WO2024066183A1

WO2024066183A1 - Aluminum-fluorine co-doped cobaltosic oxide, and preparation method therefor and use thereof

Info

Publication number: WO2024066183A1
Application number: PCT/CN2023/077911
Authority: WO
Inventors: 胡海涵; 卢星华; 阮丁山; 李长东; 周思源; 刘更好
Original assignee: 广东邦普循环科技有限公司; 湖南邦普循环科技有限公司
Priority date: 2022-09-28
Filing date: 2023-02-23
Publication date: 2024-04-04
Also published as: CN115571924A; CN115571924B

Abstract

The present application provides an aluminum-fluorine co-doped cobaltosic oxide, and a preparation method therefor and the use thereof. The structural formula of the aluminum-fluorine co-doped cobaltosic oxide is Co3-xAlxFyO4-y, where 0.048≤x≤0.105, and 0.024≤y≤0.21. In the aluminum-fluorine co-doped cobaltosic oxide provided in the present application, aluminum and fluorine are uniformly distributed, such that by means of the synergistic effect of aluminum and fluorine, a lithium cobalt oxide material prepared from the aluminum-fluorine co-doped cobaltosic oxide can reduce the crystal size change during the lithium deintercalation process, reduce the lattice stress and improve the structural stability; moreover, the material can resist the erosion of hydrofluoric acid in an electrolyte solution and has good cycling stability and thermal stability, thus further improving the electrochemical performance of a lithium battery.

Description

Aluminum-fluorine co-doped cobalt oxide and its preparation method and application

Technical Field

The present application belongs to the technical field of battery production and manufacturing, and in particular relates to an aluminum-fluorine co-doped cobalt tetroxide and a preparation method and application thereof.

Background technique

With the rapid development of electronic products, people's requirements for the battery life and volume of lithium batteries are constantly increasing, and lithium-ion batteries with higher energy density have become the key to promoting the upgrading of intelligent high-end products. Among them, increasing the working voltage of lithium cobalt oxide positive electrode materials is one of the effective methods to improve the energy density of batteries, and element doping is an effective measure to improve the structural instability of lithium cobalt oxide under high voltage operation. At present, cobalt oxide and lithium source are usually mixed and sintered to obtain lithium cobalt oxide, and thus the element doping effect of lithium cobalt oxide is often achieved by element doping of cobalt oxide.

CN112723422A discloses an aluminum-doped cobalt oxide core-shell material and a preparation method thereof, wherein the core of the aluminum-doped cobalt oxide core-shell material is aluminum-doped cobalt oxide, and the shell is cobalt oxide. The preparation method is as follows: firstly, a cobalt carbonate seed slurry is prepared in a reactor: a mixed solution of cobalt salt and aluminum salt and a precipitant are added to the reactor at the same time for reaction, the reaction temperature is controlled to be 50-60°C, the rotation speed is 600-800rpm, and the feeding is stopped when the particles grow to a median particle size of 18-20μm: the reaction temperature is adjusted to 45-50°C, the rotation speed is 400-600rpm, a cobalt salt solution and a precipitant are added for reaction, the particles continue to grow to a median particle size of 20-23μm, washing, drying, and calcining to obtain the aluminum-doped cobalt oxide core-shell material.

CN111646519A discloses a method for preparing aluminum-doped cobalt tetroxide, which comprises the following steps: step one, preparing a solution: preparing an aluminum-doped cobalt solution and an ammonium bicarbonate solution; step two, synthesizing crystal seeds; step three, growing cobalt carbonate; step four, washing and drying; step five, calcining; step six, mixing and packaging.

CN108807881A discloses a method for preparing bulk aluminum-doped cobalt tetroxide. The method uses a cobalt solution of a certain concentration as a cobalt source, a sodium hydroxide solution as a precipitant, an ammonia solution as a complexing agent, a hydrazine hydrate solution as a reducing agent, and an aluminum salt ethanol solution as a doping agent for a synthesis reaction. During the reaction, the aluminum salt anhydrous ethanol solution is added to a reactor by a dispersed liquid addition method to participate in the reaction; after the synthesis reaction is completed, under a certain pH value, the synthetic product is oxidized into cobalt hydroxide oxide by using a hydrogen peroxide solution, and then the mixture is washed, dried, and calcined to obtain a bulk aluminum-doped cobalt tetroxide product, and the production efficiency is high.

Existing cobalt tetroxide doping methods usually only dope with aluminum, and due to the difference in sedimentation rates between aluminum and cobalt and the presence of metastable aluminum on the surface, it is difficult to ensure the uniformity of the distribution of the doping element, thereby failing to effectively improve the structural stability of lithium cobalt oxide under high pressure.

Summary of the invention

The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

In view of the shortcomings of the prior art, the purpose of the present application is to provide an aluminum-fluorine co-doped cobalt oxide and a preparation method and application thereof, wherein aluminum and fluorine are uniformly distributed in the cobalt oxide, and the lithium cobalt oxide material prepared therefrom can reduce the change in crystal size during lithium insertion and extraction, reduce lattice stress, and improve structural stability through the synergistic effect of aluminum and fluorine; and can resist the corrosion of hydrofluoric acid in the electrolyte, and has excellent cycle stability and thermal stability, thereby further improving the electrochemical performance of lithium batteries.

To achieve this goal, this application adopts the following technical solutions:

In a first aspect, the present application provides an aluminum-fluorine co-doped cobalt oxide, wherein the aluminum-fluorine co-doped cobalt oxide has a structural formula of Co _3-x Al _x F _y O _4-y , wherein 0.048≤x≤0.105, and 0.024≤y≤0.21.

Wherein, x can be 0.048, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, 0.095, 0.1 or 0.105, and y can be 0.024, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2 or 0.21, but are not limited to the values listed. Other values not listed in the numerical range are also included. The same applies to the values given above.

In the present application, aluminum and fluorine are doped into cobalt tetroxide at the same time, and an [AlF] ²⁺ complex is formed through the strong attraction between aluminum and fluorine. The [AlF] ²⁺ complex can balance the sedimentation rates of aluminum and cobalt, promote the uniform distribution of aluminum, and avoid the aluminum segregation phenomenon caused by uneven aluminum distribution due to the difference in the sedimentation rates of aluminum and cobalt. At the same time, the [AlF] ²⁺ complex can bind and fix aluminum in a metastable state, inhibiting the enrichment of doped aluminum to form aluminum flakes.

Therefore, in the present application, aluminum and fluorine are uniformly dispersed in cobalt oxide, wherein aluminum doping can increase the c-axis spacing of the lithium cobalt oxide material, reduce the change in crystal size during lithium insertion and extraction, reduce lattice stress, and the aluminum-oxygen bond is conducive to stabilizing the layered structure with oxygen as the skeleton; and the electronegativity of the fluorine element is greater than that of oxygen. After fluorine replaces oxygen, it will not undergo redox changes during the charge and discharge process, and the bond with cobalt is stronger, further improving the structural stability of the lithium cobalt oxide material. The aluminum-fluorine co-doped cobalt oxide provided in the present application is a spinel structure with stable structure and high crystallinity, uniform morphology, and excellent performance.

In addition, when the aluminum-fluorine co-doped cobalt oxide provided in the present application is prepared into a lithium cobalt oxide positive electrode material, the doped fluorine will form fluoride oxide in the lithium cobalt oxide positive electrode material, which can resist the corrosion of HF in the electrolyte and improve the cycle stability; therefore, the lithium cobalt oxide positive electrode material prepared by using the aluminum-fluorine co-doped cobalt oxide provided in the present application has excellent cycle stability and thermal stability, and can meet the requirements of high voltage conditions for lithium cobalt oxide materials.

It should be noted that in the aluminum-fluorine co-doped cobalt tetroxide structural formula Co _3-x Al _x F _y O _4-y in the present application, the subscripts of the elements represent the molar ratios of the elements.

As a preferred technical solution of the present application, x:y is 0.5-2, for example, it can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

The present application defines the molar ratio of aluminum to fluorine in aluminum-fluorine co-doped cobalt oxide as 0.5 to 2. When the molar ratio of aluminum to fluorine is lower than 0.5, excessive fluorine combines with lithium to form dead lithium, thereby hindering the deintercalation of lithium ions and causing the rate performance of the lithium cobalt oxide positive electrode material to decrease. When the molar ratio of aluminum to fluorine is higher than 2, the capacity of the lithium cobalt oxide positive electrode material will decrease, because aluminum is a non-electrochemically active element and cannot provide capacity.

Optionally, the particle size of the aluminum-fluorine co-doped cobalt oxide is 2 to 20 μm, for example, 2 μm, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the specific surface area of the aluminum-fluorine co-doped cobalt oxide is 2 to 5.5 m ² /g, for example, 2 m ² /g, 3 m ² /g, 3.2 m 2 /g, 3.4 m ² ^/ ^g , 3.6 m ² /g, 4 m ² /g, 4.2 m ² /g, 4.4 m 2 /g, 4.6 m ² /g, 4.8 m ² /g or 5 m ² /g, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

Optionally, the tap density of the aluminum-fluorine co-doped cobalt oxide is 1.5-3 g/cm ³ , for example, 1.5 g/cm ³ , 1.7 g/cm ³ , 1.9 g/cm ³ , 2 g/cm ³ , 2.2 g/cm ³ , 2.4 g/cm ³ , 2.6 g/cm ³ , 2.8 g/cm ³ or 3 g/cm ³ , but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

Optionally, the bulk density of the aluminum-fluorine co-doped cobalt oxide is 0.8-2.2 g/cm ³ , for example, 0.8 g/cm ³ , 1.0 g/cm ³ , 1.2 g/cm ³ , 1.4 g/cm ³ , 1.6 g/cm ³ , 1.8 g/cm ³ , 2.0 g/cm ³ or 2.2 g/cm ³ , but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

In a second aspect, the present application provides a method for preparing aluminum-fluorine co-doped cobalt oxide according to the first aspect, the preparation method comprising:

The aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution are injected into the reactor in parallel, and react to generate an intermediate material during the injection process, and then the intermediate material is sintered to obtain the aluminum-fluorine co-polymer. Doped with cobalt tetroxide.

The present application adopts a method of injecting an aluminum-cobalt mixed solution, a fluorine solution and a precipitant solution into a reactor in parallel to react and generate an intermediate material, that is, aluminum and fluorine are both doped by a wet method. During the synthesis process, aluminum and fluorine have a strong mutual attraction to form an [AlF] ²⁺ complex, thereby slowing down the sedimentation rate of aluminum, effectively ensuring the uniformity of element distribution, and achieving a better doping effect. The preparation method provided by the present application can obtain aluminum-fluorine co-doped cobalt tetroxide with a spinel structure, which has a stable structure, high crystallinity, uniform morphology and excellent performance.

As a preferred technical solution of the present application, the preparation method further comprises: separately preparing the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution.

Optionally, a cobalt source, an aluminum source and a solvent are mixed to obtain the aluminum-cobalt mixed solution.

Optionally, the cobalt source includes any one of cobalt chloride, cobalt sulfate or cobalt nitrate, or a combination of at least two of them.

Optionally, the cobalt concentration in the aluminum-cobalt mixed solution is 0.5-3 mol/L, for example, it can be 0.5 mol/L, 0.7 mol/L, 0.9 mol/L, 1 mol/L, 1.2 mol/L, 1.4 mol/L, 1.6 mol/L, 1.8 mol/L, 2 mol/L, 2.2 mol/L, 2.4 mol/L, 2.6 mol/L, 2.8 mol/L or 3 mol/L, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the aluminum source includes aluminum sulfate 18hydrate.

Optionally, the mass ratio of aluminum to cobalt in the aluminum-cobalt mixed solution is 0.008 to 0.0165, for example, it can be 0.008, 0.009, 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016 or 0.0165, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, a fluorine source and a solvent are mixed to prepare the fluorine solution.

Optionally, the fluorine source includes any one of sodium fluoride, potassium fluoride, ammonium fluoride or ammonium bifluoride, or a combination of at least two thereof.

Optionally, the fluorine concentration in the fluorine solution is 0.5-1 mol/L, for example, it can be 0.5 mol/L, 0.55 mol/L, 0.6 mol/L, 0.65 mol/L, 0.7 mol/L, 0.75 mol/L, 0.8 mol/L, 0.85 mol/L, 0.9 mol/L, 0.95 mol/L or 1 mol/L, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the precipitant solution is prepared by mixing a precipitant and a solvent.

Optionally, the precipitant concentration in the precipitant solution is 2 to 3 mol/L, for example, it can be 2mol/L, 2.1mol/L, 2.2mol/L, 2.3mol/L, 2.4mol/L, 2.5mol/L, 2.6mol/L, 2.7mol/L, 2.8mol/L, 2.9mol/L or 3mol/L, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the precipitating agent comprises a carbonate.

Optionally, the carbonate includes any one of ammonium bicarbonate, ammonium carbonate or sodium carbonate, or a combination of at least two of them.

Optionally, the solvents all include deionized water.

As a preferred technical solution of the present application, the aluminum-cobalt mixed solution is injected into the reactor at a flow rate of 7 to 35 L/h, for example, it can be 7 L/h, 10 L/h, 12 L/h, 15 L/h, 17 L/h, 20 L/h, 23 L/h, 25 L/h, 27 L/h, 30 L/h, 32 L/h or 35 L/h, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the fluorine solution is injected into the reactor at a flow rate of a molar ratio of aluminum to fluorine of 0.5 to 2, for example, it can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

It should be noted that the fluorine solution in this application is fed at a molar ratio of aluminum to fluorine of 0.5 to 2, which means that during the co-current injection process, the aluminum in the aluminum-cobalt mixed solution flowing into the reactor is equal to the aluminum in the cobalt mixed solution flowing into the reactor. The molar ratio of fluorine in the fluorine solution is 0.5-2.

The present application limits the flow rate of the aluminum-cobalt mixed solution injected into the reactor to 7 to 35 L/h, and limits the flow rate of the fluorine solution injected into the reactor at a molar ratio of aluminum to fluorine of 0.5 to 2. That is, by regulating the injection flow rates of the aluminum-cobalt mixed solution and the fluorine solution, the formation of an [AlF] ²⁺ complex between aluminum and fluorine can be further promoted. This is because the strong electrostatic force between aluminum and fluorine forms an ionic bond.

Optionally, the precipitant solution is injected into the reactor at a flow rate of 2.2 to 3 in a molar ratio of precipitant to cobalt source; for example, it can be 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

In the present application, the amount of the precipitant solution added is kept in excess.

Optionally, before the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution are injected into the reactor in parallel, a bottom liquid is added into the reactor.

In the present application, before the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution are injected into the reactor in parallel, the purpose of adding the bottom liquid into the reactor is to provide a stable environment for the preparation process of the intermediate material.

Optionally, the concentration of the base solution is 0.5-3 mol/L, for example, it can be 0.5 mol/L, 0.7 mol/L, 1 mol/L, 1.2 mol/L, 1.4 mol/L, 1.6 mol/L, 1.8 mol/L, 2 mol/L, 2.2 mol/L, 2.4 mol/L, 2.6 mol/L, 2.8 mol/L or 3 mol/L, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the volume of the base liquid accounts for 0.3 to 0.6 of the total volume of the reactor, for example, it can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55 or 0.6, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the base liquid comprises a carbonate solution.

Optionally, the carbonate in the base liquid includes any one of ammonium bicarbonate, ammonium carbonate or sodium carbonate, or a combination of at least two of them.

As a preferred technical solution of the present application, the preparation process of the intermediate material includes:

(1) Under stirring conditions, the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution are injected into the reactor in parallel until the reactor is full, the feeding and stirring are stopped, and the supernatant liquid is extracted after standing;

(2) Repeating the operation of step (1) until the D50 of the product reaches a certain value, transferring part of the material in the reactor to another reactor to complete the reactor separation process;

(3) Repeating steps (1) and (2) for each of the reactors until the D50 of the product reaches the target particle size, thereby obtaining the intermediate material.

In the present application, the process of injecting the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution into the reactor in parallel is the feeding process, and the present application is more conducive to crystal growth through the coordination between the feeding, filling the reactor, i.e. standing and draining, and separating the reactor steps, and the reaction conditions are coordinated to obtain a large-particle intermediate material, i.e., a large-particle aluminum-fluorine co-doped cobalt tetroxide material.

Optionally, 1/2 of the material in the reactor is transferred to another reactor to complete the reactor separation process.

Optionally, the target particle size D50 of the product is 18 to 22 μm, for example, it can be 18 μm, 18.2 μm, 18.4 μm, 18.6 μm, 18.8 μm, 19 μm, 19.2 μm, 19.4 μm, 19.8 μm, 20 μm or 22 μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, when the D50 of the product reaches 8.5-13 μm, a first separation process is performed, and when the D50 of the product reaches 14-16 μm, a second separation process is performed; then, the operation of step (1) is repeated until the D50 of the product reaches 18-22 μm to obtain the intermediate material.

The process for preparing the large-particle intermediate material in the present application can be: (1) under stirring, injecting the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution into the reactor in parallel until the reactor is full, and then stopping. Feed and stir, let stand and extract the supernatant, then repeat the above-mentioned process of feeding-filling the kettle, i.e., letting stand and extracting, until the D50 of the product reaches 8.5-13 μm, and transfer part of the materials in the reactor to another reactor to complete the first separation process; (2) the two reactors are injected with aluminum-cobalt mixed solution, fluorine solution and precipitant solution in parallel until the reactor is full, stop feeding and stirring, let stand and extract the supernatant, then repeat the process of feeding-filling the kettle, i.e., letting stand and extracting, until the D50 of the product reaches 14-16 μm, and transfer part of the materials in the two reactors to the other two reactors respectively to complete the second separation process; (3) the four reactors are injected with aluminum-cobalt mixed solution, fluorine solution and precipitant solution in parallel until the reactor is full, stop feeding and stirring, let stand and extract the supernatant, then repeat the process of feeding-filling the kettle, i.e., letting stand and extracting, until the D50 of the product reaches 18-22 μm, and obtain a large-particle intermediate material.

Optionally, the intermediate material is prepared at a temperature of 35-50°C, for example, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the stirring speed is 12 to 28 Hz, for example, 12 Hz, 14 Hz, 16 Hz, 18 Hz, 20 Hz, 22 Hz, 24 Hz, 26 Hz or 28 Hz, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

The present application limits the preparation temperature of large-particle intermediate materials to 35-50°C. When the temperature is lower than 35°C, the particle size increase will be too slow, and small nuclei will be easily produced in the later stage of the reaction. This is because the nucleation rate is greater than the growth rate at this time; when the temperature is higher than 50°C, the reaction time will be too short and the material crystal form will be incomplete. This is because high temperature will promote the growth of particles. The present application also limits the stirring speed to 12-28Hz. When the stirring speed is lower than 12Hz, particles will easily agglomerate. This is due to insufficient stirring and poor dispersion. When the stirring speed is higher than 28Hz, small nuclei will be easily produced in the later stage of the reaction. This is because under high stirring force, the reactants stay on the particle surface for too short a time and do not have time to grow, thus nucleating individually. Therefore, the present application The preparation temperature is adjusted within the range of 35 to 50° C. and the stirring speed is adjusted within the range of 12 to 28 Hz, so that the particle size of the intermediate can be more effectively controlled to obtain a large-particle aluminum-fluorine co-doped cobalt oxide material.

The aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution are injected into the reactor in parallel until the D50 of the product reaches the target particle size to obtain the intermediate material.

The present application prepares the intermediate material by directly reacting in a reactor by regulating the reaction conditions, without the need to carry out the process of standing the reactor to pump out the waste and separating the reactors, thereby obtaining an intermediate material with a small particle size, that is, a small particle size aluminum-fluorine co-doped cobalt tetroxide material.

Optionally, the target particle size D50 of the intermediate material is 2 to 5 μm, for example, it can be 2 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm or 5 μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the intermediate material is prepared at a temperature of 35-45°C, for example, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C or 45°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the intermediate material is prepared under stirring conditions.

Optionally, the stirring speed is 30-50 Hz, for example, it can be 30 Hz, 32 Hz, 34 Hz, 36 Hz, 38 Hz, 40 Hz, 42 Hz, 44 Hz, 46 Hz, 48 Hz or 50 Hz, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

The present application limits the preparation temperature of the small-particle intermediate material to 35-45°C. When the temperature is lower than 35°C, the reaction temperature control will be unstable. This is because the motor will generate heat during the reaction and the actual temperature is likely to be higher than the set value. When the temperature is higher than 45°C, the primary particles of the particles will become coarse. This is because the growth rate at high temperature is greater than the nucleation rate.

The present application also limits the stirring speed to 30-50 Hz. When the stirring speed is lower than 30 Hz, the initial The initial particle size is too large, which affects the sphericity of the finished product. This is due to the large initial particle size, short reaction time, low solid content at the end of the reaction, and low probability of collision between particles; when the stirring speed is higher than 50Hz, it generally exceeds the rated frequency of the motor, and long-term high stirring will greatly reduce the service life of the motor. Therefore, the present application adjusts the preparation temperature to within the range of 35 to 45°C and the stirring speed to within the range of 30 to 50Hz, which can more effectively control the particle size of the intermediate and obtain a small-particle aluminum-fluorine co-doped cobalt tetroxide material.

The present application provides a preparation method of a large-particle intermediate material and a preparation method of a small-particle intermediate material, respectively, so that two products, large-particle aluminum-fluorine co-doped cobalt tetroxide and small-particle aluminum-fluorine co-doped cobalt tetroxide, can be prepared respectively.

As a preferred technical solution of the present application, the intermediate material is centrifugally washed and then sintered to obtain the aluminum-fluorine co-doped cobalt tetroxide.

Optionally, the washing water used in the centrifugal washing includes pure water with a temperature of 50-70°C, for example, it can be 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C or 70°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the centrifugal washing has a centrifugal frequency of 20 to 45 Hz, for example, 20 Hz, 25 Hz, 30 Hz, 32 Hz, 34 Hz, 36 Hz, 38 Hz, 40 Hz, 42 Hz, 44 Hz or 45 Hz, but is not limited to the listed values, and other unlisted values within the range are also applicable.

Optionally, after the centrifugal washing, the water content of the intermediate material is 10wt% to 20wt%, for example, it can be 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

The present invention does not need to use a drying device to dry the intermediate material, thus avoiding the problem of agglomeration of the intermediate material (such as cobalt carbonate material doped with aluminum and fluorine) during the drying process; and after adjusting the water content of the intermediate material by centrifugal washing, the intermediate material is directly fed into a rotary kiln for calcination and decomposition. The particles are not agglomerated during the centrifugal washing process, so during the high-temperature decomposition process, a large amount of water vapor suddenly expands and escapes in a short period of time to destroy the soft agglomeration between particles, which is conducive to the formation of fine particles and reduces agglomeration. At the same time, the drying stage is omitted in the preparation process, shortening the process.

The present application defines the water content of the intermediate material after centrifugal washing as 10wt% to 20wt%. When the water content is too low, the ability to destroy particle agglomeration is weakened due to insufficient water vapor; when the water content is too high, it is easy to stick to the wall of the rotary kiln, resulting in uneven heating. At the same time, the reason for selecting 50-70℃ pure water for centrifugal washing is to facilitate the removal of impurities such as chlorine or sulfur in the system.

Optionally, the sintering includes one-stage sintering, two-stage sintering and three-stage sintering performed sequentially.

In the present application, the main purpose of the first-stage sintering is to remove the moisture in the intermediate material with a water content of 10wt% to 20wt%, and the large amount of water vapor generated at the same time can effectively destroy the agglomeration between the particles; the main purpose of the second-stage sintering is to react, that is, the intermediate material reacts to be converted into cobalt tetroxide; the main purpose of the third-stage sintering is to regulate the crystallinity of cobalt tetroxide and other aspects.

Optionally, the temperature of the first sintering stage is 120-200°C, for example, it can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the sintering time is 2 to 3 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the heating rate of the first sintering stage is 1 to 5°C/min, for example, it can be 1°C/min, 1.5°C/min, 2°C/min, 2.5°C/min, 3°C/min, 3.5°C/min, 4°C/min, 4.5°C/min or 5°C/min, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the temperature of the second stage sintering is 350-450°C, for example, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C or 450°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the second-stage sintering time is 2 to 3 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the heating rate of the second-stage sintering is 1 to 5°C/min, for example, it can be 1°C/min, 1.5°C/min, 2°C/min, 2.5°C/min, 3°C/min, 3.5°C/min, 4°C/min, 4.5°C/min or 5°C/min, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the temperature of the three-stage sintering is 650-800°C, for example, it can be 650°C, 670°C, 690°C, 700°C, 720°C, 740°C, 760°C, 780°C or 800°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the three-stage sintering time is 2 to 3 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Optionally, the heating rate of the three-stage sintering is 1 to 5°C/min, for example, it can be 1°C/min, 1.5°C/min, 2°C/min, 2.5°C/min, 3°C/min, 3.5°C/min, 4°C/min, 4.5°C/min or 5°C/min, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

The present application specifies that the temperature of the first sintering is 120-200°C, the temperature of the second sintering is 350-450°C, and the temperature of the third sintering is 650-800°C. This is because in the first sintering, the water content is fully converted into water vapor; the phase transition from cobalt carbonate to cobalt tetroxide occurs in the second sintering area; the third sintering can make the crystalline structure of cobalt tetroxide more complete, thereby further improving the aluminum-fluorine co-doped cobalt tetroxide material. In addition, the time and heating rate of the first stage sintering, the second stage sintering and the third stage sintering can be the same or different.

In a third aspect, the present application provides a lithium cobalt oxide positive electrode material, wherein the lithium cobalt oxide positive electrode material comprises the aluminum-fluorine co-doped cobalt oxide described in the first aspect.

In a fourth aspect, the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises the lithium cobalt oxide positive electrode material described in the third aspect.

Compared with the prior art, the beneficial effects of this application are:

The aluminum and fluorine are evenly distributed in the aluminum-fluorine co-doped cobalt tetroxide provided in the present application. The lithium cobalt oxide material prepared therefrom can reduce the change in crystal size during lithium insertion and extraction, reduce lattice stress, and improve structural stability through the synergistic effect of aluminum and fluorine; and can resist the corrosion of hydrofluoric acid in the electrolyte, and has excellent cycle stability and thermal stability, thereby further improving the electrochemical performance of the lithium battery.

Other aspects will be apparent upon reading and understanding the drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

FIG. 1 is a SEM image of the intermediate material provided in Example 1 of the present application.

FIG. 2 is a SEM image of the intermediate material provided in Example 1 of the present application.

FIG3 is a SEM image of aluminum-fluorine co-doped cobalt tetroxide provided in Example 2 of the present application.

FIG. 4 is a SEM image of aluminum-fluorine co-doped cobalt tetroxide provided in Example 2 of the present application.

FIG5 is a cross-sectional SEM image of the intermediate material provided in Example 3 of the present application.

FIG6 is a cross-sectional SEM image of the intermediate material provided in Example 3 of the present application.

Detailed ways

The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations of the present application.

Example 1

This embodiment provides a method for preparing aluminum-fluorine co-doped cobalt oxide, the preparation method comprising:

(1) mixing cobalt chloride, aluminum sulfate 18hydrate and deionized water to obtain an aluminum-cobalt mixed solution, wherein the cobalt concentration in the aluminum-cobalt mixed solution is 2 mol/L, and the mass ratio of aluminum to cobalt is 0.01; mixing sodium fluoride and deionized water to obtain a fluorine solution with a fluorine concentration of 0.5 mol/L; and mixing ammonium bicarbonate and deionized water to obtain a precipitant solution with a concentration of 2 mol/L;

(2) adding a 1 mol/L ammonium bicarbonate solution as a base liquid to the reactor, the volume of the base liquid accounting for 0.4 of the volume of the reactor, and then raising the temperature in the reactor to 46° C.;

(3) After adjusting the stirring speed in the reactor to 20 Hz, the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solvent are injected into the reactor in parallel, wherein the flow rate of the aluminum-cobalt mixed solution is 25 L/h, the fluorine solution is fed at a molar ratio of aluminum to fluorine of 1, and the precipitant solution is fed at a molar ratio of carbonate to cobalt chloride of 2.2, until the reactor is full, stop feeding and stirring, let it stand and extract the supernatant;

(4) Repeat step (3) until the D50 of the product in the reactor rises to 9.5 μm, and transfer 1/2 of the material in the reactor to another reactor to complete a split reactor process;

(5) Repeat step (3) in both reactors until the D50 of the product in the reactor rises to 15 μm, and transfer 1/2 of the material in the two reactors to the other two reactors to complete the secondary separation process;

(6) Repeat the operation of step (3) in four reactors until the D50 of the product in the reactor rises to 19 μm, and the reaction is completed to obtain the intermediate material;

(7) The intermediate material was centrifuged and washed with pure water at a temperature of 50°C to obtain a water content of 15wt% of the intermediate material, wherein the frequency of the centrifuge used for centrifugal washing is 35Hz;

(8) The intermediate material with a water content of 15 wt% is subjected to a first-stage sintering at a temperature of 150°C, a second-stage sintering at a temperature of 400°C and a third-stage sintering at a temperature of 750°C in sequence to obtain aluminum-fluorine co-doped cobalt tetroxide, wherein the time for the first-stage sintering, the second-stage sintering and the third-stage sintering is 2.5 h.

The aluminum-fluorine co-doped cobalt oxide prepared in this embodiment has a structural formula of Co _2.94 Al _0.06 F _0.06 O _3.94 , a particle size D50 of 19.12 μm, a tap density of 2.59 g/cm ³ , an apparent density of 2.1 g/cm ³ , and a specific surface area of 3.74 m ² /g; wherein the percentage of cobalt is 46.6 wt %, the percentage of aluminum is 0.45 wt %, and the percentage of fluorine is 0.32 wt %.

The intermediate material in this example was tested by scanning electron microscopy. As shown in FIG. 1 and FIG. 2 , the intermediate material prepared in this example has uniform particle size, large particle size, smooth surface, and no enriched aluminum flakes.

Example 2

(1) mixing cobalt sulfate, aluminum sulfate 18hydrate and deionized water to obtain an aluminum-cobalt mixed solution, wherein the cobalt concentration in the aluminum-cobalt mixed solution is 1.5 mol/L, and the mass ratio of aluminum to cobalt is 0.008; mixing potassium fluoride and deionized water to obtain a fluorine solution with a fluorine concentration of 1 mol/L; and mixing ammonium carbonate and deionized water to obtain a precipitant solution with a concentration of 3 mol/L;

(2) adding a 1 mol/L ammonium carbonate solution as a base liquid to the reactor, the volume of the base liquid accounting for 0.5 of the volume of the reactor, raising the temperature in the reactor to 35°C, adjusting the stirring speed in the reactor to 30 Hz, and then injecting the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solvent into the reactor in parallel, wherein the flow rate of the aluminum-cobalt mixed solution is 35 L/h, the fluorine solution is fed at a molar ratio of aluminum to fluorine of 0.5, and the precipitant solution is fed at a molar ratio of carbonate to cobalt sulfate of 3, until the D50 of the product rises to 4.5 μm, and the reaction is continued. The intermediate material is obtained at the end;

(3) centrifugally washing the intermediate material with pure water at a temperature of 60° C. to obtain an intermediate material with a water content of 20 wt %, wherein the frequency of the centrifuge used for the centrifugal washing is 45 Hz;

(4) The intermediate material with a water content of 20 wt% is subjected to a first-stage sintering at a temperature of 200°C, a second-stage sintering at a temperature of 350°C and a third-stage sintering at a temperature of 650°C in sequence to obtain aluminum-fluorine co-doped cobalt tetroxide, wherein the time for the first-stage sintering, the second-stage sintering and the third-stage sintering is 2.5 h.

The aluminum-fluorine co-doped cobalt oxide prepared in this embodiment has a structural formula of Co _2.952 Al _0.048 F _0.024 O _3.976 , a particle size D50 of 4.48 μm, a tap density of 2.18 g/cm ³ , an apparent density of 1.1 g/cm ³ , and a specific surface area of 3 m ² /g; wherein the percentage of cobalt is 47.1 wt %, the percentage of aluminum is 0.36 wt %, and the percentage of fluorine is 0.13 wt %.

The aluminum-fluorine co-doped cobalt oxide in this embodiment was tested by scanning electron microscope. As shown in FIG3 and FIG4 , the aluminum-fluorine co-doped cobalt oxide obtained in this embodiment has a smaller particle size, better dispersion, and no agglomeration behavior.

Example 3

(1) mixing cobalt nitrate, aluminum sulfate 18hydrate and deionized water to obtain an aluminum-cobalt mixed solution, wherein the cobalt concentration in the aluminum-cobalt mixed solution is 1 mol/L, and the mass ratio of aluminum to cobalt is 0.0165; mixing ammonium fluoride and deionized water to obtain a fluorine solution with a fluorine concentration of 0.8 mol/L; and mixing sodium carbonate and deionized water to obtain a precipitant solution with a concentration of 2.5 mol/L;

(2) adding a 1 mol/L sodium carbonate solution as a base liquid to the reactor, the volume of the base liquid accounting for 0.3 of the volume of the reactor, and then raising the temperature in the reactor to 48° C.;

(3) After adjusting the stirring speed in the reactor to 28 Hz, the aluminum-cobalt mixed solution, fluorine solution and precipitate were added. The precipitant solvent is injected into the reactor in parallel, wherein the flow rate of the aluminum-cobalt mixed solution is 7 L/h, the fluorine solution is fed at a molar ratio of aluminum to fluorine of 2, and the precipitant solution is fed at a molar ratio of carbonate to cobalt nitrate of 2.5, until the reactor is filled, the feeding and stirring are stopped, and the supernatant is extracted after standing;

(4) Repeat step (3) until the D50 of the product in the reactor rises to 10 μm, and transfer 1/2 of the material in the reactor to another reactor to complete a split reactor process;

(5) Repeat step (3) in both reactors until the D50 of the product in the reactor rises to 15.5 μm, and transfer 1/2 of the material in the two reactors to the other two reactors to complete the secondary separation process;

(6) Repeat the operation of step (3) in four reactors until the D50 of the product in the reactor rises to 18 μm, and the reaction is completed to obtain the intermediate material;

(7) centrifugally washing the intermediate material with pure water at a temperature of 70° C. to obtain an intermediate material with a water content of 10 wt %, wherein the frequency of the centrifuge used for the centrifugal washing is 40 Hz;

(8) The intermediate material with a water content of 10 wt% is subjected to a first-stage sintering at a temperature of 120°C, a second-stage sintering at a temperature of 450°C and a third-stage sintering at a temperature of 800°C in sequence to obtain aluminum-fluorine co-doped cobalt tetroxide, wherein the time for the first-stage sintering, the second-stage sintering and the third-stage sintering is 2.5 h.

The aluminum-fluorine co-doped cobalt oxide prepared in this embodiment has a structural formula of Co _2.903 Al _0.097 F _0.194 O _3.806 , a particle size D50 of 18.16 μm, a tap density of 2.23 g/cm ³ , an apparent density of 1.99 g/cm ³ , and a specific surface area of 3.56 m ² /g; wherein the percentage of cobalt is 46.9wt%, the percentage of aluminum is 0.77wt%, and the percentage of fluorine is 1.08wt%.

The intermediate material in this embodiment was tested by scanning electron microscope. As shown in FIG. 5 and FIG. 6 , the intermediate material prepared in this embodiment has a smooth cross section, a uniform composition, no voids, and no aluminum enrichment.

Comparative Example 1

The difference between this comparative example and Example 1 is that the preparation of the fluorine solution is omitted in step (1), and step (3) The process of injecting the fluorine solution into the reactor is omitted, and the other process parameters and operating conditions are the same as those in Example 1.

Comparative Example 2

The difference between this comparative example and Example 1 is that in step (1), a cobalt solution is prepared instead of an aluminum-cobalt solution, and in step (3), the cobalt solution, the fluorine solution and the precipitant solution are injected into the reactor in parallel. The other process parameters and operating conditions are the same as those in Example 1.

Comparative Example 3

This comparative example provides a method for preparing aluminum-fluorine co-doped cobalt oxide, the preparation method comprising:

(1) mixing cobalt chloride, aluminum sulfate 18hydrate and deionized water to obtain an aluminum-cobalt mixed solution, wherein the cobalt concentration in the aluminum-cobalt mixed solution is 2 mol/L, and the mass ratio of aluminum to cobalt is 0.01; mixing ammonium bicarbonate and deionized water to obtain a precipitant solution with a concentration of 2 mol/L;

(3) After adjusting the stirring speed in the reactor to 20 Hz, the aluminum-cobalt mixed solution and the precipitant solvent are injected into the reactor in parallel, wherein the flow rate of the aluminum-cobalt mixed solution is 25 L/h, and the precipitant solution is fed according to a molar ratio of carbonate to cobalt chloride of 2.2 until the reactor is full, and the feeding and stirring are stopped, and the supernatant is extracted after standing;

(6) Repeat step (3) for all four reactors until the D50 of the product in the reactor rises. to 19 μm, the reaction is completed and the intermediate material is obtained;

(7) centrifugally washing the intermediate material with pure water at a temperature of 50° C. to obtain an intermediate material with a water content of 15 wt %, wherein the frequency of the centrifuge used for the centrifugal washing is 35 Hz;

(8) The process of calcining the doped fluorine element by pyrometallurgy: The intermediate material is heated in an oven at 120°C for 12 hours to obtain a dried intermediate material powder. The intermediate material powder is fully mixed with lithium fluoride, and then sintered in one stage at 200°C, two stages at 350°C, and three stages at 650°C. The time for the first stage, the second stage, and the third stage is 2.5 hours to obtain aluminum-fluorine co-doped cobalt oxide with a structural formula of Co _2.94 Al _0.06 F _0.06 O _3.94 .

The cobalt oxide material doped with aluminum and/or fluorine in Examples 1-3 and Comparative Examples 1-3 was uniformly mixed with lithium carbonate at a molar ratio of Li:Co of 1.05, placed in a push plate kiln for high-temperature solid-phase sintering at 950°C for 12 hours to obtain a lithium cobalt oxide positive electrode material, and its electrochemical properties were tested. Specific steps for electrochemical performance test: a certain amount of lithium cobalt oxide positive electrode material, polyvinylidene fluoride (PVDF) and acetylene black were weighed according to a mass ratio of 8:1:1, the three were placed in an agate mortar and uniformly mixed, and N-methyl-2-pyrrolidone (NMP) was added dropwise to make a uniform slurry. The slurry was evenly applied to the surface of the aluminum foil, vacuum dried, and punched into a circular positive electrode sheet. Afterwards, metallic lithium was used as the negative electrode to form a CR2025 button battery in a glove box. The electrical performance test was carried out using a CT2001A blue electric test system, with a test voltage range of 3.0 to 4.55V and a current density of 1C = 200mA g ^-1 .

The performance of lithium-ion batteries prepared from the cobalt tetroxide materials doped with aluminum and/or fluorine in Examples 1-3 and Comparative Examples 1-3 was tested, and the results are shown in Table 1.

Table 1

From the data analysis of Table 1, it can be seen that Examples 1-3 have higher first-cycle discharge capacity and capacity retention rate at room temperature and high temperature.

The sample of Comparative Example 1, due to the absence of fluorine element, has a rapid decrease in reversible capacity during high-temperature cycling and poor high-temperature cycling stability.

For the sample of Comparative Example 2, since there is no aluminum element, the proportion of cobalt that can provide valence change is increased, so the first-cycle discharge capacity is slightly improved, but the lack of aluminum's fixing effect on the structure leads to poor room temperature cycle stability.

Compared with Example 1, the room temperature and high temperature cycle stability of Comparative Example 3 is slightly worse, mainly because it is difficult to achieve uniform doping of elements by the solid phase doping method, resulting in a weakened doping effect.

The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in the present application are within the protection scope and disclosure scope of the present application.

Claims

Aluminum-fluorine co-doped cobalt oxide, wherein the structural formula of the aluminum-fluorine co-doped cobalt oxide is Co 3-x Al x F y O 4-y , wherein 0.048≤x≤0.105, 0.024≤y≤0.21.
The aluminum-fluorine co-doped cobalt oxide according to claim 1, wherein x:y is 0.5 to 2;

The particle size of the aluminum-fluorine co-doped cobalt oxide is 2 to 20 μm;

The specific surface area of the aluminum-fluorine co-doped cobalt oxide is 2 to 5.5 m 2 /g;

The tap density of the aluminum-fluorine co-doped cobalt oxide is 1.5 to 3 g/cm 3 ;

The bulk density of the aluminum-fluorine co-doped cobalt oxide is 0.8-2.2 g/cm 3 .
A method for preparing aluminum-fluorine co-doped cobalt oxide according to claim 1 or 2, wherein the preparation method comprises:

The aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution are injected into the reactor in parallel, reacted during the injection process to generate an intermediate material, and then the intermediate material is sintered to obtain the aluminum-fluorine co-doped cobalt tetroxide.
The preparation method according to claim 3, wherein the preparation method further comprises: preparing the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution respectively;

Mixing a cobalt source, an aluminum source and a solvent to obtain the aluminum-cobalt mixed solution;

Mixing a fluorine source and a solvent to obtain the fluorine solution;

Mixing a precipitant and a solvent to obtain the precipitant solution;

The solvents all include deionized water.
The preparation method according to claim 4, wherein the cobalt source comprises any one or a combination of at least two of cobalt chloride, cobalt sulfate or cobalt nitrate;

Optionally, the cobalt concentration in the aluminum-cobalt mixed solution is 0.5 to 3 mol/L;

Optionally, the aluminum source includes aluminum sulfate 18hydrate;

Optionally, the mass ratio of aluminum to cobalt in the aluminum-cobalt mixed solution is 0.008 to 0.0165.
The preparation method according to claim 4, wherein the fluorine source comprises any one of sodium fluoride, potassium fluoride, ammonium fluoride or ammonium bifluoride, or a combination of at least two thereof;

Optionally, the fluorine concentration in the fluorine solution is 0.5 to 1 mol/L;
The preparation method according to claim 4, wherein the concentration of the precipitant in the precipitant solution is 2 to 3 mol/L;

Optionally, the precipitant comprises a carbonate;

Optionally, the carbonate includes any one of ammonium bicarbonate, ammonium carbonate or sodium carbonate, or a combination of at least two of them.
The preparation method according to any one of claims 3 to 7, wherein the aluminum-cobalt mixed solution is injected into the reactor at a flow rate of 7 to 35 L/h;

Optionally, the fluorine solution is injected into the reactor at a flow rate of 0.5 to 2 molar ratio of aluminum to fluorine;

Optionally, the precipitant solution is injected into the reactor at a flow rate of 2.2 to 3 molar ratio of the precipitant to the cobalt source;

Optionally, before the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution are injected into the reactor in parallel, a bottom liquid is added into the reactor;

Optionally, the concentration of the base solution is 0.5 to 3 mol/L;

Optionally, the volume of the bottom liquid accounts for 0.3 to 0.6 of the total volume of the reactor;

Optionally, the base liquid comprises a carbonate solution;

Optionally, the carbonate in the base liquid includes any one of ammonium bicarbonate, ammonium carbonate or sodium carbonate, or a combination of at least two of them.
The preparation method according to any one of claims 3 to 8, wherein the preparation process of the intermediate material comprises:

(1) under stirring, mixing the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution The liquid is injected into the reactor in parallel until the reactor is full, the feeding and stirring are stopped, and the supernatant is extracted after standing;

(2) Repeating the operation of step (1) until the D50 of the product reaches a certain value, transferring part of the material in the reactor to another reactor to complete the reactor separation process;

(3) Repeating the operations of step (1) and step (2) for each of the reaction kettles until the D50 of the product reaches the target particle size, thereby obtaining the intermediate material;

Optionally, half of the material in the reactor is transferred to another reactor to complete the reactor separation process;

Optionally, the target particle size D50 of the product is 18 to 22 μm;

Optionally, when the D50 of the product reaches 8.5 to 13 μm, a first separation process is performed, and when the D50 of the product reaches 14 to 16 μm, a second separation process is performed; then, the operation of step (1) is repeated until the D50 of the product reaches 18 to 22 μm, thereby obtaining the intermediate material;

Optionally, the intermediate material is prepared at a temperature of 35 to 50°C;

Optionally, the stirring speed is 12 to 28 Hz.
The preparation method according to any one of claims 3 to 8, wherein the preparation process of the intermediate material comprises:

Injecting the aluminum-cobalt mixed solution, the fluorine solution and the precipitant solution into the reactor in parallel until the D50 of the product reaches the target particle size to obtain the intermediate material;

Optionally, the target particle size D50 of the intermediate material is 3 to 5 μm;

Optionally, the intermediate material is prepared at a temperature of 35 to 45°C;

Optionally, the intermediate material is prepared under stirring conditions;

Optionally, the stirring speed is 30 to 50 Hz.
The preparation method according to any one of claims 3 to 10, wherein the intermediate material is subjected to Perform centrifugal washing, and then perform sintering to obtain the aluminum-fluorine co-doped cobalt tetroxide;

Optionally, the washing water used in the centrifugal washing includes pure water at a temperature of 50 to 70°C;

Optionally, the centrifugal washing has a centrifugal frequency of 20 to 45 Hz;

Optionally, after the centrifugal washing, the water content of the intermediate material is 10 to 20 wt %;

Optionally, the sintering includes one-stage sintering, two-stage sintering and three-stage sintering performed sequentially;

Optionally, the temperature of the first stage sintering is 120-200°C;

Optionally, the sintering time is 2 to 3 hours;

Optionally, the heating rate of the first stage sintering is 1 to 5°C/min;

Optionally, the temperature of the second stage sintering is 350-450°C;

Optionally, the second stage sintering time is 2 to 3 hours;

Optionally, the heating rate of the second-stage sintering is 1 to 5°C/min;

Optionally, the temperature of the three-stage sintering is 650-800°C;

Optionally, the three-stage sintering time is 2 to 3 hours;

Optionally, the heating rate of the three-stage sintering is 1-5°C/min.
A lithium cobalt oxide positive electrode material, wherein the lithium cobalt oxide positive electrode material comprises the aluminum-fluorine co-doped cobalt oxide according to claim 1 or 2.
A lithium-ion battery, wherein the lithium-ion battery comprises the lithium cobalt oxide positive electrode material according to claim 12.