POSITIVE ELECTRODE MATERIAL, AND PREPARATION METHOD THEREFOR AND USE THEREOF

Abstract

Provided in the present application are a positive electrode material, and a preparation method therefor and the use thereof. The chemical formula of the positive electrode material is xLi.sub.2MnO.sub.3:(1-x-y)LiNi.sub.aT.sub.M(1-a)O.sub.2.Math.yLiMn.sub.bA.sub.(1-b)PO.sub.4, wherein O<x<1, 0<y<1, 0a1, 0.5b1, and T.sub.M and A respectively and independently comprise a metal element. The positive electrode material can form continuous phase transformation, has a super-domain structure and a stable layered structure, and can stabilize lattice oxygen and reduce voltage drop, such that the cycling performance of a battery under a high voltage can be significantly improved.

Claims

1. A cathode material, which has a chemical formula of xLi.sub.2MnO.sub.3.Math.(1-x-y)LiNi.sub.aT.sub.M(1-a)O.sub.2.Math.yLiMn.sub.bA.sub.(1-b)PO.sub.4, wherein 0<x<1, 0<y<1, 0a1, 0.5b1, and T.sub.M and A each independently comprise a metal element.

2. The cathode material according to claim 1, wherein TM comprises any one or a combination of at least two of Mn, Ni, Co, Al, Ti, W, Nb, Zr, Y, Sr or Fe.

3. The cathode material according to claim 1, wherein A comprises any one or a combination of at least two of Ni, V, Mg, Al, Nb, Zr, Cr, Si, Zn, Ti, Co or Fe.

4. The cathode material according to claim 1, wherein 0<y0.3.

5. A preparation method for the cathode material according to claim 1, which comprises the following steps: (1) mixing and drying a lithium source, a precursor of LiNi.sub.aT.sub.M(1-a)O.sub.2, and LiMn.sub.bA.sub.(1-b)PO.sub.4 to obtain raw powder of the cathode material; and (2) sintering the raw powder of the cathode material obtained in step (1) to obtain the cathode material.

6. The preparation method according to claim 5, wherein in step (1), LiMn.sub.bA.sub.(1-b)PO.sub.4 is in the form of sol-gel solution to be mixed with the lithium source and the precursor of LiNi.sub.aT.sub.M(1-a)O.sub.2.

7. The preparation method according to claim 6, wherein the sol-gel solution of LiMn.sub.bA.sub.(1-b)PO.sub.4 is prepared by the following method: mixing a lithium source, a manganese source, a phosphorus source, a metal A source and a solvent according to a formula amount, then adding an acid and a chelating agent, and stirring to obtain the sol-gel solution of LiMn.sub.bA.sub.(1-b)PO.sub.4.

8. The preparation method according to claim 7, wherein a mixed solution obtained by mixing the lithium source, the manganese source, the phosphorus source, the element A source and the solvent according to the formula amount has a concentration of 0.1-1 mol/L.

9. The preparation method according to claim 7, wherein a concentration of the acid is 0.1-1 mol/L; optionally, the acid comprises any one or a combination of at least two of citric acid, salicylic acid, oxalic acid or EDTA.

10. The preparation method according to claim 7, wherein a concentration of the chelating agent is 1-2 mol/L; optionally, the chelating agent comprises polyethylene glycol.

11. The preparation method according to claim 7, wherein the stirring is performed at a temperature of 25-50 C.

12. The preparation method according to claim 5, wherein the drying in step (1) is performed in a manner of spray drying; optionally, the spray drying is performed at a temperature of 100-300 C.

13. The preparation method according to claim 5, wherein a molar ratio of lithium ions to T.sub.M ions in a mixture obtained by the mixing in step (1) is (1.20-1.36):1; optionally, a molar percentage of LiMn.sub.bA.sub.(1-b)PO.sub.4 in the mixture obtained by the mixing in step (1) is 0.01-30%.

14. The preparation method according to claim 5, wherein the mixing in step (1) is performed until a particle size D50 of a mixture is 0.2-1.5 m; optionally, the mixing is performed in a manner comprising ball milling.

15. The preparation method according to claim 5, wherein the precursor of LiNi.sub.aT.sub.M(1-a)O.sub.2 in step (1) comprises Ni.sub.aMn.sub.(1-a)(OH).sub.2, which is prepared by the following method: mixing a precipitant, a complexant, and a Ni and/or T.sub.M metal source to obtain a reaction solution, and then subjecting the reaction solution to a reaction to obtain the precursor of LiNi.sub.aT.sub.M(1-a)O.sub.2; optionally, a pH of the reaction solution is 7-12; optionally, a concentration of complex ions in the reaction solution is 0.1-1 mol/L; optionally, the reaction is performed at a temperature of 40-60 C.; optionally, the reaction is performed until a particle size of the precursor of LiNi.sub.aT.sub.M(1-a)O.sub.2 is 3-10 m.

16. The preparation method according to claim 5, wherein the sintering in step (2) is performed at a temperature of 800-1000 C. for a period of 24-48 h; optionally, crushing and screening with magnetic impurities removed are further performed after the sintering in step (2); optionally, a particle size D50 of the cathode material in step (2) is 2-5 m, and a size of primary particles is within the range of 0.4-2 m.

17. The preparation method according to claim 5, which comprises the following steps: (1) mixing a sol-gel solution of LiMn.sub.bA.sub.(1-b)PO.sub.4, the precursor of LiNi.sub.aT.sub.M(1-a)O.sub.2 and the lithium source by ball milling until a particle size D50 of the mixture is 0.2-1.5 m, and subjecting the mixture to spray drying at 100-300 C. to obtain the raw powder of the cathode material, wherein in the mixture, a molar ratio of lithium ions to T.sub.M ions is (1.20-1.36):1 and a molar percentage of LiMn.sub.bA.sub.(1-b)PO.sub.4 is 0.01-30%; the precursor of LiNi.sub.aT.sub.M(1-a)O.sub.2 is Ni.sub.aMn.sub.(1-a)(OH).sub.2, and the sol-gel solution of LiMn.sub.bA.sub.(1-b)PO4 is prepared by the following method: mixing a lithium source, a manganese source, a phosphorus source, a metal A source and a solvent according to a formula amount to obtain a mixed solution with a concentration of 0.1-1 mol/L, then adding an acid and a chelating agent to the mixed solution and stirring to obtain the sol-gel solution of LiMn.sub.bA.sub.(1-b)PO.sub.4; and (2) subjecting the raw powder of the cathode material obtained in step (1) to sintering at a temperature of 800-1000 C., then crushing, and screening with magnetic impurities removed to obtain the cathode material with a particle size D50 of 2-5 m and primary particles having a size distributed within the range of 0.4-2 m.

18. A lithium-ion battery, which comprises the cathode material according to claim 1.

Description

DETAILED DESCRIPTION

Example 1

[0062] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li.sub.2MnO.sub.3.Math.0.55LiNi.sub.0.5Mn.sub.0.5O.sub.2.Math.0.25LiMn.sub.0.7V.sub.0.3PO.sub.4;

[0063] The preparation method for the cathode material includes the following steps: [0064] (1) the sol-gel solution of LiMn.sub.0.7V.sub.0.3PO.sub.4, Li.sub.2CO.sub.3, and Ni.sub.0.5Mn.sub.0.5(OH)2 were mixed by ball milling until the particle size D50 of the mixture was 1.0 m, and then the mixture was subjected to spray drying at 200 C. for 1 min to obtain raw powder of the cathode material, wherein in the mixture, the molar ratio of lithium ions to T.sub.M ions was 1.3:1 and the molar percentage of LiMn.sub.0.7V.sub.0.3PO.sub.4 was 25%; [0065] the sol-gel solution of LiMn.sub.0.7V.sub.0.3PO.sub.4 was prepared by the following method: [0066] LiNO.sub.3, vanadium nitrate, Mn(NO.sub.3).sub.2, NH.sub.4H.sub.2PO.sub.4 and distilled water were mixed according to the formula amount to obtain a mixed solution with a concentration of 0.5 mol/L, then citric acid with a concentration of 0.5 mol/L and polyethylene glycol with a concentration of 1.5 mol/L were added to the mixed solution and stirred at 40 C. to obtain the sol-gel solution of LiMn.sub.0.7V.sub.0.3PO.sub.4; [0067] the Ni.sub.0.5Mn.sub.0.5(OH).sub.2 was prepared by the following method:

[0068] the mixed solution of manganese sulfate and nickel sulfate with a concentration of 1 mol/L, sodium hydroxide solution with a concentration of 1.2 mol/L, and ammonia water with a concentration of 0.5 mol/L were introduced into a reaction kettle in parallel, the pH was controlled to 10, and a reaction was carried out at a temperature of 50 C. until Ni.sub.0.5Mn.sub.0.5(OH).sub.2 with a particle size D50 of 7 m was obtained; and [0069] (2) the raw powder of cathode material obtained in step (1) was sintered at 900 C. for 36 h, then crushed, and screened with magnetic impurities removed to give the cathode material with a particle size D50 of 4 m and primary particles having a size distributed within the range of 0.4-2 m.

Example 2

[0070] This example provides a cathode material, and the chemical formula of the cathode material is 0.25Li.sub.2MnO.sub.3.Math.0.65LiNi.sub.0.5Mn.sub.0.5O.sub.2.Math.0.1LiMn.sub.0.7V.sub.0.3PO.sub.4;

[0071] The preparation method for the cathode material includes the following steps: [0072] (1) the sol-gel solution of LiMn.sub.0.7V.sub.0.3PO.sub.4, Li.sub.2CO.sub.3, and Ni.sub.0.5Mn.sub.0.5(OH).sub.2 were mixed by ball milling until the particle size D50 of the mixture was 0.2 m, and then the mixture was subjected to spray drying at 100 C. for 2 min to obtain raw powder of the cathode material, wherein in the mixture, the molar ratio of lithium ions to TM ions was 1.36:1 and the molar percentage of LiMn.sub.0.7V.sub.0.3PO.sub.4 was 10%; [0073] the sol-gel solution of LiMn.sub.0.7V.sub.0.3PO.sub.4 was prepared by the following method: [0074] LiNO.sub.3, vanadium nitrate, Mn(NO.sub.3).sub.2, NH.sub.4H.sub.2PO.sub.4 and distilled water were mixed according to the formula amount to obtain a mixed solution with a concentration of 1 mol/L, then citric acid with a concentration of 1 mol/L and polyethylene glycol with a concentration of 2 mol/L were added to the mixed solution and stirred at 50 C. to obtain the sol-gel solution of LiMn.sub.0.7V.sub.0.3PO.sub.4; [0075] the Ni.sub.0.5Mn.sub.0.5(OH).sub.2 was prepared by the following method:

[0076] the mixed solution of manganese sulfate and nickel sulfate with a concentration of 0.1 mol/L, sodium hydroxide solution with a concentration of 2 mol/L, and ammonia water with a concentration of 0.1 mol/L were introduced into a reaction kettle in parallel, the pH was controlled to 12, and a reaction was carried out at a temperature of 40 C. until Ni.sub.0.5Mn.sub.0.5(OH).sub.2 with a particle size D50 of 10 m was obtained; and [0077] (2) the raw powder of cathode material obtained in step (1) was sintered at 800 C. for 48 h, then crushed, and screened with magnetic impurities removed to give the cathode material with a particle size D50 of 2 m and primary particles having a size distributed within the range of 0.5-1.5 m.

Example 3

[0078] This example provides a cathode material, and the chemical formula of the cathode material is 0.25Li.sub.2MnO.sub.3.Math.0.65LiMn.sub.0.5Ni.sub.0.5O.sub.2.Math.0.1LiMn.sub.0.7Ni.sub.0.3PO.sub.4;

[0079] The preparation method for the cathode material includes the following steps: [0080] (1) the sol-gel solution of LiMn.sub.0.7Ni.sub.0.3PO.sub.4, Li.sub.2CO.sub.3, and Ni.sub.0.5Mn.sub.0.5 (OH).sub.2 were mixed by ball milling until the particle size D50 of the mixture was 1.5 m, and then the mixture was subjected to spray drying at 300 C. for 30 s to obtain raw powder of the cathode material, wherein in the mixture, the molar ratio of lithium ions to T.sub.M ions was 1.20:1 and the molar percentage of LiMn.sub.0.7Ni.sub.0.3PO.sub.4 was 10%; [0081] the sol-gel solution of LiMn.sub.0.7Ni.sub.0.3PO.sub.4 was prepared by the following method: [0082] LiNO.sub.3, nickel nitrate, Mn(NO.sub.3).sub.2, NH.sub.4H.sub.2PO.sub.4 and distilled water were mixed according to the formula amount to obtain a mixed solution with a concentration of 0.1 mol/L, then EDTA with a concentration of 0.1 mol/L and polyethylene glycol with a concentration of 1 mol/L were added to the mixed solution and stirred at 25 C. to obtain the sol-gel solution of LiMn.sub.0.7Ni.sub.0.3PO.sub.4; [0083] the Ni.sub.0.5Mn.sub.0.5(OH).sub.2 was prepared by the following method: [0084] the mixed solution of manganese sulfate and cobalt sulfate with a concentration of 2 mol/L, sodium hydroxide solution with a concentration of 0.1 mol/L, and ammonia water with a concentration of 1 mol/L were introduced into a reaction kettle in parallel, the pH was controlled to 7, and a reaction was carried out at a temperature of 60 C. until Ni.sub.0.5Mn.sub.0.5(OH).sub.2 with a particle size D50 of 3 m was obtained; and [0085] (2) the raw powder of cathode material obtained in step (1) was sintered at 1000 C. for 24 h, then crushed, and screened with magnetic impurities removed to give the cathode material with a particle size D50 of 5 m and primary particles having a size distributed within the range of 0.4-2 m.

Example 4

[0086] This example provides a cathode material, and the cathode material is the same as that of Example 1 except that the chemical formula of the cathode material is 0.2Li.sub.2MnO.sub.3.Math.0.55LiNi.sub.0.5Mn.sub.0.5O.sub.2.Math.0.25LiMnPO.sub.4; [0087] the preparation method for the cathode material was the same as that of Example 1 except that adaptive changes were made to raw materials according to the chemical formula.

Example 5

[0088] This example provides a cathode material, and the cathode material is the same as that of Example 1 except that the chemical formula of the cathode material is 0.1Li.sub.2MnO.sub.3.Math.0.45LiNi.sub.0.5Mn.sub.0.5O.sub.2.Math.0.45LiMn.sub.0.7V.sub.0.3PO.sub.4;

[0089] the preparation method for the cathode material was the same as that of Example 1 except that adaptive changes were made to raw materials according to the chemical formula.

Example 6

[0090] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li.sub.2MnO.sub.3.Math.0.55LiNi.sub.0.5Mn.sub.0.5O.sub.2.Math.0.25LiMn.sub.0.7V.sub.0.3PO.sub.4; [0091] the preparation method for the cathode material was the same as that of Example 1 except that the LiMn.sub.0.7V.sub.0.3PO.sub.4 powder was mixed with Li.sub.2CO.sub.3 and Ni.sub.0.5Mn.sub.0.5(OH).sub.2 in step (1), wherein the LiMn.sub.0.7V.sub.0.3PO.sub.4 powder was obtained by drying and grinding the sol-gel solution in Example 1.

Example 7

[0092] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li.sub.2MnO.sub.3.Math.0.55LiNi.sub.0.5Mn.sub.0.5O.sub.2.Math.0.25LiMn.sub.0.7V.sub.0.3PO.sub.4; [0093] the preparation method for the cathode material was the same as that of Example 1 except that in step (1), the spray drying was not performed, and a blast drying at a temperature of 200 C. was performed instead.

Example 8

[0094] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li.sub.2MnO.sub.3.Math.0.55LiNi.sub.0.5Mn.sub.0.5O.sub.2.Math.0.25LiMn.sub.0.7V.sub.0.3PO.sub.4; [0095] the preparation method for the cathode material was the same as that of Example 1 except that in step (1), the particle size D50 of the mixture was 0.05 m.

Example 9

[0096] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li.sub.2MnO.sub.3.Math.0.55LiNi.sub.0.5Mn.sub.0.5O.sub.2.Math.0.25LiMn.sub.0.7V.sub.0.3PO.sub.4; [0097] the preparation method for the cathode material was the same as that of Example 1 except that in step (1), the particle size D50 of the mixture was 3 m.

Example 10

[0098] This example provides a cathode material, and the chemical formula of the cathode material is 0.2Li.sub.2MnO.sub.3.Math.0.55LiNi.sub.0.5Mn.sub.0.5O.sub.2.Math.0.25LiMn.sub.0.7V.sub.0.3PO.sub.4;

[0099] The preparation method for the cathode material includes the following steps: [0100] (1) 0.27Li.sub.2MnO.sub.3.Math.0.73LiNi.sub.0.5Mn.sub.0.5O.sub.2 and LiMn.sub.0.7V.sub.0.3PO.sub.4 were mixed by ball milling according to the formula amount until the particle size D50 of the mixture was 1.0 m, then the mixture was dried at a temperature of 200 C. to obtain raw powder of the cathode material; and [0101] (2) the raw powder of the cathode material in step (1) was sintered at a temperature of 900 C., then crushed, and screened with magnetic impurities removed to give the cathode material with a particle size D50 of 4 m and primary particles having a size distributed within the range of 0.4-2 m.

Comparative Example 1

[0102] This comparative example provides a cathode material, and the chemical formula of the cathode material is 1/3Li.sub.2MnO.sub.3.Math.2/3LiMn.sub.0.5Ni.sub.0.5O.sub.2;

[0103] the preparation method for the cathode material was the same as that of Example 1 except that the sol-gel solution of LiMn.sub.0.7V.sub.0.3PO.sub.4 was not added and adaptive changes were made to the additive amounts of raw materials.

Comparative Example 2

[0104] This comparative example provides a cathode material, and the chemical formula of the cathode material is 0.27Li.sub.2MnO.sub.3.Math.0.73LiMn.sub.0.5Ni.sub.0.5O.sub.2; [0105] the preparation method for the cathode material was the same as that of Example 1 except that the sol-gel solution of LiMn.sub.0.7V.sub.0.3PO.sub.4 was not added.

[0106] The cathode material obtained in the above Examples and Comparative Examples were mixed with conductive carbon black, binder PVDF and NMP to prepare a slurry, then the slurry was coated on an aluminum foil, baked at a temperature of 120 C., and then roller-pressed to prepare a cathode plate, and the cathode plate was assembled with a lithium plate, a separator, and anode and cathode shells to form a button cell for performance tests; the capacity per gram under the condition of 0.1 C and 2.5-4.6 V, the capacity retention rate after 100 cycles of charging and discharging at 45 C., 2.5-4.6 V and 1 C, and the voltage drop after 100 cycles of charging and discharging at 45 C., 2.5-4.6 V and 1 C are shown in Table 1:

TABLE-US-00001 TABLE 1 Capacity retention Capacity per rate after 100 Voltage drop after gram (mAh/g) cycles (%) 100 cycles (mV) Example 1 265 95 60 Example 2 255 90 90 Example 3 250 85 120 Example 4 200 90 90 Example 5 180 95 40 Example 6 235 80 110 Example 7 210 80 130 Example 8 245 90 90 Example 9 220 95 90 Example 10 200 80 120 Comparative 245 70 180 Example 1 Comparative 235 80 170 Example 2

[0107] It can be seen from the above table:

[0108] The cathode material in the present application can significantly improve the cycling performance of the battery and reduce the voltage drop. Specifically, it can be seen from Example 1 and Example 4 that the third lithiation compound is preferably doped with metal A element, which can further improve the structural stability of the cathode material and improve the performance of the material; it can be seen from Example 1 and Example 5 that the proportions of the three phases should cooperate with each other, and the proportion of the third lithiation compound within the further preferred range, instead of being overly high, can further ensure the comprehensive electrochemical performance of the material; it can be seen from Example 1 and Examples 6-7 that in the preparation process of the present application, where the sol-gel solution of the third lithiation compound is used as a raw material and combined with spray drying, is not only conducive to uniformly mixed components, but also conducive to the formation of super-crystalline domain structure; it can be seen from Example 1 and Examples 8-9 that by controlling the size of the particles within the preferred range before spray drying, the performance of the material can be further improved; it can be seen from Example 1 and Example 10 that a uniformly distributed solid solution material cannot be obtained by directly mixing various phases, and in the present application, specific raw materials are mixed in the preparation process, which can uniformly distribute each phase and is conducive to the formation of super-crystalline domain structure having continuous phases; it can be seen from Example 1 and Comparative Examples 1-2 that introduction of the third lithiation compound in the present application facilitates the formation of super-crystalline domain structure having continuous phase transition from the two phases of the lithium-rich manganese-based material, thereby reducing the evolution of lattice O and reducing the voltage drop.

[0109] In summary, the present application provides a cathode material, and a preparation method therefor and use thereof, and especially a hyper-lithiation manganese-based cathode material, and a preparation method therefor and use thereof. The cathode material can form continuous phase transition, and has a super-crystalline domain structure and a stable layered structure, which can stabilize the lattice oxygen, reduce the voltage drop, and significantly improve the cycling performance of the cathode material at a high voltage.