A modification method of high nickel oxide, positive electrode material, and lithium ion battery

Abstract

The present invention belongs to the technical field of positive electrode materials for batteries, and specifically relates to a method for modifying high-nickel oxide and a positive electrode material and lithium-ion battery prepared thereby. The modification method comprises mixing an organic acid with a volatile organic solvent to prepare an organic acid solution, then mixing the high-nickel oxide with the organic acid solution, and reacting under stirring; the organic acid is at least one of capric acid, oxalic acid, and tartaric acid. Since the present invention utilizes the above-mentioned specific organic acid to neutralize the residual alkali on the surface of the high-nickel oxide at a lower temperature, the present invention can solve the problem of residual alkali on the surface of the high-nickel oxide without affecting the performance of the high-nickel oxide. The positive electrode material comprises a high-nickel oxide and a modified layer coating at least a portion of the surface of the high-nickel oxide. The high-nickel oxide modified with the lithium salt of the organic acid exhibits good structural stability and mechanical integrity, and exhibits good capacity retention in long-term cycle tests.

Description

Technical Field

[0001] The present invention belongs to the technical field of positive electrode materials for batteries, and particularly relates to a method for modifying high-nickel oxide and a positive electrode material and a lithium-ion battery prepared thereby. Background Art

[0002] Lithium-ion batteries are widely used as a rechargeable power source for portable electronic products and electric vehicles due to their relatively high energy density. In order to further improve the energy density of lithium batteries, nickel-rich layered oxides such as LiNi x Co y Mn z O2 (x ≥ 0.6) is considered one of the most promising cathode materials for lithium-ion batteries. However, the higher the Ni content in nickel-rich cathode materials, the more serious the problems of surface pulping, structural degradation, parasitic side reactions at the interface, and mechanical cracking. Among them, the degradation of the material structure starts from the surface and extends to the matrix, which inevitably leads to slow diffusion of lithium ions, thereby deteriorating the electrochemical performance and causing rapid decay of capacity and potential. In addition, another important problem of nickel-rich cathode materials is the residual lithium compounds such as LiOH and Li2CO3 on the surface, which inevitably form on the material surface during the synthesis process.

[0003] In order to reduce the negative impact of residual alkali, surface modification is one of the most effective means to improve the cycle stability of nickel-rich positive electrode materials. Chinese patent document CN114937771A discloses a method of mixing and coating high nickel positive electrode materials with supramolecular polymers formed by nitrogen-containing organic matter and acidic organic matter, and placing the polymer-coated high nickel positive electrode material in an oxygen-containing atmosphere for heat treatment, thereby forming a first coating layer of organic salt and a second coating layer of graphite phase carbon nitride on the surface of the high nickel positive electrode material; the combined effect of the double coating layers can improve the structural stability of the high nickel positive electrode material, promote the improvement of cycle performance, and reduce the residual alkali on the surface of the material, overcome the problems of high impedance and irreversible capacity decay caused by residual alkali, and significantly improve the conductivity of the coating layer. However, in order to form graphite phase carbon nitride, the above technology needs to heat treat the polymer at a higher temperature (400-600°C) for 2-8 hours. Although the heat treatment is carried out in an oxygen environment, it is inevitable that Ni in the high nickel positive electrode material will 4+ When NiO is reduced, this leads to the formation of a NiO-like rock salt impurity phase in the cathode material, which increases the charge transfer resistance and thus reduces the electrochemical performance of the high-nickel cathode. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is that the existing method of reducing the residual alkali on the surface of high nickel positive electrode materials will cause Ni 4+The reduced alkali metals affect the electrochemical performance of the high nickel positive electrode, thereby providing a method for effectively reducing the residual alkali on the surface of the high nickel positive electrode material without affecting its electrochemical performance.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] According to an embodiment of the present invention, in a first aspect, the present invention provides a method for modifying a high-nickel oxide, comprising the following steps:

[0007] An organic acid solution is prepared by mixing an organic acid with a volatile organic solvent; the organic acid is at least one of capric acid, oxalic acid, and tartaric acid;

[0008] The high nickel oxide is mixed with the organic acid solution, reacted under stirring, the volatile organic solvent is removed, and the mixture is dried.

[0009] In an embodiment of the present invention, the molar concentration of the organic acid in the organic acid solution is 2-4 mol / L.

[0010] In an embodiment of the present invention, the molar ratio of the high nickel oxide to the organic acid is 1:0.01-0.04.

[0011] In an embodiment of the present invention, the chemical structure of the high nickel oxide is Li 1.06 Ni a Co b Mn c O2, where 0.95≤a≤0.99, 0.005≤b≤0.03, 0.005≤c≤0.15, and a+b+c=1.

[0012] In an embodiment of the present invention, the reaction temperature is 60-80° C., and the reaction time is 15-30 h.

[0013] In an embodiment of the present invention, the volatile organic solvent is at least one of acetone, butanone, cyclohexanone, dioxane, trichloroethylene, and dichloromethane.

[0014] In an embodiment of the present invention, the drying temperature is 100-150° C., and the drying time is 5-10 hours.

[0015] According to an embodiment of the present invention, in a second aspect, the present invention provides a positive electrode material prepared by the above method, wherein the specific surface area of the positive electrode material is 0.62 to 0.65 m 2 / g.

[0016] In an embodiment of the present invention, the positive electrode material includes a high-nickel oxide and a modified layer covering at least a portion of the surface of the high-nickel oxide, and the modified layer is a lithium salt of an organic acid.

[0017] In an embodiment of the present invention, the median particle size of the positive electrode material is 9.0 to 11.0 μm.

[0018] According to an embodiment of the present invention, in a third aspect, the present invention further provides a lithium-ion battery comprising the above-mentioned positive electrode material.

[0019] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0020] 1. The modification method of high nickel oxide provided by the present invention comprises mixing an organic acid with a volatile organic solvent to prepare an organic acid solution, then mixing the high nickel oxide with the organic acid solution, and reacting them under stirring; wherein the organic acid is at least one of decanoic acid, oxalic acid, tartaric acid, etc. After a large number of experiments, the present invention surprisingly found that the use of the above-mentioned specific organic acid can neutralize the residual alkali on the surface of the high nickel oxide, overcoming the problem of high material impedance and irreversible capacity decay caused by the presence of residual alkali; because the neutralization reaction of the present invention can be carried out at a relatively low temperature (not exceeding 80°C), the modification method of the present invention can avoid the Ni in the high nickel oxide. 4+ The present invention uses an organic solvent to avoid problems such as increased side reactions and surface structural reorganization on the surface of high-nickel oxides caused by the presence of water. In other words, the modification method of the present invention can solve the problem of residual alkali on the surface of high-nickel positive electrode materials without affecting their performance.

[0021] 2. The positive electrode material provided by the present invention comprises a high-nickel oxide and a modified layer coating at least a portion of the surface of the high-nickel oxide, wherein the modified layer is a lithium salt of an organic acid. The specific organic acid lithium salt of the present invention is selected as the modified layer coating the high-nickel oxide. During the battery cycle, the modified layer can be stably present and inhibit direct contact between the electrolyte and the positive electrode material, thereby improving the electrochemical stability and ionic conductivity of the positive electrode material. This allows the modified high-nickel oxide to exhibit good structural stability and mechanical integrity, and exhibit good capacity retention in long-term cycle tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the specific embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is the SEM image of the positive electrode material prepared in Example 1.

[0024] Figure 2 for Figure 1 A partial enlarged view of .

[0025] Figure 3 This is the SEM image of the positive electrode material prepared in Comparative Example 1.

[0026] Figure 4 for Figure 3 A partial enlarged view of .

[0027] Figure 5 This is the SEM image of the positive electrode material prepared in Comparative Example 2.

[0028] Figure 6 for Figure 5 A partial enlarged view of . DETAILED DESCRIPTION

[0029] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0030] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0031] According to an embodiment of the present invention, in a first aspect, the present invention provides a method for modifying a high-nickel oxide, comprising the following steps:

[0032] Mixing an organic acid with a volatile organic solvent to prepare an organic acid solution, wherein the organic acid is at least one of capric acid, oxalic acid, and tartaric acid;

[0033] The high nickel oxide is mixed with the organic acid solution and reacted under stirring. After the reaction is completed, the volatile organic solvent is removed and the mixture is dried.

[0034] In an embodiment of the present invention, the molar concentration of the organic acid in the organic acid solution is 2 to 4 mol / L. This concentration facilitates the full ionization of the organic acid in the present invention, generating sufficient hydrogen ions for the neutralization reaction. If the organic acid concentration is too low, the amount of hydrogen ions generated is too small, requiring a large amount of organic acid solution, resulting in a waste of resources. If the organic acid concentration is too high, the amount of hydrogen ions generated is excessive, which can corrode the high-nickel oxide and affect the electrochemical properties of the material.

[0035] In an embodiment of the present invention, the molar ratio of the high-nickel oxide to the organic acid is 1:0.01-0.04. At this ratio, the organic acid can neutralize and remove most of the residual alkali on the surface of the high-nickel oxide, so that the presence of the remaining residual alkali will not have an adverse effect on the battery performance. At the same time, the specific surface area of the positive electrode material can also be regulated within an appropriate range, which is beneficial to improving the electrical properties of the material.

[0036] In an embodiment of the present invention, the chemical structure of the high nickel oxide is Li 1.06 Ni a Co b Mn c O2, wherein 0.95≤a≤0.99, 0.005≤b≤0.03, 0.005≤c≤0.15, and a+b+c=1. The higher the nickel content in the nickel oxide, the greater the amount of residual alkali on its surface. The modification method of the present invention can solve the problem of residual alkali on the surface of high-nickel oxide without affecting the material properties.

[0037] In the embodiment of the present invention, the organic acid solution can react with the residual alkali such as LiOH, Li2O, and Li2CO3 on the surface of the high-nickel oxide at room temperature to undergo a neutralization reaction. Properly increasing the reaction temperature to 60-80°C can accelerate the reaction rate and shorten the reaction time.

[0038] Taking decanoic acid as an example, the reaction formula is as follows:

[0039] 2CH3(CH2)8COOH+Li2O=2CH3(CH2)8COOLi+H2O

[0040] CH3(CH2)8COOH+LiOH=CH3(CH2)8COOLi+H2O

[0041] 2CH3(CH2)8COOH+Li2CO3=2CH3(CH2)8COOLi+H2O+CO2

[0042] In an embodiment of the present invention, the volatile organic solvent is at least one of acetone, butanone, cyclohexanone, dioxane, trichloroethylene, and dichloromethane. The use of a volatile organic solvent allows the desolventizing step to be performed at a lower temperature, thereby preventing the effects of high temperature on the high-nickel oxide. It also avoids the use of aqueous solvents, thereby preventing increased side reactions and surface structural reorganization on the high-nickel oxide surface.

[0043] After a large number of experiments, the present invention surprisingly found that the use of the above-mentioned specific organic acid can neutralize the residual alkali on the surface of the high nickel oxide, overcoming the problems of high material impedance and irreversible capacity degradation caused by the presence of residual alkali; because the neutralization reaction of the present invention can be carried out at a relatively low temperature (not exceeding 80°C), the modification method of the present invention can avoid the Ni in the high nickel oxide. 4+ The present invention uses an organic solvent to avoid problems such as increased side reactions and surface structural reorganization on the surface of high-nickel oxides caused by the presence of water. In other words, the modification method of the present invention can solve the problem of residual alkali on the surface of high-nickel oxides without affecting their performance.

[0044] According to an embodiment of the present invention, in a second aspect, the present invention provides a positive electrode material prepared by the above method, wherein the specific surface area of the positive electrode material is 0.62 to 0.65 m 2 / g. A larger specific surface area increases the contact area between the positive electrode material and the electrolyte, leading to more side reactions and poorer electrical performance. However, if the specific surface area is too small, the contact area between the positive electrode material and the electrolyte is too small, hindering lithium ion transfer and resulting in poorer electrical performance. The specific surface area of the positive electrode material produced by the present invention is within the above range, which not only ensures lithium ion transfer but also reduces side reactions on the positive electrode material surface, thus improving the material's electrical performance.

[0045] In an embodiment of the present invention, the positive electrode material includes a high-nickel oxide and a modified layer coating at least a portion of the surface of the high-nickel oxide, wherein the modified layer is a lithium salt of an organic acid. The specific organic acid lithium salt of the present invention is selected as the modified layer coating the high-nickel oxide. During the battery cycle, the modified layer can be stably present and inhibit direct contact between the electrolyte and the positive electrode material, thereby improving the electrochemical stability and ionic conductivity of the positive electrode material. This allows the modified high-nickel oxide to exhibit good structural stability and mechanical integrity, and exhibits good capacity retention in long-term cycle tests.

[0046] In an embodiment of the present invention, the median particle size of the positive electrode material is 9.0 to 11.0 μm. If the particle size is too small, the material's specific surface area is relatively large, resulting in a large contact area with the electrolyte, increased side reactions, and damage to the positive electrode structure, leading to poor cycle performance. If the particle size is too large, the lithium ion transmission path becomes longer, increasing resistance and reducing battery capacity. Therefore, the present invention selects a positive electrode material particle size within the above range to achieve a balanced battery performance.

[0047] According to an embodiment of the present invention, in a third aspect, the present invention further provides a lithium-ion battery, which comprises the above-mentioned positive electrode material and thus has a higher 0.1C discharge specific capacity, first efficiency and cycle retention rate.

[0048] The modification method of the high nickel oxide provided by the present invention and the positive electrode material and lithium ion battery prepared thereby are described in detail below with reference to specific embodiments.

[0049] Example 1

[0050] The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0051] (1) Ni 0.96 Co 0.02 Mn 0.02 (OH)2 and LiOH were dry mixed in a molar ratio of 1:1.06, and after mixing evenly, sintered at 690℃ in an O2 (purity 99.99%) atmosphere for 10h to obtain a high nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O2;

[0052] (2) The high nickel polycrystalline positive electrode material obtained in step (1) was mixed with a 2 mol / L decanoic acid (chemical formula: CH3(CH2)8COOH) acetone solution, and the mixture was evenly mixed according to a molar ratio of the high nickel polycrystalline positive electrode material to the decanoic acid of 1:0.03, and stirred in a constant temperature water bath at 80°C for 15 hours. After the solvent was completely evaporated, the mixture was placed in a vacuum drying oven at 150°C for 8 hours to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O2﹒ (CH3(CH2)8COOLi) 0.03 .

[0053] Example 2

[0054] The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0055] The high nickel polycrystalline positive electrode material obtained in step (1) of Example 1 was mixed with a 2 mol / L decanoic acid (chemical formula: CH3(CH2)8COOH) acetone solution, and the mixture was uniformly mixed according to a molar ratio of high nickel polycrystalline positive electrode material to decanoic acid of 1:0.02. The mixture was stirred in a constant temperature water bath at 80°C for 15 hours. After the solvent was completely evaporated, the mixture was placed in a vacuum drying oven at 150°C and dried for 8 hours to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O2﹒ (CH3(CH2)8COOLi) 0.02 .

[0056] Example 3

[0057] The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0058] The high nickel polycrystalline positive electrode material obtained in step (1) of Example 1 was mixed with a 2 mol / L decanoic acid (chemical formula: CH3(CH2)8COOH) acetone solution, and the mixture was evenly mixed according to a molar ratio of high nickel polycrystalline positive electrode material to decanoic acid of 1:0.04. The mixture was stirred in a constant temperature water bath at 80°C for 15 hours, and after the solvent was completely evaporated, it was placed in a vacuum drying oven at 150°C and dried for 8 hours to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O2﹒ (CH3(CH2)8COOLi) 0.04 .

[0059] Example 4

[0060] The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0061] The high nickel polycrystalline positive electrode material obtained in step (1) of Example 1 was mixed with a 3 mol / L decanoic acid (chemical formula: CH3(CH2)8COOH) acetone solution, and the mixture was evenly mixed according to a molar ratio of high nickel polycrystalline positive electrode material to decanoic acid of 1:0.03. The mixture was stirred in a constant temperature water bath at 80°C for 15 hours, and after the solvent was completely evaporated, it was placed in a vacuum drying oven at 150°C and dried for 8 hours to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O2﹒ (CH3(CH2)8COOLi) 0.03 .

[0062] Example 5

[0063] The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0064] The high nickel polycrystalline positive electrode material obtained in step (1) of Example 1 was mixed with a 4 mol / L decanoic acid (chemical formula: CH3(CH2)8COOH) acetone solution, and the mixture was evenly mixed according to a molar ratio of high nickel polycrystalline positive electrode material to decanoic acid of 1:0.03. The mixture was stirred in a constant temperature water bath at 80°C for 15 hours, and after the solvent was completely evaporated, it was placed in a vacuum drying oven at 150°C and dried for 8 hours to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O2﹒ (CH3(CH2)8COOLi) 0.03 .

[0065] Example 6

[0066] The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0067] (1) Ni 0.95 Co 0.03 Mn 0.02 (OH)2 and LiOH were dry mixed in a molar ratio of 1:1.06, and after mixing evenly, sintered at 690℃ in an O2 (purity 99.99%) atmosphere for 10h to obtain a high nickel polycrystalline positive electrode material Li 1.06 Ni 0.95 Co 0.03 Mn 0.02 O2;

[0068] (2) The high nickel polycrystalline positive electrode material obtained in step (1) was mixed with a 2 mol / L decanoic acid (chemical formula: CH3(CH2)8COOH) acetone solution, and the mixture was evenly mixed according to a molar ratio of the high nickel polycrystalline positive electrode material to the decanoic acid of 1:0.03, and stirred in a constant temperature water bath at 80°C for 15 hours. After the solvent was completely evaporated, the mixture was placed in a vacuum drying oven at 150°C for 8 hours to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.95 Co 0.03 Mn 0.02 O2﹒ (CH3(CH2)8COOLi) 0.03 .

[0069] Example 7

[0070] The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0071] (1) Ni 0.99 Co 0.05 Mn 0.005 (OH)2 and LiOH were dry mixed in a molar ratio of 1:1.06, and after mixing evenly, sintered at 690℃ in an O2 (purity 99.99%) atmosphere for 10h to obtain a high nickel polycrystalline positive electrode material Li 1.06 Ni 0.99 Co 0.005 Mn 0.005 O2;

[0072] (2) The high nickel polycrystalline positive electrode material obtained in step (1) was mixed with a 2 mol / L decanoic acid (chemical formula: CH3(CH2)8COOH) acetone solution, and the mixture was evenly mixed according to a molar ratio of the high nickel polycrystalline positive electrode material to the decanoic acid of 1:0.03, and stirred in a constant temperature water bath at 80°C for 15 hours. After the solvent was completely evaporated, the mixture was placed in a vacuum drying oven at 150°C for 8 hours to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.99Co 0.005 Mn 0.005 O2﹒ (CH3(CH2)8COOLi) 0.03 .

[0073] Example 8

[0074] The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0075] The high nickel polycrystalline positive electrode material obtained in step (1) of Example 7 was mixed with a 2.5 mol / L tartaric acid (chemical formula: CH3(COOH)3) cyclohexanone solution, and the mixture was evenly mixed according to a molar ratio of high nickel polycrystalline positive electrode material to tartaric acid of 1:0.01. The mixture was stirred in a constant temperature water bath at 60°C for 20 h, and after the solvent was completely evaporated, it was placed in a vacuum drying oven at 120°C and dried for 10 h to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.99 Co 0.005 Mn 0.005 O2﹒ (CH3(COOLi)3) 0.01 .

[0076] Example 9

[0077] The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0078] The high nickel polycrystalline positive electrode material obtained in step (1) of Example 7 was mixed with a 3.5 mol / L dichloromethane solution of oxalic acid (chemical formula: HOOCCOOH), and the mixture was evenly mixed according to a molar ratio of 1:0.01 between the high nickel polycrystalline positive electrode material and the oxalic acid. The mixture was stirred in a constant temperature water bath at 70°C for 30 hours, and after the solvent was completely evaporated, the mixture was placed in a vacuum drying oven at 100°C for 5 hours to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.99 Co 0.005 Mn 0.005 O2﹒ (LiOOCCOOLi) 0.01 .

[0079] Comparative Example 1

[0080] The preparation method of the positive electrode material provided in this comparative example comprises the following steps:

[0081] The high nickel polycrystalline cathode material precursor Ni 0.96 Co 0.02 Mn 0.02 (OH)2 and LiOH were dry mixed in a molar ratio of 1:1.06, and after mixing evenly, sintered at 690℃ in an O2 (purity 99.99%) atmosphere for 10h to obtain a high nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co0.02 Mn 0.02 O2.

[0082] Comparative Example 2

[0083] The preparation method of the positive electrode material provided in this comparative example comprises the following steps:

[0084] The high nickel polycrystalline positive electrode material obtained in step (1) of Example 1 was mixed with the same volume of acetone solution of Example 1, stirred in a constant temperature water bath at 80°C for 15 h, and dried in a vacuum drying oven at 150°C for 8 h after the solvent was completely evaporated to obtain a high nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O2.

[0085] Comparative Example 3

[0086] The preparation method of the positive electrode material provided in this comparative example comprises the following steps:

[0087] The high nickel polycrystalline positive electrode material obtained in step (1) of Example 1 was mixed with a 2 mol / L decanoic acid (chemical formula: CH3(CH2)8COOH) acetone solution, and the mixture was evenly mixed according to a molar ratio of high nickel polycrystalline positive electrode material to decanoic acid of 1:0.05. The mixture was stirred in a constant temperature water bath at 80°C for 15 hours, and after the solvent was completely evaporated, it was placed in a vacuum drying oven at 150°C and dried for 8 hours to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O2﹒ (CH3(CH2)8COOLi) 0.05 .

[0088] Comparative Example 4

[0089] The preparation method of the positive electrode material provided in this comparative example comprises the following steps:

[0090] The high nickel polycrystalline positive electrode material obtained in step (1) of Example 1 was mixed with a 2 mol / L acetic acid (chemical formula: CH3COOH) acetone solution, and the mixture was evenly mixed according to a molar ratio of the high nickel polycrystalline positive electrode material to the acetic acid of 1:0.03. The mixture was stirred in a constant temperature water bath at 80°C for 15 hours, and after the solvent was completely evaporated, it was placed in a vacuum drying oven at 150°C and dried for 8 hours to obtain a modified high nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O2﹒ (CH3COOLi) 0.03 .

[0091] Comparative Example 5

[0092] The preparation method of the positive electrode material provided in this comparative example is the same as that of Example 1 in the specification of Chinese patent document CN114937771A.

[0093] Experimental Example 1

[0094] The positive electrode materials prepared in Example 1 and Comparative Examples 1-2 were tested using a scanning electron microscope. The microscopic morphology of the positive electrode material prepared in Example 1 is as follows: Figures 1-2 As shown, from Figures 1-2 It can be seen from the figure that the surface of the positive electrode material prepared in Example 1 has an obvious coating, which is the lithium decanoate modified layer; the particle size of the positive electrode material is 10.0 μm.

[0095] However, no coating was observed on the surface of the positive electrode materials synthesized in Comparative Examples 1 and 2. Figures 3 to 6 .

[0096] Experimental Example 2

[0097] The specific surface areas (SSA) of the cathode materials prepared in Examples 1 to 9 and Comparative Examples 1 to 5 were measured using a Bester surface area tester in a liquid nitrogen atmosphere at 200° C. for 1 hour. The results are shown in Table 1.

[0098] Table 1

[0099] LiOH / % <![CDATA[Li2CO3 / %]]> Total alkali / % <![CDATA[SSA(m 2 / g)]]> Example 1 0.11 0.34 0.45 0.62 Example 2 0.09 0.38 0.47 0.63 Example 3 0.09 0.34 0.43 0.62 Example 4 0.10 0.39 0.49 0.63 Example 5 0.11 0.35 0.46 0.65 Example 6 0.06 0.34 0.4 0.64 Example 7 0.07 0.39 0.46 0.64 Example 8 0.09 0.40 0.49 0.63 Example 9 0.08 0.40 0.48 0.64 Comparative Example 1 0.94 0.85 1.79 1.25 Comparative Example 2 0.88 0.90 1.78 1.14 Comparative Example 3 0.10 0.41 0.51 0.84 Comparative Example 4 0.87 0.95 1.82 0.95 Comparative Example 5 0.91 0.92 1.83 0.99

[0100] According to Table 1, compared with Comparative Examples 1 to 5, the total alkali content of the positive electrode materials synthesized in Examples 1 to 9 is lower, and the specific surface area SSA meets 0.62 m 2 / g≤SSA≤0.65m 2 / g, which shows that the high-nickel oxide modification method provided by the present invention treats the high-nickel oxide by using a specific organic acid, that is, the organic acid reacts chemically with the residual alkali (Li2O, LiOH, Li2CO3) on the surface of the high-nickel oxide, thereby reducing the residual alkali content and forming a lithium salt modification layer of the organic acid covering the surface of the high-nickel oxide. The modification layer can effectively control the specific surface area of the positive electrode material within the above-mentioned suitable range.

[0101] Experimental Example 3

[0102] An appropriate amount of the positive electrode materials of Examples 1 to 9 and Comparative Examples 1 to 5 were prepared into a homogenous slurry and coated on aluminum foil to prepare a positive electrode sheet; by mass ratio, the positive electrode material: conductive carbon black: polyvinylidene fluoride glue = 92:4:4, and the solid content of the polyvinylidene fluoride glue was 6.05%.

[0103] The prepared positive electrode sheet was assembled with a BR2032 shell (button batteries are composed of a complete set of button battery shells and internal components. Common button battery shell models include BR2032, CR2032, CR2025 and CR2016. BR2032 or CR2032 battery shells are commonly used in laboratories). Then, electrochemical tests were performed on a battery performance test system with a test voltage range of 3.0 to 4.3 V. The battery was subjected to a charge and discharge cycle test at a discharge efficiency of 0.1C. After two weeks of cycling, the charge and discharge test was performed at 1C for 50 cycles. The average value of each group was taken. The test results of the average first discharge specific capacity, average first discharge efficiency (ie, first efficiency) and room temperature cycle retention rate (ie, 50-week retention rate) of the battery are shown in Table 2.

[0104] Table 2

[0105]

[0106] According to Table 2, compared with Comparative Examples 1 to 5, Examples 1 to 9 effectively reduce the surface residual alkali of the high-nickel polycrystalline positive electrode material after being treated with the specific organic acid of the present invention, and coat a layer of organic acid lithium salt, so that the positive electrode material has a higher 0.1C discharge capacity, first efficiency and cycle retention rate. This shows that the organic acid lithium salt modified layer in the positive electrode material provided by the present invention can improve the conductivity of lithium ions, which is beneficial to the transfer of electrons, thereby improving the 0.1C discharge capacity and first efficiency of the positive electrode material. At the same time, the modified layer can effectively inhibit the contact between the electrolyte and the positive electrode material, reduce the occurrence of side reactions, and thus improve the cycle performance of the positive electrode material. The electrochemical performance of Comparative Examples 1 and 2 is poor, which may be because there is still a lot of residual alkali on the surface of the positive electrode material, which inhibits the diffusion and transfer of lithium ions and electrons in the positive electrode material, thereby reducing the electrochemical performance of the positive electrode material.

[0107] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A positive electrode material, characterized in that The specific surface area of the positive electrode material is 0.62 to 0.65 m 2 / g, the preparation method of the positive electrode material comprises: Mixing an organic acid with a volatile organic solvent to prepare an organic acid solution, wherein the organic acid is at least one of capric acid, oxalic acid, and tartaric acid; Mixing the high nickel oxide with the organic acid solution, reacting under stirring, removing the volatile organic solvent, and drying; The molar ratio of the high nickel oxide to the organic acid is 1:0.01-0.04; The molar concentration of the organic acid in the organic acid solution is 2 to 4 mol / L; The chemical structure of the high nickel oxide is Li 1.06 Ni a Co b Mn c O2, where 0.95 < a ≤ 0.99, 0.005 ≤ b ≤ 0.03, 0.005 ≤ c ≤ 0.15, and a + b + c = 1; The positive electrode material includes a high nickel oxide and a modified layer covering at least a portion of the surface of the high nickel oxide, wherein the modified layer is a lithium salt of the organic acid; The reaction temperature is 60-80°C, and the reaction time is 15-30h.

2. The positive electrode material according to claim 1, characterized in that The median particle size of the positive electrode material is 9.0 to 11.0 μm.

3. The positive electrode material according to claim 1, characterized in that The volatile organic solvent is at least one of acetone, butanone, cyclohexanone, dioxane, trichloroethylene, and dichloromethane.

4. The positive electrode material according to claim 1, characterized in that The drying temperature is 100-150°C and the drying time is 5-10 hours.

5. A lithium-ion battery, characterized in that: The positive electrode material comprises the positive electrode material according to any one of claims 1 to 4.

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