THE USAGE OF FATTY ACID IN THE PREPARATION OF LITHIUM-ION BATTERIES AND THE METHOD FOR MANUFACTURING ELECTRODE MATERIALS

Abstract

The use of a C10~C34 fatty acids compound in the preparation of a the electrode materials for lithium-ion battery improves the coating uniformity of electrode materials prepared with solid-state method. The fatty acid provided by the invention is a dispersant, which achieves the uniformly dispersion of the coating material on the surface of battery material, and significantly increases the coating uniformity of the electrode material coated with solid-state method, it greatly improves the feasibility of manufacturing the electrode material of lithium-ion battery with solid-state method, and is conducive to the more economical and simpler manufacture of electrode material.

Claims

1. The usage of a compound in the preparation of electrode materials for lithium-ion battery, it improves the coating uniformity of electrode materials prepared with solid-state method, wherein the said compound is C10-C34 fatty acid used as a dispersant in a preparation of electrode materials for lithium-ion battery, the weight ratio of the electrode material to the coating material is 0.1~10 wt%, the said electrode material of lithium-ion battery is shown in Li.sub.1±mNi.sub.xCo.sub.yMn.sub.zM.sub.1-x- .sub.y-zO.sub.2, wherein M is Cr, Mg, Al, Ti, Zr, Zn, CA, Nb and W, and m is 0.005 to 0.2; and x, y and z are independently selected from any number from 0 to 1, the coating material is selected from one or more of the following groups of compounds: metal oxides, including MgO, ZnO, CaO, BaO, A1.sub.2O.sub.3, Fe.sub.2O.sub.3, La.sub.2O.sub.3, TiO.sub.2 and ZrO.sub.2, metal fluoride, including LiF, MgF.sub.2, CaF.sub.2 and AlF.sub.3, and metal carbonates, including Li.sub.2CO.sub.3, MgCO.sub.3, CaCO.sub.3 and Al.sub.2(CO.sub.3).sub.3.

2. (canceled)

3. (canceled)

4. The usage according to claim 1, wherein the said fatty acid is saturated fatty acid or unsaturated fatty acid.

5. The usage according to claim 1, wherein the said fatty acid is used as a regulator for the balance adjustment of the initial energy density of electrode material and improving the cycle life of electrode material.

6. The usage according to claim 1, wherein the said fatty acid is used as a regulator for personalized preparation of electrode materials for lithiumion battery according to the requirements of initial discharge and cycle life.

7. The usage according to claim 1, wherein the said fatty acid is shown as CH.sub.3(CH.sub.2).sub.nCOOH, and n is an integer from 8 to 32.

8. The usage according to claim 7, wherein n is 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 or 32.

9-11. (canceled)

12. The usage according to claim 1, wherein the said fatty acid is mixed with the coating material to make a coating precursor, which is sintered after mixing with the battery material, so that the coating material is evenly dispersed on the surface of the electrode material.

13. A method for preparing electrode material for lithium-ion battery is characterized by: the coating precursor is prepared by mixing the compound with the coating material according to the weight ratio of 1:1~20, and then it is mixed with the lithium-ion battery material. The coating material is evenly dispersed on the surface of the electrode material of lithium-ion battery prepared by sintering. The said compound is C10-C34 fatty acid, and the ratio of the amount of the said coating material to the said lithium-ion battery material is 0.1~ 10 wt%, the said electrode material of lithium-ion battery is shown in Li.sub.1±.sub.mNi.sub.xCo.sub.yMn.sub.zM.sub.1-x- .sub.y-zO.sub.2, wherein M is Cr, Mg, Al, Ti, Zr, Zn, CA, Nb and W, and m is 0.005 to 0.2; and x, y and z are independently selected from any number from 0 to 1, the coating material is selected from one or more of the following groups of compounds: metal oxides, including MgO, ZnO, CaO, BaO, A1.sub.2O.sub.3, Fe.sub.2O.sub.3, La.sub.2O.sub.3, TiO.sub.2 and ZrO.sub.2, metal fluoride, including LiF, MgF.sub.2, CaF.sub.2 and AlF.sub.3, and metal carbonates, including Li.sub.2CO.sub.3, MgCO.sub.3, CaCO.sub.3 and Al.sub.2(CO.sub.3).sub.3.

14. The method according to claim 13, wherein the said sintering temperature is between 200° C. ~1000° C.

15. The method according to claim 14, wherein the said heating rate for the sintering is 1~10° C./min.

16. The method according to claim 14, wherein the said sintering is held from 2 hours to 24 hours.

17. The method according to claim 13, wherein the electrode material is in the form of powder.

18. The method according to claim 13, wherein the particle size of the said coating material is 10 nm~500 nm.

19. The method according to claim 13, wherein the fatty acid is saturated fatty acid or unsaturated fatty acid.

20. The method according to claim 13, wherein the fatty acid is shown as CH.sub.3(CH.sub.2).sub.nCOOH, and n is an integer from 8 to 32.

21. The method according to claim 20 characterized in that the n is 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 or 32.

22. (canceled)

23. (canceled)

24. A lithium-ion battery electrode, which is characterized in that it comprises a battery material and a coating material, and the coating material is evenly distributed on the surface of the battery material, the weight ratio of the electrode material to the coating material is 0.1~10 wt%, the said electrode material of lithium-ion battery is shown in Li.sub.1±mNi.sub.xCo.sub.yMn.sub.zM.sub.1-x- .sub.y-zO.sub.2, wherein M is Cr, Mg, Al, Ti, Zr, Zn, CA, Nb and W, and m is 0.005 to 0.2; and x, y and z are independently selected from any number from 0 to 1, the coating material is selected from one or more of the following groups of compounds: metal oxides, including MgO, ZnO, CaO, BaO, A1.sub.2O.sub.3, Fe.sub.2O.sub.3, La.sub.2O.sub.3, TiO.sub.2 and ZrO.sub.2, metal fluoride, including LiF, MgF.sub.2, CaF.sub.2 and AlF.sub.3, and metal carbonates, including Li.sub.2CO.sub.3, MgCO.sub.3, CaCO.sub.3 and Al.sub.2(CO.sub.3).sub.3.

25. (canceled)

26. A lithium-ion battery comprising the lithium-ion battery electrode according to claim 24.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 refers to a schematic diagram of an example of the process of coating lithium -ion battery materials with solid-state method,

[0035] FIG. 2 refers to the XRD data of NCM523 material,

[0036] FIG. 3 refers to a curve of the thermogravimetric analysis (TGA) of stearic acid,

[0037] FIG. 4 refers to the elements distribution graph of uncoated NCM523,

[0038] FIG. 5 refers to the elements distribution graph of NCM523 coated with 2 wt% Al.sub.2O.sub.3 that is prepared without using dispersant,

[0039] FIG. 6 refers to the elements distribution graph of NCM523 coated with 2 wt% Al.sub.2O.sub.3 using stearic acid dispersant,

[0040] FIG. 7 refers to the comparison graph of charge/discharge curves achieved by electrode material prepared with uncoated NCM523 material and prepared with NCM523 material coated with different methods,

[0041] FIG. 8 refers to a comparison graph of Al element distribution in NCM523 coated with different amounts of Al.sub.2O.sub.3,

[0042] FIG. 9 refers to a comparison graph of charge/discharge curves achieved by the electrode materials prepared from NCM523 materials coated with different amounts of Al.sub.2O.sub.3,

[0043] FIG. 10 refers to a charge/discharge curve of NCM23 coated with Al.sub.2O.sub.3 using lauric acid dispersant,

[0044] FIG. 11 refers to a charge/ discharge curve of NCM811 coated with Al.sub.2O.sub.3 using lauric acid dispersant.

DETAILED DESCRIPTION

[0045] The technical scheme of the invention is described in detail below in combination with the attached figures. The examples of the invention are only used to elaborate instead of limiting the technical scheme of the invention. Although the invention is described in detail with reference to the better examples, general technical personnel in this field should understand that the technical scheme of the invention can be modified or equivalently replaced without deviating from the spirit and scope of the technical scheme of the invention, and all of them shall be covered in the claims of the invention.

[0046] Considering the limitations of traditional liquid-state and solid-state coating methods in the industry, in these examples, C10-C34 fatty acids are used as dispersant and mechanically blended with coating materials to make packaging materials (hereinafter referred to as coating precursor or precursor in these examples) in the subsequent solid-state synthesis, the dispersant with low melting point will be liquefied first, so that the coating material can be better dispersed on the surface of the battery material, and the dispersant will decompose and volatilize during high-temperature sintering and will not remain in the prepared electrode material. FIG. 1 is a schematic diagram of an example of the process of coating lithium-ion battery materials with solid-state method. As shown in FIG. 1, the technical process and coating effect of the existing solid-state coating method and the solid-state coating method using dispersant described in the present invention. As can be seen in the figure, the application can simply and efficiently prepare the electrode material of lithium-ion battery uniformly coated with the coating material by using the dispersant.

Example 1

[0047] (1) The fatty acids used in this example include lauric acid, myristic acid, palmitic acid, stearic acid and arachidic acid; The coating materials used include nano alumina (Al.sub.2O.sub.3), nano magnesium oxide (MgO), nano titanium oxide (TiO.sub.2), nano lanthanum oxide (La.sub.2O.sub.3), nano zirconia (ZrO.sub.2), nano zinc oxide (ZnO), nano aluminum fluoride (AlF.sub.3) and nano magnesium fluoride(MgF.sub.2). The battery materials used include LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2, LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2, 0.5Li.sub.2MnO.sub.3.Math.0.5LiMn.sub.0.375Ni.sub.0.375Co.sub.0.25O.sub.2, LiCoO.sub.2, LiFePO.sub.4, LiNi.sub.0.5Mn.sub.1.5O.sub.4, Li.sub.4Ti.sub.sO.sub.12, Si, SiO and Co.sub.3O.sub.4.

[0048] (2) The particle size of the coating material is 10~500 nm.

[0049] (3) Firstly, prepare the mixture of 3 g fatty acid and nano coating material, in which the mass percentage of fatty acid is controlled at 3-30%.

[0050] (4) In the above mixture, add 10 to 30 g of ball milling beads for high-speed ball milling. The ball milling time is set to 1 to 5 hours and the ball milling speed is set to 100 to 600 rmp.

[0051] (5) After mixing is over, collect the mixture of fatty acid and nano coating material, i.e. coating precursor.

[0052] (6) Take an appropriate amount of electrode material and add the corresponding coating precursor (i.e. the mixture of stearic acid and nano coating material) into it, so that the mass percentage of coating material is 0.1-5%. Put the electrode material and the coating precursor into the mixer and mix for 1~ 8 hours.

[0053] (7) Heat the above mixture to 200-1000° C. at the rate of 1~10° C./min, maintain at this temperature for 1~24 hours, and then cool to room temperature within the furnace to complete the coating process.

[0054] (8) Disperse and sieve the prepared product to obtain electrode material for coating. See Table 1 for the preparation parameters of all coating materials.

TABLE-US-00001 Coating precursor Electrode material Mass percentage of coating material in electrode material after coating, wt% Dispersant Coating material Mass percentage of dispersant in coating precursor, wt% Stearic acid Al.sub.2O.sub.3 9 LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2 2 Lauric acid MgO 12 LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2 2 Stearic acid TiO.sub.2 15 0.5Li.sub.2MnO.sub.3.Math.0.5LiMn.sub.0.375Ni.sub.0.375Co.sub.0.25O.sub.2 1 Stearic acid La.sub.2O.sub.3 9 LiCoO.sub.2 0.5 Arachidic acid AlF.sub.3 18 LiFePO.sub.4 0.5 Myristic acid MgF.sub.2 15 LiNi.sub.0.5Mn.sub.1.5O.sub.4 1 Stearic acid ZrO.sub.2 5 Li.sub.4Ti.sub.sO.sub.12 1 Lauric acid Al.sub.2O.sub.3 15 Si 1 Palmitic acid TiO.sub.2 12 SiO 0.5 Stearic acid ZnO 20 Co.sub.3O.sub.4 1

Example 2

[0055] (1) The fatty acid used in this example is stearic acid, the coating material is nano alumina (Al.sub.2O.sub.3), and the particle size of Al.sub.2O.sub.3 is 20-30 nm. The chemical formula of the electrode material used in this example is LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2 (NCM523 in brief).

[0056] (2) Firstly, prepare the mixture of 3 g stearic acid and nano Al.sub.2O.sub.3, in which the mass percentage of stearic acid is controlled at 3-30%.

[0057] (3) In the above mixture, add 10 to 30 g of ball milling beads for high-speed ball milling. The ball milling time is set to 1 to 5 hours and the ball milling speed is set to 100 to 600 rmp.

[0058] (4) After mixing is over, collect the mixture of stearic acid and nano Al.sub.2O.sub.3, that is, the coating precursor.

[0059] (5) Take an appropriate amount of NCM523 and add the corresponding coating precursor (i.e. the mixture of stearic acid and nano Al.sub.2O.sub.3), so that the mass percentage of Al.sub.2O.sub.3 is 0.1-5%. Put NCM523 and coating precursor into a mixer and mix for 1 to 8 hours.

[0060] (6) Heat the above mixture to 200-1000° C. at a rate of 1-10° C./min, maintain at this temperature for 1-24 hours, and then cool to room temperature with the furnace to complete the coating process.

[0061] Disperse and sieve the reaction products to obtain the final Al.sub.2O.sub.3 coated NCM523.

[0062] Characterize the synthesized samples by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy scattering X-ray spectroscopy (EDS).

[0063] Mix the prepared coated NCM523 with conductive agent, binder and solvent to prepare electrode slurry, then coat it on aluminum-based collector, dry to prepare electrode, and assemble the electrode into coin cells for electrochemical performance test.

[0064] (10) Cycle all coin cells first for 4 cycles at 2.75-4.4 V with 0.1 C, and then test for cycle life with 0.2 C using the same voltage range.

Example 1 for Comparison

[0065] (1) The chemical formula of the electrode material used in this comparison example is LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2 (NCM523 in brief).

[0066] (2) Characterize NCM523 by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy scattering X-ray spectroscopy (EDS).

[0067] (3) Mix NCM523 with conductive agent, binder and solvent to prepare electrode slurry, then coat it on aluminum-based collector, dry to prepare electrode, and assemble into coin cells for electrochemical performance test.

[0068] (4) Cycle all coin cells first for 4 cycles at 2.75-4.4 V with 0.1 C, and then test for cycle life with 0.2 C using the same voltage range.

Example 2 for Comparison

[0069] (1) The coating material used in this comparison example is nano alumina (Al.sub.2O.sub.3), and the particle size of Al.sub.2O.sub.3 is 20-30 nm. The chemical formula of the electrode material used in this comparison example is LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2 (NCM523 in brief).

[0070] (2) Take an appropriate amount of NCM523, add an appropriate amount of nano Al.sub.2O.sub.3, put them into the mixer and mix them for 3 to 8 hours.

[0071] (3) Heat the above mixture to 500° C. at a rate of 5° C./min, maintain at 500° C. for 10 hours, and then cool to room temperature with the furnace to complete the coating process.

[0072] (4) Disperse and sieve the samples to obtain the final Al.sub.2O.sub.3 coated electrode material.

[0073] (5) Characterize the synthesized samples by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy scattering X-ray spectroscopy (EDS).

[0074] (6) Mix NCM523 prepared by coating with conductive agent, binder and solvent to prepare electrode slurry, then coat it on aluminum-based collector, dry to prepare electrode, and assemble into coin cells for electrochemical performance test.

[0075] (7) Cycle all coin cells first for 4 cycles at 2.75-4.4 V with 0.1 C, and then test for cycle life with 0.2 C using the same voltage range.

[0076] FIG. 2 is the XRD data of NCM523 material. As shown in FIG. 2, the X-ray diffraction (XRD) data show that the uncoated NCM523 is a pure R-3m layered structure. The XRD test for 2 wt% Al.sub.2O.sub.3 coated NCM523 material with stearic acid as dispersant shows that the coated NCM523 is also a pure R-3m layered structure. The data show that 2 wt% Al.sub.2O.sub.3 coating on NCM523 will not produce any impurity phase. Thermogravimetric analysis of stearic acid shows that stearic acid will gradually volatilize during solid-state synthesis. When the heating temperature is greater than 400° C., 100% of stearic acid will volatilize and decompose (see FIG. 3). Therefore, stearic acid as a dispersant will not introduce impurities in the coating process, nor will it affect the original battery material NCM523. The X-ray diffraction test in FIG. 2 shows that Al.sub.2O.sub.3 coated NCM523 with stearic acid also shows a pure R-3m layered structure.

[0077] Scanning electron microscopy (SEM) and energy scattering X-ray spectroscopy (EDS) are conducted on these three samples above, the data are shown in FIG. 4, FIG. 5 and FIG. 6. NCM523 sample has spherical secondary particle morphology, and its particle size is roughly about 15 .Math.m. Energy scattering X-ray spectrum element distribution analysis (EDS mapping) shows that nickel (Ni), cobalt (Co) and manganese (Mn) elements in uncoated NCM523 are evenly distributed on the particle surface, while the aluminum (Al) element signal is weak and basically negligible. For the coated samples prepared with or without stearic acid dispersant, the A1 signal can be clearly displayed on the surface of particles of electrode material. The Al element distribution in NCM523 sample using stearic acid as dispersant is evenly distributed on the surface of particles of electrode material (see FIG. 5). The distribution effect of Al element in NCM523 sample without dispersant is poor, and even agglomeration occurs. EDS mapping shows that stearic acid as a dispersant plays a positive role in the dispersion of Al.sub.2O.sub.3.

[0078] The charge and discharge curves of these three samples during the formation process are also compared (see FIG. 7). Since the coating material Al.sub.2O.sub.3 has no electrochemical activity, the specific discharge capacity of NCM523 coated with Al.sub.2O.sub.3 is slightly smaller than that of uncoated NCM523. At the same time, it is observed that although the coating weight ratio of Al.sub.2O.sub.3 is controlled to 2% with or without dispersant coating, the specific discharge capacity of NCM523 coated with dispersant is slightly less than that of NCM523 not coated with dispersant, which is due to the better coating effect of NCM523 coated with dispersant. At the same time, the comparison of cycle life shows that the cycle life of Al.sub.2O.sub.3 coated NCM523 is significantly higher than that of uncoated NCM523. The cycle life of NCM523 coated with stearic acid as dispersant is better. The comparison of cycle life shows that the use of stearic acid can greatly improve the uniformity of Al.sub.2O.sub.3 coating, so as to effectively improve the cycle life of electrode materials.

Example 3

[0079] (1) The fatty acid used in this example is stearic acid, the coating material is nano alumina (Al.sub.2O.sub.3), and the particle size of Al.sub.2O.sub.3 is 20-30 nm. The chemical formula of the electrode material used in this example is LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2 (NCM523 in brief).

[0080] (2) Firstly, prepare the mixture of 3 g stearic acid and nano Al.sub.2O.sub.3, in which the mass percentage of stearic acid is controlled at 3-30%.

[0081] (3) In the above mixture, add 10 to 30 g of ball milling beads for high-speed ball milling. The ball milling time is set from 1 to 5 hours and the ball milling speed is set from 100 to 600 rmp.

[0082] (4) After mixing is over, collect the mixture of stearic acid and nano Al.sub.2O.sub.3, that is, the coating precursor.

[0083] (5) Take an appropriate amount of NCM523 in batches and add the corresponding coating precursor (i.e. the mixture of stearic acid and nano Al.sub.2O.sub.3) to achieve the mass percentage of Al.sub.2O.sub.3 of 0.5%, 1% and 2%. Put NCM523 and coating precursor into a mixer and mix for 1 to 8 hours.

[0084] (6) Heat the above mixture to 200-1000° C. at a rate of 1-10° C./min, maintain at this temperature for 1-24 hours, and then cool to room temperature within the furnace to complete the coating process.

[0085] (7) Disperse and sieve the reaction products to obtain the final Al.sub.2O.sub.3 coated NCM523.

[0086] (8) Characterize the synthesized samples by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy scattering X-ray spectroscopy (EDS).

[0087] (9) Mix NCM523 prepared by coating with conductive agent, binder and solvent to prepare electrode slurry, then coat it on aluminum-based collector, dry to prepare electrode, and assemble into button battery for electrochemical performance test.

[0088] (10) Cycle all coin cells first for 4 cycles at 2.75-4.4 V with 0.1 C, and then test for cycle life with 0.2 C using the same voltage range.

[0089] In this example, a comparison is made for the NCM523 particles coated with different amounts of Al.sub.2O.sub.3 using stearic acid dispersant. Stearic acid dispersant can be well used for Al.sub.2O.sub.3 coated electrode materials with various concentration ratios. The analysis of Al element distribution for samples with different Al.sub.2O.sub.3 coating amount shows that (see FIG. 8), all samples show uniform distribution of Al element, and the signal strength of Al element increases with the increase of Al.sub.2O.sub.3 coating amount. The charge/discharge curves of the three samples above and the uncoated NCM523 material during the formation process are compared (see FIG. 9). All samples show similar charge/ discharge curves, and the specific discharge capacity of NCM523 material decreases with the increase of Al.sub.2O.sub.3 coating amount. This example fully shows that the uniform distribution of coating material alumina can be realized in the process of coating NCM523 with different amounts of alumina using fatty acid as dispersant, which provides guarantee for adjusting the initial discharge capacity of NCM523 and improving the optimization of its cycle life.

Example 4

[0090] (1) The fatty acid used in this example is lauric acid, the coating material is nano alumina (Al.sub.2O.sub.3), and the particle size of Al.sub.2O.sub.3 is 20-30 nm. The chemical formula of the electrode material used in this example is LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2 (NCM523 in brief).

[0091] (2) Firstly, prepare the mixture of 3 g lauric acid and nano Al.sub.2O.sub.3, in which the mass percentage of lauric acid is controlled at 3-30%.

[0092] (3) In the above mixture, add 10 to 30 g of ball milling beads for high-speed ball milling. The ball milling time is set from 1 to 5 hours and the ball milling speed is set from 100 to 600 rmp.

[0093] (4) After ball milling is over, collect the mixture of lauric acid and nano Al.sub.2O.sub.3, i.e. coating precursor.

[0094] (5) Take an appropriate amount of NCM523 and add the corresponding coating precursor (i.e. the mixture of lauric acid and nano Al.sub.2O.sub.3), so that the mass percentage of Al.sub.2O.sub.3 is 2%. Put NCM523 and coating precursor into a mixer and mix for 1 to 8 hours.

[0095] (6) Heat the above mixture to 200-1000° C. at a rate of 1-10° C./min, maintain at this temperature for 1-24 hours, and then cool to room temperature within the furnace to complete the coating process.

[0096] (7) Disperse and sieve the reaction products to obtain the final Al.sub.2O.sub.3 coated electrode material.

[0097] (8) Characterize the synthesized samples by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy scattering X-ray spectroscopy (EDS).

[0098] (9) Mix NCM523 prepared by coating with conductive agent, binder and solvent to prepare electrode slurry, then coat it on aluminum-based collector, dry to prepare electrode, and assemble into button battery for electrochemical performance test.

[0099] (10) Cycle all coin cells first for 4 cycles at 2.75-4.4 V with 0.1 C, and then test for cycle life with 0.2 C using the same voltage range.

[0100] This example tests the coating effect of NCM523 particles using lauric acid as dispersant. The electrode material NCM523 can also be well coated with lauric acid as dispersant. The charge/discharge curve of NCM523 coated with Al.sub.2O.sub.3 using lauric acid dispersant is shown in FIG. 10.

Example 5

[0101] (1) The fatty acid used in this example is lauric acid, the coating material is nano alumina (Al2O3), and the particle size of Al.sub.2O.sub.3 is 20-30 nm. The chemical formula of the electrode material used in this example is LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2 (NCM811 in brief).

[0102] (2) Firstly, prepare the mixture of 3 g lauric acid and nano Al.sub.2O.sub.3, in which the mass percentage of lauric acid is controlled at 3-30%.

[0103] (3) In the above mixture, add 10 to 30 g of ball milling beads for high-speed ball milling. The ball milling time is set from 1 to 5 hours and the ball milling speed is set from 100 to 600 rmp.

[0104] (4) After ball milling is over, collect the mixture of lauric acid and nano Al.sub.2O.sub.3, i.e. coating precursor.

[0105] (5) Take an appropriate amount of NCM811 and add the corresponding coating precursor (i.e. the mixture of lauric acid and nano Al.sub.2O.sub.3), so that the mass percentage of Al.sub.2O.sub.3 is 2%. Put NCM811 and coating precursor into a mixer and mix for 1 to 8 hours.

[0106] (6) Heat the above mixture to 200-1000° C. at a rate of 1-10° C./min, maintain at this temperature for 1-24 hours, and then cool to room temperature within the furnace to complete the coating process.

[0107] (7) Disperse and sieve the reaction products to obtain the final Al.sub.2O.sub.3 coated electrode material.

[0108] (8) Characterize the synthesized samples by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy scattering X-ray spectroscopy (EDS).

[0109] (9) Mix NCM811 prepared by coating with conductive agent, binder and solvent to prepare electrode slurry, then coat it on aluminum based collector, dry to prepare electrode, and assemble into button battery for electrochemical performance test.

[0110] (10) Cycle all coin cells first for 4 cycles at 2.75-4.4 V with 0.1 C, and then test for cycle life with 0.2 C using the same voltage range.

[0111] In this example, the coating effect of NCM811 particles with lauric acid as dispersant is tested. As shown in FIG. 11, the electrode material NCM811 can also be well coated with lauric acid as a dispersant.