Cathode material and preparation method thereof, and lithium ion battery

Abstract

The application provides a positive electrode material and a preparation method thereof and a lithium ion battery, and relates to the technical field of lithium ion batteries. The positive electrode material comprises a ternary matrix material and a coating layer located at least partially on the surface of the ternary matrix material; the coating layer comprises a first coating layer and a second coating layer located at least partially on the surface of the first coating layer, the first coating layer comprises an anionic covalent organic framework composite material, and the second coating layer comprises a metallic glass. The positive electrode material provided by the application can significantly reduce the surface residual alkali of the positive electrode material, establish a fast lithium ion transmission channel, improve the electrical conductivity of the positive electrode material, reduce the specific surface area caused by the composite material coating layer, and significantly improve the stability and mechanical strength of the positive electrode material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery cathode material, and particularly relates to a cathode material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] For high-nickel cathode materials (Ni>0.8), due to the high theoretical reversible capacity, they have become the focus of future power battery research and industrialization. However, the high-nickel cathode material has the problem of high total residual lithium content, which seriously affects the processing performance of the battery. At present, the commonly used binder in the lithium battery industry is polyvinylidene fluoride (PVDF), but its alkali resistance is poor, and it can react with alkali to eliminate HF to generate double bonds, crosslink between PVDF molecular chains, and then form a gel to cause coating failure. In view of this situation, water washing is currently the most mainstream method to remove residual alkali on the surface of high-nickel ternary cathode material and thus improve the processing performance. By optimizing the water washing temperature and time, washing water amount and times, and drying temperature, the content of residual lithium on the surface of high-nickel ternary material can be significantly reduced, and the processing performance of the electrode material is improved.

[0003] Water washing also brings some defects to the battery cathode material in actual application, causing the chemical properties of the surface of the cathode material particles to change, causing a side reaction between the material surface and the electrolyte to form a NiO-like rock salt phase, resulting in an increase in the surface resistance of the cathode material, and a higher interface lattice strain between the layered and rock salt structures due to lattice mismatch, thereby reducing the electrochemical performance of the battery. These problems will become more and more obvious as the nickel content in the ternary material gradually increases. Generally speaking, the higher the nickel content, the more sensitive the cathode material is to water, and the more side reactions caused by water washing, so the water washing process is no longer so suitable. Based on this, a new technical solution is needed to solve the problem of residual alkali on the surface of the cathode material without affecting the electrochemical performance of the cathode material in the battery. SUMMARY

[0004] Therefore, the present application provides a cathode material, a preparation method thereof and a lithium ion battery, which effectively reduces the residual alkali on the surface of the material by using an anionic covalent organic framework to remove the residual alkali on the surface of the high-nickel material in one step and generate a specific coating layer, while improving the thermal stability and cycle performance of the high-nickel cathode material.

[0005] To achieve the above object, the technical scheme of the present application is as follows:

[0006] In a first aspect, a cathode material includes a ternary base material and a coating layer at least partially on the surface of the ternary base material.

[0007] The coating layer comprises a first coating layer and a second coating layer at least partially on the surface of the first coating layer, the first coating layer comprises an anionic covalent organic framework material, and the second coating layer comprises a metallic glass.

[0008] In some embodiments, the ternary matrix material has a chemical formula of Li a Ni x Co y M z O2, wherein 0.95≤a≤1.1, 0.7≤x<1, 0<y+z≤0.3, x+y+z=1, and M comprises at least one of Mn and Al.

[0009] In some embodiments, the anionic covalent organic framework material comprises a conjugated organic compound comprising anionic groups, the anionic groups comprising at least one of an acidic group and an imidazole group.

[0010] In some embodiments, the anionic covalent organic framework material comprises a covalent organic framework material comprising anionic groups, the anionic groups comprising an acidic group, the acidic group comprising at least one of a sulfonic acid group, a carboxylic acid group, and a silicic acid group.

[0011] In some embodiments, the metallic glass comprises a composite of a metal and boron.

[0012] In some embodiments, the metal comprises at least one of nickel, zinc, cobalt, iron, titanium, tungsten, zirconium, aluminum, magnesium, yttrium, and niobium.

[0013] In some embodiments, the positive electrode material is a spherical particulate material.

[0014] In some embodiments, the particle size of the positive electrode material is 3.5 μm-17 μm.

[0015] In some embodiments, the specific surface area of the positive electrode material is 0.2 m 2 / g-0.7 m 2 / g.

[0016] In some embodiments, the I 003 / I 004 peak intensity ratio of the positive electrode material is 0.9-1.1.

[0017] In a second aspect, the application provides a preparation method of the positive electrode material of the first aspect, comprising:

[0018] dry-coating the ternary matrix material with the anionic covalent organic framework material to obtain a ternary material with a first coating layer on the surface of the ternary matrix material, the first coating layer comprising the anionic covalent organic framework material.

[0019] wet-coating the solution containing the metal glass preparation solution with the ternary material to obtain the positive electrode material coated with a second coating layer on the surface of the ternary material, the second coating layer comprising the metal glass.

[0020] In some embodiments, the ternary precursor and the lithium source are mixed and sintered to obtain the ternary matrix material.

[0021] In some embodiments, the two-dimensional covalent organic framework material, the solvent and the anionic monomer are mixed and reacted to obtain the anionic covalent organic framework composite material.

[0022] In some embodiments, the ternary precursor comprises an oxide or hydroxide containing Ni x Co y M z , wherein 0.7≤x<1, 0

[0023] In some embodiments, the lithium source comprises at least one of lithium hydroxide and lithium carbonate.

[0024] In some embodiments, the ratio of the total molar content of Ni, Co and M in the ternary precursor to the molar content of Li element in the lithium source is 1:(0.95-1.1).

[0025] In some embodiments, the sintering is performed in an oxygen atmosphere, the content of oxygen in the oxygen atmosphere being ≥95%.

[0026] In some embodiments, the sintering is performed at a temperature of 600-950℃ for 8-20h, and the temperature rising speed in the range of 450-650℃ is 0.5-3℃ / min.

[0027] In some embodiments, the sintering further comprises: crushing the ternary matrix material to obtain particles with a particle size of 3.5-17μm.

[0028] In some embodiments, the molar ratio of the two-dimensional covalent organic framework material to the anionic monomer is (0.1-1):(0.5-2).

[0029] In some embodiments, the two-dimensional covalent organic framework material comprises at least one of aldehyde, catechol, hydroxyarene, alkoxyl compound, amine and hydrazine.

[0030] In some embodiments, the aldehyde includes at least one of trimesaldehyde, 1,3,5-benzene tricarboxaldehyde, and trihydroxybenzene, the hydroxyaromatic includes at least one of 9-10-dimethyl-2,3,6,7-tetrahydroxyanthracene and hexahydroxytriphenylbenzene, and the amine includes at least one of sulfamic acid and diamino diphenyl dicarboxylic acid.

[0031] In some embodiments, the anionic monomer includes at least one of 1-vinylimidazole, 1-methylimidazole, 2-nitroimidazole, 1-imidazole acetic acid, 4-imidazole, 4-hydroxymethyl imidazole, 1-acetylimidazole, trimethyl borate, triphenyl boron, diphenyl borate, benzene sulfonic acid, sulfamic acid, 2,5-diaminobenzenesulfonic acid, diamino benzene disulfonic acid, and sodium methyl silicate, potassium methyl silicate, and ethyl silicate.

[0032] In some embodiments, the solvent includes at least one of DMF, tetrahydrofuran, methanol, acetone, and n-hexane.

[0033] In some embodiments, the stirring is performed under an atmosphere of an inert gas, and the frequency of the stirring is between 10 Hz and 50 Hz.

[0034] In some embodiments, the temperature of the reaction is between 100°C and 120°C, and the time is between 60 h and 84 h.

[0035] In some embodiments, the reaction is followed by filtering, washing, and drying, and the temperature of the drying is between 60°C and 100°C, and the time is between 5 h and 20 h.

[0036] In some embodiments, the solution for preparing a metallic glass includes a mixed solution obtained by stirring a metallic nitrate, a compound containing an N element, and an organic solvent, and the N element is a non-metallic element.

[0037] In some embodiments, the metallic nitrate includes at least one of nickel, zinc, cobalt, iron, titanium, tungsten, zirconium, aluminum, magnesium, yttrium, and niobium.

[0038] In some embodiments, the boron hydride compound includes at least one of NaBH4 and KBH4.

[0039] In some embodiments, the organic solvent includes at least one of anhydrous ethanol, diethyl ether, methanol, acetone, pentane, and hexane.

[0040] In some embodiments, the molar ratio of the metallic nitrate, the compound containing an N element, and the organic solvent is between (0.08-0.25):(0.5-1):(4-10).

[0041] In some embodiments, the wet coating comprises: slowly dropping the solution containing the metallic glass into the ternary material under stirring.

[0042] In some embodiments, the dropping speed is 0.5 L / min-3 L / min.

[0043] In some embodiments, the wet coating is performed in a single cone.

[0044] In some embodiments, after the wet coating, drying is further performed for 1 h-4 h.

[0045] In some embodiments, the mass ratio of the ternary matrix material to the anionic covalent organic framework material is (0.9-0.99):(0.1-0.01).

[0046] In some embodiments, the chemical general formula of the ternary matrix material is Li a Ni x Co y M z O2, wherein 0.95≤a≤1.1, 0.7≤x<1, 0<y+z≤0.3, x+y+z=1, M comprises at least one of Mn and Al.

[0047] In a third aspect, the application further provides a lithium ion battery comprising the positive electrode material of the first aspect or the positive electrode material prepared by the preparation method of the second aspect.

[0048] Advantages of the application:

[0049] In the positive electrode material of the application, the anionic covalent organic framework composite material is coated on the surface of the ternary matrix material. The covalent organic framework material has a large conjugated system of delocalized π electrons and excellent chemical and thermodynamic stability. After the anionic covalent organic framework composite material is further formed, because the anionic monomer is negatively charged, a positive electric channel can be constructed in the composite material, a fast lithium ion transmission channel is established, and the electrical conductivity of the positive electrode material is improved. In addition, the outermost metal glass has super high ductility and fluidity, can effectively fill the gaps of the organic coating layer, and even penetrate into the primary particles in the material; it also has super strong stability, can effectively isolate the side reaction between the surface of the positive electrode material and the coating layer and the electrolyte, significantly reduce the specific surface area increase caused by the coating of the covalent organic framework composite material, and significantly improve the stability and mechanical strength of the positive electrode material.

[0050] In the preparation method of the positive electrode material of the present application, the anion covalent organic framework composite material system is constructed by using in-situ reaction, and the composite material is dry coated with the ternary matrix material to realize controllable preparation of the coating layer. The process is simple and low in cost, and is suitable for large-scale production. In addition, the coating layer formed by dry coating has strong particle feeling, and the voids can be effectively filled by wet coating with the metal glass solution having super high ductility and fluidity, thereby significantly reducing the specific surface area of the positive electrode material and improving the stability and continuous strength of the positive electrode material.

[0051] In the lithium ion battery of the present application, the positive electrode material prepared by using the above positive electrode material or the preparation method is used, which effectively improves the processing performance and safety performance of the lithium ion battery, and enhances the rate performance and cycle performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0052] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope of the present application.

[0053] Figure 1 High-magnesium positive electrode material of Example 1 high-magnification SEM image;

[0054] Figure 2 Capacity retention rate curve of the battery of Example 1 and Comparative Example 1 after 50 cycles. DETAILED DESCRIPTION

[0055] As used herein, the term:

[0056] “Prepared from” is synonymous with “comprising”. The terms “comprising”, “including”, “having” or “containing” or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0057] The conjunction “consisting of’ excludes any element, step, or ingredient not specified. If used in a claim, this phrase shall exclude any element not specified, but shall not exclude elements required under patent law. When the phrase “consisting of’ follows the introductory language “comprising” or “comprising,” the contents of the clause that follows shall be construed as consisting of the elements only listed in that clause, and not of any other elements.

[0058] When expressing amounts, concentrations, or other values or parameters of a range, either preferred range, or series of upper preferred values and lower preferred values, it is to be understood that all ranges formed by any pair of any upper range limit or preferred value, and any lower range limit or preferred value, regardless of whether such ranges are separately disclosed, are expressly disclosed. For example, where a range of "1 to 5" is disclosed, the disclosure is to be interpreted to include ranges of "1 to 4," "1 to 3," "1 to 2," "1 to 2 and 4 to 5," "1 to 3 and 5," etc. When numerical ranges are disclosed herein, unless otherwise stated, the range is intended to include both the upper and lower values and all intervening values of the range, as well as any and all subranges thereof.

[0059] In these examples, unless otherwise indicated, the parts and percentages are by mass.

[0060] "Mass parts" refers to a basic unit of measurement that represents the proportional relationship of the mass of multiple components, 1 part can represent any unit mass, such as 1 g, 2.689 g, etc. If we say that the mass parts of component A is a parts, and the mass parts of component B is b parts, it means that the ratio of the mass of component A to the mass of component B is a:b. Or, it means that the mass of component A is aK, and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It should not be misunderstood that unlike mass parts, the sum of the mass parts of all components is not limited to 100 parts.

[0061] "and / or" is used to indicate that one or both of the described conditions can occur, for example, A and / or B includes (A and B) and (A or B).

[0062] The positive electrode material provided by the present application comprises a ternary base material and a coating layer at least partially located on the surface of the ternary base material; the coating layer comprises a first coating layer and a second coating layer at least partially located on the surface of the first coating layer, the first coating layer comprises an anionic covalent organic framework composite material, and the second coating layer comprises a metallic glass.

[0063] By coating the ternary matrix material with an anionic covalent organic framework composite material, the covalent organic framework material has a large conjugated system of delocalized π electrons, and has excellent chemical and thermodynamic stability. After the anionic covalent organic framework composite material is further formed, because the anionic monomer is negatively charged, a positive electric channel can be constructed in the formed composite material, a fast lithium ion transmission channel is established, and the electrical conductivity of the positive electrode material is improved. In addition, the outermost metal glass has super high ductility and flowability, which can effectively fill the gaps of the organic coating layer, and even penetrate into the primary particles of the material; it also has super strong stability, which can effectively isolate the surface of the positive electrode material and the side reaction of the coating layer and the electrolyte, significantly reduce the specific surface area caused by the coating of the covalent organic framework composite material, and significantly improve the stability and mechanical strength of the positive electrode material; the first coating layer and the second coating layer have a synergistic effect, which improves the stability of the positive electrode material.

[0064] In some embodiments, the chemical formula of the ternary matrix material is Li a Ni x Co y M z O2, wherein 0.95≤a≤1.1, 0.7≤x<1, 0<y+z≤0.3, x+y+z=1, and M includes Mn or Al. It can be understood that using nickel-cobalt-manganese or nickel-cobalt-aluminum ternary material as the positive electrode active material to prepare a lithium ion battery, the battery has higher energy density, better cycle performance, and lower cost than commonly used lithium iron phosphate batteries.

[0065] In some embodiments, the anionic covalent organic framework material includes a conjugated organic compound containing an anionic group, the anionic group including at least one of an acidic group and an imidazole group; the acidic group and the imidazole group can react with residual alkali on the surface of the positive electrode material, thereby reducing the content of residual alkali on the surface of the positive electrode material.

[0066] The anionic covalent organic framework material is obtained by reacting a two-dimensional covalent organic framework material with an anionic monomer, that is, a coordination reaction between the covalent organic framework material and the anionic group in the anionic monomer. Finally, an anionic covalent organic framework material modified by a specific acidic group is obtained. For example, it can include a Schiff base reaction of phloroglucinol and sulfonic acid, a condensation reaction of hydroxyanthracene and methyl silicate, and an ester exchange reaction of γ-cyclodextrin and fatty acid.

[0067] In some embodiments, the acidic group includes at least one of a sulfonic acid group, a carboxylic acid group, and a silicic acid group.

[0068] It should be noted that the construction reaction of the covalent organic framework material mainly includes borate dehydration trimerization, condensation of boric acid and catechol compound, cyanogen self-polymerization and Schiff base reaction (dehydration condensation reaction of aldehyde and amine, hydrazine, hydrazone, etc.). The organic small molecule unit is connected by covalent bond atom to form a material with periodic porous framework structure, that is, a covalent organic framework material. In the two-dimensional covalent organic framework material, it is generally a two-dimensional polygonal sheet connected by covalent bond. These sheets can be stacked layer by layer to form a periodic π array, which can promote the carrier transmission in the stacking direction.

[0069] In some embodiments, the metallic glass includes a composite of a metal and boron, the metal including at least one of nickel, zinc, cobalt, iron, titanium, tungsten, zirconium, aluminum, magnesium, yttrium, and niobium.

[0070] It can be understood that the metallic glass is an amorphous alloy, and the metallic glass is formed by covalently bonding metal atoms and light element non-metals.

[0071] In the positive electrode material of the present application, first, an anionic covalent organic framework composite material is coated on the surface of the ternary base material to form a first coating layer. Specifically, by utilizing the acidic groups on the surface of the anionic covalent organic framework composite material, chemical bonding reaction occurs with the residual alkali such as OH - and CO3 2- on the surface of the positive electrode material, thereby enhancing the connection strength between the first coating layer and the ternary base material, and further significantly reducing the surface residual alkali of the ternary positive electrode material.

[0072] Further, by constructing the anionic covalent organic framework composite material system, the problem of low electrical conductivity of single material is also solved. The two-dimensional covalent organic framework material has a large conjugated system of delocalized π electrons, and has excellent chemical and thermodynamic stability. As a kind of organic functional sensitized material with excellent performance, it can be stably coupled with anionic groups through covalent or supramolecular interaction. Since the anionic groups are negatively charged, these anionic groups can construct a positive channel in the ring structure of the organic framework, which is conducive to the transmission of lithium ions and improves the lithium ion transmission performance. Further, coating the anionic covalent organic framework composite material on the surface of the ternary base material can establish a fast lithium ion transmission channel and improve the electrical conductivity of the positive electrode material.

[0073] In addition, the metallic glass of the second coating layer has super high ductility and fluidity, which can effectively fill the gaps of the first coating layer and even enter the primary particles of the material. The metallic glass is selected as the material of the second coating layer in the application, which has super high ductility and fluidity, and also has super strong stability, which can effectively isolate the surface of the positive electrode material and the side reaction of the coating layer and the electrolyte, significantly reduce the specific surface area increase caused by the coating of the covalent organic framework composite material, and significantly improve the stability and mechanical strength of the positive electrode material. Even at a high temperature of about 900℃, the metallic glass has excellent oxidation resistance, and even if the metallic glass reacts with oxygen, a dense and healable passivation layer will be formed at the interface, which will not affect the performance of the internal material and can prevent the oxidation of the internal material by the external environment.

[0074] In some embodiments, the positive electrode material comprises a spherical particulate material. Further, the particle size of the positive electrode material is 3.5 μm-17 μm, for example, it can be 3.5 μm, 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, 14 μm, 15 μm, 17 μm or any value between 3.5 μm and 17 μm.

[0075] In some embodiments, the specific surface area of the positive electrode material is 0.2 m 2 / g-0.7 m 2 / g, for example, it can be 0.2 m 2 / g, 0.3 m 2 / g, 0.4 m 2 / g, 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g or any value between 0.2 m 2 / g and 0.7 m 2 / g.

[0076] In some embodiments, the I 003 / I 004 peak intensity ratio of the positive electrode material is 0.9-1.1, for example, it can be 0.9, 0.95, 1.0, 1.05, 1.1 or any value between 0.9 and 1.1.

[0077] The application also provides a preparation method of the above positive electrode material, comprising:

[0078] (1) mixing and sintering a ternary precursor and a lithium source to obtain a ternary matrix material;

[0079] (2) mixing and reacting a two-dimensional covalent organic framework material, a solvent and an anion monomer to obtain an anionic covalent organic framework composite material with acid groups on the surface;

[0080] (3) dry-coating the ternary base material with the anionic covalent organic framework composite material to obtain a ternary material coated with a first coating layer on the surface of the ternary base material;

[0081] (4) wet-coating the ternary material with a solution containing a metallic glass to obtain the positive electrode material coated with a second coating layer on the surface of the ternary material.

[0082] In some embodiments, the ternary precursor in step (1) comprises an oxide or hydroxide containing Ni x Co y M z , wherein 0.7≤x<1, 0

[0083] In some embodiments, the lithium source comprises at least one of lithium hydroxide and lithium carbonate, more preferably lithium hydroxide.

[0084] In some embodiments, the ratio of the total molar content of Ni, Co, M in the ternary precursor to the molar content of Li element in the lithium source is 1:(0.95-1.1), for example, it can be 1:0.95, 1:0.98, 1:1, 1:1.02, 1:1.05, 1:1.08, 1:1.1 or any value between 1:(0.95-1.1). More preferably, the molar ratio is 1:1.02.

[0085] In some embodiments, the sintering in step (1) is performed in an oxygen atmosphere, wherein the content of oxygen in the oxygen atmosphere is ≥95%.

[0086] In some embodiments, the sintering is performed at a temperature of 600-950℃, for example, it can be 600℃, 700℃, 800℃, 900℃, 950℃ or any value between 600-950℃, and the sintering is performed for a time of 8-20h, for example, it can be 8h, 10h, 12h, 14h, 16h, 18h, 20h or any value between 8-20h.

[0087] It should be noted that when the temperature sintering is carried out, when the temperature reaches the temperature range of 450-650℃, it is necessary to ensure that the heating rate is 0.5-3℃ / min, for example, it can be 0.5℃ / min, 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min or any value between 0.5-3℃ / min. If the heating rate is too large, it is easy to make the internal elements of the prepared ternary matrix material not uniform, and the internal lithium content is too small, which affects the performance of the positive electrode material; and if the heating rate is too small, the production efficiency is greatly reduced, the production cost is increased, and the waste of resources is easy to cause.

[0088] In some embodiments, step (1) needs to be ground uniformly before sintering, and then heated for sintering, which is also to ensure that all raw materials can fully react. After sintering, the obtained ternary matrix material is crushed, and the particle size after crushing is 3.5-17μm, for example, it can be 3.5μm, 5μm, 7μm, 9μm, 10μm, 12μm, 14μm, 15μm, 17μm or any value between 3.5-17μm.

[0089] In order to prevent the performance of the sintered ternary matrix material from being changed by the outside world, the sintered material is generally stored in a PE bag and sealed with an aluminum plastic film.

[0090] It should be noted that step 1) can also be omitted, and the ternary matrix material can be directly purchased on the market.

[0091] In some embodiments, the solvent in step (2) includes at least one of DMF, tetrahydrofuran, methanol, acetone, and n-hexane. The solvent is mainly used to dissolve the anionic monomer, so that the anion group in the anionic monomer can react with the covalent organic framework.

[0092] In some embodiments, the molar ratio of the two-dimensional covalent organic framework material to the anionic monomer is (0.1-1):(0.5-2), for example, it can be 0.1:0.5, 0.3:0.5, 0.5:1, 0.8:1, 1:1.5 or any value between (0.1-1):(0.5-2), and more preferably 0.5:1.

[0093] In some embodiments, the reaction in step (2) includes stirring under an inert gas atmosphere, and the stirring frequency required is 10-50Hz, for example, it can be 10Hz, 20Hz, 30Hz, 40Hz, 50Hz or any value between 10-50Hz, and more preferably 30Hz.

[0094] In some embodiments, the temperature of the reaction in step (2) is 100-120 °C, for example, it can be 100, 110, 120 or any value between 100-120 °C, and the reaction time is 60-84 h, for example, it can be 60 h, 68 h, 72 h, 80 h, 84 h or any value between 60-84 h.

[0095] In some embodiments, after the reaction is completed, further comprising filtering, washing, and drying to obtain a solid anionic covalent organic framework composite material. It should be noted that when drying, the required temperature is 60-100 °C, and the time is 5-20 h, more preferably 10 h. If the drying temperature is too high or the time is too long, it is easy to affect the performance of the composite material, especially the stability of the conjugated system or anion group in the composite material, thereby causing the disappearance of the electron / ion transmission channel and reducing the electrical conductivity of the material.

[0096] In some embodiments, the mass ratio of the ternary matrix material to the anionic covalent organic framework material in step (3) is (0.9-0.99):(0.1-0.01), for example, it can be 0.9:0.1, 0.93:0.07, 0.95:0.05, 0.97:0.03, 0.99:0.01 or any value between (0.9-0.99):(0.1-0.01), more preferably 0.96:0.04.

[0097] In some embodiments, the two-dimensional covalent organic framework material comprises at least one of aldehyde, catechol, hydroxyarene, alkoxyl compound, amine and hydrazine.

[0098] In some embodiments, the aldehyde includes, but is not limited to, triformylphloroglucinol, 1,3,5-benzene tricarboxaldehyde, triformylphloroglucinol; the hydroxyarene includes 9-10-dimethyl-2,3,6,7-tetrahydroxyanthracene, hexahydroxytriphenylbenzene; the amine includes sulfamic acid, diamino diphenyl dicarboxylic acid, etc.

[0099] In some embodiments, the anionic monomer includes at least one of 1-vinylimidazole, 1-methylimidazole, 2-nitroimidazole, 1-imidazole acetic acid, 4-imidazole, 4-hydroxymethyl imidazole, 1-acetylimidazole, trimethyl borate, triphenyl boron, diphenyl borate, benzene sulfonic acid, sulfamic acid, 2,5-diaminobenzenesulfonic acid, diamino benzene disulfonic acid, and sodium methyl silicate, potassium methyl silicate, ethyl silicate.

[0100] It should be noted that when performing dry coating in step (3), a dry coating machine can be selected to mix and coat the ternary matrix material and the anionic covalent organic framework material particles to obtain a ternary material coated with a first coating layer of anionic covalent organic framework material.

[0101] When coating the first coating layer, no secondary heat treatment is required, which can effectively retain the conjugated system in the covalent organic framework material, so that the efficient electron / ion transmission channel on the surface of the material can be retained, which greatly improves the electronic and lithium ion conductivity of the positive electrode material, thereby significantly enhancing its rate performance and cycle performance.

[0102] In some embodiments, the solution containing the metallic glass in step (4) includes a mixed solution obtained by stirring a metal nitrate, a boron hydride compound, and an organic solvent.

[0103] In some optional embodiments, the metal in the metal nitrate includes at least one of nickel, zinc, cobalt, iron, titanium, tungsten, zirconium, aluminum, magnesium, yttrium and niobium.

[0104] In some optional embodiments, the boron hydride compound includes at least one of NaBH4 and KBH4.

[0105] In some optional embodiments, the organic solvent includes at least one of anhydrous ethanol, ether, methanol, acetone, pentane, and hexane.

[0106] In some optional embodiments, the molar ratio of the metal nitrate, the boron hydride and the organic solvent is (0.08-0.25):(0.5-1):(4-10), for example, it can be 0.08:0.5:4, 0.1:0.5:6, 0.2:0.8:8, 0.25:1:10 or any value between (0.08-0.25):(0.5-1):(4-10), more preferably 0.1:1:6.

[0107] In some embodiments, the wet coating in step (4) includes slowly dropping a solution containing metallic glass into the ternary material and stirring.

[0108] In some optional embodiments, the dripping speed is 0.5L / min-3L / min, for example, it can be 0.5L / min, 1L / min, 1.5L / min, 2L / min, 2.5L / min, 3L / min or any value between 0.5L / min-3L / min, more preferably 1L / min.

[0109] In some embodiments, the wet coating in step (4) is performed in a single cone. Further, after the coating is completed, the coating may be dried in the single cone for 1-4 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, or any value between 1 hour and 4 hours, more preferably 2 hours.

[0110] It should be noted that the process of wet coating is used in step (4) because the coating layer particles of dry coating are too strong, and the metal glass coated by wet coating can effectively fill the voids, completely cover the surface of the secondary particles of the ternary positive electrode material, and in the metal fluid state, it can also be injected between the primary particles of the positive electrode material with a zero balance contact angle.

[0111] The second coating layer metal glass of the present application can be synthesized at room temperature, thereby eliminating the complexity of subsequent high temperature treatment, and the metal glass has excellent oxidation resistance even at high temperatures of about 900℃. Even if the metal glass reacts with oxygen, a dense and healable passivation layer will be formed at the interface. In addition, the metal glass is widely used in metal part coatings to improve its corrosion resistance and wear resistance, so it is not easy to be broken or cracked at the nanoscale, and has good mechanical properties.

[0112] The present application also provides a lithium ion battery, and a preparation method thereof, which comprises: mixing the above-prepared positive electrode material with a conductive agent and a binder in a certain proportion, uniformly adding a solvent to form a uniform slurry, then uniformly coating the slurry on an aluminum foil, vacuum drying to obtain a positive electrode sheet, and then assembling the prepared positive electrode sheet with other components in the battery to obtain a lithium ion battery.

[0113] The embodiments of the present application will be described in detail below with specific examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. The specific conditions are not specified in the examples, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0114] Example 1

[0115] The present application provides a positive electrode material, and a preparation method thereof, which comprises:

[0116] 1) LiOH and ternary material nickel-cobalt-manganese precursor Ni 0.85 Co 0.1 Mn 0.05 (OH)2 are pulverized and ground in a molar ratio of 1.02:1;

[0117] 2) The mixture in step 1) is heated at 2℃ / min in a muffle furnace, and the temperature is increased at 1℃ / min in the range of 500℃-600℃, the sintering temperature is controlled at 750℃, and sintering is performed for 15h;

[0118] 3) The high-nickel ternary positive electrode material after sintering in step 2) is crushed to a particle size of about 12μm, and the crushed material is stored in a PE bag and sealed with an aluminum plastic film;

[0119] 4) Prepare a stirring tank, add 50 g of DMF, then weigh 2 g of γ-cyclodextrin (γ-CD) (organic framework material), 1 g of trimethyl borate, and add them to the stirring tank, stir at 110°C at 30 Hz, after 72 h of reaction, cool, filter, wash, and dry for 10 h to obtain anion-covalent organic framework material particles;

[0120] 5) Prepare a dry coating machine, mix and coat 96 g of high-nickel ternary material in step 3) and 4 g of anion-covalent organic framework material particles in step 4) to obtain coated ternary positive electrode material;

[0121] 6) Prepare a stirring tank, add cobalt nitrate, NaBH4, and anhydrous ethanol in a ratio of 0.1:1:6, and stir vigorously;

[0122] 7) Put the coated ternary material obtained in step 5) into a single cone, slowly add the solution obtained in step 6), stir vigorously again, and dry for 2 h to obtain high-nickel ternary positive electrode material finished product.

[0123] The high-nickel ternary positive electrode material obtained in this example is Li 1.02 Ni 0.85 Co 0.1 Mn 0.05 O2, the first coating layer anion-covalent organic framework material is iCOF, and the second coating layer metallic glass is CoB, which is specifically represented as iCOF-CoB:Li 1.02 Ni 0.85 Co 0.1 Mn 0.05 O2; as Figure 1 shown, the high-nickel ternary positive electrode material is in the form of spherical particles, and the average particle size of the positive electrode active material is 11.04 μm, and the specific surface area is 0.596 m 2 / g.

[0124] Example 2

[0125] The same as example 1, except that in step 6), zirconium nitrate, NaBH4, and anhydrous ethanol are added in a ratio of 0.1:1:6.

[0126] The high-nickel ternary positive electrode material obtained in this example is iCOF-ZrB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; the positive electrode material is in the form of spherical particles, and the specific surface area is 0.584 m 2 / g.

[0127] Example 3

[0128] Same as Example 1, except that in step 6), magnesium nitrate, NaBH4 and anhydrous ethanol are added in a ratio of 0.1:1:6.

[0129] The high nickel ternary cathode material obtained in this embodiment is iCOF-MgB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; The positive electrode material is spherical particles with a specific surface area of ​​0.566m 2 / g.

[0130] Example 4

[0131] Same as Example 1, except that in step 6), titanium nitrate, NaBH4 and anhydrous ethanol are added in a ratio of 0.1:1:6.

[0132] The high nickel ternary cathode material obtained in this embodiment is iCOF-TiB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; The positive electrode material is spherical particles with an average particle size and a specific surface area of ​​0.554m 2 / g.

[0133] Example 5

[0134] Same as Example 1, except that in step 4), 2 g of 9,10-dimethyl-2,3,6,7-tetrahydroxyanthracene and 0.2 g of sodium methyl silicate were taken.

[0135] The high nickel ternary cathode material obtained in this embodiment is iCOF-CoB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; The positive electrode material is spherical particles with a specific surface area of ​​0.633m 2 / g.

[0136] Example 6

[0137] Same as Example 5, except that in step 6), zirconium nitrate, NaBH4 and anhydrous ethanol are added in a ratio of 0.1:1:6.

[0138] The high nickel ternary cathode material obtained in this embodiment is iCOF-ZrB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; The positive electrode material is spherical particles with a specific surface area of ​​0.612m 2 / g.

[0139] Example 7

[0140] The same as example 5, except that: in step 6), magnesium nitrate, NaBH4 and anhydrous ethanol were added in the ratio of 0.1:1:6.

[0141] The high-nickel ternary positive electrode material obtained in this example is iCOF-MgB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; the positive electrode material is spherical particle, and the specific surface area is 0.603 m 2 / g.

[0142] Example 8

[0143] The same as example 5, except that: in step 6), titanium nitrate, NaBH4 and anhydrous ethanol were added in the ratio of 0.1:1:6.

[0144] The high-nickel ternary positive electrode material obtained in this example is iCOF-TiB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; the positive electrode material is spherical particle, and the specific surface area is 0.612 m 2 / g.

[0145] Example 9

[0146] The same as example 1, except that: in step 4), 2g of 1,3,5-triformylphloroglucinol, 0.2g of aminobenzene disulfonic acid were taken.

[0147] The high-nickel ternary positive electrode material obtained in this example is iCOF-CoB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; the positive electrode material is spherical particle, and the specific surface area is 0.678 m 2 / g.

[0148] Example 10

[0149] The same as example 9, except that: in step 6), zirconium nitrate, NaBH4 and anhydrous ethanol were added in the ratio of 0.1:1:6.

[0150] The high-nickel ternary positive electrode material obtained in this example is iCOF-ZrB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; the positive electrode material is spherical particle, and the specific surface area is 0.687 m 2 / g.

[0151] Example 11

[0152] The same as example 9, except that: in step 6), magnesium nitrate, NaBH4 and anhydrous ethanol are added in the ratio of 0.1:1:6.

[0153] The high-nickel ternary positive electrode material obtained in this example is iCOF-MgB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; the positive electrode material is spherical particle, and the specific surface area is 0.661 m 2 / g.

[0154] Example 12

[0155] The same as example 9, except that: in step 6), titanium nitrate, NaBH4 and anhydrous ethanol are added in the ratio of 0.1:1:6.

[0156] The high-nickel ternary positive electrode material obtained in this example is iCOF-TiB:Li 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2; the positive electrode material is spherical particle, and the specific surface area is 0.692 m 2 / g.

[0157] Comparative Example 1

[0158] The same as example 1, except that: after drying in step 7), the obtained solid is calcined in oxygen atmosphere at 500°C for 6h, and after the reaction is completed, the high-nickel positive electrode ternary material is obtained, and the specific surface area is 0.452 m 2 / g.

[0159] Comparative Example 2

[0160] The same as example 1, except that: in step 4), only 2g of flexible γ-cyclodextrin (γ-CD) is weighed in DMF and added to the stirring tank, and stirring is carried out at 110°C and 30Hz for 10h to obtain the covalent organic framework material, and the specific surface area is 0.503 m 2 / g.

[0161] Comparative Example 3

[0162] The same as example 1, except that: after the end of step 5), the ternary positive electrode material finished product is directly obtained, and the specific surface area is 3.503 m 2 / g.

[0163] Comparative Example 4

[0164] The same as Example 1, except that: in step 6), 2 g of cobalt oxide particles were continuously added for dry coating in a dry coating machine, to obtain a high-nickel ternary positive electrode material product, and the specific surface area was 2.398 m 2 / g.

[0165] Test method:

[0166] Particle size test:

[0167] A Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK was used.

[0168] Test method for observing the micro-morphology of the powder particles of the positive electrode material:

[0169] A Tecnai G2 F20 high-resolution scanning electron microscope (HRSEM) was used to observe the surface morphology of the material.

[0170] Specific surface area test:

[0171] The nitrogen adsorption specific surface area analysis test was performed using a Tri Star II specific surface and pore analyzer from Micromeritics, USA, and the BET (Brunauer Emmett Teller) method was used for calculation.

[0172] Test method for residual alkali:

[0173] A certain amount of positive electrode material was dispersed in deionized water, stirred and dispersed for a certain time (more than 30 minutes), then filtered to obtain the supernatant, and acid-base titration was performed using a calibrated dilute hydrochloric acid, with phenolphthalein and methyl orange as indicators for the titration end point, to obtain two titration end points, and the contents of LiOH and Li2CO3 (or LiHCO3) and the total residual alkali content were calculated. The positive electrode material products in Example 1, Comparative Example 1 and Comparative Example 2 were tested for carbonate content, and the test results are shown in Table 1.

[0174] The prepared positive electrode material was evaluated for electrochemical performance using a button-type half-cell, and the specific method was as follows: the positive electrode active material, SP and polyvinylidene fluoride (PVDF) were weighed according to a mass ratio of 8:1:1, added with N-methyl pyrrolidone at a solid content of 50%, and adjusted into a viscous slurry using a high-speed dispersing machine, and then uniformly coated on an aluminum foil, baked in an 80°C oven, rolled, and cut into positive electrode sheets with a diameter of 14 mm. A lithium sheet with a diameter of 16 mm was used as the negative electrode sheet, a Celgard polyethylene PP film was used as the separator, and a solution of LiPF6 with a concentration of 1 mol / L in carbonate (DEC / EC volume ratio 1:1) was used as the electrolyte, and the assembly was performed in an argon-filled glove box.

[0175] The discharge capacity, first circle charge-discharge efficiency performance test was carried out at 25℃, 3.0V-4.3V by using LAND battery test system, the reference capacity was set to 200mA / g, 1C corresponding current density was 200mA / g. The test results are shown in Table 2.

[0176] Table 1

[0177] Finished carbonate content (ppm) Example 1 3780 Comparative Example 1 6010 Comparative Example 2 5401

[0178] According to the results in Table 1, it can be found that: the comparative example 1 is a ternary positive electrode material prepared by secondary sintering in an oxygen atmosphere, the surface of the positive electrode material prepared by this method has a higher lithium carbonate relative to example 1, because the organic polymer material in the coating layer will react with lithium again at high temperature to generate lithium carbonate. Comparative example 2 only uses covalent organic framework for modification, and there are not enough acidic groups to convert the surface lithium hydroxide and lithium carbonate, only the method of physical covering is used, so that the surface residual alkali is still high.

[0179] The positive electrode materials of examples 1-12 and comparative examples 1-4 above were made into batteries with the same specifications, and the batteries were subjected to electrochemical performance test, and the test results of the batteries prepared by examples 1-12 and comparative examples 1-4 under different test conditions are listed in Table 2. Figure 2 The capacity retention rate curve of the battery prepared by example 1 and comparative example 1 after 50 cycles is given.

[0180] Table 2

[0181]

[0182]

[0183] According to the results in Table 2, it can be found that: the metal glass coating layer formed by selecting different metal elements and the anion type covalent organic framework composite coating layer prepared by selecting different raw materials in examples 1-12 have little effect on the electrochemical performance of the battery. However, in comparative example 1, the secondary sintering will destroy the organic framework structure of the surface coating layer (the specific surface area decreases obviously), which causes the structure stability of the positive electrode material to decrease, so that the cycle retention rate is lower than that of example 1; in comparative example 2, the absence of anion monomers causes the lithium ion surface transmission performance to decrease significantly, the ion transmission channel is missing, and the discharge capacity decreases obviously, which is 5.8mAh / g lower than that of example 1; in comparative example 3, the surface is coated only by anion type covalent organic framework composite, so the specific surface area of the material increases significantly (reaches 3.503m 2 / g), so that the contact area with the electrolyte is increased, and after a long cycle process, the surface structure is more obviously damaged, the side reaction increases, so that the cycle is significantly reduced; Comparative Example 4 is to use metal oxide to replace metal glass to modify high-nickel ternary material, but this method is compared with Comparative Example 3, and the specific surface of the material is not significantly reduced to (2.398 m 2 / g), because the metal oxide particles cannot fill the gap of the ion-covalent organic framework layer, so that the surface coating is loose, and the surface structure is damaged in the multiple cycle process, so that the cycle performance continues to decline (90.1%), close to the level of Comparative Example 3.

[0184] Finally, it should be pointed out that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0185] In addition, those skilled in the art can understand that although some embodiments herein include certain features included in other embodiments rather than other features, the combination of features of different embodiments means to be within the scope of the present application and forms different embodiments. For example, in the above claims, any one of the claimed embodiments can be used in any combination. The information disclosed in the background section is only intended to deepen the understanding of the overall background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A positive electrode material, characterized in that It comprises a ternary base material and a coating layer at least partially located on the surface of the ternary base material; The coating layer includes a first coating layer and a second coating layer at least partially located on the surface of the first coating layer, the first coating layer includes an anionic covalent organic framework material, and the second coating layer includes metallic glass; The anionic covalent organic framework material includes a covalent organic framework material containing an anionic group, and the anionic group includes at least one of an acidic group and an imidazole group.

2. The positive electrode material according to claim 1, wherein The chemical formula of the ternary matrix material is Li a Ni x Co y M z O2, wherein 0.95≤a≤1.1, 0.7≤x<1, 0<y+z≤0.3, x+y+z =1, and M includes at least one of Mn and Al.

3. The positive electrode material according to claim 1, wherein The anionic covalent organic framework material includes a covalent organic framework material containing anionic groups, wherein the anionic groups include acidic groups, and the acidic groups include at least one of sulfonic acid groups, carboxylic acid groups, and silicic acid groups.

4. The positive electrode material according to claim 1, wherein The metallic glass includes a composite of metal and boron.

5. The positive electrode material according to claim 4, characterized in that The metal includes at least one of nickel, zinc, cobalt, iron, titanium, tungsten, zirconium, aluminum, magnesium, yttrium, and niobium.

6. The positive electrode material according to any one of claims 1 to 5, characterized in that Satisfy at least one of the following characteristics ad: a. The positive electrode material is a spherical granular material; b. The particle size of the positive electrode material is 3.5 μm-17 μm; c. The specific surface area of ​​the positive electrode material is 0.2m 2 / g-0.7m 2 / g; d. I of the positive electrode material 003 / I 004 The peak intensity ratio is 0.9-1.

1.

7. A method for preparing the positive electrode material according to any one of claims 1 to 6, characterized in that: include: dry-coating a ternary matrix material with an anionic covalent organic framework material to obtain a ternary material having a first coating layer coated on the surface of the ternary matrix material, wherein the first coating layer includes the anionic covalent organic framework material; The solution containing the prepared metallic glass is wet-coated with the ternary material to obtain the positive electrode material having a second coating layer coated on the surface of the ternary material, wherein the second coating layer includes metallic glass.

8. The method for preparing the positive electrode material according to claim 7, wherein: Satisfy at least one of the following characteristics ab: a. mixing the ternary precursor and the lithium source and sintering to obtain the ternary matrix material; b. mixing and reacting a two-dimensional covalent organic framework material, a solvent and an anionic monomer to obtain the anionic covalent organic framework composite material.

9. The method for preparing the positive electrode material according to claim 8, wherein: The ternary precursor includes Ni x Co y M z oxides or hydroxides, wherein 0.7≤x<1, 0<y+z≤0.3, x+y+z =1, and M includes at least one of Mn and Al.

10. The method for preparing the positive electrode material according to claim 8, wherein: The lithium source includes at least one of lithium hydroxide and lithium carbonate.

11. The method for preparing the positive electrode material according to claim 8, wherein: The ratio of the total molar content of Ni, Co, and M in the ternary precursor to the molar content of the Li element in the lithium source is 1:(0.95-1.1).

12. The method for preparing the positive electrode material according to claim 8, wherein: The sintering is carried out in an oxygen atmosphere, and the oxygen content in the oxygen atmosphere is ≥95%.

13. The method for preparing the positive electrode material according to claim 8, wherein: The sintering temperature is 600° C.-950° C., the sintering time is 8 h-20 h, and the heating rate in the range of 450° C.-650° C. is 0.5° C. / min-3° C. / min.

14. The method for preparing the positive electrode material according to claim 8, wherein: After the sintering, the method further comprises: crushing the ternary matrix material to obtain particles with a particle size of 3.5 μm-17 μm.

15. The method for preparing the positive electrode material according to claim 8, wherein: The molar ratio of the two-dimensional covalent organic framework material to the anionic monomer is (0.1-1): (0.5-2).

16. The method for preparing the positive electrode material according to claim 8, wherein: The two-dimensional covalent organic framework material includes at least one of hydroxyaromatic hydrocarbons, alkoxy compounds, amines and hydrazines.

17. The method for preparing the positive electrode material according to claim 8, wherein: The two-dimensional covalent organic framework material includes at least one of trimesaldehyde, trialdehyde phloroglucinol, 9-10-dimethyl-2,3,6,7-tetrahydroxyanthracene, hexahydroxytriphenylenebenzene, and diaminobiphenyl dicarboxylic acid.

18. The method for preparing the positive electrode material according to claim 8, wherein: The anionic monomer includes at least one of 1-vinylimidazole, 1-methylimidazole, 2-nitroimidazole, 1-imidazoleacetic acid, 4-imidazole, 4-hydroxymethylimidazole, 1-acetylimidazole, trimethyl borate, triphenylboron, diphenylboric acid, benzenesulfonic acid, aminosulfonic acid, 2,5-diaminobenzenesulfonic acid, diaminobenzenedisulfonic acid and sodium methyl silicate, potassium methyl silicate and ethyl silicate.

19. The method for preparing the positive electrode material according to claim 8, wherein: The solvent includes at least one of DMF, tetrahydrofuran, methanol, acetone, and n-hexane.

20. The method for preparing the positive electrode material according to claim 8, wherein: The reaction comprises stirring under an inert gas atmosphere, and the stirring frequency is 10 Hz to 50 Hz.

21. The method for preparing the positive electrode material according to claim 8, wherein: The reaction temperature is 100° C.-120° C., and the reaction time is 60 h-84 h.

22. The method for preparing the positive electrode material according to claim 8, wherein: After the reaction, the process further includes filtering, washing and drying. The drying temperature is 60° C.-100° C. and the drying time is 5 h-20 h.

23. The method for preparing the positive electrode material according to claim 7, wherein: The solution containing the metal glass comprises a mixed solution obtained by stirring metal nitrate, boron hydride and an organic solvent.

24. The method for preparing the positive electrode material according to claim 23, wherein: The metal in the metal nitrate includes at least one of nickel, zinc, cobalt, iron, titanium, tungsten, zirconium, aluminum, magnesium, yttrium and niobium.

25. The method for preparing the positive electrode material according to claim 23, wherein: The boron hydride compound includes at least one of NaBH4 and KBH4.

26. The method for preparing the positive electrode material according to claim 23, wherein: The organic solvent includes at least one of anhydrous ethanol, ether, methanol, acetone, pentane, and hexane.

27. The method for preparing the positive electrode material according to claim 23, wherein: The molar ratio of the metal nitrate, the boron hydride compound and the organic solvent is (0.08-0.25): (0.5-1): (4-10).

28. The method for preparing the positive electrode material according to claim 7, wherein: Satisfy at least one of the following characteristics ad: a. The wet coating comprises: slowly adding the solution containing the prepared metallic glass dropwise to the ternary material and stirring; b. The dropping rate is 0.5L / min-3L / min; c. The wet coating is carried out in a single cone; d. After the wet coating is completed, it is necessary to dry it for 1h-4h.

29. The method for preparing a positive electrode material according to any one of claims 7 to 28, wherein: The mass ratio of the ternary matrix material to the anionic covalent organic framework material is (0.9-0.99): (0.1-0.01); And / or, the chemical formula of the ternary matrix material is Li a Ni x Co y M z O2, wherein 0.95≤a≤1.1, 0.7≤x<1, 0<y+z≤0.3, x+y+z =1, and M includes at least one of Mn and Al.

30. A lithium ion battery, characterized in that: The lithium-ion battery comprises the positive electrode material according to any one of claims 1 to 6, or the positive electrode material prepared by the preparation method according to any one of claims 7 to 29.

Images