9 m.sup.2/g; or when the coating layer is the P compound and the Al compound, the lithium nickel manganate positive electrode material has a BET of 0.6-0.9 m.sup.2/g.

    5. The lithium nickel manganate positive electrode material according to claim 1, wherein the lithium nickel manganate positive electrode material has at least one of the following properties that residual lithium on a surface of the lithium nickel manganate positive electrode material is 500 ppm; a DSC decomposition temperature is 275-295 C.; a powder compaction density at 3.5 T is 2.8-3.2 g/cm.sup.3; and D50 is 4-10 m.

    6. A preparation method of the lithium nickel manganate positive electrode material according to claim 1, comprising the following steps: S1. mixing a precursor, a lithium source and a single-crystal dispersant and evenly stirring them to obtain a mixture; S2. performing a first sintering on the mixture in an atmospheric environment to obtain a high single-crystal dispersion material; S3. mixing the high single-crystal dispersion material and a coating agent, and evenly stirring them to obtain a secondary mixture; wherein the coating agent is at least one of a P source and an Al source; S4. performing a second sintering on the secondary mixture in the atmospheric environment to obtain the lithium nickel manganate positive electrode material.

    7. The preparation method of the lithium nickel manganate positive electrode material according to claim 6, wherein when the coating agent contains the Al source, the Al source has a particle size of 30-60 nm.

    8. The preparation method of the lithium nickel manganate positive electrode material according to claim 7, wherein the Al source comprises at least one of Al.sub.2O.sub.3, AlPO.sub.4, or Al(OH).sub.3.

    9. The preparation method of the lithium nickel manganate positive electrode material according to claim 6, wherein when the coating agent contains the P source, the P source has a particle size of 3-5 m.

    10. The preparation method of the lithium nickel manganate positive electrode material according to claim 9, wherein the P source comprises at least one of Li.sub.3PO.sub.4, AlPO.sub.4, LiFePO.sub.4, FePO.sub.4, NH.sub.4H.sub.2PO.sub.4 or (NH.sub.4).sub.2HPO.sub.4.

    11. The preparation method of the lithium nickel manganate positive electrode material according to claim 6, wherein the precursor has a molecular formula of Ni.sub.Mn.sub.2-(OH).sub.4, wherein 0.40.6; the precursor has at least one of the following properties that the precursor has a D50 of 2-8 m; the precursor has a specific surface area of 10-30 m.sup.2/g; and the precursor has a tap density of 0.8-1.5 g/cm.sup.3.

    12. The preparation method of the lithium nickel manganate positive electrode material according to claim 6, wherein that the single-crystal dispersant comprises at least one of V.sub.2O.sub.5, NH.sub.4VO.sub.3, Nb.sub.2O.sub.5, LiNbO.sub.3, Ta.sub.2O.sub.5, LiTaO.sub.3, H.sub.2MoO.sub.4, (NH.sub.4).sub.2MoO.sub.4, H.sub.2WO.sub.4 or WO.sub.3.

    13. The preparation method of the lithium nickel manganate positive electrode material according to claim 6, wherein a molar ratio of the precursor to the lithium source is 1:(0.5-1.1); and an additive amount of the single-crystal dispersant is 0.1%-1% of a mass of the precursor.

    14. The preparation method of the lithium nickel manganate positive electrode material according to claim 6, wherein the atmospheric environment has an oxygen concentration of 15%-40%.

    15. The preparation method of the lithium nickel manganate positive electrode material according to claim 6, wherein the first sintering is: heating from room temperature up to 800-1000 C. at a rate of 1-5 C./min, calcining for 6-15 h, and then cooling down to 600-800 C. at a rate of 0.1-2 C./min, keeping the temperature for 1-10 h, and finally, naturally cooling down to the room temperature.

    16. The preparation method of the lithium nickel manganate positive electrode material according to claim 6, wherein the high single-crystal dispersion material has a BET of 0.3-0.5 m.sup.2/g.

    17. The preparation method of the lithium nickel manganate positive electrode material according to claim 6, wherein the second sintering is: heating from room temperature up to 300-600 C. at a heating rate of 1-5 C./min, calcining for 6-15 h, and then naturally cooling down to the room temperature.

    18. A lithium battery, having the lithium nickel manganate positive electrode material according to claim 1.

    19. An electrical device, having the lithium battery according to claim 18.

    20. An electric vehicle, having the lithium battery according to claim 18.

    Description

    BRIEF DESCRIPTION OF DRAWINGS

    [0052] FIG. 1 is an SEM image of a sample after a first sintering in Example 1.

    [0053] FIG. 2 is an SEM image of a sample after a first sintering in Example 2.

    [0054] FIG. 3 is an SEM image of a sample after a first sintering in Example 3.

    [0055] FIG. 4 is an SEM image of a sample after a first sintering in Example 4.

    [0056] FIG. 5 is an SEM image of a sample after a first sintering in Example 5.

    [0057] FIG. 6 is an SEM image of a sample after being coated with P in Example 5.

    [0058] FIG. 7 is an EDS Mapping of P in a P-coated sample in Example 5.

    [0059] FIG. 8 is an SEM image of a sample after being coated with Al in Example 10.

    [0060] FIG. 9 is an EDS Mapping of Al in an Al-coated sample in Example 10.

    [0061] FIG. 10 is an SEM image of a sample after a first sintering in Comparative example 2.

    [0062] FIG. 11 is an SEM image of a sample after being co-coated with P and Al in Example 15.

    [0063] FIG. 12 is an EDS Mapping of Al in a PAl co-coated sample in Example 15.

    [0064] FIG. 13 is an EDS Mapping of P in a PAl co-coated sample in Example 15.

    DESCRIPTION OF EMBODIMENTS

    [0065] In order to make the person skilled in the art to better understand the technical solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the examples of the present application. Apparently, the described embodiments are a part rather than all embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative work shall fall within the protection scope of the present application.

    [0066] A lithium nickel manganate material is described in the present application, having a molecular formula: Li.sub.Ni.sub.Mn.sub.2-M.sub.O.sub.4-/N, where 0.951.1, 0.40.6, 0.00050.02, 00.2; M is a single-crystal dispersing element, and M is at least one of V, Nb, Ta, Mo or W; N represents a coating layer, and the coating layer includes a P compound and/or an Al compound; the coating amount of N is 500-10000 ppm.

    [0067] Further, when the coating layer is the P compound and the Al compound, a mass ratio of Al to P is (0.2-3):1, and may be selected from 0.2:1, 0.33:1, 0.5:1, 1:1, 2:1 or 3:1.

    [0068] Further, a coating rate S1/(S1+S2) of P and/or Al is 20%-80%, where S1 is a peak area corresponding to a content m.sub.1 of P and/or Al, and S2 is a peak area corresponding to a content m.sub.2 of Ni and Mn elements, the covering rate may be selected from 20%, 30%, 40%, 50%, 60%, 70% or 80%.

    [0069] Further, when the coating layer is the P compound, the lithium nickel manganate positive electrode material has a BET of 0.4-0.7 m.sup.2/g.

    [0070] Further, when the coating layer is the Al compound, the lithium nickel manganate positive electrode material has a BET of 0.6-0.9 m.sup.2/g.

    [0071] Further, when the coating layer is the P compound and Al compound, the lithium nickel manganate positive electrode material has a BET of 0.6-0.9 m.sup.2/g.

    [0072] Further, residual lithium on a surface of the lithium nickel manganate positive electrode material is 500 ppm.

    [0073] Further, a DSC decomposition temperature of the lithium nickel manganate positive electrode material is 275-295 C.

    [0074] Further, a powder compaction density of the lithium nickel manganate positive electrode material is 2.8-3.2 g/cm.sup.3 at 3.5 T.

    [0075] Further, D50 of the lithium nickel manganate positive electrode material is 4-10 m.

    [0076] The present application further provides a preparation method for the above-mentioned lithium nickel manganate positive electrode material to explain the preparation process of the above-mentioned lithium nickel manganate positive electrode material, however the preparation of the above-mentioned lithium nickel manganate positive electrode material is not limited to this method. The preparation method used as an example includes but is not limited to the following steps.

    [0077] S1: a precursor, a lithium source, and a single-crystal dispersant are mixed and stirred evenly.

    [0078] Where, the molecular formula of the precursor is: Ni.sub.Mn.sub.2-(OH).sub.4, with 0.40.6; the precursor has at least one of the following properties that the D50 of the precursor is 2-8 m; the specific surface area of the precursor is 10-30 m.sup.2/g; and the tap density of the precursor is 0.8-1.5 g/cm.sup.3.

    [0079] In an embodiment, the may be 0.4, 0.5 or 0.6.

    [0080] In an embodiment, D50 of the precursor is 2 m, 4 m, 7 m or 8 m.

    [0081] In an embodiment, the specific surface area of the precursor is 10 m.sup.2/g, 18 m.sup.2/g, 24 m.sup.2/g or 30 m.sup.2/g.

    [0082] In an embodiment, the tap density of the precursor is 0.8 g/cm.sup.3, 1 g/cm.sup.3, 1.2 g/cm.sup.3, 1.3 g/cm.sup.3 or 1.5 g/cm.sup.3.

    [0083] In an embodiment, the lithium source is at least one of lithium carbonate, lithium hydroxide, lithium oxalate, lithium nitrate, lithium chloride, lithium fluoride or lithium acetate.

    [0084] In an embodiment, the single-crystal dispersant includes at least one of V.sub.2O.sub.5, NH.sub.4VO.sub.3, Nb.sub.2O.sub.5, LiNbO.sub.3, Ta.sub.2O.sub.5, LiTaO.sub.3, H.sub.2MoO.sub.4, (NH.sub.4).sub.2MoO.sub.4, H.sub.2WO.sub.4 or WO.sub.3.

    [0085] Where, a molar ratio of the precursor to the lithium source is 1:0.5-1.1, and the added amount of the single-crystal dispersant is 0.1%-1% of the mass of the precursor.

    [0086] In an embodiment, when the lithium source is lithium carbonate, the molar ratio of the precursor to lithium carbonate is 1:0.5, 1:0.51, 1:0.52, 1:0.54 or 1:0.55; when the lithium source is lithium hydroxide, lithium oxalate, lithium nitrate, lithium chloride, lithium fluoride or lithium acetate, the molar ratio of the precursor to the lithium source is 1:1, 1:1.02, 1:1.04, 1:1.08 or 1:1.1; and the added amount of the single-crystal dispersant is 0.1%, 0.3%, 0.5%, 0.8% or 1.0% of the mass of the precursor.

    [0087] S2: the mixture is subjected to a first sintering in an atmospheric environment to obtain a high single-crystal dispersion material.

    [0088] Where, an oxygen concentration of the atmospheric environment is 15%-40%.

    [0089] In an embodiment, the oxygen concentration of the atmospheric environment is 15%, 18%, 20%, 25%, 30%, 35% or 40%.

    [0090] Where, the first sintering is: heating from room temperature up to 800-1000 C. at a rate of 1-5 C./min, calcining for 6-15 h, and then cooling down to 600-800 C. at a rate of 0.1-2 C./min, keeping the temperature for 1-10 h, and finally, naturally cooling down to room temperature.

    [0091] In an embodiment, the following are performed: heating up to 800 C. at a rate of 2 C./min, calcining for 6 hours, then cooling down to 600 C. at a rate of 0.1 C./min, keeping the temperature for 1 h, and finally, naturally cooling down to room temperature.

    [0092] Alternatively, in an embodiment, the following are performed: heating up to 900 C. at a rate of 3 C./min, calcining for 10 hours, then cooling down to 700 C. at a rate of 0.5 C./min, keeping the temperature for 5 h, and finally, naturally cooling down to room temperature.

    [0093] Alternatively, in an embodiment, the following are performed: heating up to 1000 C. at a rate of 5 C./min, calcining for 15 hours, then cooling down to 800 C. at a rate of 2 C./min, keeping the temperature for 10 h, and finally, naturally cooling down to room temperature.

    [0094] Where, the BET of the high single-crystal dispersion material is 0.3-0.5 m.sup.2/g.

    [0095] S3: the high single-crystal dispersion material and a coating agent are mixed and evenly stirred to obtain a secondary mixture.

    [0096] In an embodiment, when the coating agent contains an Al source, the particle size of the Al source is 30-60 nm. The Al source includes at least one of Al.sub.2O.sub.3, AlPO.sub.4, or Al(OH).sub.3.

    [0097] In an embodiment, when the coating agent contains a P source, the particle size of the P source is 3-5 m. The P source includes at least one of Li.sub.3PO.sub.4, AlPO.sub.4, LiFePO.sub.4, FePO.sub.4, NH.sub.4H.sub.2PO.sub.4 or (NH.sub.4).sub.2HPO.sub.4.

    [0098] S4: the secondary mixture is subjected to a second sintering in the atmospheric environment to obtain the lithium nickel manganate positive electrode material as described.

    [0099] Where, the coating agent is a P source and/or an Al source.

    [0100] Where, the second sintering is: heating from room temperature up to 300-600 C. at a heating rate of 1-5 C./min, calcining for 6-15 h, and then naturally cooling down to room temperature.

    [0101] In an embodiment, the following are performed: heating from room temperature up to 300 C. at a heating rate of 1 C./min, calcining for 6 h, and then naturally cooling down to room temperature.

    [0102] Alternatively, in an embodiment, the following are performed: heating from room temperature up to 400 C. at a heating rate of 2 C./min, calcining for 8 h, and then naturally cooling down to room temperature.

    [0103] Alternatively, in an embodiment, the following are performed: heating from room temperature up to 500 C. at a heating rate of 4 C./min, calcining for 10 h, and then naturally cooling down to room temperature.

    [0104] Alternatively, in an embodiment, the following are performed: heating from room temperature up to 600 C. at a heating rate of 5 C./min, calcining for 15 h, and then naturally cooling down to room temperature.

    [0105] The lithium nickel manganate positive electrode material of the present application may be applied to a lithium-ion battery. The lithium-ion battery may be used in an electrical device, and the electrical device may specifically be a 3 C electronic product, a power tool, etc. The lithium-ion battery may also be used in an electric vehicle. The lithium-ion battery may also be used in the field of energy storage.

    Example 1

    [0106] (1) 1000 g of a precursor Ni.sub.0.5Mn.sub.1.5(OH).sub.4, 205.6 g of lithium carbonate, and 3 g of a single-crystal dispersant V.sub.2O.sub.5 were added into a high-speed mixer, and mixed and stirred evenly, with a stirring speed of 800 rpm and a stirring time of 20 min, and after being mixed evenly, the mixture was placed in an atmosphere box type furnace for a first sintering. During the first sintering, the temperature was raised to 900 C. at a rate of 3 C./min and kept for 8 h, then it was cooled to 650 C. at a rate of 0.5 C./min and kept at 650 C. for 10 h, then was naturally cooled down to room temperature.

    [0107] (2) The product after the first sintering was crushed and sieved to obtain a high-voltage nickel manganese material having high dispersity of single crystals, the chemical formula of which was LiNi.sub.0.5Mn.sub.1.5V.sub.0.005904; the BET of the sample after the first sintering was 0.37 m.sup.2/g, and an SEM scanning image was shown in FIG. 1. It can be seen that when V.sub.2O.sub.5 was used as a single-crystal dispersant, the effect of single crystal dispersion was good.

    [0108] (3) 1000 g of the lithium nickel manganate positive electrode material having high dispersity of single crystals dispersion and a coating agent NH.sub.4H.sub.2PO.sub.4 were mixed and stirred evenly, with a stirring speed of 800 rpm and a stirring time of 20 min, and after being mixed, the mixture was placed in the atmosphere box type furnace for a second sintering. During the second sintering, the temperature was raised to 450 C. at a rate of 4 C./min and kept for 10 h, and then was naturally cooled down to room temperature.

    [0109] (4) The product after the second sintering was crushed and sieved to obtain a coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5V.sub.0.0059O.sub.4/P. The BET of the coated sample was 0.47 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 1500 ppm.

    [0110] Full cell preparation: the positive electrode active material, conductive carbon Super P, KS6 and polyvinylidene fluoride (HSV900) were mixed according to a mass ratio of 94.5%: 2%: 1%: 2.5% to form an uniform slurry, and then the slurry was uniformly coated on an aluminum foil and dried, with a surface density controlled at 16 mg/cm.sup.2 on a single side. Then the latter was rolled by using a roller machine to obtain a positive electrode sheet having a compaction density of 3.0 g/cm.sup.3, and then the positive electrode sheet was put into a vacuum drying box and dried at 120 C. for 10 h. The positive electrode sheet, a separator, and a negative electrode sheet were wound into a battery cell. The battery cell was designed to have a nominal capacity of 600 mAh, a NP ratio of 1.12, an injected liquid of 3 g, the separator was a PP/PE composite separator, the negative electrode was graphite, and the electrolyte was a high-voltage electrolyte (Xinzhoubang LBC502A50). The full cell was placed for 1 day for formation, with a voltage range of 3.4-4.85V. It was charged with 0.05 C constant current for 1 h, with 0.1 C constant current for 1 h, and with 0.2 C constant current for 1 h to 4.85V. It was charged at a constant voltage of 4.85V until the current is less than 0.05 C, discharged at 0.33 C to 3.4V, so as to obtain an initial capacity for 0.33 C. After the full cell was aged for 3 days, then was subjected to capacity sorting, followed by cycle and gas generation tests. The cycle test was 500 times of charging and discharging with 1 C under 25 C., and the gas generation test was made in a situation that the full cell was fully charged and then stored for 7 days under 45 C.

    [0111] An initial capacity for 0.33 C was tested to be 129.5 mAh/g, a capacity retention rate after 500 cycles was tested to be 67.5%, and a gas generated was tested to be 5.6 mL/Ah.

    Example 2

    [0112] The difference between Example 2 and Example 1 was that the single-crystal dispersant used in Example 2 was Nb.sub.2O.sub.5. The BET of the sample after the first sintering was 0.36 m.sup.2/g; as can be seen from the SEM scanning image shown in FIG. 2, the effect of single crystal dispersion was good when Nb.sub.2O.sub.5 was used as a single-crystal dispersant. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5Nb.sub.0.0041O.sub.4/P was obtained, with the BET of the coated sample being 0.45 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 1500 ppm.

    [0113] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.2 mAh/g, the capacity retention rate after 500 cycles was tested to be 72.9%, and a gas generated was 5.8 mL/Ah.

    Example 3

    [0114] The difference between Example 3 and Example 1 was that the single-crystal dispersant used in Example 3 was Ta.sub.2O.sub.5. The BET of the sample after the first sintering was 0.47 m.sup.2/g; as can be seen from the SEM scanning image shown in FIG. 3, the effect of single crystal dispersion was good when Ta.sub.2O.sub.5 was used as a single-crystal dispersant. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5Ta.sub.0.0024O.sub.4/P was obtained, with the BET of the coated sample being 0.56 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 1500 ppm.

    [0115] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 132.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 78.5%, and a gas generated was 4.8 mL/Ah.

    Example 4

    [0116] The difference between Example 4 and Example 1 was that the single-crystal dispersant used in Example 4 was H.sub.2MoO.sub.4. The BET of the sample after the first sintering was 0.48 m.sup.2/g; as can be seen from the SEM scanning image shown in FIG. 4, the effect of single crystal dispersion was good when H.sub.2MoO.sub.4 was used as a single-crystal dispersant. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5Mo.sub.0.0033O.sub.4/P was obtained, with the BET of the coated sample being 0.59 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 1500 ppm.

    [0117] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 128.6 mAh/g, the capacity retention rate after 500 cycles was tested to be 68.2%, and a gas generated was 6.7 mL/Ah.

    Example 5

    [0118] The difference between Example 5 and Example 1 was that the single-crystal dispersant used in Example 5 was WO.sub.3. The BET of the sample after the first sintering was 0.35 m.sup.2/g; as can be seen from the SEM scanning image shown in FIG. 5, the effect of single crystal dispersion was good when WO.sub.3 was used as a single-crystal dispersant. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained, with the BET of the coated sample being 0.49 m.sup.2/g, the residual lithium on the surface being 105 ppm, the DSC decomposition temperature being 291 C., and the powder compaction density at 3.5 T being 3.10 g/cm.sup.3. The SEM scanning image and the EDS Mapping of P were shown in FIG. 6 and FIG. 7, it can be seen that the P coating was uniform without agglomeration. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 1500 ppm.

    [0119] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.9 mAh/g, the capacity retention rate after 500 cycles was tested to be 70.5%, and a gas generated was 6.1 mL/Ah.

    Example 6

    [0120] (1) 1000 g of a precursor Ni.sub.0.5Mn.sub.1.5(OH).sub.4, 205.6 g of lithium carbonate, and 3 g of a single-crystal dispersant V.sub.2O.sub.5 were added into a high-speed mixer, and mixed and stirred evenly, with a stirring speed of 800 rpm and a stirring time of 20 min, and after being mixed evenly, the mixture was placed in an atmosphere box type furnace for a first sintering. During the first sintering, the temperature was raised to 900 C. at a rate of 3 C./min and kept for 8 h, then it was cooled to 650 C. at a rate of 0.5 C./min and kept at 650 C. for 10 h, then was naturally cooled down to room temperature.

    [0121] (2) The product after the first sintering was crushed and sieved to obtain a high-voltage nickel manganese material having high single-crystal dispersion, and the chemical formula of which was LiNi.sub.0.5Mn.sub.1.5V.sub.0.0059O.sub.4; the BET of the sample after the first sintering was 0.37 m.sup.2/g, and an SEM scanning image was shown in FIG. 1.

    [0122] (3) 1000 g of the lithium nickel manganate positive electrode material having high single-crystal dispersion and a coating agent Al.sub.2O.sub.3 were mixed and stirred evenly, with a stirring speed of 800 rpm and a stirring time of 20 min, and after being mixed, the mixture was placed in an atmosphere box type furnace for a second sintering. During the second sintering, the temperature was raised to 450 C. at a rate of 4 C./min and kept for 10 h, and then was naturally cooled down to room temperature.

    [0123] (4) the product after the second sintering was crushed and sieved to obtain a coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5V.sub.0.0059O.sub.4/Al. The BET of the coated sample was 0.75 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 1500 ppm.

    [0124] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 128.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 65.5%, and a gas generated was 5.9 mL/Ah.

    Example 7

    [0125] The difference between Example 7 and Example 6 was that the single-crystal dispersant used in Example 7 was Nb.sub.2O.sub.5. The BET of the sample after the first sintering was 0.36 m.sup.2/g; the SEM scanning image was shown in FIG. 2. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5Nb.sub.0.0041O.sub.4/Al was obtained, with the BET of the coated sample being 0.78 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 1500 ppm.

    [0126] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.2 mAh/g, the capacity retention rate after 500 cycles was tested to be 69.8%, and a gas generated was 5.7 mL/Ah.

    Example 8

    [0127] The difference between Example 8 and Example 6 was that the single-crystal dispersant used in Example 8 was Ta.sub.2O.sub.5. The BET of the sample after the first sintering was 0.47 m.sup.2/g; the SEM scanning image was shown in FIG. 3. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5Ta.sub.0.0024O.sub.4/Al was obtained, with the BET of the coated sample being 0.86 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 1500 ppm.

    [0128] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.5 mAh/g, the capacity retention rate after 500 cycles was tested to be 74.2%, and a gas generated was 5 mL/Ah.

    Example 9

    [0129] The difference between Example 9 and Example 6 was that the single-crystal dispersant used in Example 9 was H.sub.2MoO.sub.4. The BET of the sample after the first sintering was 0.48 m.sup.2/g; the SEM scanning image was shown in FIG. 4. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5Mo.sub.0.0033O.sub.4/Al was obtained, with the BET of the coated sample being 0.82 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 1500 ppm.

    [0130] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.3 mAh/g, the capacity retention rate after 500 cycles was tested to be 70.5%, and a gas generated was 5.8 mL/Ah.

    Example 10

    [0131] The difference between Example 10 and Example 6 was that the single-crystal dispersant used in Example 10 was WO.sub.3. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained, with the BET of the coated sample being 0.81 m.sup.2/g, the residual lithium on the surface being 237 ppm, the DSC decomposition temperature being 287 C., and the powder compaction density at 3.5 T being 3.04 g/cm.sup.3. The SEM scanning image and the EDS Mapping of Al were shown in FIG. 8 and FIG. 9 respectively, it can be seen that the Al coating was uniform without agglomeration. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 1500 ppm.

    [0132] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.5 mAh/g, the capacity retention rate after 500 cycles was tested to be 68.4%, and a gas generated was 5.2 mL/Ah.

    Comparative Example 1

    [0133] (1) 1000 g of a precursor Ni.sub.0.5Mn.sub.1.5(OH).sub.4, 205.6 g of lithium carbonate and 3 g of single-crystal dispersant WO.sub.3 were added into a high-speed mixer, and mixed and stirred evenly, with a stirring speed of 800 rpm and a stirring time of 20 min, and after being mixed evenly, the mixture was placed in an atmosphere box type furnace for a first sintering. During the first sintering, the temperature was raised to 900 C. at a rate of 3 C/min and kept for 8 h, then it was cooled to 650 C. at a rate of 0.5 C./min and kept at 650 C. for 10 h, then was naturally cooled down to room temperature.

    [0134] (2) The product after the first sintering was crushed and sieved to obtain a high-voltage nickel manganese material having high single-crystal dispersion, and the chemical formula of which was LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4.

    [0135] The full cell preparation was the same as that of Example 1. The initial capacity at 0.33 C was tested to be 129.2 mAh/g, the capacity retention rate after 500 cycles was tested to be 39.6%, and a gas generated was 9.4 mL/Ah.

    Comparative Example 2

    [0136] The difference between Comparative example 2 and Example 1 was that in Comparative example 2, no single-crystal dispersant and coating agent were used, and the second sintering was not conducted. The lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5O.sub.4 was obtained, the BET of the sample after the first sintering was 0.67 m.sup.2/g, and as can be seen from the SEM scanning image shown in FIG. 10, the effect of single crystal dispersion was not good with partial agglomeration.

    [0137] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.9 mAh/g, the capacity retention rate after 500 cycles was tested to be 35.4%, and a gas generated was 12.1 mL/Ah.

    Comparative Example 3

    [0138] The difference between Comparative example 3 and Example 5 was that the coating agent used in Comparative example 3 was ZnO, with an amount of 1500 ppm. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Zn was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Zn was 1500 ppm.

    [0139] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 45.1%, and a gas generated was 9.2 mL/Ah.

    Comparative Example 4

    [0140] The difference between Comparative example 4 and Example 5 was that the coating agent used in Comparative example 4 was Cr.sub.2O.sub.3. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Cr. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Cr was 1500 ppm.

    [0141] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.8 mAh/g, the capacity retention rate after 500 cycles was tested to be 49.8%, and a gas generated was 8.7 mL/Ah.

    Example 11

    [0142] (1) 1000 g of a precursor Ni.sub.0.5Mn.sub.1.5(OH).sub.4, 205.6 g of lithium carbonate, and 3 g of single-crystal dispersant V.sub.2O.sub.5 were added into a high-speed mixer, and mixed and stirred evenly, with a stirring speed of 800 rpm and a stirring time of 20 min, and after being mixed evenly, the mixture was placed in an atmosphere box type furnace for a first sintering. During the first sintering, the temperature was raised to 900 C. at a rate of 3 C./min and kept for 8 h, then it was cooled to 650 C. at a rate of 0.5 C./min and kept at 650 C. for 10 h, then was naturally cooled down to room temperature.

    [0143] (2) The product after the first sintering was crushed and sieved to obtain a high-voltage nickel manganese material having high single-crystal dispersion, and the chemical formula of which was LiNi.sub.0.5Mn.sub.1.5V.sub.0.0059O.sub.4; the BET of the sample after the first sintering was 0.37 m.sup.2/g, and an SEM scanning image is shown in FIG. 1.

    [0144] (3) 1000 g of lithium nickel manganate positive electrode material having high single-crystal dispersion and a coating agent NH.sub.4H.sub.2PO.sub.4 and Al.sub.2O.sub.3 were mixed and stirred evenly, with a stirring speed of 800 rpm and a stirring time of 20 min, and after being mixed, the mixture was placed in an atmosphere box type furnace for a second sintering. During the second sintering, the temperature was raised to 450 C. at a rate of 4 C./min and kept for 10 h, and then was naturally cooled down to room temperature.

    [0145] (4) The product after the second sintering was crushed and sieved to obtain a coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5V.sub.0.0059O.sub.4/PAl. The BET of the coated sample was 0.66 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 500 ppm and 750 ppm respectively.

    [0146] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 66.4%, and a gas generated was 5.7 mL/Ah.

    Example 12

    [0147] The difference between Example 12 and Example 11 was that the single-crystal dispersant used in Example 12 was Nb.sub.2O.sub.5. The BET of the sample after the first sintering was 0.36 m.sup.2/g; the SEM scanning image was shown in FIG. 2. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5Nb.sub.0.0041O.sub.4/PAl was obtained, with the BET of the coated sample being 0.69 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 500 ppm and 750 ppm respectively.

    [0148] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.5 mAh/g, the capacity retention rate after 500 cycles was tested to be 70.1%, and a gas generated was 5.8 mL/Ah.

    Example 13

    [0149] The difference between Example 13 and Example 11 was that the single-crystal dispersant used in Example 13 was Ta.sub.2O.sub.5. The BET of the sample after the first sintering was 0.47 m.sup.2/g; the SEM scanning image was shown in FIG. 3. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5Ta.sub.0.0024O.sub.4/PAl was obtained, with the BET of the coated sample being 0.71 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 500 ppm and 750 ppm respectively.

    [0150] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.2 mAh/g, the capacity retention rate after 500 cycles was tested to be 72.3%, and a gas generated was 5.4 mL/Ah.

    Example 14

    [0151] The difference between Example 14 and Example 11 was that the single-crystal dispersant used in Example 14 was H.sub.2MoO.sub.4. The BET of the sample after the first sintering was 0.48 m.sup.2/g; the SEM scanning image was shown in FIG. 4. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5Mo.sub.0.0033O.sub.4/Al was obtained, with the BET of the coated sample being 0.74 m.sup.2/g. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 500 ppm and 750 ppm respectively.

    [0152] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 65.9%, and a gas generated was 6.2 mL/Ah.

    Example 15

    [0153] The difference between Example 15 and Example 11 was that the single-crystal dispersant used in Example 15 was WO.sub.3. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained, with the BET of the coated sample being 0.64 m.sup.2/g, the residual lithium on the surface being 246 ppm, the DSC decomposition temperature being 288 C., and the powder compaction density at 3.5 T being 3.03 g/cm.sup.3. The SEM scanning image and the EDS Mapping of P and Al were shown in FIG. 11, FIG. 12 and FIG. 13 respectively, it can be seen that the PAl co-coating is uniform without agglomeration. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 500 ppm and 750 ppm respectively.

    [0154] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 66.4%, and a gas generated was 6.4 mL/Ah.

    TABLE-US-00001 TABLE 1 Electrochemical properties for Examples 1 to 15 and Comparative examples 1 to 4 Capacity BET retention after the Capacity rate after Single first Coating for 500 Gas Serial crystal sintering amount 0.33 C cycles generation number dispersant (m.sup.2/g) Coating agent (ppm) (mAh/g) (%) (mL/Ah) Example 1 V.sub.2O.sub.5 0.37 NH.sub.4H.sub.2PO.sub.4 1500 129.5 67.5 5.6 Example 2 Nb.sub.2O.sub.5 0.36 NH.sub.4H.sub.2PO.sub.4 1500 131.2 72.9 5.8 Example 3 Ta.sub.2O5 0.47 NH.sub.4H.sub.2PO.sub.4 1500 132.1 78.5 4.8 Example 4 H.sub.2MoO.sub.4 0.48 NH.sub.4H.sub.2PO.sub.4 1500 128.6 68.2 6.7 Example 5 WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 1500 129.9 70.5 6.1 Example 6 V.sub.2O.sub.5 0.37 Al.sub.2O.sub.3 1500 128.4 65.5 5.9 Example 7 Nb.sub.2O.sub.5 0.36 Al.sub.2O.sub.3 1500 130.2 69.8 5.7 Example 8 Ta.sub.2O.sub.5 0.47 Al.sub.2O.sub.3 1500 131.5 74.2 5 Example 9 H.sub.2MoO.sub.4 0.48 Al.sub.2O.sub.3 1500 129.3 70.5 5.8 Example 10 WO.sub.3 0.35 Al.sub.2O.sub.3 1500 129.5 68.4 5.2 Comparative WO.sub.3 0.35 Un-coated / 129.2 39.6 9.4 example 1 Comparative Un-added 0.67 / / 130.9 35.4 12.1 example 2 Comparative WO.sub.3 0.35 ZnO 1500 129.4 45.1 9.2 example 3 Comparative WO.sub.3 0.35 Cr203 1500 129.8 49.8 8.7 example 4 Example 11 V.sub.2O.sub.5 0.37 NH.sub.4H.sub.2PO.sub.4 500 + 130.1 66.4 5.7 and Al.sub.2O.sub.3 750 Example 12 Nb.sub.2O.sub.5 0.36 NH.sub.4H.sub.2PO.sub.4 500 + 130.5 70.1 5.8 and Al.sub.2O.sub.3 750 Example 13 Ta.sub.2O.sub.5 0.47 NH.sub.4H.sub.2PO.sub.4 500 + 131.2 72.3 5.4 and Al.sub.2O.sub.3 750 Example 14 H.sub.2MoO.sub.4 0.48 NH.sub.4H.sub.2PO.sub.4 500 + 130.4 65.9 6.2 and Al.sub.2O.sub.3 750 Example 15 WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 500 + 131.1 66.4 6.4 and Al.sub.2O.sub.3 750

    [0155] It can be seen from Table 1 that in Examples 1-15, the BET after the first sintering was between 0.3-0.5 m.sup.2/g, the single crystal dispersion was good, and the electrochemical performance was good after the coating of P compound and/or Al compound.

    [0156] In Comparative example 1, even if the single-crystal dispersing element was added to obtain the positive electrode material having good single crystal dispersion, its electrochemical performance was not as good as that of the coated positive electrode materials in Examples 1 to 15, and its performance in terms of cycling and gas generation was significantly worse, since it was not subjected to coating.

    [0157] In Comparative example 2, no single-crystal dispersing element was added and no coating was performed, resulting in poor single crystal dispersion and poor electrochemical performance of the prepared positive electrode material.

    [0158] In Comparative example 3 and Comparative example 4, although the single-crystal dispersing element was added, and the obtained positive electrode material had good single crystal dispersion, the electrochemical performance was not good since other coating agents ZnO and Cr.sub.2O.sub.3 were used.

    Example 16

    [0159] The difference between Example 16 and Example 5 was that the coating agent used in Example 16 was (NH.sub.4).sub.2HPO.sub.4. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 1500 ppm.

    [0160] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.2 mAh/g, the capacity retention rate after 500 cycles was tested to be 68.7%, and a gas generated was 5.9 mL/Ah.

    Example 17

    [0161] The difference between Example 17 and Example 5 was that the coating agent used in Example 17 was Li.sub.3PO.sub.4. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 1500 ppm.

    [0162] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.8 mAh/g, the capacity retention rate after 500 cycles was tested to be 72.4%, and a gas generated was 5.6 mL/Ah.

    Example 18

    [0163] The difference between Example 18 and Example 5 was that the coating agent used in Example 18 was FePO.sub.4. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 1500 ppm.

    [0164] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.5 mAh/g, the capacity retention rate after 500 cycles was tested to be 73.5%, and a gas generated was 5.7 mL/Ah.

    Example 19

    [0165] The difference between Example 19 and Example 5 was that the coating agent used in Example 19 was LiFePO.sub.4. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 1500 ppm.

    [0166] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.7 mAh/g, the capacity retention rate after 500 cycles was tested to be 69.3%, and a gas generated was 6.1 mL/Ah.

    Example 20

    [0167] The difference between Example 20 and Example 10 was that the coating agent used in Example 20 was Al(OH).sub.3. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 1500 ppm.

    [0168] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.5 mAh/g, the capacity retention rate after 500 cycles was tested to be 67.4%, and a gas generated was 6.5 mL/Ah.

    Example 21

    [0169] The difference between Example 21 and Example 10 was that the coating agent used in Example 21 was LiAlO.sub.2. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 1500 ppm.

    [0170] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.3 mAh/g, the capacity retention rate after 500 cycles was tested to be 71.6%, and a gas generated was 5.4 mL/Ah.

    Example 22

    [0171] The difference between Example 22 and Example 15 was that the coating agent used in Example 22 was AlPO.sub.4. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 760 ppm and 660 ppm respectively.

    [0172] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.2 mAh/g, the capacity retention rate after 500 cycles was tested to be 72.6%, and a gas generated was 5.2 mL/Ah.

    Example 23

    [0173] The difference between Example 23 and Example 15 was that the coating agents used in Example 23 were (NH.sub.4).sub.2HPO.sub.4 and Al.sub.2O.sub.3. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 750 ppm and 750 ppm respectively.

    [0174] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.8 mAh/g, the capacity retention rate after 500 cycles was tested to be 70.5%, and a gas generated was 6.1 mL/Ah.

    Example 24

    [0175] The difference between Example 24 and Example 15 was that the coating agents used in Example 24 were FePO.sub.4 and Al.sub.2O.sub.3. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 750 ppm and 750 ppm respectively.

    [0176] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 72.4%, and a gas generated was 6 mL/Ah.

    Example 25

    [0177] The difference between Example 25 and Example 15 was that the coating agents used in Example 25 were (NH.sub.4).sub.2HPO.sub.4 and Al(OH).sub.3. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 750 ppm and 750 ppm respectively.

    [0178] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 69.8%, and a gas generated was 6.2 mL/Ah.

    TABLE-US-00002 TABLE 2 Electrochemical performance for Examples 16 to 25 BET Capacity after the Capacity retention Single first Coating for rate after Gas Serial crystal sintering Coating amount 0.33 C 500 cycles generation number dispersant (m.sup.2/g) agent (ppm) (mAh/g) (%) (mL/Ah) Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 1500 130.2 68.7 5.9 16 Example WO.sub.3 0.35 Li.sub.3PO.sub.4 1500 130.8 72.4 5.6 17 Example WO.sub.3 0.35 FePO.sub.4 1500 131.5 73.5 5.7 18 Example WO.sub.3 0.35 LiFePO.sub.4 1500 130.7 69.3 6.1 19 Example WO.sub.3 0.35 Al(OH).sub.3 1500 129.5 67.4 6.5 20 Example WO.sub.3 0.35 LiAlO.sub.2 1500 130.3 71.6 5.4 21 Example WO.sub.3 0.35 AlPO.sub.4 P~760; 131.2 72.6 5.2 22 Al~660 Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~750; 129.8 70.5 6.1 23 and Al.sub.2O.sub.3 Al~750 Example WO.sub.3 0.35 FePO.sub.4 and P~750; 130.1 72.4 6 24 Al.sub.2O.sub.3 Al~750 Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~750; 130.4 69.8 6.2 25 and Al(OH).sub.3 Al~750

    [0179] It can be seen from Table 2 that in Examples 16-25, after the single-crystal dispersant WO.sub.3 was added and the first sintering was performed, the BET was 0.35 m.sup.2/g, and the single crystal dispersion was good; after P or/and Al coating, the electrochemical performance was good, and the full cell's cycle performance and gas generation were more excellent.

    [0180] Although different P and Al sources results in different electrochemical performance effects, they are overall significantly better than the situation of no coating or coating with other substances. In terms of comprehensive cost and performance, the P sources mainly are (NH.sub.4).sub.2HPO.sub.4, NH.sub.4H.sub.2PO.sub.4 and FePO.sub.4, Al sources mainly are Al.sub.2O.sub.3 and Al(OH).sub.3, and AlPO.sub.4 is mainly used for co-coating.

    Comparative Example 5

    [0181] The difference between Comparative example 5 and Example 5 was that the coating amount of P in Comparative example 5 was 200 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 200 ppm, and the coating rate of P was 12%.

    [0182] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 59.7%, and a gas generated was 7.5 mL/Ah.

    Example 26

    [0183] The difference between Example 26 and Example 5 was that the coating amount of P in Example 26 was 500 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 500 ppm, and the coating rate of P was 35%.

    [0184] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 132.5 mAh/g, the capacity retention rate after 500 cycles was tested to be 69.3%, and a gas generated was 6.5 mL/Ah.

    Example 27

    [0185] The difference between Example 27 and Example 5 was that the coating amount of P in Example 27 was 1000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 1000 ppm, and the coating rate of P was 57%.

    [0186] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 72.5%, and a gas generated was 5.2 mL/Ah.

    Example 28

    [0187] The difference between Example 28 and Example 5 was that the coating amount of P in Example 28 was 2000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 2000 ppm, and the coating rate of P was 62%.

    [0188] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 132.2 mAh/g, the capacity retention rate after 500 cycles was tested to be 70.3%, and a gas generated was 6.7 mL/Ah.

    Example 29

    [0189] The difference between Example 29 and Example 5 was that the coating amount of P in Example 29 was 3000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 3000 ppm, and the coating rate of P was 69%.

    [0190] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 132.0 mAh/g, the capacity retention rate after 500 cycles was tested to be 71.9%, and a gas generated was 6.2 mL/Ah.

    Example 30

    [0191] The difference between Example 30 and Example 5 was that the coating amount of P in Example 30 was 4000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 4000 ppm, and the coating rate of P was 73%.

    [0192] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 133.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 72.5%, and a gas generated was 5.1 mL/Ah.

    Example 31

    [0193] The difference between Example 31 and Example 5 was that the coating amount of P in Example 31 was 5000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 5000 ppm, and the coating rate of P was 75%.

    [0194] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 133 mAh/g, the capacity retention rate after 500 cycles was tested to be 69.4%, and a gas generated was 5.5 mL/Ah.

    Example 32

    [0195] The difference between Example 32 and Example 5 was that the coating amount of P in Example 32 was 8000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 8000 ppm, and the coating rate of P was 79%.

    [0196] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 69.9%, and a gas generated was 6.5 mL/Ah.

    Example 33

    [0197] The difference between Example 33 and Example 5 was that the coating amount of P in Example 33 was 10000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 10000 ppm, and the coating rate of P was 80%.

    [0198] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 133.6 mAh/g, the capacity retention rate after 500 cycles was tested to be 65.8%, and a gas generated was 7.1 mL/Ah.

    Comparative Example 6

    [0199] The difference between Comparative example 6 and Example 5 was that the coating amount of P in Comparative example 6 was 20000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/t; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.0.5W.sub.0.0023O.sub.4/P was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of P was 20000 ppm, and the coating rate of (P was 82%.

    [0200] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.9 mAh/g, the capacity retention rate after 500 cycles was tested to be 54.7%, and a gas generated was 7.8 mL/Ah.

    TABLE-US-00003 TABLE 3 Electrochemical performance for Examples 26 to 33 and Comparative examples 5 and 6 Capacity BET retention after the Capacity rate after Single first Coating for 500 Gas Coating Serial crystal sintering Coating amount 0.33 C cycles generation rate number dispersant (m.sup.2/g) agent (ppm) (mAh/g) (%) (mL/Ah) (%) Comparative WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 200 130.1 59.7 7.5 12% example 5 Example 26 WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 500 132.5 69.3 6.5 35% Example 27 WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 1000 131.4 72.5 5.2 57% Example 28 WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 2000 132.2 70.3 6.7 62% Example 29 WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 3000 132 71.9 6.2 69% Example 30 WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 4000 133.1 72.5 5.1 73% Example 31 WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 5000 133 69.4 5.5 75% Example 32 WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 8000 131.1 69.9 6.5 79% Example 33 WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 10000 133.6 65.8 7.1 80% Comparative WO.sub.3 0.35 NH.sub.4H.sub.2PO.sub.4 20000 131.9 54.7 7.8 82% example 6

    [0201] It can be seen from Table 3 that the electrochemical performance was better in Examples 26 to 33 when the coating amount was 500-10000 ppm. In Comparative example 5, the coating amount was less, resulting in poor coating effect, and the electrochemical performance was significantly worse. In Comparative example 6, the coating amount was too much, resulting in too large interface resistance, and the electrochemical performance was poor.

    [0202] In general, with the coating amount of P increasing, the coating rate gradually increases, reaching a maximum of about 80%. The coating amount is 1000-4000 ppm, and the coated lithium nickel manganate positive electrode material has good electrochemical performance.

    Comparative Example 7

    [0203] The difference between Comparative example 7 and Example 10 was that the coating amount of Al in Comparative example 7 was 200 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 200 ppm, and the coating rate of Al was 15%.

    [0204] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.2 mAh/g, the capacity retention rate after 500 cycles was tested to be 56.7%, and a gas generated was 7.8 mL/Ah.

    Example 34

    [0205] The difference between Example 34 and Example 10 was that the coating amount of Al in Example 34 was 500 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 500 ppm, and the coating rate of Al was 33%.

    [0206] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 62.4%, and a gas generated was 7.1 mL/Ah.

    Example 35

    [0207] The difference between Example 35 and Example 10 was that the coating amount of Al in Example 35 was 1000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 1000 ppm, and the coating rate of Al was 56%.

    [0208] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.8 mAh/g, the capacity retention rate after 500 cycles was tested to be 67.4%, and a gas generated was 6.7 mL/Ah.

    Example 36

    [0209] The difference between Example 36 and Example 10 was that the coating amount of Al in Example 36 was 2000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 2000 ppm, and the coating rate of Al was 65%.

    [0210] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.5 mAh/g, the capacity retention rate after 500 cycles was tested to be 69.8%, and a gas generated was 6.3 mL/Ah.

    Example 37

    [0211] The difference between Example 37 and Example 10 was that the coating amount of Al in Example 37 was 3000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 3000 ppm, and the coating rate of Al was 71%.

    [0212] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.9 mAh/g, the capacity retention rate after 500 cycles was tested to be 68.5%, and a gas generated was 6.6 mL/Ah.

    Example 38

    [0213] The difference between Example 38 and Example 10 was that the coating amount of Al in Example 38 was 4000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 4000 ppm, and the coating rate of Al was 73%.

    [0214] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 128.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 69.9%, and a gas generated was 6.7 mL/Ah.

    Example 39

    [0215] The difference between Example 39 and Example 10 was that the coating amount of Al in Example 39 was 5000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 5000 ppm, and the coating rate of Al was 75%.

    [0216] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 128.6 mAh/g, the capacity retention rate after 500 cycles was tested to be 64.1%, and a gas generated was 6.9 mL/Ah.

    Example 40

    [0217] The difference between Example 40 and Example 10 was that the coating amount of Al in Example 40 was 8000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 8000 ppm, and the coating rate of Al was 79%.

    [0218] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 128.7 mAh/g, the capacity retention rate after 500 cycles was tested to be 62.7%, and a gas generated was 7.2 mL/Ah.

    Example 41

    [0219] The difference between Example 41 and Example 10 was that the coating amount of Al in Example 41 was 10000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 10000 ppm, and the coating rate of Al was 80%.

    [0220] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 128.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 60.8%, and a gas generated was 7.9 mL/Ah.

    Comparative Example 8

    [0221] The difference between Comparative example 8 and Example 10 was that the coating amount of Al in Comparative example 8 was 20000 ppm. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/Al was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amount of Al was 20000 ppm, and the coating rate of Al was 86%.

    [0222] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 127.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 39.7%, and a gas generated was 8.9 mL/Ah.

    TABLE-US-00004 TABLE 4 Electrochemical performance for Examples 34 to 41 and Comparative examples 7 and 8 Capacity retention BET rate after the Capacity after Single first Coating for 500 Gas Coating Serial crystal sintering Coating amount 0.33 C cycles generation rate number dispersant (m.sup.2/g) agent (ppm) (mAh/g) (%) (mL/Ah) (%) Comparative WO.sub.3 0.35 Al.sub.2O.sub.3 200 130.2 56.7 7.8 15% example 7 Example 34 WO.sub.3 0.35 Al.sub.2O.sub.3 500 130.4 62.4 7.1 33% Example 35 WO.sub.3 0.35 Al.sub.2O.sub.3 1000 129.8 67.4 6.7 56% Example 36 WO.sub.3 0.35 Al.sub.2O.sub.3 2000 129.5 69.8 6.3 65% Example 37 WO.sub.3 0.35 Al.sub.2O.sub.3 3000 129.9 68.5 6.6 71% Example 38 WO.sub.3 0.35 Al.sub.2O.sub.3 4000 128.4 69.9 6.7 73% Example 39 WO.sub.3 0.35 Al.sub.2O.sub.3 5000 128.6 64.1 6.9 75% Example 40 WO.sub.3 0.35 Al.sub.2O.sub.3 8000 128.7 62.7 7.2 79% Example 41 WO.sub.3 0.35 Al.sub.2O.sub.3 10000 128.1 60.4 7.9 80% Comparative WO.sub.3 0.35 Al.sub.2O.sub.3 20000 127.4 39.7 8.9 86% example 8

    [0223] It can be seen from Table 4 that the electrochemical performance was better in Examples 34 to 41 when the coating amount was 500-10000 ppm. In Comparative example 7, the coating amount was less, resulting in poor coating effect, and the electrochemical performance was significantly worse. In Comparative example 8, the coating amount was too much, resulting in too large interface resistance, and the electrochemical performance was poor.

    [0224] In general, with the coating amount of Al increasing, the coating rate gradually increases, reaching a maximum of about 86%. The coating amount is 1000-4000 ppm, and the coated lithium nickel manganate positive electrode material has good electrochemical performance.

    Comparative Example 9

    [0225] The difference between Comparative example 9 and Example 22 was that the coating amounts of P and Al in Comparative example 9 were 100 ppm and 80 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 100 ppm and 90 ppm respectively.

    [0226] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.5 mAh/g, the capacity retention rate after 500 cycles was tested to be 58.4%, and a gas generated was 7.8 mL/Ah.

    Example 42

    [0227] The difference between Example 42 and Example 22 was that the coating amounts of P and Al in Example 42 were 250 ppm and 220 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 270 ppm and 230 ppm respectively.

    [0228] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.9 mAh/g, the capacity retention rate after 500 cycles was tested to be 67.9%, and a gas generated was 7.3 mL/Ah.

    Example 43

    [0229] The difference between Example 43 and Example 22 was that the coating amounts of P and Al in Example 43 were 500 ppm and 440 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 500 ppm and 440 ppm respectively.

    [0230] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 132.7 mAh/g, the capacity retention rate after 500 cycles was tested to be 71.5%, and a gas generated was 7.1 mL/Ah.

    Example 44

    [0231] The difference between Example 44 and Example 22 was that the coating amounts of P and Al in Example 44 were 1000 ppm and 880 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 1000 ppm and 880 ppm respectively.

    [0232] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 132.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 75.4%, and a gas generated was 6.5 mL/Ah.

    Example 45

    [0233] The difference between Example 45 and Example 22 was that the coating amounts of P and Al in Example 45 were 1500 ppm and 130 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 1500 ppm and 130 ppm respectively.

    [0234] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.9 mAh/g, the capacity retention rate after 500 cycles was tested to be 72.1%, and a gas generated was 6.7 mL/Ah.

    Example 46

    [0235] The difference between Example 46 and Example 22 was that the coating amounts of P and Al in Example 46 were 2000 ppm and 1800 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 2000 ppm and 1800 ppm respectively.

    [0236] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 132.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 73.9%, and a gas generated was 6.2 mL/Ah.

    Example 47

    [0237] The difference between Example 47 and Example 22 was that the coating amounts of P and Al in Example 47 were 2500 ppm and 2200 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 2500 ppm and 2200 ppm respectively.

    [0238] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.7 mAh/g, the capacity retention rate after 500 cycles was tested to be 70.1%, and a gas generated was 6.4 mL/Ah.

    Example 48

    [0239] The difference between Example 48 and Example 22 was that the coating amounts of P and Al in Example 48 were 4000 ppm and 3500 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 4000 ppm and 3500 ppm respectively.

    [0240] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 64.7%, and a gas generated was 6.9 mL/Ah.

    Example 49

    [0241] The difference between Example 49 and Example 22 was that the coating amounts of P and Al in Example 48 were 5000 ppm and 4400 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 5000 ppm and 4400 ppm respectively.

    [0242] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 61.5%, and a gas generated was 7.3 mL/Ah.

    Comparative Example 10

    [0243] The difference between Comparative example 10 and Example 22 was that the coating amounts of P and Al in Comparative example 10 were 10000 ppm and 8800 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 10000 ppm and 8800 ppm respectively.

    [0244] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.5 mAh/g, the capacity retention rate after 500 cycles was tested to be 45.9%, and a gas generated was 8.1 mL/Ah.

    TABLE-US-00005 TABLE 5 Electrochemical performance of Examples 42 to 49 and Comparative examples 9 and 10 Capacity BET retention after the Capacity rate after Single first Coating for 500 Gas Serial crystal sintering Coating amount 0.33 C cycles generation number dispersant (m.sup.2/g) agent (ppm) (mAh/g) (%) (mL/Ah) Comparative WO.sub.3 0.35 AlPO.sub.4 100 + 131.5 58.4 7.8 example 9 90 Example 42 WO.sub.3 0.35 AlPO.sub.4 P~270 131.9 67.9 7.3 Al~230 Example 43 WO.sub.3 0.35 AlPO.sub.4 P~500; 132.7 71.5 7.1 Al~440 Example 44 WO.sub.3 0.35 AlPO.sub.4 P~1000; 132.1 75.4 6.5 Al~880 Example 45 WO.sub.3 0.35 AlPO.sub.4 P~1500 131.9 72.1 6.7 Al~130 Example 46 WO.sub.3 0.35 AlPO.sub.4 P~2000 132.4 73.9 6.2 Al~1800 Example 47 WO.sub.3 0.35 AIPO4 P~2500 131.7 70.1 6.4 Al~2200 Example 48 WO.sub.3 0.35 AlPO.sub.4 P~4000 130.4 64.7 6.9 Al~3500 Example 49 WO.sub.3 0.35 AlPO.sub.4 P~5000 130.1 61.5 7.3 Al~4400 Comparative WO.sub.3 0.35 AlPO.sub.4 P~10000 129.5 45.9 8.1 example 10 Al~8800

    [0245] It can be seen from Table 5 that in Examples 42 to 49, the coating amount of P plus Al ranged from 270+230 ppm to 5000+4400 ppm, and the obtained lithium nickel manganate positive electrode materials had better electrochemical performance. In Comparative example 9, the coating amount is less, resulting in poor coating effect, and the electrochemical performance is significantly worse. In Comparative example 10, the coating amount was too much, resulting in too large interface resistance, and the electrochemical performance was poor.

    [0246] For example, the coating amount of P plus Al ranged from 500+440 ppm to 2500+2200 ppm.

    Example 50

    [0247] The difference between Example 50 and Example 23 was that the coating amounts of P and Al in Example 50 were 5000 ppm and 1000 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 5000 ppm and 1000 ppm respectively.

    [0248] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.7 mAh/g, the capacity retention rate after 500 cycles was tested to be 62.8%, and a gas generated was 7.5 mL/Ah.

    Example 51

    [0249] The difference between Example 51 and Example 23 was that the coating amounts of P and Al in Example 50 were 4000 ppm and 1000 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 4000 ppm and 1000 ppm respectively.

    [0250] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.9 mAh/g, the capacity retention rate after 500 cycles was tested to be 68.7%, and a gas generated was 7.1 mL/Ah.

    Example 52

    [0251] The difference between Example 52 and Example 23 was that the coating amounts of P and Al in Example 52 were 3000 ppm and 1000 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 5000 ppm and 3000 ppm respectively.

    [0252] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 70.9%, and a gas generated was 6.8 mL/Ah.

    Example 53

    [0253] The difference between Example 53 and Example 23 was that the coating amounts of P and Al in Example 53 were 2000 ppm and 1000 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.002034/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 2000 ppm and 1000 ppm respectively.

    [0254] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 132.9 mAh/g, the capacity retention rate after 500 cycles was tested to be 72.6%, and a gas generated was 6.7 mL/Ah.

    Example 54

    [0255] The difference between Example 54 and Example 23 was that the coating amounts of P and Al in Example 54 were 1000 ppm and 1000 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.00203O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 1000 ppm and 1000 ppm respectively.

    [0256] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 132.4 mAh/g, the capacity retention rate after 500 cycles was tested to be 71.8%, and a gas generated was 6.9 mL/Ah.

    Example 55

    [0257] The difference between Example 55 and Example 23 was that the coating amounts of P and Al in Example 55 were 500 ppm and 1000 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 500 ppm and 1000 ppm respectively.

    [0258] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 131.5 mAh/g, the capacity retention rate after 500 cycles was tested to be 70.2%, and a gas generated was 6.8 mL/Ah.

    Example 56

    [0259] The difference between Example 56 and Example 23 was that the coating amounts of P and Al in Example 56 were 1000 ppm and 1500 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 1000 ppm and 1500 ppm respectively.

    [0260] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.9 mAh/g, the capacity retention rate after 500 cycles was tested to be 71.9%, and a gas generated was 6.8 mL/Ah.

    Example 57

    [0261] The difference between Example 57 and Example 23 was that the coating amounts of P and Al in Example 57 were 1000 ppm and 2000 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 1000 ppm and 2000 ppm respectively.

    [0262] The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 130.1 mAh/g, the capacity retention rate after 500 cycles was tested to be 65.1%, and a gas generated was 7.4 mL/Ah.

    Example 58

    [0263] The difference between Example 58 and Example 23 was that the coating amounts of P and Al in Example 58 were 1000 ppm and 3000 ppm respectively. The BET of the sample after the first sintering was 0.35 m.sup.2/g; the SEM scanning image was shown in FIG. 5. The coated lithium nickel manganate positive electrode material LiNi.sub.0.5Mn.sub.1.5W.sub.0.0023O.sub.4/PAl was obtained. The coated lithium nickel manganate positive electrode material was subjected to an ICP test, and the coating amounts of P and Al were 1000 ppm and 3000 ppm respectively. The full cell preparation was the same as that of Example 1. The initial capacity for 0.33 C was tested to be 129.6 mAh/g, the capacity retention rate after 500 cycles was tested to be 61.4%, and a gas generated was 7.7 mL/Ah.

    TABLE-US-00006 TABLE 6 Electrochemical performance for Examples 50 to 58 Capacity BET retention after the Capacity rate after Single first Coating for 500 Gas Serial crystal sintering amount 0.33 C cycles generation number dispersant (m.sup.2/g) Coating agent (ppm) (mAh/g) (%) (mL/Ah) Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~5000 130.7 62.8 7.5 50 and Al.sub.2O.sub.3 Al~1000 Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~4000 130.9 68.7 7.1 51 and Al.sub.2O.sub.3 Al~1000 Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~3000 131.4 70.9 6.8 52 and Al.sub.2O.sub.3 Al~1000 Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~2000 132.9 72.6 6.7 53 and Al.sub.2O.sub.3 Al~1000 Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~1000 132.4 71.8 6.9 54 and Al.sub.2O.sub.3 Al~1000 Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~500 131.5 70.2 6.8 55 and Al.sub.2O.sub.3 Al~1000 Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~1000 130.9 71.9 6.8 56 and Al.sub.2O.sub.3 Al~1500 Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~1000 130.1 65.1 7.4 57 and Al.sub.2O.sub.3 Al~2000 Example WO.sub.3 0.35 (NH.sub.4).sub.2HPO.sub.4 P~1000 129.6 61.4 7.7 58 and Al.sub.2O.sub.3 Al~3000

    [0264] It can be seen from Table 6 that in Examples 50 to 58, the ratio of the coating amounts of Al to P for co-coating was 0.2-3, the electrochemical performance was better. When the coating amount of Al was higher, the material had lower interface resistance and poor cycling. A ratio of the coating amounts of Al to P for co-coating was 0.33-1.5.

    [0265] The above are only the embodiments of the present application. It should be noted that the person skilled in the art may also make several improvements and supplements without departing from the methods of the present application, and these improvements and supplements should also be regarded within the protection scope of the present application.