A positive electrode lithium supplement material, preparation method and application thereof

Abstract

The present invention provides a positive electrode lithium replenishing material, a preparation method, and its application. The positive electrode lithium replenishing material includes a positive electrode lithium replenishing agent and a hydrophobic layer coated on the surface of the positive electrode lithium replenishing agent; the positive electrode lithium replenishing agent is Li2NiO2 and / or Li5FeO4; the hydrophobic layer is a continuous phase formed by uniformly mixing inorganic carbon and a small molecule organic substance having a hydrophobic group; wherein the hydrophobic group is selected from one or more of a hydrocarbon group, an ester group, and a polyoxyalkylene group. The present invention coats the surface of the positive electrode lithium replenishing agent with a continuous phase formed by uniformly mixing inorganic carbon and a small molecule organic substance having a hydrophobic group as a hydrophobic layer, and utilizes the hydrophobic property of the hydrophobic group to weaken the alkalinity, thereby improving the hydrophobic property and air stability of the positive electrode lithium replenishing material.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a positive electrode lithium supplement material, a preparation method and an application thereof. Background Art

[0002] Lithium-ion batteries are widely used in consumer electronics, new energy passenger vehicles, and large-scale power station energy storage due to their high energy density, environmental friendliness, and long service life. During the initial charge and discharge phase of a lithium-ion battery, the organic electrolyte forms a solid electrolyte interface (SEI) composed primarily of lithium salts at the interface of the negative electrode material. The formation of the SEI film is an irreversible process that permanently consumes a large amount of active lithium from the positive electrode, resulting in a low coulombic efficiency (ICE) in the first cycle and reducing the capacity and energy density of the lithium-ion battery.

[0003] To address the aforementioned issue of active lithium depletion, researchers conducted a systematic analysis of "pre-lithiation" technology. The main mechanism of "pre-lithiation" (also known as "pre-lithiation" or "lithium replenishment technology") is to add additional active lithium to the lithium-ion battery before operation to replenish the consumed lithium ions. Pre-lithiation replenishes the electrode material with lithium, offsetting the irreversible lithium loss caused by the formation of the SEI film to ensure the battery's total capacity and energy density. Pre-lithiation technologies include negative electrode lithium replenishment, positive electrode lithium replenishment, and separator lithium replenishment. Negative electrode lithium replenishment methods include lithium foil replenishment, lithium powder replenishment, lithium silicide powder replenishment, and lithium salt solution replenishment. However, because metallic lithium is a highly reactive alkali metal that reacts violently with water, it has very high requirements for the production and use environment. Furthermore, it is incompatible with conventional solvents, binders, and heat treatment processes. Consequently, both negative electrode lithium replenishment processes require significant investment in production line and equipment modifications, resulting in negative electrode lithium replenishment still being limited by technical challenges in battery manufacturing. Compared to the complex and costly process of replenishing negative electrode lithium, replenishing positive electrode lithium is much simpler. A typical positive electrode replenishment process involves adding a small amount of a high-capacity lithium replenishing additive to the positive electrode during homogenization. During charging, excess lithium is released from these high-capacity positive electrode materials and embedded in the negative electrode to replenish the irreversible capacity of the initial charge and discharge. Positive electrode replenishment holds the greatest promise for industrial application due to its high safety and the fact that it does not require changes to existing battery production processes.

[0004] A perfect positive electrode lithium replenishment material needs to meet four basic requirements: 1) The delithiation potential is lower than the upper voltage limit of the positive electrode material, and the lithium insertion potential is lower than the lower voltage limit of the positive electrode material, that is, the additive needs to irreversibly delithiate within the battery operating voltage; 2) The lithium replenishment material should have a high specific capacity and volume energy density to ensure efficient pre-lithiation; 3) The lithium replenishment material should be compatible with the current common manufacturing process and battery system, that is, the lithium replenishment material and its decomposition products need to be stable in traditional electrolytes and will not cause the performance of lithium-ion batteries to deteriorate; 4) The lithium replenishment material has good environmental stability, that is, it needs to remain stable in air or a relatively dry environment. At present, the positive electrode lithium supplement materials include lithium-rich compounds, nanocomposites based on conversion reactions and binary lithium compounds, mainly Li2NiO2, Li5FeO4, Li2MnO3, Li6CoO4, Li6MnO4, Li5ReO6, nanocomposites of Co and lithium salts (such as Li2S / Co, LiF / Co and Li2O / Co), etc. Among them, Li2NiO2 and Li5FeO4 are very ideal lithium supplement additives for lithium ion positive electrode materials, which can theoretically provide 2 and 5 Li per mole respectively. + The specific capacity can be as high as 486mAh / g and 867mAh / g. By mixing a certain amount of lithium-supplementing materials into traditional positive electrode materials, the initial efficiency and energy density of lithium-ion batteries can be significantly improved.

[0005] Patent CN109301242A discloses a method for preparing Li5FeO4, a lithium-ion battery cathode lithium-supplementing material. The method comprises: first, mixing a lithium source compound, an iron source compound, a chelating agent, and a solvent as raw materials to produce a sol; then, drying the sol to produce a xerogel; then, ball-milling the xerogel to produce a powder; and then, under inert gas protection, pre-treating the powder at a low temperature, grinding it, heating it to a high temperature, and sintering it to produce the lithium-ion battery cathode lithium-supplementing material Li5FeO4. However, the Li5FeO4 material produced by this method suffers from uncontrollable residual alkali content and hygroscopicity on its surface, which compromises battery safety. In the prior art, both Li2NiO2 and Li5FeO4 are synthesized under a protective atmosphere and stored in a vacuum or inert atmosphere because these two cathode lithium-supplementing materials are unstable in air. Li2NiO2 and Li5FeO4 have high alkalinity, corrosiveness and strong water absorption, which leads to a strong agglomeration effect between the material particles, resulting in a certain degree of "jelly-like" problem of the slurry during use and extremely easy oxidation; in addition, the pre-lithiation process may produce gas. If the reaction is incomplete, the battery will swell in subsequent cycles, affecting the safety performance of the battery.

[0006] Therefore, the moisture content of the material must be strictly controlled during use. Once water is absorbed, a large amount of residual alkali will be generated and the device will be lost. When the moisture content in the battery electrode is high (over 600ppm), more moisture will diffuse into the electrolyte, reacting with the lithium salt in the electrolyte to generate highly corrosive HF, which will destroy the structure of the lithium-ion battery and cause the battery capacity to decay; especially during the charge and discharge process, the higher the HF content, the faster the battery decays. Therefore, the presence of high moisture content in the battery not only causes the decomposition of lithium salts in the electrolyte, and has a certain corrosive effect on the positive and negative electrode materials and current collectors, but also leads to reduced cycle performance and safety performance of the battery. For this reason, controlling the moisture content of the positive electrode lithium supplement material is an important technical barrier in its commercial application. Summary of the Invention

[0007] In view of the shortcomings and defects of the existing technology, the present invention aims to provide a positive electrode lithium replenishment material, preparation method and application thereof. The present invention coats the surface of the positive electrode lithium replenishment agent (Li2NiO2 and / or Li5FeO4) with a continuous phase formed by uniformly mixing inorganic carbon and small molecule organic matter with hydrophobic groups as a hydrophobic layer, and uses the hydrophobic property of the hydrophobic group to weaken the alkalinity, thereby improving the hydrophobic property and air stability of the positive electrode lithium replenishment material; the present invention uses surfactants to attach to the material to induce porous sites, and prepares a high-purity and porous solid-phase precursor according to the stoichiometric ratio through the sol-gel method. The liquid phase reaction system is homogeneous and the reaction is more sufficient. The synthesized material has a small and uniform particle size, and then undergoes nucleation and crystallization through high-temperature sintering. The material is then crushed to obtain a nano- or micron-sized positive electrode lithium replenisher (particle size of 0.2-5 μm), with no obvious agglomeration within this particle size range. Finally, the positive electrode lithium replenisher is dispersed in an organic solvent containing hydrophobic organic matter. The hydrophobic organic matter is subjected to spray pyrolysis treatment, which allows the hydrophobic organic matter to be pyrolyzed but not completely carbonized, so that the continuous phase formed by the uniform mixing of inorganic carbon and small molecular organic matter with hydrophobic groups is coated on the surface of the positive electrode lithium replenisher in the form of a hydrophobic layer, thereby obtaining a positive electrode lithium replenisher material.

[0008] The positive electrode lithium replenishing material prepared by the present invention not only has a porous structure, which is conducive to increasing the contact area between the material and the electrolyte, effectively shortening the migration path of electrons and lithium ions, and can fully exert the lithium replenishing performance of the material and extend the service life of the lithium ion battery; and the hydrophobic layer coated on the surface can not only maintain the structural stability of the material, but also weaken the alkalinity and improve the air stability of the material, thereby improving its comprehensive performance; in addition, the positive electrode lithium replenishing material prepared by the present invention has a small and uniform particle size, and is added to the positive electrode active material during homogenization to prepare the positive electrode sheet, which is conducive to improving the capacity and first coulomb efficiency of the positive electrode active material.

[0009] In order to achieve the above objectives, the first aspect of the present invention provides a positive electrode lithium supplement material, which adopts the following technical solution:

[0010] A positive electrode lithium replenishing material, comprising: a positive electrode lithium replenishing agent and a hydrophobic layer coated on the surface of the positive electrode lithium replenishing agent; the positive electrode lithium replenishing agent is Li2NiO2 and / or Li5FeO4;

[0011] The hydrophobic layer is a continuous phase formed by a uniform mixture of inorganic carbon and small molecule organic matter with hydrophobic groups;

[0012] Wherein, the hydrophobic group is selected from one or more of hydrocarbon groups, ester groups, and polyoxyalkylene groups.

[0013] In the above-mentioned positive electrode lithium replenishing material, as a preferred embodiment, the hydrophobic layer is made of hydrophobic organic matter as a raw material and is coated on the surface of the positive electrode lithium replenishing agent through spray pyrolysis treatment; the hydrophobic organic matter is selected from one or more of polyvinylidene fluoride (PVDF), polyoxyolefin copolymer, cholesterol dodecyl carbonate (cholesterol lauryl carbonate), methacrylate, and polydiene; the polyoxyolefin copolymer is preferably one or two of methyl allyl polyoxyethylene polyoxypropylene ether and allyl polyethylene glycol.

[0014] In the above-mentioned positive electrode lithium supplement material, as a preferred embodiment, the hydrophobic organic substance is preferably a copolymer of polyvinylidene fluoride and polyoxyolefin.

[0015] In the above-mentioned positive electrode lithium supplement material, as a preferred embodiment, the hydrophobic organic matter is preferably polyvinylidene fluoride and cholesterol dodecyl carbonate.

[0016] In the present invention, hydrophobic organic matter is subjected to spray pyrolysis treatment in a spray dryer. By controlling the conditions of the spray pyrolysis treatment, the hydrophobic organic matter can be pyrolyzed but not completely carbonized. At this time, the continuous phase formed by the uniform mixing of inorganic carbon and small molecular organic matter with hydrophobic groups will be coated on the surface of the positive electrode lithium replenisher in the form of a hydrophobic layer, thereby obtaining a positive electrode lithium replenisher material. Among them, the inorganic carbon can increase the conductivity of the positive electrode lithium replenisher material and reduce the impedance; the hydrophobicity of the hydrophobic group can weaken the alkalinity, thereby improving the hydrophobic performance and air stability of the positive electrode lithium replenisher material.

[0017] The hydrophobic organic matter is selected from organic matters having hydrophobic groups such as hydrocarbon groups, ester groups, and polyoxyalkylene groups, including: one or more of polyvinylidene fluoride (PVDF), polyoxyalkylene copolymers, cholesterol dodecyl carbonate (cholesterol lauryl carbonate), methacrylate, and polydiene compounds; in particular, when the above-mentioned specific PVDF and polyoxyalkylene copolymers and PVDF and cholesterol dodecyl carbonate are selected as the hydrophobic organic matter, the prepared positive electrode lithium replenishing material has excellent hydrophobic properties, with a saturated water absorption of <500ppm, achieving a positive electrode lithium replenishing material with ppm-level hydrophobicity. The main reason is that in addition to having hydrophobic groups, PVDF can also act as a chelating agent to enhance the bonding performance between the polyoxyalkylene copolymer or cholesterol dodecyl carbonate and the positive electrode lithium replenishing material.

[0018] In the above-mentioned positive electrode lithium replenishing material, as a preferred embodiment, the particle size of the positive electrode lithium replenishing material is 0.2-5μm (such as 0.25μm, 0.28μm, 0.3μm, 0.35μm, 0.4μm, 0.45μm), and the thickness of the hydrophobic layer is 3-8nm (such as 4nm, 5nm, 6nm, 7nm).

[0019] In the present invention, the particle size of the positive electrode lithium replenishing material is limited to 0.2-5μm. Within this particle size range, it is added to the positive electrode active material during homogenization to prepare the positive electrode plate, which is beneficial to improving the capacity and first coulombic efficiency of the positive electrode active material; if the particle size of the positive electrode lithium replenishing material is too large, there will be no small particles filling in the large particles, the porosity is large, resulting in a low tap density of the material and a short lithium ion diffusion distance, thereby reducing the first coulombic efficiency and energy density of the battery; if the particle size of the positive electrode lithium replenishing material is too small, due to its high surface energy, the particles are easy to agglomerate, causing unevenness when mixed with the positive electrode active material, and side reactions are easy to occur on the surface, thereby reducing the capacity and first coulombic efficiency of the battery.

[0020] In the above-mentioned positive electrode lithium replenishing material, as a preferred embodiment, the porosity of the positive electrode lithium replenishing material is 12%-28% (such as 15%, 17%, 19%, 20%, 22%, 25%, 27%).

[0021] The porosity of the positive electrode lithium replenishing material in the present invention is limited to 12%-28%. Within this range, it is beneficial to increase the contact area between the material and the electrolyte, effectively shorten the migration path of electrons and lithium ions, and fully utilize the lithium replenishing performance of the material, thereby extending the service life of the lithium-ion battery.

[0022] A second aspect of the present invention provides a method for preparing the above-mentioned positive electrode lithium supplement material, comprising:

[0023] (1) First, a surfactant is dissolved in a solvent to obtain a surfactant solution, and then a lithium source and an M-containing compound are added, followed by stirring until the solvent evaporates, and then grinding to obtain a solid-phase precursor;

[0024] (2) sintering the solid-phase precursor obtained in step (1) under an inert gas, cooling it, and then crushing it to obtain a positive electrode lithium supplement;

[0025] (3) dissolving the hydrophobic organic matter in an organic solvent, adding the positive electrode lithium replenishing agent obtained in step (2), and then performing spray pyrolysis treatment to obtain a positive electrode lithium replenishing material.

[0026] In the present invention, a lithium source and an M-containing compound are first added to a surfactant solution, stirred to completely evaporate the solvent, and then ground to obtain a solid-phase precursor. The surfactant can enhance the surface activation energy of the material, thereby inducing ion bonding in the liquid phase system to obtain a high-purity and porous solid-phase precursor. The liquid phase reaction system has the advantages of homogeneity and more complete reaction. The solid-phase precursor is then sintered and crushed to obtain a positive electrode lithium supplement. During the sintering process, the solid-phase precursor undergoes nucleation and crystallization under an inert gas to grow into primary particles, which are then crushed. The secondary agglomerates are dispersed uniformly to obtain a nano- or micron-sized positive electrode lithium replenisher (particle size of 0.2-5 μm), and within this particle size range, the positive electrode lithium replenisher has no obvious agglomeration phenomenon; finally, the positive electrode lithium replenisher is dispersed in an organic solvent containing hydrophobic organic matter, and subjected to spray pyrolysis treatment to pyrolyze the hydrophobic organic matter but not completely carbonize it, so that a continuous phase formed by a uniform mixture of inorganic carbon and small molecular organic matter with hydrophobic groups is coated on the surface of the positive electrode lithium replenisher in the form of a hydrophobic layer, thereby obtaining a positive electrode lithium replenisher material, thereby improving the hydrophobic properties and air stability of the positive electrode lithium replenisher material.

[0027] In the above preparation method, as a preferred embodiment, in step (1), the surfactant is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, cetyltrimethylammonium bromide, polyvinylpyrrolidone, ethylene glycol, polyethylene glycol and oleylamine; preferably, the solvent is deionized water; preferably, in the surfactant solution, the molar concentration of the surfactant is 0.01-0.5 mol / L (such as 0.02 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L); preferably, the mass of the surfactant is 0.5-5% (such as 0.8%, 1%, 2%, 3%, 4%, 4.5%) of the mass of the M-containing compound.

[0028] In the present invention, surfactants are used to form porous sites on the material, thereby preparing a positive electrode lithium replenishing material with a porous structure. The porous structure is conducive to increasing the contact area between the material and the electrolyte, effectively shortening the migration path of electrons and lithium ions, and can fully realize the lithium replenishing performance of the material and extend the service life of the lithium-ion battery.

[0029] In the above preparation method, as a preferred embodiment, in step (1), the lithium source is selected from one or more of lithium carbonate, lithium hydroxide, lithium metaborate, lithium molybdate, lithium sulfate, lithium tetrafluoroborate, lithium phosphate, lithium tetrachlorocuprate, lithium tetraborate, lithium oxalate, lithium acetate, lithium nitrate, lithium chloride, lithium fluoride, lithium chromate, and lithium trifluoromethanesulfonate; preferably, the lithium source is selected from one or more of lithium carbonate, lithium nitrate, lithium oxalate, lithium acetate, and lithium hydroxide.

[0030] In the above preparation method, as a preferred embodiment, in step (1), the M-containing compound is selected from an iron-containing compound and / or a nickel-containing compound; preferably, the iron-containing compound is selected from one or more of ferric oxide, ferrous sulfate, ferrous chloride, ferric phosphate, ferrous nitrate, ferrous oxalate, ferric citrate and ferric hydroxide; preferably, one or more of ferric oxide, ferric nitrate, ferric phosphate, ferrous oxalate and ferrous chloride;

[0031] Preferably, the nickel-containing compound is selected from one or more of nickelous oxide, nickel trioxide, nickel hydroxide, nickel hydroxide (Ni(OH)3), nickel carbonate, nickel nitrate, nickel oxalate, nickel acetate, nickel fluoride, nickel chloride, nickel bromide, nickel sulfate, nickel bis(hexafluoroethylacetone), nickel sulfamate, basic nickel carbonate, nickel acetylacetonate dihydrate, nickel trifluoromethanesulfonate, nickel benzenesulfonate, nickel acetylacetonate, and nickel fluoroborate; preferably, it is one or more of nickelous oxide, nickel trioxide, nickel hydroxide, nickel hydroxide, nickel oxalate, nickel carbonate, nickel acetate, and nickel nitrate; preferably, the molar ratio of the lithium element in the lithium source to the M element in the M-containing compound is 2-5:1 (e.g., 2.5:1, 3:1, 4:1, 4.5:1).

[0032] In the above preparation method, as a preferred embodiment, in step (1), the stirring treatment temperature is 120-180°C (such as 130°C, 140°C, 150°C, 160°C, 170°C).

[0033] In the above preparation method, as a preferred embodiment, in step (2), the conditions of the sintering treatment are: heating to 350°C-650°C (such as 380°C, 400°C, 450°C, 500°C, 550°C, 600°C, 620°C) at a heating rate of 5°C / min-20°C / min (such as 6°C / min, 8°C / min, 10°C / min, 15°C / min, 18°C / min), and keeping warm for 6-18h (such as 8h, 10h, 12h, 15h); the inert gas is nitrogen, argon or helium.

[0034] The present invention limits the temperature of the sintering treatment in step (2) to 350°C-650°C, which is conducive to the nucleation and crystallization of Li2NiO2 and / or Li5FeO4 materials within this temperature range; if the sintering temperature is too low, it will lead to incomplete crystallization of the material, produce more impurities, and thus affect the integrity of the material crystal structure, increasing the resistance to lithium ion escape; if the sintering temperature is too high, it will cause the particles to continue to grow, and the material particle size is too large, so that there will be no small particles filling in the large particles, and the porosity is large, resulting in a low tap density of the material and a short lithium ion diffusion distance, thereby reducing the first coulombic efficiency and energy density of the battery.

[0035] In the above preparation method, as a preferred embodiment, in step (2), the particle size of the positive electrode lithium supplement obtained by pulverization is 0.2-5 μm (such as 0.25 μm, 0.28 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm).

[0036] The present invention obtains primary particles with a particle size of 0.2-5 μm through high-temperature crystal growth, and the main function of the pulverization process is to disperse the secondary agglomerates uniformly.

[0037] In the above preparation method, as a preferred embodiment, in step (3), the hydrophobic organic matter is selected from one or more of polyvinylidene fluoride (PVDF), polyoxyolefin copolymers, cholesterol dodecyl carbonate (cholesterol lauryl carbonate), methacrylate, and polydiene; the polyoxyolefin copolymer is selected from one or two of methyl allyl polyoxyethylene polyoxypropylene ether and allyl polyethylene glycol.

[0038] Preferably, the organic solvent is selected from one of ethanol, methanol and acetone; preferably, the mass of the hydrophobic organic matter is 0.5-2% (such as 0.6%, 0.7%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%) of the mass of the positive electrode lithium replenisher; preferably, the mass ratio of the organic solvent to the positive electrode lithium replenisher is 5-9:1-5 (such as 6:2, 6:3, 6:4, 7:2, 7:3, 7:4, 8:3).

[0039] In the present invention, the mass of the hydrophobic organic matter is limited to 0.5-2% of the mass of the positive electrode lithium replenisher. Within this range, it is beneficial to obtain a hydrophobic layer with a thickness of 3-8 nm. If the mass of the added hydrophobic organic matter is too low, the hydrophobic performance of the positive electrode lithium replenisher will not be improved effectively. If the mass of the added hydrophobic organic matter is too high, the lithium ion intercalation and deintercalation of the positive electrode lithium replenisher will be hindered, the conductive performance will be reduced, and excessive organic matter remaining on the surface of the positive electrode lithium replenisher will cause gas production in the battery system, which is not conducive to the safety performance of the battery.

[0040] In the above preparation method, as a preferred embodiment, in step (3), the spray pyrolysis treatment is carried out in a spray dryer under compressed air or inert atmosphere at a temperature of 180-260°C (e.g., 185°C, 190°C, 200°C, 210°C, 230°C, 240°C, 250°C).

[0041] In the present invention, the temperature of the spray pyrolysis treatment is limited to 180-260°C. At this temperature, the hydrophobic organic matter can be pyrolyzed but not completely carbonized, thereby forming a continuous phase formed by a uniform mixture of inorganic carbon and small molecular organic matter with hydrophobic groups; if the temperature of the spray pyrolysis treatment is too low, the organic solvent will not be completely volatilized, and the organic solvent will remain on the surface of the material, thereby affecting its conductive properties and being detrimental to the safety performance of the battery; if the temperature of the spray pyrolysis treatment is too high, the hydrophobic organic matter will be excessively carbonized and the hydrophobic groups will be excessively decomposed, thereby making the hydrophobic performance of the material poor.

[0042] The third aspect of the present invention provides a positive electrode material, comprising: a positive electrode active material and the above-mentioned positive electrode lithium replenishing material or the positive electrode lithium replenishing material prepared by the above-mentioned preparation method; preferably, the positive electrode active material comprises lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based positive electrode material; preferably, the mass of the positive electrode lithium replenishing material is 0.5%-5% (for example, 1%, 2%, 3%, 4%, 4.5%) of the mass of the positive electrode active material.

[0043] A fourth aspect of the present invention provides a use of the above-mentioned positive electrode material in a lithium-ion battery.

[0044] Compared with the prior art, the present invention has the following advantages:

[0045] (1) The present invention prepares a high-purity and porous positive electrode lithium supplement (particle size of 0.2-5 μm) by a sol-gel method. The liquid phase reaction system is homogeneous and the reaction is more complete. The synthesized material has a small and uniform particle size, which is conducive to the material's gram capacity.

[0046] (2) The present invention utilizes surface activity to attach to the material to induce porous sites, thereby improving the contact between the material and the electrolyte, effectively shortening the migration path of electrons and lithium ions, and can fully utilize the lithium replenishment performance of the material, thereby extending the service life of the lithium-ion battery.

[0047] (3) The present invention uses a continuous phase formed by uniformly mixing inorganic carbon and small molecular organic matter with hydrophobic groups as a hydrophobic layer to coat the surface of the positive electrode lithium replenisher (Li2NiO2 and / or Li5FeO4), and uses the hydrophobic properties of the hydrophobic groups to weaken the alkalinity, thereby improving the hydrophobic properties and air stability of the positive electrode lithium replenisher material, thereby improving the overall performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the XRD pattern of the positive electrode lithium supplement material prepared in Example 1 of the present invention;

[0049] Figure 2 This is a TEM image of the positive electrode lithium supplement material prepared in Example 1 of the present invention;

[0050] Figure 3 This is the charge and discharge curve of a button cell assembled with the positive lithium replenishing material prepared in Example 1 of the present invention at a rate of 0.1C. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention.

[0052] The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally based on conventional conditions.

[0053] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0054] Throughout the present invention, unless otherwise specified and / or explained, all references to component amounts are in parts by weight. Process parameters in the following examples, where specific conditions are not specified, generally follow conventional conditions. The raw materials described in the following examples were all obtained from publicly available commercial sources.

[0055] A specific embodiment of the present invention provides a method for preparing a positive electrode lithium supplement material, comprising:

[0056] (1) First, a surfactant (one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, polyvinyl pyrrolidone, ethylene glycol, polyethylene glycol and oleylamine) is weighed and dissolved in deionized water to prepare a surfactant solution of 0.01-0.5 mol / L, and then a lithium source (the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium metaborate, lithium molybdate, lithium sulfate, lithium tetrafluoroborate, lithium phosphate, lithium tetrachlorocuprate, lithium tetraborate, lithium oxalate, lithium acetate, lithium nitrate, lithium chloride, lithium fluoride, lithium chromate and lithium trifluoromethanesulfonate) is added thereto; The method comprises the following steps: preparing a first reaction mixture of iron source, nickel oxide, nickel hydroxide, nickel hydroxide, nickel carbonate, nickel nitrate, nickel oxalate, nickel acetate, nickel fluoride, nickel chloride, nickel bromide, nickel sulfate, nickel bis(hexafluoroethylacetone), nickel sulfamate, basic nickel carbonate, nickel acetylacetonate dihydrate, nickel trifluoromethanesulfonate, nickel benzenesulfonate, nickel acetylacetonate, and nickel fluoroborate; wherein the mass of the surfactant is 0.5-5% of the mass of the iron source and / or nickel source; and the molar ratio of lithium element in the lithium source to iron element and / or nickel element in the iron source and / or nickel source is 2-5:1; stirring the mixture at 120° C.-180° C. until the solvent evaporates, and grinding the mixture to obtain a solid phase precursor.

[0057] (2) The solid-phase precursor is placed in an inert gas (nitrogen, argon, helium, etc.) atmosphere, heated to 350°C-650°C at a heating rate of 5-20°C / min, and kept warm for 6-18 hours. After cooling to room temperature, it is crushed to obtain a positive electrode lithium supplement (particle size of 0.2-5 μm).

[0058] (3) dissolving a hydrophobic organic substance (the hydrophobic organic substance is selected from one or more of (PVDF), polyoxyolefin copolymer, cholesterol dodecyl carbonate, methacrylate, and polydiene) in an organic solvent (ethanol, methanol, and acetone), and then adding the positive electrode lithium replenisher obtained in step (2), wherein the mass of the hydrophobic organic substance is 0.5-2% of the mass of the positive electrode lithium replenisher, and the mass ratio of the organic solvent to the mass of the positive electrode lithium replenisher is 5-9:1-5; and obtaining the positive electrode lithium replenisher material by spray pyrolysis (180-260° C.) in a spray dryer under compressed air or an inert atmosphere.

[0059] The present invention will be further described in detail below with reference to specific embodiments.

[0060] Example 1 A method for preparing a positive electrode lithium supplement material comprises:

[0061] (1) First, 4.2 g of polyvinyl pyrrolidone (M w =12000) was added to 250 mL of deionized water to obtain a 0.014 mol / L surfactant solution, and then 120 g of lithium hydroxide and 143.9 g of ferrous oxalate were added thereto. After mixing, the mixture was stirred at 130° C. until the solvent was completely evaporated, and then ground to obtain a solid precursor;

[0062] (2) sintering the solid-phase precursor obtained in step (1) in a nitrogen atmosphere under the following conditions: heating to 450°C at a heating rate of 10°C / min and keeping the temperature for 10 hours; cooling and then crushing to obtain a positive electrode lithium supplement Li5FeO4 with an average particle size of 0.4 μm;

[0063] (3) 0.6 g PVDF and 0.6 g methallyl polyoxyethylene polyoxypropylene ether (M w =3500) was dissolved in 500 mL of ethanol, and 125 g of the positive electrode lithium replenishing agent Li5FeO4 obtained in step (2) was added, and then spray pyrolysis treatment was performed at a temperature of 210° C. in a spray dryer under a nitrogen atmosphere to obtain a positive electrode lithium replenishing material.

[0064] Figure 1 This is the XRD pattern of the positive electrode lithium replenishing material prepared in Example 1 of the present invention, indicating that the positive electrode lithium replenishing agent Li5FeO4 was successfully prepared;

[0065] Figure 2 This is a TEM image of the positive electrode lithium supplement material prepared in Example 1 of the present invention. Figure 2 (b) It can be seen that the thickness of the hydrophobic layer is 5 nm.

[0066] The porosity of the positive electrode lithium supplement material prepared in Example 1 was measured by nitrogen adsorption-desorption method to be 24.7%.

[0067] Example 2 A method for preparing a positive electrode lithium supplement material comprises:

[0068] (1) First, 4.2 g of polyvinyl pyrrolidone (M w =12000) was added to 500 mL of deionized water to obtain a 0.014 mol / L surfactant solution, and then 120 g of lithium hydroxide and 143.9 g of ferrous oxalate were added thereto. After mixing, the mixture was stirred at 130° C. until the solvent was completely evaporated, and then ground to obtain a solid precursor;

[0069] (2) sintering the solid-phase precursor obtained in step (1) in a nitrogen atmosphere under the following conditions: heating to 450°C at a heating rate of 10°C / min and keeping the temperature for 10 hours; cooling and then crushing to obtain a positive electrode lithium supplement Li5FeO4 with an average particle size of 0.4 μm;

[0070] (3) 1.2 g PVDF and 1.2 g methallyl polyoxyethylene polyoxypropylene ether (M w =3500) was dissolved in 500 mL of ethanol, and 125 g of the positive electrode lithium replenisher Li₅FeO₄ obtained in step (2) was added. The mixture was then spray-pyrolyzed at 210°C in a spray dryer under a nitrogen atmosphere to obtain a positive electrode lithium replenisher material. The hydrophobic layer had a thickness of 8 nm and a porosity of 21.3%.

[0071] Example 3 A method for preparing a positive electrode lithium supplement material, comprising:

[0072] (1) First, 9.3 g of hexadecyltrimethylammonium bromide was added to 250 mL of deionized water to obtain a 0.1 mol / L surfactant solution. Then, 50 g of lithium hydroxide and 248.8 g of nickel acetate tetrahydrate were added thereto. After mixing, the mixture was stirred at 130° C. until the solvent was completely evaporated, and then ground to obtain a solid-phase precursor.

[0073] (2) sintering the solid-phase precursor obtained in step (1) in a nitrogen atmosphere under the following conditions: heating to 450°C at a heating rate of 10°C / min and keeping the temperature for 10 hours; cooling and then crushing to obtain a positive electrode lithium supplement Li2NiO2 with an average particle size of 0.5 μm;

[0074] (3) 0.4 g of PVDF and 0.4 g of cholesterol dodecyl carbonate were dissolved in 500 mL of ethanol, and 93 g of the positive electrode lithium replenisher Li2NiO2 obtained in step (2) was added. The mixture was then spray pyrolyzed at 230° C. in a spray dryer under a nitrogen atmosphere to obtain a positive electrode lithium replenisher material having a hydrophobic layer thickness of 4 nm and a porosity of 18.6%.

[0075] Example 4 A method for preparing a positive electrode lithium supplement material comprises:

[0076] (1) First, 7.2 g of sodium dodecyl sulfate was added to 250 mL of deionized water to obtain a 0.1 mol / L surfactant solution, and then 202.0 g of lithium oxalate and 92.7 g of nickel hydroxide were added thereto. After mixing, the mixture was stirred at 150° C. until the solvent was completely evaporated, and then ground to obtain a solid-phase precursor;

[0077] (2) sintering the solid-phase precursor obtained in step (1) in a nitrogen atmosphere under the following conditions: heating to 550°C at a heating rate of 10°C / min and keeping the temperature for 8 hours; cooling and then crushing to obtain a positive electrode lithium supplement Li2NiO2 with an average particle size of 1.3 μm;

[0078] (3) 0.4 g of PVDF and 0.4 g of cholesterol dodecyl carbonate were dissolved in 500 mL of ethanol, and 93 g of the positive electrode lithium replenisher Li2NiO2 obtained in step (2) was added. The mixture was then spray pyrolyzed at 230° C. in a spray dryer under a nitrogen atmosphere to obtain a positive electrode lithium replenisher material having a hydrophobic layer thickness of 5 nm and a porosity of 24.1%.

[0079] Example 5

[0080] The difference between Example 5 and Example 1 is that in step (3), 1.2 g of PVDF is dissolved in 500 mL of ethanol, and 125 g of the positive electrode lithium replenisher Li5FeO4 obtained in step (2) is added, and then spray pyrolysis treatment is performed at a temperature of 210°C in a spray dryer under a nitrogen atmosphere to obtain a positive electrode lithium replenishing material. The rest is the same as in Example 1, the hydrophobic layer thickness is 3 nm, and the porosity is 19.3%.

[0081] Example 6

[0082] The difference between Example 6 and Example 1 is that in step (3), 1.2 g of methyl allyl polyoxyethylene polyoxypropylene ether (M w =3500) was dissolved in 500 mL of ethanol, and 125 g of the positive electrode lithium replenishing agent Li5FeO4 obtained in step (2) was added. Then, the mixture was spray pyrolyzed at a temperature of 210° C. in a spray dryer under a nitrogen atmosphere to obtain a positive electrode lithium replenishing material. The rest was the same as in Example 1, the hydrophobic layer had a thickness of 3 nm, and the porosity was 19.7%.

[0083] Comparative Example 1 A method for preparing a positive electrode lithium supplement material comprises:

[0084] (1) First, 4.2 g of polyvinyl pyrrolidone (M w =12000) was added to 250 mL of deionized water to obtain a 0.014 mol / L surfactant solution, and then 120 g of lithium hydroxide and 143.9 g of ferrous oxalate were added thereto. After mixing, the mixture was stirred at 130° C. until the solvent was completely evaporated, and then ground to obtain a solid precursor;

[0085] (2) The solid-phase precursor obtained in step (1) was sintered in a nitrogen atmosphere under the following sintering conditions: heating to 450°C at a heating rate of 10°C / min and keeping the temperature for 10 hours; after cooling, the solid-phase precursor was pulverized to obtain a positive electrode lithium supplement Li5FeO4 with an average particle size of 0.4 μm and a porosity of 21.5%.

[0086] Comparative Example 2 A method for preparing a positive electrode lithium supplement material comprises:

[0087] (1) First, 120 g of lithium hydroxide and 143.9 g of ferrous oxalate were added to 500 mL of deionized water, mixed, and stirred at 130° C. until the solvent was completely evaporated, and then ground to obtain a solid precursor;

[0088] (2) sintering the solid-phase precursor obtained in step (1) in a nitrogen atmosphere under the following conditions: heating to 450°C at a heating rate of 10°C / min and keeping the temperature for 10 hours; cooling and then crushing to obtain a positive electrode lithium supplement Li5FeO4 with an average particle size of 0.4 μm;

[0089] (3) 0.6 g PVDF and 0.6 g methallyl polyoxyethylene polyoxypropylene ether (M w =3500) was dissolved in 500 mL of ethanol, and 125 g of the positive electrode lithium replenisher Li5FeO4 obtained in step (2) was added. The mixture was then spray pyrolyzed at 210° C. in a spray dryer under a nitrogen atmosphere to obtain a positive electrode lithium replenishing material having a coating layer thickness of 5 nm and a porosity of 13.2%.

[0090] Comparative Example 3: A method for preparing a positive electrode lithium supplement material, comprising:

[0091] (1) First, 4.2 g of polyvinyl pyrrolidone (M w =12000) was added to 250 mL of deionized water to obtain a 0.014 mol / L surfactant solution, and then 120 g of lithium hydroxide and 143.9 g of ferrous oxalate were added thereto. After mixing, the mixture was stirred at 130° C. until the solvent was completely evaporated, and then ground to obtain a solid precursor;

[0092] (2) sintering the solid-phase precursor obtained in step (1) in a nitrogen atmosphere under the following conditions: heating to 300°C at a heating rate of 10°C / min and keeping the temperature for 8 hours; cooling and then crushing to obtain a positive electrode lithium supplement Li5FeO4 with an average particle size of 0.16 μm;

[0093] (3) 0.6 g PVDF and 0.6 g methallyl polyoxyethylene polyoxypropylene ether (M w=3500) was dissolved in 500 mL of ethanol, and 125 g of the positive electrode lithium replenisher Li5FeO4 obtained in step (2) was added. The mixture was then spray pyrolyzed at 210° C. in a spray dryer under a nitrogen atmosphere to obtain a positive electrode lithium replenisher material having a coating layer thickness of 4 nm and a porosity of 20.8%.

[0094] Comparative Example 4: A method for preparing a positive electrode lithium supplement material, comprising:

[0095] (1) First, 4.2 g of polyvinyl pyrrolidone (M w =12000) was added to 250 mL of deionized water to obtain a 0.014 mol / L surfactant solution, and then 120 g of lithium hydroxide and 143.9 g of ferrous oxalate were added thereto. After mixing, the mixture was stirred at 130° C. until the solvent was completely evaporated, and then ground to obtain a solid precursor;

[0096] (2) sintering the solid-phase precursor obtained in step (1) in a nitrogen atmosphere under the following conditions: heating to 450°C at a heating rate of 10°C / min and keeping the temperature for 10 hours; cooling and then crushing to obtain a positive electrode lithium supplement Li5FeO4 with an average particle size of 0.5 μm;

[0097] (3) 0.14 g PVDF and 0.14 g methallyl polyoxyethylene polyoxypropylene ether (M w =3500) was dissolved in 500 mL of ethanol, and then 125 g of the positive electrode lithium replenishing agent Li5FeO4 obtained in step (2) was added, and then spray pyrolysis treatment was performed at a temperature of 210° C. to obtain a positive electrode lithium replenishing material, the coating layer of which had a thickness of 3 nm and a porosity of 20.3%.

[0098] Comparative Example 5

[0099] The difference between Comparative Example 5 and Example 1 is that in step (3), 0.6 g of PVDF and 0.6 g of methyl allyl polyoxyethylene polyoxypropylene ether (M w =3500) was dissolved in 500 mL of ethanol, and then 125 g of the positive electrode lithium replenishing agent Li5FeO4 obtained in step (2) was added, and then spray pyrolysis treatment was performed at a temperature of 150° C. in a spray dryer under a nitrogen atmosphere to obtain a positive electrode lithium replenishing material with a coating layer thickness of 6 nm and a porosity of 17.2%.

[0100] Comparative Example 6

[0101] The difference between Comparative Example 6 and Example 1 is that in step (3), 0.6 g of PVDF and 0.6 g of methyl allyl polyoxyethylene polyoxypropylene ether (M w=3500) was dissolved in 500 mL of ethanol, and 125 g of the positive electrode lithium replenishing agent Li5FeO4 obtained in step (2) was added, and then spray pyrolysis treatment was performed at a temperature of 300° C. in a spray dryer under a nitrogen atmosphere to obtain a positive electrode lithium replenishing material with a coating layer thickness of 4 nm and a porosity of 19.6%.

[0102] Performance testing

[0103] The positive electrode lithium replenishing materials prepared in Examples 1-6 and Comparative Examples 1-6 were placed in an environment with a humidity greater than 80% for 24 hours at room temperature (25±2°C), and then taken out and tested for moisture content using a Karl Fischer moisture meter. The positive electrode lithium replenishing materials prepared in Examples 1-6 and Comparative Examples 1-6 were used as active materials and mixed with polyvinylidene fluoride (PVDF) and superconducting carbon black (Super P) in a mass ratio of 94:3:3. The mixture was ball-milled for 60 minutes using NMP as a solvent to prepare a slurry and its solid content was tested. The slurry viscosity was tested using a rotational viscometer over a 24-hour period, and the 24-hour viscosity change rate was calculated. The slurry was then evenly coated on a metal aluminum foil and vacuum-dried at 80°C for 2 hours. Finally, a circular electrode piece with a diameter of 14 mm was cut using a punch as a working electrode. In a purified glove box filled with Ar (O2 content less than 0.1 ppm, H2O content less than 0.1 ppm), a metal lithium sheet was used as a counter electrode, and Celgard 2400 porous polypropylene film (PP) is used as the separator, the electrolyte is 1 mol / L lithium hexafluorophosphate (LiPF6) solution, and the solvent is a mixture of ethylene carbonate (EC) and ethyl carbonate (DMC) in a volume ratio of 1:1. R2032 button cells are prepared according to a certain assembly process. After completion, the battery is left to stand for 3 hours to allow the electrolyte and electrode materials to fully penetrate. At room temperature (25℃±1), the Li / Li + The battery constant current charge and discharge experiment was carried out, and the test results are shown in Table 1.

[0104] The positive electrode lithium supplement materials prepared in Examples 1-6 and Comparative Examples 1-6 were respectively mixed with the positive electrode active material lithium iron phosphate to obtain a positive electrode material, wherein the positive electrode lithium supplement material accounted for 2% of the mass of the positive electrode active material. The positive electrode material was then mixed with a binder PVDF and a conductive agent superconducting carbon black in a mass ratio of 97.0:2.0:1.0, and ball milled for 60 minutes using NMP as a solvent to obtain a slurry, which was then evenly coated on a metal aluminum foil to obtain a positive electrode sheet. Artificial graphite was used as the negative electrode material, a thickener CMC, a binder SBR, and a conductive agent SP in a mass ratio of 95.3:1.2:1.5:2.0, and deionized water was used as a solvent for the slurry. The slurry was prepared by ball milling for 60 min and then evenly coated on a metal copper foil to prepare a negative electrode sheet. A coefficient of 1.15 was designed according to the N / P ratio (negative electrode active material gram capacity × negative electrode surface density × negative electrode active material content ratio ÷ (positive electrode active material gram capacity × positive electrode surface density × positive electrode active material content ratio). A soft-pack full battery with a capacity of 3.0 Ah was assembled and charged and discharged at a constant current and constant voltage of 1C / 1C in the voltage range of 2.5 to 3.65 V at room temperature (25°C ± 1) (charging at a constant current of 1C to 3.65 V, and then at a low current of 0.05C at a voltage platform of 3.65 V until charging is completed). The test results are shown in Table 2.

[0105] Table 1

[0106]

[0107]

[0108] Table 2

[0109]

[0110]

[0111] Note: The capacity improvement rate refers to (actual capacity - 3.0) / 3.0 of the soft-pack batteries prepared in each embodiment and comparative example.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A positive electrode lithium supplement material, characterized in that: include: A positive electrode lithium replenisher and a hydrophobic layer coated on the surface of the positive electrode lithium replenisher; the positive electrode lithium replenisher is Li2NiO2 and / or Li5FeO4; The hydrophobic layer is a continuous phase formed by a uniform mixture of inorganic carbon and small molecule organic matter with hydrophobic groups; Wherein, the hydrophobic group is selected from one or more of hydrocarbon groups, ester groups, and polyoxyalkylene groups; The particle size of the positive electrode lithium supplement material is 0.2-5 μm; The preparation method of the positive electrode lithium supplement material comprises: (1) First, a surfactant is dissolved in a solvent to obtain a surfactant solution, and then a lithium source and an M-containing compound are added. The solution is then stirred until the solvent evaporates, and then ground to obtain a solid-phase precursor. (2) sintering the solid-phase precursor obtained in step (1) under an inert gas, cooling it, and then crushing it to obtain a positive electrode lithium supplement; (3) dissolving the hydrophobic organic matter in an organic solvent, adding the positive electrode lithium replenishing agent obtained in step (2), and then performing a spray pyrolysis treatment to obtain a positive electrode lithium replenishing material; In step (1), the surfactant is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, cetyltrimethylammonium bromide, polyvinylpyrrolidone, ethylene glycol, polyethylene glycol and oleylamine; the M-containing compound is selected from iron-containing compounds and / or nickel-containing compounds; In step (3), the mass of the hydrophobic organic matter is 0.5-2% of the mass of the positive electrode lithium supplement agent; the spray pyrolysis treatment is carried out in a spray dryer under compressed air or inert atmosphere at a temperature of 180-260°C.

2. The positive electrode lithium supplement material according to claim 1, characterized in that The hydrophobic layer is made of hydrophobic organic matter and is coated on the surface of the positive electrode lithium supplement agent through spray pyrolysis treatment; the hydrophobic organic matter is selected from one or more of polyvinylidene fluoride, polyoxyolefin copolymer, cholesterol dodecyl carbonate, methacrylate, and polydiene.

3. The positive electrode lithium supplement material according to claim 2, characterized in that The polyoxyolefin copolymer is one or both of methyl allyl polyoxyethylene polyoxypropylene ether and allyl polyethylene glycol.

4. The positive electrode lithium supplement material according to claim 2, characterized in that The hydrophobic organic substance is a copolymer of polyvinylidene fluoride and polyoxyolefin, or the hydrophobic organic substance is polyvinylidene fluoride and cholesterol dodecyl carbonate.

5. The positive electrode lithium supplement material according to claim 1, characterized in that The thickness of the hydrophobic layer is 3-8 nm; and / or the porosity of the positive electrode lithium supplement material is 12%-28%.

6. The positive electrode lithium supplement material according to claim 1, characterized in that In step (1), the solvent is deionized water; in the surfactant solution, the molar concentration of the surfactant is 0.01-0.5 mol / L; the mass of the surfactant is 0.5-5% of the mass of the M-containing compound; And / or, the lithium source is selected from one or more of lithium carbonate, lithium hydroxide, lithium metaborate, lithium molybdate, lithium sulfate, lithium tetrafluoroborate, lithium phosphate, lithium tetrachlorocuprate, lithium tetraborate, lithium oxalate, lithium acetate, lithium nitrate, lithium chloride, lithium fluoride, lithium chromate, and lithium trifluoromethanesulfonate; And / or, the iron-containing compound is selected from one or more of ferric oxide, ferrous sulfate, ferrous chloride, ferric phosphate, ferric nitrate, ferrous oxalate, ferric citrate and ferric hydroxide; the nickel-containing compound is selected from one or more of nickelous oxide, nickel trioxide, nickel hydroxide, nickel hydroxide, nickel carbonate, nickel nitrate, nickel oxalate, nickel acetate, nickel fluoride, nickel chloride, nickel bromide, nickel sulfate, bis(hexafluoroethylacetone)nickel, nickel sulfamate, basic nickel carbonate, nickel acetylacetonate dihydrate, nickel trifluoromethanesulfonate, nickel benzenesulfonate, nickel acetylacetonate and nickel fluoroborate; And / or, the molar ratio of lithium element in the lithium source to M element in the M-containing compound is 2-5:

1.

7. The positive electrode lithium supplement material according to claim 1, characterized in that In step (1), the stirring temperature is 120-180°C; And / or, in step (2), the sintering treatment conditions are: heating to 350°C-650°C at a heating rate of 5°C / min-20°C / min, and keeping the temperature for 6-18 hours; the inert gas is nitrogen, argon or helium; And / or, in step (2), the particle size of the positive electrode lithium supplement obtained by pulverization is 0.2-5 μm.

8. The positive electrode lithium supplement material according to claim 1, characterized in that In step (3), the hydrophobic organic substance is selected from one or more of polyvinylidene fluoride, polyoxyolefin copolymer, cholesterol dodecyl carbonate, methacrylate, and polydiene; And / or, the organic solvent is selected from one of ethanol, methanol and acetone; the mass ratio of the organic solvent to the positive electrode lithium replenisher is 5-9:1-5.

9. The positive electrode lithium supplement material according to claim 8, characterized in that The polyoxyolefin copolymer is one or both of methyl allyl polyoxyethylene polyoxypropylene ether and allyl polyethylene glycol.

10. A positive electrode material, characterized in that include: A positive electrode active material and a positive electrode lithium supplement material according to any one of claims 1 to 9; the positive electrode active material is selected from one or more of lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based positive electrode materials; the mass of the positive electrode lithium supplement material is 0.5%-5% of the mass of the positive electrode active material.

11. Use of the positive electrode material according to claim 10 in a lithium ion battery.

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