CN118867200A - A nickel-rich ternary positive electrode material with double modified structure and its preparation method and application - Google Patents

Abstract

The application discloses a modified nickel-rich ternary positive electrode material, and a preparation method and application thereof, and belongs to the technical field of battery material preparation. In particular to a modified nickel-rich ternary positive electrode material which is a nano-scale Li ₅GaO₄ coated and uniform Ga-doped LiNi _0.83Co_0.12Mn_0.05O₂ lithium ion battery positive electrode material. In the preparation method provided by the application, firstly, a wet coating method is used for mixing and stirring a precursor Ni _0.83Co_0.12Mn_0.05(OH)₂ and a Ga source (such as Ga (NO ₃)₃·9H₂ O)), oil bath is evaporated, then mixed LiOH.H2 ₂ O is ground uniformly, and the mixture is sintered at high temperature in a tube furnace, so that the preparation method comprises a calcining process, and the purpose is that Ga fully permeates into a positive electrode material to replace Ni ²⁺ to enter a transition metal plate layer, and on the other hand, residual lithium impurities (such as Li ₂CO₃、LiOH·H₂ O) on the surface react with Ga to generate a nano-scale Li ₅GaO₄ coating film.

Description

A nickel-rich ternary positive electrode material with a double-modified structure and its preparation method and application

Technical Field

The present application relates to the technical field of lithium-ion battery materials, and more specifically, to a nickel-rich ternary positive electrode material with a double-modified structure and an application of a preparation method thereof.

Background Art

Lithium-ion batteries have become one of the indispensable energy storage devices in modern society due to their high energy density, small size, and long life. At present, due to the rapid development of electric bicycles and electronic mobile devices, lithium-ion batteries are considered to be the most promising power source, so the demand for lithium-ion batteries in many fields is also increasing. Although they are widely adopted in electric vehicles, they are still plagued by range anxiety due to their relatively low energy density compared to traditional internal combustion engines. This limitation is mainly attributed to the performance of the cathode material. Therefore, it is urgent to develop cathode materials with both high capacity and long-lasting durability.

Nickel-rich ternary cathode materials are the preferred cathode materials for lithium-ion batteries in electric vehicle applications due to their inherent high redox potential and energy density. However, excessive nickel content (>80%) will suffer severe chemical and mechanical damage in practical applications. Therefore, nickel-rich ternary cathode materials are prone to low cycle stability and poor thermal stability when used.

Application Contents

In order to overcome at least one problem existing in the prior art, the present application provides a modified nickel-rich ternary positive electrode material with a double-modified structure and a preparation method thereof. The purpose is to provide a modified nickel-rich ternary positive electrode material with a double-modified structure to solve the problems of low cycle stability and poor thermal stability of the nickel-rich ternary positive electrode material.

In order to solve the above technical problems, the technical solution adopted in this application is:

A nickel-rich ternary positive electrode material with a double-modified structure comprises a nano-scale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles.

The present application also provides a method for preparing the above-mentioned nickel-rich ternary positive electrode material with a double-modified structure, which comprises the following steps:

S1. In a container, Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor and gallium source are mixed in anhydrous ethanol, stirred evenly, heated in an oil bath until the anhydrous ethanol evaporates, and the solid product obtained after evaporation is evenly ground to obtain Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder;

S2. The Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder described in step S1 is mixed and ground evenly with a lithium salt compound to obtain a lithium-mixed Ni _0.83 Co _0.12 Mn _0.05 (OH) _2, Ga@NCM yellow-brown powder;

S3. The Ga@NCM yellow-brown powder obtained in step S2 is placed in a tubular furnace for sintering treatment. First, it is pre-sintered at 300-550°C for 2-6 hours, and then the temperature is increased to calcine to obtain a nickel-rich ternary positive electrode material with a double-modified structure, including a nano-scale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles.

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

On the one hand, in the preparation method provided by the present application, spherical particles with a surface nanoscale Li ₅ GaO ₄ coating layer and Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ are formed simultaneously, which effectively utilizes the residual lithium compounds on the surface, constructs a strong, thin and uniform cathode protection layer, and provides a fast lithium ion transmission channel. The uniform doping of Ga suppresses the instability of lattice oxygen, increases the oxygen vacancy formation energy of the material, improves the cycle stability of the material, and enhances the thermal stability.

On the other hand, the precursors, gallium source compounds, and lithium source compounds used in the preparation method of the present application are all green and environmentally friendly; the calcination temperature is generally not higher than 780° C. during heat treatment under an oxygen atmosphere, and the production process is safe and very simple.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a SEM image of a precursor of a modified nickel-rich ternary cathode material prepared in Example 1 of the present application;

FIG2 is a SEM image of the modified nickel-rich ternary positive electrode material prepared in Example 1 of the present application;

FIG3 is a SEM image of a nickel-rich ternary positive electrode material prepared in a comparative example of the present application;

4 is an XRD diagram of the modified nickel-rich ternary positive electrode materials prepared in Examples 1, 2, 3 and 4 of the present application and the nickel-rich ternary positive electrode materials prepared in the comparative example;

FIG. 5 is a HRTEM image of the Li ₅ GaO ₄ coating layer of the modified nickel-rich ternary cathode material in Example 1 of the present application.

6 is a TEM image and EDS line scan spectrum data of the interface of the modified nickel-rich ternary positive electrode material prepared by FIB in Example 1 of the present application.

7 is a charge-discharge curve of the first cycle of the modified nickel-rich ternary positive electrode material prepared by S2 in Example 1 of the present application and the nickel-rich ternary positive electrode material prepared in the comparative example at a current of 0.1C;

8 is a graph showing the rate performance of the modified nickel-rich ternary positive electrode material prepared by S2 in Example 1 of the present application and the nickel-rich ternary positive electrode material prepared in the comparative example in the voltage range of 2.7-4.5V and 0.2-10C;

9 is a cycle performance diagram of the modified nickel-rich ternary positive electrode material prepared for S2 in Example 1 of the present application and the nickel-rich ternary positive electrode material prepared in the comparative example at a current of 1C and a voltage range of 2.7-4.3V;

Figure 10 is a cycling performance graph of the modified nickel-rich ternary positive electrode material prepared by S2 in Example 1 of the present application and the nickel-rich ternary positive electrode material prepared in the comparative example at a current of 5C and a voltage range of 2.7-4.5V.

FIG11 is a comparison chart of differential scanning calorimeter (DSC) tests of Ga@NCM prepared in Example 1 of the present application and NCM prepared in the comparative example after being fully charged at a cutoff voltage of 4.5V.

DETAILED DESCRIPTION

The following will be described in detail with reference to the embodiments of the present application, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to normal conditions or manufacturer recommendations. The reagents used or the instruments that do not specify the manufacturer are all conventional products that can be purchased commercially. In the following examples, the term XRD art-specific term that appears refers to an X-ray diffractometer.

It should be noted that:

In this application, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

In the present application, unless otherwise specified, each reaction or operation step can be carried out sequentially or in a sequential manner. Preferably, the reaction method herein is carried out sequentially.

Unless otherwise specified, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to the present application.

The applicant discovered during the research that nickel-rich ternary cathode materials (LiNi _x Co _y Mn _1-xy O ₂ , x>0.8, x+y≤1) will suffer severe chemical and mechanical damage in practical applications due to their excessive nickel content (>80%). This can be attributed to two main factors. First, the release of lattice oxygen will produce many oxygen vacancies and cause local structural collapse, promoting the formation of inactive NiO-like rock salt structures, thereby reducing the cathode capacity. Secondly, under high pressure, the electrostatic interaction between local oxygen vacancies and neighboring ions causes the unit cell volume to increase, resulting in significant stress accumulation, causing the material to crack or even completely break. In addition, the gas release caused by unstable lattice oxygen also poses a safety hazard that cannot be ignored. These problems seriously limit the commercialization process and large-scale application of nickel-rich ternary cathode materials. For the above problems, the following methods can be used to modify the cathode materials: single crystallization and core-shell structure; surface modification, such as phosphate coating, transition metal oxide coating; ion doping, etc.

The present application provides a nickel-rich ternary positive electrode material with a double-modified structure, wherein the nickel-rich ternary positive electrode material with a double-modified structure comprises a nano-scale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles.

The present application also provides a method for preparing the above-mentioned nickel-rich ternary positive electrode material with a double-modified structure, comprising the following steps:

S1. In a container, Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor and gallium source are mixed in anhydrous ethanol, stirred evenly, heated in an oil bath until the anhydrous ethanol evaporates, and the solid product obtained after evaporation is evenly ground to obtain Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder;

S2. The Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder described in step S1 is mixed and ground evenly with a lithium salt compound to obtain a lithium-mixed Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ ,Ga@NCM yellow-brown powder;

S3. The Ga@NCM yellow-brown powder obtained in step S2 is placed in a tubular furnace for sintering treatment. First, it is pre-sintered at 300-550°C for 2-6 hours, and then the temperature is increased to calcine to obtain a nickel-rich ternary positive electrode material with a double-modified structure, including a nano-scale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles.

In the preparation method of the modified nickel-rich ternary positive electrode material provided in the present application, a precursor material of a mixed gallium source (e.g., Ga(NO ₃ ) ₃ ·9H ₂ O) is first prepared by a wet coating method (i.e., step S1), and then a lithium source (e.g., LiOH·H ₂ O) is mixed and ground evenly therewith. The modified nickel-rich ternary positive electrode material obtained after pre-sintering and sintering has more excellent electrochemical properties, that is, the ionic conductivity and oxygen vacancy formation energy are improved by nano-scale Li5GaO4 coating and uniform Ga doping, thereby achieving more excellent electrochemical performance and thermal stability.

In some preferred embodiments, in step S2, the lithium salt is at least one of Li ₂ CO ₃ , LiOH·H ₂ O, CH ₃ COOLi and Li ₂ C ₂ O ₄ .

In some more preferred embodiments, in step S2, the molar ratio of the lithium element in the lithium salt to the metal element in the precursor is (0.96-1.12):1.

In some more preferred embodiments, the gallium source is at least one of Ga(NO ₃ ) ₃ ·9H ₂ O and GaCl ₃ .

In some more preferred embodiments, the amount of the gallium source added is 0.2% to 3% of the mass of the precursor, calculated based on the chemical elements to be added.

In some preferred embodiments, the pre-sintering temperature in step S3 is 500° C. and the pre-sintering time is 5 hours. This step is equivalent to a pre-oxidation process.

In some preferred embodiments, the calcination temperature in step S3 is 720-780° C. and the calcination time is 12-15 hours. This step plays a role in sintering.

In some more preferred embodiments, the calcination in step S3 is performed at 740° C. for 12 hours.

The present application firstly prepares a Ga-coated precursor material by a wet coating method (ie, step S1), and then uses a pre-sintering and sintering process to modify the nickel-rich ternary positive electrode material.

This application design includes two modified structures:

①Ga can enter the bulk of the material during high-temperature sintering to replace Ni ²⁺ sites, achieving uniform doping;

②Ga can react with residual lithium on the surface of the material to form a uniform nanoscale Li ₅ GaO ₄ coating in situ. The double-modified structure gives the nickel-rich ternary cathode material more excellent electrochemical performance and thermal stability.

In addition, the precursors, gallium source compounds, and lithium source compounds used in the preparation method are all green and environmentally friendly, and no harmful waste liquid is generated during the synthesis process; the heat treatment is carried out under an oxygen atmosphere, and the calcination temperature is generally not higher than 800°C, and the production process is safe and very simple.

The present application also provides the application of the above nickel-rich ternary positive electrode material with a double-modified structure in the field of lithium-ion batteries.

Next, the preparation method of the nickel-rich ternary positive electrode material with a double-modified structure in the present application is described in detail with specific examples.

Example 1 Preparation of nickel-rich ternary positive electrode material Ga@NCM (2% at) material (hereinafter referred to as Ga@NCM) with double modified structure

The preparation method comprises the following steps:

S1. In a beaker, weigh 0.184gGa(NO ₃ ) ₃ ·9H ₂ O and dissolve it completely in 50ml anhydrous ethanol, then add 2g precursor material Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ , stir in an oil bath at 80°C until the anhydrous ethanol is evaporated, then place the beaker in a vacuum drying oven at 100°C and dry overnight to obtain a mixed gallium source precursor material, i.e., mixed gallium source Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder;

S2. The Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder obtained in step S1 is mixed and ground evenly with 0.952 g of LiOH·H ₂ O powder to obtain a yellow-brown powder mixed with lithium, that is, a Ga@NCM yellow-brown powder;

S3. The Ga@NCM yellow-brown powder obtained in step S2 is placed in a tubular furnace for sintering treatment. First, it is pre-sintered at 500°C for 5 hours, and then the temperature is raised to 740°C and calcined for 12 hours to obtain a nickel-rich ternary positive electrode material with a double-modified structure, including a nano-scale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles, Ga@NCM (2at%).

Example 2 Preparation of nickel-rich ternary positive electrode material Ga@NCM (1% at) with double modified structure

The preparation method comprises the following steps:

S1. In a beaker, weigh 0.091gGa(NO ₃ ) ₃ ·9H ₂ O and dissolve it completely in 50ml anhydrous ethanol, then add 2g precursor material Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ , stir in an oil bath at 80°C until the anhydrous ethanol is evaporated, then place the beaker in a vacuum drying oven at 100°C and dry overnight to obtain a mixed gallium source precursor material, i.e., Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder;

S2. The Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder obtained in step S1 is mixed and ground evenly with 0.952 g of LiOH·H ₂ O powder to obtain a yellow-brown powder mixed with lithium, that is, a Ga@NCM yellow-brown powder;

S3. The Ga@NCM yellow-brown powder obtained in step S2 is placed in a tubular furnace for sintering treatment, first pre-sintered at 500°C for 5 hours, then heated to 740°C and sintered for 12 hours to obtain a nickel-rich ternary positive electrode material with a double-modified structure, Ga@NCM (1at%), including a nanoscale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles.

Example 3 Preparation of nickel-rich ternary positive electrode material Ga@NCM (3% at) with double modified structure

The preparation method comprises the following steps:

S1. In a beaker, weigh 0.279gGa(NO ₃ ) ₃ ·9H ₂ O and dissolve it completely in 50ml anhydrous ethanol, then add 2g precursor material Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ , stir in an oil bath at 80°C until the anhydrous ethanol is evaporated, then place the beaker in a vacuum drying oven at 100°C and dry overnight to obtain a mixed gallium source precursor material, i.e., Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder;

S2. The Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder obtained in step S1 is mixed and ground evenly with 0.952 g of LiOH·H ₂ O powder to obtain a yellow-brown powder mixed with lithium, that is, a Ga@NCM yellow-brown powder;

S3. The Ga@NCM yellow-brown powder obtained in step S2 is placed in a tube furnace for sintering treatment, first pre-sintered at 500°C for 5 hours, then heated to 740°C and sintered for 12 hours to obtain a nickel-rich ternary positive electrode material with a double-modified structure, Ga@NCM (3at%), including a nanoscale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles.

Example 4 Preparation of nickel-rich ternary positive electrode material Ga@NCM (2% at) with double modified structure

The preparation method comprises the following steps:

S1. In a beaker, weigh 0.078g GaCl _{3 and} dissolve it completely in 50ml anhydrous ethanol, then add 2g precursor material Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ , stir in an oil bath at 80°C until the anhydrous ethanol is evaporated, then place the beaker in a vacuum drying oven at 100°C and dry overnight to obtain a mixed gallium source precursor material, i.e., Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder;

S2. The Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor material obtained in step S1 is mixed and ground evenly with 0.952 g of LiOH·H ₂ O powder to obtain a yellow-brown powder mixed with lithium, that is, a Ga@NCM yellow-brown powder;

S3. The Ga@NCM yellow-brown powder obtained in step S2 is placed in a tube furnace for sintering treatment, first pre-sintered at 500°C for 5 hours, then heated to 740°C and sintered for 12 hours to obtain a nickel-rich ternary positive electrode material with a double-modified structure, Ga@NCM (2at%), including a nanoscale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles.

The raw materials prepared in Example 4 are only different from those in Examples 1, 2 and 3 in terms of gallium source, and are intended to explore the effects of different gallium sources on the materials after synthesis, such as more complete reactions and reduced impurities. Fewer impurities can lead to better performance, and also illustrate the versatility of the synthesis process, using cheaper and better-available raw materials.

Example 5 Preparation of double-modified nickel-rich ternary positive electrode material Ga@NCM material

The preparation method comprises the following steps:

S1. In a beaker, weigh 0.078g GaCl _{3 and} dissolve it completely in 50ml anhydrous ethanol, then add 2g precursor material Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ , stir in an oil bath at 80°C until the anhydrous ethanol is evaporated, then place the beaker in a vacuum drying oven at 100°C and dry overnight to obtain a mixed gallium source precursor material, i.e., Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder;

S2. The Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor material obtained in step S1 is mixed and ground evenly with 1.67 g _{Li 2} CO ₃ powder to obtain a yellow-brown powder mixed with lithium, that is, a Ga@NCM yellow-brown powder;

S3. The Ga@NCM yellow-brown powder obtained in step S2 is placed in a tube furnace for sintering treatment, first pre-sintered at 500°C for 5 hours, then heated to 740°C and sintered for 12 hours to obtain a nickel-rich ternary positive electrode material with a double-modified structure, Ga@NCM (2at%), including a nanoscale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles.

The raw materials prepared in Example 5 are only different from those in Example 4 in terms of the lithium source. This is also to illustrate the versatility of the synthesis process. Cheaper and more readily available raw materials can be used to prepare the products in this application.

Example 6 Preparation of nickel-rich ternary cathode material Ga@NCM with double modified structure

The preparation method comprises the following steps:

S1. In a beaker, weigh 0.92gGa(NO ₃ ) ₃ ·9H ₂ O and dissolve it completely in 200ml anhydrous ethanol, then add 10g precursor material Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ , stir in an oil bath at 80°C until the anhydrous ethanol is evaporated, then place the beaker in a vacuum drying oven at 100°C and dry overnight to obtain a mixed gallium source precursor material, i.e., Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder;

S2. The Ga-coated Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ precursor powder obtained in step S1 is mixed and ground with 4.76 g LiOH·H ₂ O powder to obtain a yellow-brown powder mixed with lithium, that is, a Ga@NCM yellow-brown powder;

S3. The Ga@NCM yellow-brown powder obtained in step S2 is placed in a tube furnace for sintering treatment, first pre-sintered at 500°C for 5 hours, then heated to 740°C and sintered for 12 hours to obtain a nickel-rich ternary positive electrode material with a double-modified structure, Ga@NCM (2at%), including a nanoscale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles.

Compared with the preparation method in Example 1, the only difference in the quality of the gallium source and the lithium source is that the quality of the gallium source and the lithium source is improved, but the ratio remains unchanged, in order to explore whether the high-amount reaction affects the performance of the material.

There is basically no difference between the three kinds of Ga@NCM powders prepared in Examples 4 to 6 above. The performance is improved only by adjusting the different proportions in the preparation method, the different qualities of the raw materials, and the different raw materials to explore the success factors of the synthesis process and whether the impurities are reduced.

Preparation of nickel-rich ternary positive electrode NCM black powder (hereinafter referred to as "NCM")

S1. Mix and grind 2 g of precursor material Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ and 0.952 g of LiOH·H ₂ O powder to obtain a yellow-brown powder mixed with lithium, that is, obtain NCM yellow-brown powder;

S2. The NCM yellow-brown powder obtained in step S1' is placed in a tubular furnace for sintering treatment. First, it is pre-sintered at 500°C for 5 hours, and then the temperature is raised to 740°C and sintered for 12 hours to obtain a nickel-rich ternary positive electrode NCM black powder.

Compared with Example 1, the comparative example did not modify the NCM (ie, the precursor material Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ ) black powder.

Performance Characterization

Figures 1 to 3 are SEM images of the precursor material Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ used in Example 1, Ga@NCM (2% at) prepared in Example 1, and the nickel-rich ternary positive electrode NCM black powder prepared in the comparative example. The external morphology of the three materials can be clearly seen from the SEM images, and it can be seen that Ga@NCM (2% at) has a smoother and rougher surface than the nickel-rich ternary positive electrode NCM black powder, proving the successful coating of the nano Li ₅ GaO ₄ coating layer.

FIG4 is an XRD image of the precursor used in Example 1 (indicated by “PDF#74-0919” in FIG4 ), Ga@NCM (2% at) prepared in Example 1 (indicated by “2% Ga@NCM83” in FIG4 ), Ga@NCM (1% at) prepared in Example 2 (indicated by “1% Ga@NCM83” in FIG4 ), Ga@NCM (3% at) prepared in Example 3 (indicated by “3% Ga@NCM83” in FIG4 ), and the nickel-rich ternary positive electrode NCM black powder prepared in the comparative example (indicated by “NCM83” in FIG4 ). As can be seen from FIG4 , the diffraction peaks of Ga@NCM (1% at), Ga@NCM (2% at), and Ga@NCM (3% at) materials prepared in the example have higher peak intensities than the nickel-rich ternary positive electrode NCM black powder prepared in the comparative example, and have better crystallinity.

FIG. 5 is a HRTEM image of Ga@NCM (2% at) in Example 1, in which the Li ₅ GaO ₄ nano-coating layer can be clearly seen.

FIG6 is a HAADF image of the FIB sliced sample of Ga@NCM (2% at) in Example 1 and EDS energy spectrum data for the line scan area, which proves the uniform distribution of Ga inside the material.

Application Examples

Preparation of lithium ion button cell Weigh 0.4g of positive electrode material (the positive electrode material is selected from the nickel-rich ternary lithium ion battery positive electrode material prepared in the above Example 1 and the comparative example), 0.05g of conductive carbon material (super C45), and 0.05g of binder (polyvinylidene fluoride) in a mass ratio of 8:1:1, stir and disperse in N-methylpyrrolidone solvent, and the obtained mixed slurry is evenly coated on aluminum foil, and vacuum dried at 100°C for 12h to obtain a positive electrode sheet. With a metal lithium sheet as the counter electrode, the spring sheet, gasket, counter electrode, diaphragm, and positive electrode sheet are placed in a CR2025 button cell in the order of shrapnel, gasket, counter electrode, diaphragm, and positive electrode sheet, and lithium hexafluorophosphate solute, ethylene carbonate and ethyl methyl phosphate (volume ratio of 1:3), and an electrolyte with a concentration of 1 mol/L are added, and a lithium ion button cell is obtained after packaging.

Test conditions: voltage window is 2.7～4.3V.

After the above application experiments, the test results are shown in Figures 7 to 11. Now, in conjunction with Figures 7 to 11, the experimental test results are analyzed and explained as follows:

Figure 7 is a charge-discharge curve of the first cycle of Ga@NCM prepared in Example 1 of the present application and NCM prepared in the comparative example at a current of 0.1C and a voltage range of 2.7-4.5V. Comparison of the two shows that the first coulombic efficiency of Ga@NCM (89.2%) is higher than that of NCM (87.4%). This is because during the synthesis of Ga@NCM, the gallium source combines with the residual lithium on the surface to form a lithium-rich Li ₅ GaO ₄ coating layer, which provides a superior electron conduction path, that is, improves the conductivity, and thus has a higher first coulombic efficiency.

FIG8 is a rate performance diagram of Ga@NCM prepared in Example 1 of the present application and NCM prepared in the comparative example in the voltage range of 2.7-4.5V, 0.2C-10C. It can be seen from FIG8 that Ga@NCM with a double-modified structure, i.e., Li ₅ GaO ₄ coating and uniform Ga doping, has a good rate performance, and still maintains the initial 0.1C specific capacity from 10C to 0.1C, and at a high current density of 10C, the discharge capacity of Ga@NCM reaches 121mAh g ^-1 , while that of NCM is only 96mAh g ^-1 . The reason is that the Li ₅ GaO ₄ nano-coating layer provides a superior electron conduction path, and the uniform Ga makes the material have a more stable lattice structure at high currents, thereby improving the electrochemical performance.

FIG9 is a cycle performance diagram of Ga@NCM prepared in Example 1 of the present application and NCM prepared in the comparative example at 1C current and 2.7-4.3V voltage range. The capacity retention rate of Ga@NCM after 200 cycles is 97.7%, while that of NCM is only 71.5%;

Figure 10 is a cycle performance diagram of Ga@NCM prepared in Example 1 of the present application and NCM prepared in the comparative example at 5C current and 2.7-4.5V voltage range. The capacity retention rate of Ga@NCM after 500 cycles is 88.7%, which is significantly better than NCM.

Figure 11 is a differential scanning calorimeter (DSC) test comparison chart of Ga@NCM prepared in Example 1 of the present application and NCM prepared in the comparative example after full charging at a cutoff voltage of 4.5V. The exothermic peak of NCM is 194°C, while the exothermic peak of Ga@NCM is postponed to 211°C, and the total heat release (i.e., peak area) is much smaller than that of NCM. The reason is that the uniform Ga doping has a strong adsorption effect on the lattice oxygen, stabilizes the lattice structure, and _{the Li5GaO4} coating layer isolates the direct contact between the electrode and the electrolyte, thereby improving the thermal stability.

The present application provides a nickel-rich ternary positive electrode material with a double-modified structure, which includes a nano-scale Li ₅ GaO ₄ coating layer and uniformly Ga-doped LiNi _0.83 Co _0.12 Mn _0.05 O ₂ spherical particles. In the preparation method provided by the present application, the precursor Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ is first mixed and stirred with a Ga source (such as Ga(NO ₃ ) ₃ ·9H ₂ O) by a wet coating method, evaporated in an oil bath, and then ground uniformly by mixing LiOH·H ₂ O, and sintered at high temperature in a tube furnace. The design includes a calcination process, the purpose of which is to allow Ga to fully penetrate into the positive electrode material, replace Ni ²⁺ and enter the transition metal plate layer, and on the other hand, to allow residual lithium impurities (such as Li ₂ CO ₃ , LiOH·H ₂ O) on the surface to react with Ga to form a nano-scale Li ₅ GaO ₄ coating film. The special double-modified structure design enables the nickel-rich ternary positive electrode material to obtain excellent cycle stability and thermal stability.

In summary, the preparation method of the nickel-rich ternary positive electrode material with a double-modified structure in this application has the following advantages:

(1) In the preparation method provided in the present application, a NCM precursor coated with a gallium source is first prepared by a wet coating method, and then mixed with a lithium source and calcined to form a nickel-rich ternary positive electrode material with a double-modified structure. The design includes a one-time calcination process, the purpose of which is to uniformly dope Ga into the lattice of NCM and react with the residual lithium on the surface of NCM to form a Li-rich Li ₅ GaO ₄ nano-coating layer. The nickel-rich ternary positive electrode material with a double-modified structure and maintaining the original morphology has more excellent electrochemical performance and thermal stability.

(2) The NCM precursor, gallium source compound, and lithium source compound used in this application are all green and environmentally friendly, and only N,N-dimethylformamide waste liquid is produced during the synthesis process; the calcination temperature is generally not higher than 800°C, and the production process is safe and very simple.

In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

Although several embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims (10)

1. The nickel-rich ternary positive electrode material with the double modified structure is characterized in that: the nickel-rich ternary positive electrode material with the double-modified structure comprises a nanoscale Li ₅GaO₄ coating layer and uniform Ga-doped LiNi _0.83Co_0.12Mn_0.05O₂ spherical particles.

2. The method for preparing the nickel-rich ternary cathode material with the double-modified structure, which is characterized in that: the method comprises the following steps:

S1, mixing a Ni _0.83Co_0.12Mn_0.05(OH)₂ precursor and a gallium source into absolute ethyl alcohol in a container, uniformly stirring, heating an oil bath until the absolute ethyl alcohol is evaporated, and uniformly grinding a solid product obtained after evaporation to obtain Ga-coated Ni _0.83Co_0.12Mn_0.05(OH)₂ precursor powder;

S2, uniformly mixing and grinding the Ga-coated Ni _0.83Co_0.12Mn_0.05(OH)₂ precursor powder in the step S1 and a lithium salt compound to obtain a lithium-mixed Ni _0.83Co_0.12Mn_0.05(OH)_2, Ga@NCM yellow brown powder;

s3, placing the Ga@NCM yellow brown powder obtained in the step S2 into a tube furnace for sintering treatment, pre-sintering for 2-6 hours at 300-550 ℃, and heating and calcining to obtain the nickel-rich ternary anode material with the double-modified structure, wherein the nickel-rich ternary anode material comprises a nanoscale Li ₅GaO₄ coating layer and uniform Ga-doped LiNi _0.83Co_0.12Mn_0.05O₂ spherical particles.

3. The method for preparing the nickel-rich ternary cathode material with the double-modified structure according to claim 2, which is characterized in that: in step S2, the lithium salt is at least one of Li ₂CO₃、LiOH·H₂O、CH₃ COOLi and Li ₂C₂O₄.

4. The method for preparing the nickel-rich ternary cathode material with the double-modified structure according to claim 3, wherein the method is characterized by comprising the following steps of: the molar ratio of the lithium element in the lithium salt to the metal element in the precursor is (0.96-1.12): 1.

5. The method for preparing the nickel-rich ternary cathode material with the double-modified structure according to claim 2, which is characterized in that: the gallium source is at least one of Ga (NO ₃)₃·9H₂O、GaCl₃).

6. The method for preparing the nickel-rich ternary cathode material with the double-modified structure according to claim 5, wherein the method is characterized in that: the addition amount of the gallium source is calculated by chemical elements to be added, and the mass of the gallium source is 0.2-3% of the mass of the precursor.

7. The method for preparing the nickel-rich ternary cathode material with the double-modified structure according to claim 2, which is characterized in that: the presintering temperature in the step S3 is 500 ℃, and the presintering time is 5 hours.

8. The method for preparing the nickel-rich ternary cathode material with the double-modified structure according to claim 2, which is characterized in that: the calcination temperature in the step S3 is 720-780 ℃ and the calcination time is 12-15 hours.

9. The method for preparing the nickel-rich ternary cathode material with the double-modified structure, which is characterized in that: the calcination in the step S3 is carried out at 740 ℃ for 12 hours.

10. The application of the nickel-rich ternary cathode material with the double-modified structure in the field of lithium ion batteries.