WO2024250175A1 - Ternary positive electrode material, preparation method therefor and use thereof - Google Patents

Abstract

The present disclosure belongs to the technical field of lithium battery recovery, and particularly relates to a ternary positive electrode material, a preparation method therefor and the use thereof. The method comprises placing a lithium nickel manganese cobalt oxide positive electrode material in a humid environment, such that Li2O on the surface of the material absorbs water to generate LiOH; and then subjecting same to a substitution reaction with a halogenated alkane to generate a halogenated lithium and an alcohol. The preparation method provided by the present disclosure involves a shorter technological process, and the prepared ternary positive electrode material has the advantage of low residual alkali contents. The halogenated alkane has neither strong oxidation nor acidity, and therefore does not cause damage to the structure of the ternary material, thereby enabling the positive electrode material to keep excellent electrochemical properties.

Description

A ternary positive electrode material and its preparation method and application Technical Field

The present invention relates to the technical field of lithium battery recycling, and in particular to a ternary positive electrode material and a preparation method and application thereof.

Background Art

Lithium-ion batteries are widely used in many fields such as 3C electronic products, power vehicles and chemical energy storage due to their high energy density and long cycle life. They are a hot research topic in the new energy field. With the rapid development of new energy vehicles, higher requirements are placed on the energy density of lithium-ion batteries. As one of the key materials of lithium-ion batteries, cathode materials play an important role in battery performance.

Nickel cobalt manganese oxide ternary positive electrode materials have the advantages of high specific capacity, high energy density, low price, and environmental friendliness, and have good application prospects in the field of power batteries. With the increase of nickel content, the specific capacity of ternary positive electrode materials gradually increases, but the cycle stability becomes weaker. During the sintering of high-nickel materials, excess lithium salts remain on the surface of the material in the form of oxides, and the increase in nickel content easily causes the mixing of nickel and lithium, and lithium is easy to precipitate. Residual lithium easily absorbs water and carbon dioxide in the air to form LiOH and _{Li2CO3 layers} , which will bring the following two problems: on the one hand, the slurry is very easy to form a jelly-like shape during the homogenization and coating process of battery production, resulting in uneven coating and easy capacity attenuation; on the other hand, residual alkali is easy to react with the electrolyte at high temperature to generate gas, causing battery bloating, which brings serious safety hazards.

In view of the problem of high residual alkali on the surface of high-nickel ternary materials, the commonly used method is to wash the high-nickel materials with water, but the washing process is cumbersome, requires a large amount of water resources, and there will be a certain amount of water residue after washing. In the subsequent drying process, the dissolved lithium will be precipitated again, and the residual lithium will not be removed thoroughly; washing will also destroy the structure of the ternary positive electrode material and reduce the performance of the battery. For example, CN108878863A discloses a method for improving the residual alkalinity on the surface of the ternary positive electrode material of a lithium-ion battery, mixing the nickel-cobalt-manganese layered positive electrode material with water, centrifuging to obtain a powder material after washing; adding a lithium source to anhydrous ethanol and mixing evenly, then adding the powder material after washing and mixing evenly, evaporating completely, drying, and sintering to obtain a ternary positive electrode material for a lithium-ion battery. The above method improves the performance of the material by supplementing lithium and secondary sintering the ternary material after washing, but the supplemented lithium is not easy to react completely with the material, which is easy to cause excessive lithium residue and affect the electrochemical performance of the material.

Therefore, the existing methods for removing residual alkali generally have the problem of incomplete removal of residual alkali, and are also prone to damage the structure of the positive electrode material and affect the electrochemical performance.

In view of this, the present disclosure is proposed.

Summary of the invention

The purpose of the present disclosure includes providing a ternary positive electrode material and a preparation method and application thereof, aiming to more thoroughly remove the residual alkali on the surface of the ternary positive electrode material while ensuring the electrochemical performance of the ternary positive electrode material.

In order to achieve the above-mentioned purpose of the present disclosure, the following technical solutions can be adopted:

In a first aspect, the solution provided by the present disclosure includes a method for preparing a ternary positive electrode material, comprising: subjecting a nickel cobalt manganese oxide lithium positive electrode material to a water absorption treatment and then reacting it with a halogenated alkane.

In some embodiments of the present disclosure, the halogenated alkane is selected from at least one of monohalide, dihalide, trihalide and tetrahalide, and the halogen element in the halogenated alkane is selected from at least one of fluorine, chlorine and bromine.

In some embodiments of the present disclosure, the halogenated alkane is a monohalide.

In some embodiments of the present disclosure, the halogenated alkane is selected from at least one of monofluoromethane, monofluoroethane, monochloromethane, monochloroethane, monobromomethane and monobromoethane.

In some embodiments of the present disclosure, the water absorption treatment process includes: placing the nickel cobalt lithium manganese oxide positive electrode material in a humid environment with a humidity greater than or equal to 50%.

In some embodiments of the present disclosure, the humidity of the humid environment is 60%-80%.

In some embodiments of the present disclosure, the nickel cobalt manganese oxide lithium positive electrode material is placed in a humid environment for 5 hours to 8 hours.

In some embodiments of the present disclosure, during the reaction with the halogenated alkane, the reaction temperature is controlled to be 30° C.-50° C., and the reaction time is 2 h-8 h.

In some embodiments of the present disclosure, during the reaction with the halogenated alkane, the reaction temperature is controlled to be 35° C.-45° C., and the reaction time is 2 h-5 h.

In some embodiments of the present disclosure, when the amount of nickel cobalt manganese oxide lithium positive electrode material used is 1.0 kg, the corresponding flow rate of the halogenated alkane gas is 0.05 L/min-0.15 L/min.

In some embodiments of the present disclosure, a nickel cobalt manganese oxide positive electrode material is placed in a tubular furnace, and water vapor is introduced into the tubular furnace to make the humidity in the tubular furnace meet the requirements. After being placed for 4h-10h, the introduction of water vapor is stopped, and after the temperature is raised to the reaction temperature, a halogenated alkane gas is introduced for reaction.

In some embodiments of the present disclosure, before introducing water vapor into the tube furnace, an inert gas is introduced to exhaust the air in the tube furnace.

In some embodiments of the present disclosure, water vapor is introduced into the tube furnace in a spraying manner.

In some embodiments of the present disclosure, when the halogenated alkane used contains chlorine or bromine, the preparation method further comprises: purging the obtained product after the reaction with the halogenated alkane is completed.

In some embodiments of the present disclosure, the chemical formula of the lithium nickel cobalt manganese oxide positive electrode material is LiNi _x Co _y Mn _z O ₂ , wherein Among them, 0.7≤x≤0.9, 0.05≤y≤0.15, 0.05≤z≤0.15, x+y+z=1.

In some embodiments of the present disclosure, the nickel cobalt manganese oxide lithium positive electrode material is in powder form, and the average particle size of the powder is 2 μm-15 μm.

In some embodiments of the present disclosure, the method for preparing the nickel cobalt manganese oxide positive electrode material includes: mixing a nickel cobalt manganese ternary precursor with a lithium source, calcining it once in an oxygen-containing atmosphere to obtain a primary calcined product, and then calcining the primary calcined product twice in an oxygen-containing atmosphere.

In some embodiments of the present disclosure, the calcination temperature of the primary calcination is 500° C.-600° C., and the calcination time is 4 h-7 h.

In some embodiments of the present disclosure, the calcination temperature of the secondary calcination is 700° C.-800° C., and the calcination time is 10 h-18 h.

In some embodiments of the present disclosure, the molar ratio of the total amount of nickel, cobalt and manganese to the lithium element is 1:(1.01-1.20) by controlling the amount of the nickel, cobalt and manganese ternary precursor and the lithium source.

In some embodiments of the present disclosure, the lithium source is selected from at least one of lithium hydroxide and lithium carbonate.

In some embodiments of the present disclosure, before the primary calcined product is subjected to secondary calcination, the primary calcined product is cooled and then crushed to 2 μm-15 μm.

In a second aspect, the solution provided by the present disclosure also includes a ternary positive electrode material prepared by the preparation method in any of the above embodiments.

In a third aspect, the solution provided by the present disclosure also includes a positive electrode plate for a lithium-ion battery, including a positive electrode collector and an active coating attached to the positive electrode collector, wherein the active coating contains the ternary positive electrode material in the above-mentioned embodiment.

In a fourth aspect, the solution provided by the present disclosure also includes a lithium-ion battery, including the positive electrode plate for the lithium-ion battery in the above embodiment.

In a fifth aspect, the solution provided by the present disclosure also includes an electrical device, including the lithium-ion battery in the above embodiment.

After the nickel cobalt manganese oxide positive electrode material is placed in a humid environment, the _Li2O on the surface of the material absorbs water to generate LiOH, and then undergoes a substitution reaction with a halogenated alkane to generate a halogenated lithium and an alcohol. Due to the different reaction raw materials, the generated halogenated lithium may be lithium fluoride, lithium chloride or lithium bromide. The insoluble lithium fluoride can be used as a coating layer to protect the positive electrode material; lithium chloride or lithium bromide can be dissolved in the generated alcohol, which is convenient for subsequent removal. The preparation method provided by the present disclosure has a shorter process flow, and the prepared ternary positive electrode material has the advantage of low residual alkali content; since the halogenated alkane has neither strong oxidizing property nor acidity, it will not damage the structure of the ternary material, so that the positive electrode material maintains excellent electrochemical properties.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

FIG1 is a basic process flow chart of the preparation method provided by the present disclosure;

FIG2 is a process flow chart corresponding to the main process steps in the preparation method provided by the present disclosure;

FIG3 is a scanning electron microscope image of a material before and after being treated by the method disclosed in the present invention; in the image, (a) represents before treatment, and (b) represents after treatment.

DETAILED DESCRIPTION

The embodiments of the present disclosure will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present disclosure and should not be considered to limit the scope of the present disclosure. Where specific conditions are not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased commercially.

The endpoints and any values of the ranges disclosed in this disclosure 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 endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

The solution provided by the embodiment of the present disclosure includes a method for preparing a ternary positive electrode material. As shown in FIG1 , the preparation process includes: allowing the nickel cobalt manganese oxide lithium positive electrode material to absorb water in a humid environment to obtain a positive electrode material with a surface content of LiOH, and then reacting with a halogenated alkane to remove the residual alkali on the surface through a substitution reaction.

Specifically, as shown in FIG2 , the method for preparing the ternary cathode material provided in the embodiment of the present disclosure may include the following steps:

S1. Preparation of lithium nickel cobalt manganese oxide positive electrode material

The chemical formula of the lithium nickel cobalt manganese oxide positive electrode material is LiNi _x Co _y Mn _z O ₂ , wherein 0.7≤x≤0.9, 0.05≤y≤0.15, 0.05≤z≤0.15, x+y+z＝1, and it belongs to a high nickel positive electrode material. Specifically, the value of x can be 0.70, 0.75, 0.80, 0.85, 0.90, etc., the value of y can be 0.05, 0.08, 0.10, 0.12, 0.15, etc., and the value of z can be 0.05, 0.08, 0.10, 0.12, 0.15, etc.

The nickel cobalt manganese oxide positive electrode material is preferably in powder form, so that the subsequent water absorption and substitution reaction can be carried out quickly and fully. The average particle size of the powder can be 2 μm-15 μm, such as 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc.

It should be noted that the nickel cobalt manganese oxide lithium positive electrode material can be a commercially available product or can be synthesized independently.

In some embodiments, the preparation method of the nickel cobalt manganese oxide positive electrode material includes: mixing a nickel cobalt manganese ternary precursor with a lithium source, calcining once in an oxygen-containing atmosphere to obtain a primary calcined product, and then calcining the primary calcined product for a second time in an oxygen-containing atmosphere, and preparing a nickel cobalt manganese oxide positive electrode material with excellent electrochemical properties through a two-step calcination process.

In some embodiments, the calcination temperature of the first calcination is 500°C-600°C, and the calcination time is 4h-7h; the calcination temperature of the second calcination is 700°C-800°C, and the calcination time is 10h-18h. The electrochemical performance of the prepared nickel cobalt manganese oxide lithium positive electrode material is further guaranteed by controlling the calcination temperature and time of the two-step calcination.

Specifically, the calcination temperature of the first calcination can be 500°C, 520°C, 550°C, 580°C, 600°C, etc., and the calcination time can be 4h, 5h, 6h, 7h, etc.; the calcination temperature of the second calcination can be 700°C, 720°C, 750°C, 780°C, 800°C, etc., and the calcination time can be 10h, 12h, 15h, 18h, etc. The oxygen-containing atmosphere used in the two-step calcination process can be, but is not limited to, oxygen.

In some embodiments, by controlling the amount of the nickel-cobalt-manganese ternary precursor and the lithium source, the molar ratio of the total amount of nickel-cobalt-manganese to the lithium element is 1:(1.01-1.20), that is, the lithium source is slightly excessive, so that the reaction is fully carried out. Specifically, the molar ratio of the total amount of nickel-cobalt-manganese to the lithium element can be 1:1.01, 1:1.05, 1:1.10, 1:1.15, 1:1.20, etc.

Furthermore, the lithium source is selected from at least one of lithium hydroxide and lithium carbonate, and may be any one or both of the above. In other embodiments, other commonly used lithium sources may also be used.

In some embodiments, the nickel-cobalt-manganese ternary precursor is mixed with a lithium source and ground until the mixture is uniform, and then calcined once to allow the reaction to proceed fully and improve the uniformity of the product. Similarly, before the primary calcined product is subjected to secondary calcination, the primary calcined product is cooled and then crushed to 2 μm-15 μm, such as 2 μm, 5 μm, 10 μm, 15 μm, etc.

S2. Water absorption treatment

The water absorption treatment may be placing the nickel cobalt manganese oxide lithium positive electrode material in a humid environment with a humidity greater than or equal to 50%, so that Li ₂ O on the surface of the material absorbs water to generate LiOH.

In actual operation, the positive electrode material of lithium nickel cobalt manganese oxide is placed in a tube furnace, and water vapor is introduced into the tube furnace to make the humidity in the tube furnace meet the requirements. After 4h-10h, the introduction of water vapor is stopped. The placement time depends on the ambient humidity. The higher the ambient humidity, the shorter the placement time is, so that the surface Li ₂ O can be more fully converted.

Specifically, the time of being placed in the tube furnace can be 1 hour, 3 hours, 5 hours, 8 hours, 10 hours, etc., preferably 5 hours to 8 hours. The water vapor can be introduced through a pipeline or sprayed with a nozzle. The water vapor can be formed in a manner similar to a humidifier, but is not limited thereto.

Specifically, the humidity of the humid environment can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc., preferably 60%-80% to promote rapid reaction. The humidity test method is to use a conventional test method. Use a temperature and humidity meter to test.

In some embodiments, before introducing water vapor into the tube furnace, an inert gas is introduced to exhaust the air in the tube furnace to avoid interference from oxygen. The inert gas may be nitrogen, argon, etc., but is not limited thereto.

S3, reaction with halogenated alkanes

The positive electrode material treated in step S2 is reacted with a halogenated alkane, and the halogenated alkane gas is used to undergo a substitution reaction with the residual alkali (LiOH) on the surface of the positive electrode material to generate lithium halide and alcohol, which can effectively reduce the amount of residual alkali on the surface of the material, reduce the pH value of the surface of the material, and reduce the requirements for environmental humidity for material storage.

It should be added that halogenated alkanes are neither strongly oxidizing nor acidic, and will not damage the structure of the ternary material, thus ensuring the electrochemical properties of the material.

Furthermore, the halogenated alkane is selected from at least one of a monohalide, a dihalide, a trihalide and a tetrahalide, and can be any one of the above; the halogen element in the halogenated alkane is selected from at least one of fluorine, chlorine and bromine, and can be any one or more of the above halogen elements. Preferably, the halogenated alkane is a monohalide; more preferably, the halogenated alkane is selected from at least one of monofluoromethane, monofluoroethane, monochloromethane, monochloroethane, monobromomethane and monobromoethane; further preferably, the halogenated alkane is selected from at least one of monochloroethane, monofluoroethane and monobromoethane, and the type of the halogenated alkane is optimized to further improve the removal effect of the residual alkali. The lithium chloride and lithium bromide generated by the reaction of the halogenated alkane and the residual alkali are easily soluble in alcohol, the removal process is simple, and no other byproducts remain on the surface of the positive electrode material, maintaining the electrochemical performance; the sparingly soluble lithium fluoride generated by the reaction can be used as a coating layer to protect the positive electrode material.

In some embodiments, during the reaction with the halogenated alkane, the reaction temperature is controlled to be 30°C-50°C, and the reaction time is 2h-8h; preferably, the reaction temperature is controlled to be 35°C-45°C, and the reaction time is 2h-5h. By regulating the reaction temperature and time, the reaction can be carried out more fully.

Specifically, the reaction temperature can be 30°C, 35°C, 40°C, 45°C, 50°C, etc., and the reaction time can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, etc.

In the actual operation process, after the reaction in step S2 is completed, the introduction of water vapor is stopped, and the temperature is raised to the reaction temperature before the introduction of halogenated alkane gas for reaction. When the amount of the positive electrode material of the nickel cobalt manganese oxide lithium is 0.8kg-1.2kg, the corresponding introduction flow rate of the halogenated alkane gas is 0.05L/min-0.15L/min. By further controlling the amount of the positive electrode material of the nickel cobalt manganese oxide lithium and the amount of the halogenated alkane introduced, the reaction is more complete, and the purpose of significantly reducing the residual alkali is achieved.

Specifically, the usage of lithium nickel cobalt manganese oxide positive electrode material can be 0.8kg, 0.9kg, 1.0kg, 1.1kg, 1.2kg, etc., and the corresponding flow rate of halogenated alkane gas can be 0.05L/min, 0.10L/min, 0.15L/min, etc.

In some embodiments, when the halogenated alkane used contains chlorine or bromine, the preparation method further comprises: purging after the reaction with the halogenated alkane is completed to remove the alcohol solution on the surface.

The present disclosure also provides a ternary positive electrode material prepared by the preparation method in the above embodiment. It has the advantages of low residual alkali content and excellent electrochemical performance.

The disclosed embodiment also provides a positive electrode plate for a lithium-ion battery, comprising a positive electrode current collector and an active coating attached to the positive electrode current collector, wherein the active coating contains the ternary positive electrode material in the above-mentioned embodiment.

It should be noted that the specific preparation method of the positive electrode sheet for lithium-ion batteries can refer to the existing technology, and the main steps include: mixing the ternary positive electrode material, the binder, and the conductive agent to form a slurry, applying it on the positive electrode collector, and drying it to form a coating. The specific types of the binder, the conductive agent, and the positive electrode collector are not limited.

The present disclosure also provides a lithium-ion battery, including the positive electrode sheet for lithium-ion batteries in the above embodiment, and may also include a negative electrode sheet, an electrolyte, a separator, etc., the specific types of which are not limited. The lithium-ion battery can also be used to prepare an electrical device, and the improvement of the positive electrode material gives the battery excellent electrochemical performance.

The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

Example 1

This embodiment provides a method for preparing a ternary positive electrode material, comprising the following steps:

(1) A high nickel ternary precursor NCM (nickel, cobalt and manganese molar ratio of 0.8:0.1:0.1) was mixed with lithium hydroxide in a molar ratio of 1:1.05, ground until the mixture was uniform, and calcined once in an oxygen atmosphere (purity of 96%, the same below) at a temperature of 550°C for 5 hours. After calcination, it was cooled and crushed to 5 μm to obtain a primary calcined sample powder; the primary calcined sample powder was then placed in an oxygen atmosphere for a secondary calcination at a temperature of 750°C for 15 hours to obtain a high nickel ternary positive electrode material powder.

(2) 1 kg of high-nickel ternary cathode material powder with an average particle size of 5 μm was placed in a tube furnace, and an inert gas (nitrogen, the same below) was introduced to completely exhaust the air in the tube. The chemical formula of the high-nickel ternary material was LiNi _0.8 Co _0.1 Mn _0.1 O ₂ .

(3) Water vapor is sprayed into the tube furnace to maintain the humidity in the tube furnace at 65%, and the high-nickel ternary cathode material powder is placed in a humid environment at room temperature (about 25° C., the same below) for 10 hours.

(4) Stop introducing water vapor, raise the temperature of the tube furnace to 30°C, and then introduce ethyl chloride gas at a flow rate of 0.05 L/min for 5 hours. After the generated lithium chloride and ethanol are purged and removed, a positive electrode material with low residual alkali is obtained.

Example 2

This embodiment provides a method for preparing a ternary positive electrode material, comprising the following steps:

(1) A high nickel ternary precursor NCM (nickel, cobalt and manganese molar ratio of 0.8:0.1:0.1) was mixed with lithium hydroxide in a molar ratio of 1:1.1, ground until the mixture was uniform, and calcined once in an oxygen atmosphere at a temperature of 500°C for 7 hours. After calcination, it was cooled and crushed to 10 μm to obtain a primary calcined sample powder; the primary calcined sample powder was then placed in an oxygen atmosphere for a secondary calcination at a temperature of 800°C for 12 hours to obtain a high nickel ternary positive electrode material powder.

(2) 1 kg of high nickel ternary cathode material powder with an average particle size of 10 μm was placed in a tube furnace and an inert The volatile gas completely expel the air in the tube. The chemical formula of the high-nickel ternary material is LiNi _0.8 Co _0.1 Mn _0.1 O ₂ .

(3) Water vapor is sprayed into the tubular furnace to maintain the humidity at 50%, and the high-nickel ternary cathode material powder is placed in a humid environment at room temperature for 5 hours.

(4) Stop introducing water vapor, heat the tube furnace to 40° C., and then introduce fluoroethane gas at a flow rate of 0.15 L/min for 2 h to obtain a low residual alkali positive electrode material with a lithium fluoride coating layer.

Example 3

This embodiment provides a method for preparing a ternary positive electrode material, comprising the following steps:

(1) The high-nickel ternary precursor NCM was mixed with lithium hydroxide in a molar ratio of 1:1.2, ground until the mixture was uniform, and calcined once in an oxygen atmosphere at a temperature of 600°C for 4 h. After calcination, it was cooled and crushed to 8 μm to obtain a primary calcined sample powder; the primary calcined sample powder was then placed in an oxygen atmosphere for a secondary calcination at a temperature of 700°C for 16 h to obtain a high-nickel ternary positive electrode material powder.

(2) 1 kg of high-nickel ternary cathode material powder with an average particle size of 8 μm was placed in a tube furnace, and an inert gas was introduced to completely expel the air in the tube. The chemical formula of the high-nickel ternary material was LiNi _0.8 Co _0.1 Mn _0.1 O ₂ .

(3) Water vapor is sprayed into the tubular furnace to maintain the humidity at 80%, and the high-nickel ternary cathode material powder is placed in a humid environment at room temperature for 2 hours.

(4) Stop introducing water vapor, raise the temperature of the tube furnace to 50° C., and then introduce ethyl bromide gas at a flow rate of 0.1 L/min for 4 h. After purging and removing the generated lithium bromide and ethanol, a positive electrode material with low residual alkali is obtained.

Example 4

The only difference from Example 1 is that the flow rate of monochloroethane is 0.05 L/min for 0.5 h.

Example 5

The only difference from Example 1 is that the flow rate of monochloroethane is 0.05 L/min for 1 h.

Example 6

The only difference from Example 1 is that the flow rate of monochloroethane is 0.05 L/min for 7 h.

Example 7

The only difference from Example 1 is that the flow rate of monochloroethane is 0.05 L/min for 9 hours.

Example 8

The only difference from Example 1 is that ethyl chloride is replaced by an equal amount of methyl chloride.

Example 9

The only difference from Example 1 is that ethyl chloride is replaced by an equal amount of methyl fluoride.

Example 10

The only difference from Example 1 is that ethyl chloride is replaced by an equal amount of methyl bromide.

Comparative Example 1

This comparative example provides a method for removing residual alkali by traditional water washing, and the specific steps are as follows:

(1) Disperse 1 kg of high-nickel ternary positive electrode material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder with an average particle size of 5 μm into 2 kg of clean water, stir and wash for 10 min at a stirring speed of 1000 r/min and a washing temperature of 35°C.

(2) After washing, the ternary material is separated from the water by filtration and vacuum dried at 100° C. for 4 h to obtain the washed ternary material.

Comparative Example 2

This comparative example provides a traditional method of removing residual alkali by introducing a strong oxidant, and the specific steps are as follows:

(1) 1 kg of high-nickel ternary positive electrode material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder with an average particle size of 5 μm after high-temperature calcination was placed in a tubular furnace, and ClO ₂ gas was introduced so that the amount of ClO ₂ gas was 10% of the mass of the high-nickel ternary positive electrode material, the introduction rate was 0.15 L/min, and the reaction time was 4 h.

(2) After the reaction in step (1) is completed, the treated positive electrode material is placed in a vacuum drying oven and vacuum dried at 100° C. for 2 h.

Comparative Example 3

This comparative example provides a method for removing residual alkali by pickling treatment with a traditional ethanol solution, and the specific steps are as follows:

(1) adding acetic acid to 100 g of ethanol in an amount having a molar ratio of 1.0 to the residual lithium on the surface of the high-nickel ternary positive electrode material LiNi _0.8 Co _0.1 Mn _0.1 O ₂ to be treated, stirring to completely dissolve the acetic acid, and forming an ethanol solution of acetic acid;

(2) Add 100 g of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder to the ethanol solution of acetic acid, continue stirring for 10 min, centrifuge to remove the solvent, and then dry under vacuum conditions at 70 ° C to obtain the treated high-nickel ternary positive electrode material.

Test Example 1

The residual lithium and electrochemical performance of the high-nickel ternary positive electrode materials obtained in the examples and comparative examples were tested, and the results are shown in Table 1.

Test method: The prepared high-nickel ternary positive electrode material is made into a positive electrode sheet, and the high-nickel ternary material, binder PVDF, and conductive agent SP are mixed in a mass ratio of 8:1:1, dispersed in the solvent NMP, stirred to form a slurry, and the slurry is coated on aluminum foil, dried, and made into a positive electrode sheet. The metal lithium sheet is used as the negative electrode to assemble a button battery for charge, discharge, and cycle tests. The test conditions are: All batteries are charged and discharged at a voltage range of 2.8 to 4.3V and a rate of 0.1C.

Table 1 Performance test table of embodiments and comparative examples

Examples 1-3 can effectively reduce the residual alkali content on the surface of the high-nickel ternary positive electrode material. Examples 4-5 have too little alkane gas, and the effect of removing the residual alkali is not as good as that of the examples. Examples 6-7 have too much gas, which will deposit on the surface of the positive electrode material particles and affect the discharge specific capacity. Compared with Example 1, Examples 8-10 have similar effects on the residual alkali by introducing the same amount of alkane gas of the same nature.

Comparative Example 1 uses the traditional water washing method to reduce alkali. Although the residual alkali on the surface of the material is significantly reduced, the sensitivity of high nickel to water and the residual washing water in the internal voids of the material cause a significant decline in the material's cycle performance. Comparative Example 2 uses excessive strong oxidant ClO ₂ treatment, resulting in excessive consumption of surface lithium, which reduces the initial capacity and capacity retention rate of the battery. Comparative Example 3 uses an ethanol solution system for acid washing treatment, which can remove residual alkali, but the active hydrogen of the alcohol will undergo ion exchange with the structure Li ⁺ , resulting in certain side reactions, resulting in a decline in cycle performance.

Test Example 2

The SEM images of the high-nickel ternary positive electrode materials prepared in the test examples and comparative examples are shown in FIG3 .

It can be seen that the samples before and after the treatment of Example 1 have round and uniform particle morphology, indicating that after the treatment, the material structure remains intact and is not damaged.

The preferred embodiments of the present disclosure are described in detail above, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, the technical solution of the present disclosure can be subjected to a variety of simple modifications, including combining various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present disclosure and belong to the protection scope of the present disclosure.

Industrial Applicability

The present invention discloses placing the nickel cobalt manganese oxide lithium positive electrode material in a humid environment and then reacting it with a halogenated alkane to generate a substitution reaction. The prepared ternary cathode material has the advantage of low residual alkali content; since the halogenated alkane has neither strong oxidizing property nor acidity, it will not damage the structure of the ternary material, so that the cathode material maintains excellent electrochemical performance. The above preparation method has a shorter process flow, and the raw materials used are easily available, which is convenient for industrial application.

Claims (26)

A method for preparing a ternary positive electrode material, characterized by comprising: subjecting a nickel-cobalt-manganese-oxide lithium positive electrode material to a water absorption treatment and then reacting it with a halogenated alkane. The preparation method according to claim 1 is characterized in that the halogenated alkane is selected from at least one of monohalide, dihalide, trihalide and tetrahalide, and the halogen element in the halogenated alkane is selected from at least one of fluorine, chlorine and bromine. The preparation method according to claim 2, characterized in that the halogenated alkane is a halogenated compound. The preparation method according to claim 3, characterized in that the halogenated alkane is selected from at least one of monofluoromethane, monofluoroethane, monochloromethane, monochloroethane, monobromomethane and monobromoethane. The preparation method according to any one of claims 1 to 4 is characterized in that the water absorption treatment process comprises: placing the nickel cobalt manganese oxide lithium positive electrode material in a humid environment with a humidity greater than or equal to 50%. The preparation method according to claim 5, characterized in that the humidity of the humid environment is 60%-80%. The preparation method according to claim 5 or 6 is characterized in that the nickel cobalt manganese oxide positive electrode material is placed in a humid environment for 5h-8h. The preparation method according to any one of claims 1 to 7, characterized in that during the reaction with the halogenated alkane, the reaction temperature is controlled to be 30° C.-50° C. and the reaction time is 2 h-8 h. The preparation method according to claim 8 is characterized in that, during the reaction with the halogenated alkane, the reaction temperature is controlled to be 35°C-45°C and the reaction time is 2h-5h. The preparation method according to claim 8 or 9 is characterized in that when the amount of the nickel cobalt manganese oxide lithium positive electrode material is 1.0 kg, the corresponding flow rate of the halogenated alkane gas is 0.05 L/min-0.15 L/min. The preparation method according to any one of claims 1 to 10 is characterized in that the nickel cobalt manganese oxide positive electrode material is placed in a tubular furnace, water vapor is introduced into the tubular furnace so that the humidity in the tubular furnace meets the requirements, the introduction of water vapor is stopped after being placed for 4h-10h, and the halogenated alkane gas is introduced to react after the temperature is raised to the reaction temperature. The preparation method according to claim 11 is characterized in that before introducing water vapor into the tube furnace, an inert gas is first introduced to exhaust the air in the tube furnace. The preparation method according to claim 11 or 12 is characterized in that the water vapor enters the tubular furnace in a spraying manner. The preparation method according to any one of claims 11 to 13, characterized in that when the halogenated alkane used contains chlorine or bromine, the preparation method further comprises: purging the obtained product after the reaction with the halogenated alkane is completed. The preparation method according to any one of claims 1 to 14, characterized in that the chemical formula of the lithium nickel cobalt manganese oxide positive electrode material is LiNi _x Co _y Mn _z O ₂ , wherein 0.7≤x≤0.9, 0.05≤y≤0.15, 0.05≤z≤0.15, x+y+z=1. The preparation method according to claim 15 is characterized in that the nickel cobalt manganese oxide lithium positive electrode material is in powder form, and the average particle size of the powder is 2 μm-15 μm. The preparation method according to any one of claims 1 to 16 is characterized in that the preparation method of the nickel cobalt manganese oxide positive electrode material comprises: mixing a nickel cobalt manganese ternary precursor with a lithium source, calcining it once in an oxygen-containing atmosphere to obtain a primary calcined product, and then calcining the primary calcined product twice in an oxygen-containing atmosphere. The preparation method according to claim 17 is characterized in that the calcination temperature of the primary calcination is 500° C.-600° C., and the calcination time is 4 h-7 h. The preparation method according to claim 17 or 18 is characterized in that the calcination temperature of the secondary calcination is 700° C.-800° C., and the calcination time is 10 h-18 h. The preparation method according to any one of claims 17 to 19 is characterized in that the molar ratio of the total amount of nickel, cobalt and manganese to the lithium element is 1:(1.01-1.20) by controlling the amount of the nickel, cobalt and manganese ternary precursor and the lithium source. The preparation method according to any one of claims 17 to 20, characterized in that the lithium source is selected from at least one of lithium hydroxide and lithium carbonate. The preparation method according to any one of claims 17 to 21, characterized in that before the primary calcined product is subjected to secondary calcination, the primary calcined product is cooled and then crushed to 2 μm-15 μm. A ternary positive electrode material, characterized in that it is prepared by the preparation method described in any one of claims 1 to 22. A positive electrode plate for a lithium-ion battery, characterized in that it includes a positive electrode collector and an active coating attached to the positive electrode collector, wherein the active coating contains the ternary positive electrode material according to claim 23. A lithium-ion battery, characterized by comprising the positive electrode sheet for a lithium-ion battery according to claim 24. An electrical device, characterized by comprising the lithium-ion battery according to claim 25.