阅读说明：本技术 一种原位包覆锆酸铝锂的单晶ncm三元材料 (Single crystal NCM ternary material coated with lithium aluminum zirconate in situ ) 是由 陈来 张其雨 苏岳锋 卢赟 李宁 包丽颖 聂启军 丁瑞 黄擎 曹端云 陈实 吴 于 2021-07-09 设计创作，主要内容包括：本发明涉及一种原位包覆锆酸铝锂的单晶NCM三元材料,属于化学储能电池领域。首先通过共沉淀法合成单晶NCM三元材料的前驱体,随后将其与锂盐按照一定比例混合,并干混入同时作为助熔剂和包覆原料的铝和锆的无机盐,在高温下进行煅烧,最终制备得到原位包覆锆酸铝锂的单晶NCM三元材料。所述单晶NCM三元材料表面包覆的锆酸铝锂能够隔绝电解液与单晶NCM三元材料的直接接触,从而降低界面副反应,提高单晶NCM材料的化学稳定性和结构稳定性；同时锆酸铝锂具有快离子导体特性,能够加快锂离子的输运,从而降低材料极化现象,提高其电化学性能。(The invention relates to a monocrystal NCM ternary material coated with lithium aluminum zirconate in situ, belonging to the field of chemical energy storage batteries. Firstly, synthesizing a precursor of the single crystal NCM ternary material by a coprecipitation method, then mixing the precursor with lithium salt according to a certain proportion, dry-mixing the precursor and the lithium salt into inorganic salts of aluminum and zirconium which are used as a fluxing agent and coating raw materials at the same time, and calcining at high temperature to finally prepare the single crystal NCM ternary material in which the lithium aluminum zirconate is coated in situ. The lithium aluminum zirconate coated on the surface of the single crystal NCM ternary material can isolate the direct contact between electrolyte and the single crystal NCM ternary material, so that the interface side reaction is reduced, and the chemical stability and the structural stability of the single crystal NCM material are improved; meanwhile, the lithium aluminum zirconate has the characteristic of fast ion conductor, and can accelerate the transportation of lithium ions, thereby reducing the polarization phenomenon of the material and improving the electrochemical performance of the material.)

1. A monocrystal NCM ternary material in which lithium aluminum zirconate is coated in situ is characterized in that: the material is prepared by the following method, and the method comprises the following steps:

(1) mixing nickel-cobalt-manganese hydroxide and lithium salt according to a molar ratio of 1: 1.07-1: 1.5, adding absolute ethyl alcohol, and grinding to be dry to obtain mixed powder 1;

(2) mixing and uniformly grinding mixed powder 2 formed by aluminum-containing fluxing agent and zirconium-containing fluxing agent with the mixed powder 1 to obtain mixed powder 3; wherein the mass fraction of the mixed powder 2 in the mixed powder 3 is 5-80%;

(3) heating the mixed powder 3 to 500-600 ℃ at a heating rate of 2-5 ℃/min in an oxygen atmosphere, and preserving heat for 3-7 h, then heating to 800-1100 ℃ at a heating rate of 0.2-1 ℃/min, and preserving heat for 10-20 h to obtain a solid block material;

(4) and crushing and grinding the solid block material, then adding water with the purity higher than that of deionized water, stirring for 10-60 min at the temperature of 40-80 ℃, carrying out solid-liquid separation, collecting the solid, and drying to obtain the in-situ coated aluminum lithium zirconate single crystal NCM ternary material.

2. The in-situ coated lithium aluminum zirconate single crystal NCM ternary material of claim 1 wherein: the molar ratio of the nickel-cobalt-manganese hydroxide to the lithium salt in the step (1) is 1: 1.1-1.3.

3. The in-situ coated lithium aluminum zirconate single crystal NCM ternary material of claim 1 wherein: the chemical formula of the nickel-cobalt-manganese hydroxide in the step (1) is Ni_xCo_yMn_1-x-y(OH)₂，0.6＜x＜1，y>0，1-x-y>0，0<x+y<0.4; the nickel-cobalt-manganese hydroxide is prepared by a hydroxide coprecipitation method.

4. The in-situ coated lithium aluminum zirconate single crystal NCM ternary material of claim 1 wherein: in the step (1), the lithium salt is more than one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium sulfate and lithium oxide.

5. The in-situ coated lithium aluminum zirconate single crystal NCM ternary material of claim 1 wherein: in the step (2), the molar ratio of the aluminum-containing flux to the zirconium-containing flux in the mixed powder 2 is 1:1.

6. The in-situ coated lithium aluminum zirconate single crystal NCM ternary material of claim 1 wherein: the aluminum-containing fluxing agent in the step (2) is more than one of aluminum sulfate, aluminum nitrate and aluminum carbonate; the zirconium-containing fluxing agent is more than one of zirconium carbonate, zirconium acetate and zirconium nitrate.

7. The in-situ coated lithium aluminum zirconate single crystal NCM ternary material of claim 1 wherein: and (3) adding other fluxing agents into the step (2), wherein the other fluxing agents are more than one of sodium chloride, potassium sulfate, sodium sulfate, calcium oxide and magnesium oxide.

8. The in-situ coated lithium aluminum zirconate single crystal NCM ternary material of claim 5 wherein: the mass fraction of the other fluxing agents is 20-80% of the mixed powder 3.

9. The in-situ coated lithium aluminum zirconate single crystal NCM ternary material of claim 1 wherein: in the step (3), the mixed powder 3 is heated to 500-600 ℃ at a heating rate of 2-5 ℃/min in an oxygen atmosphere and is subjected to heat preservation for 3-7 h, and then heated to 800-1100 ℃ at a heating rate of 0.2-1 ℃/min and is subjected to heat preservation for 10-20 h, so that a solid block material is obtained.

10. A lithium ion battery, characterized by: the battery positive electrode material adopts the single crystal NCM ternary material which is coated with the lithium aluminum zirconate in situ according to any one of claims 1 to 9.

Technical Field

The invention relates to a monocrystal NCM ternary material coated with lithium aluminum zirconate in situ, belonging to the field of chemical energy storage batteries.

Background

Under the large background that China vigorously promotes the development of green energy industry, new energy automobiles are widely concerned as the primary choice for replacing traditional fuel automobiles. Compared with the traditional fuel automobile, the new energy automobile adopts the power battery as the energy output device, but the performance of the current automobile power battery cannot completely replace the position of an engine of the fuel automobile, and the main reason is that the energy density of the power battery at the present stage is low, so that the problem of mileage anxiety of people to the electric automobile cannot be completely solved. The anode material commonly adopted by the high-energy density power battery at the present stage is a nickel-cobalt-manganese (NCM) ternary material, wherein Ni containsThe higher the amount, the more Li is taken out of the material during charging⁺The more, the higher the specific discharge capacity of the NCM ternary material. Therefore, NCM positive electrode materials with high nickel content have been developed in recent years.

The traditional NCM cathode material is generally synthesized by a coprecipitation method and a calcination method. To achieve higher compaction densities to increase their volumetric energy density, NCM ternary materials are typically designed as spherical, polycrystalline secondary particles. The secondary particles are formed by randomly stacking a plurality of small nano-scale single crystal primary particles. During charging and discharging, Li⁺Deintercalation or intercalation from Li layer, corresponding primary particle unit cell volume according to Li⁺And the surrounding primary particles are squeezed or pulled. Repeated changes in the volume of primary particles of polycrystalline NCM ternary material during long cycling can cause secondary particles of polycrystalline NCM ternary material to crack along grain boundaries between the primary particles, which in turn exacerbates electrolyte penetration and erosion of the cathode material. In view of the structural characteristics of polycrystalline NCM materials, research and development of single crystal NCM ternary materials have also attracted attention in recent years. Compared with the traditional polycrystalline material, the single crystal NCM ternary material has no primary particle and grain boundary structure, so that the possibility of cracking of particles along the grain boundary does not exist. However, the single crystal NCM ternary material is generally micron-sized single crystal particles, and the specific surface area thereof is larger than that of the polycrystalline NCM material, so that the single crystal NCM ternary material is more likely to generate an interfacial side reaction with an electrolyte, which causes problems such as metal ion dissolution and surface phase change, and deteriorates the electrochemical performance of the single crystal NCM ternary material.

Disclosure of Invention

In view of the above, the present invention aims to provide a single crystal NCM ternary material in which lithium aluminum zirconate is coated in situ. Firstly, synthesizing a precursor of the single crystal NCM ternary material by a coprecipitation method, then mixing the precursor with lithium salt according to a certain proportion, then dry-mixing an aluminum-containing fluxing agent and a zirconium-containing fluxing agent, and calcining at a high temperature to finally prepare the single crystal NCM ternary material in which the aluminum lithium zirconate is coated in situ. The aluminum lithium zirconate coated on the surface of the single crystal NCM ternary material can isolate the direct contact between the electrolyte and the single crystal NCM ternary material, thereby reducing the interface side reaction and improving the chemical stability and the structural stability of the single crystal NCM material. Meanwhile, the lithium aluminum zirconate has the characteristic of fast ion conductor, and can accelerate the transportation of lithium ions, thereby reducing the polarization phenomenon of the material and improving the electrochemical performance of the material.

The purpose of the invention is realized by the following technical scheme:

a single crystal NCM ternary material coated with lithium aluminum zirconate in situ is prepared by the following method steps:

(1) mixing nickel-cobalt-manganese hydroxide and lithium salt according to a molar ratio of 1: 1.07-1: 1.5, adding absolute ethyl alcohol, and grinding to be dry to obtain mixed powder 1;

(2) mixing and uniformly grinding mixed powder 2 formed by aluminum-containing fluxing agent and zirconium-containing fluxing agent with the mixed powder 1 to obtain mixed powder 3; wherein the mass fraction of the mixed powder 2 in the mixed powder 3 is 5-80%;

(3) heating the mixed powder 3 to 500-600 ℃ at a heating rate of 2-5 ℃/min in an oxygen atmosphere, and preserving heat for 3-7 h, then heating to 800-1100 ℃ at a heating rate of 0.2-1 ℃/min, and preserving heat for 10-20 h to obtain a solid block material;

(4) and crushing and grinding the solid block material, then adding water with the purity higher than that of deionized water, stirring for 10-60 min at the temperature of 40-80 ℃, carrying out solid-liquid separation, collecting the solid, and drying to obtain the in-situ coated aluminum lithium zirconate single crystal NCM ternary material.

Preferably, the molar ratio of the nickel-cobalt-manganese hydroxide to the lithium salt in the step (1) is 1: 1.1-1.3.

Preferably, the chemical formula of the nickel cobalt manganese hydroxide in the step (1) is Ni_xCo_yMn_1-x-y(OH)₂，0.6＜x＜1，y>0，1-x-y>0，0<x+y<0.4; the nickel-cobalt-manganese hydroxide is prepared by a hydroxide coprecipitation method.

Preferably, in the step (1), the lithium salt is one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium sulfate and lithium oxide.

Preferably, the molar ratio of the aluminum-containing flux to the zirconium-containing flux in the mixed powder 2 in the step (2) is 1:1.

Preferably, the aluminum-containing flux in the step (2) is one or more of aluminum sulfate, aluminum nitrate and aluminum carbonate; the zirconium-containing fluxing agent is more than one of zirconium carbonate, zirconium acetate and zirconium nitrate.

Preferably, other fluxing agents can be added in the step (2), and the other fluxing agents are sodium chloride (NaCl), potassium chloride (KCl) and potassium sulfate (K)₂SO₄) Sodium sulfate (Na)₂SO₄) One or more of calcium oxide (CaO) and magnesium oxide (MgO).

Preferably, the mass fraction of the other flux is 20% to 80% of the mixed powder 3.

Preferably, in the step (3), the mixed powder 3 is heated to 500-600 ℃ at a heating rate of 2-5 ℃/min in an oxygen atmosphere and is subjected to heat preservation for 3-7 hours, and then the mixed powder is heated to 800-1100 ℃ at a heating rate of 0.2-1 ℃/min and is subjected to heat preservation for 10-20 hours, so as to obtain a solid block material.

The invention relates to a lithium ion battery, wherein the anode material of the battery adopts the single crystal NCM ternary material which is coated with lithium aluminum zirconate in situ.

Advantageous effects

According to the method, firstly, an NCM ternary positive electrode material precursor is mixed with lithium salt, aluminum salt and zirconium salt are added, then the mixed powder is subjected to heat treatment in an oxygen atmosphere, and then crushing, dissolving and solid-liquid separation are performed, wherein the aluminum salt and the zirconium salt can be used as fluxing agents and can promote the growth of single crystal NCM ternary positive electrode material particles in the early stage of high-temperature calcination, and meanwhile, the aluminum salt, the zirconium salt and the lithium salt react to generate aluminum zirconate to be coated on the surface of the single crystal NCM ternary positive electrode material in the later stage of high-temperature calcination, so that the micron-sized NCM ternary material with a good in-situ coated aluminum zirconate lithium single crystal appearance is finally obtained.

In the material prepared by the method, the aluminum lithium zirconate coating layer can inhibit the contact of electrolyte and the single crystal NCM material, so that the interface side reaction is reduced, the structure stability of the material is maintained, and meanwhile, the aluminum lithium zirconate serving as a fast ion conductor can accelerate the lithium ion transmission and improve the electrochemical performance of the single crystal NCM ternary material.

In the method, other fluxing agents are added at the powder mixing stage to further promote the growth of the single crystal NCM ternary positive electrode material particles.

In the method, a better appearance of the single crystal NCM ternary material can be obtained by adopting a first-speed and second-speed two-stage heating rate in a high-temperature calcination stage.

Detailed Description

For a better understanding of the present invention, the present invention is described in further detail below with reference to specific embodiments. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation. Additionally, the endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In the following examples and comparative examples:

scanning Electron Microscope (SEM) testing: scanning electron microscope, instrument model: FEI Quanta, the netherlands.

X-ray diffraction (XRD) test: x-ray diffractometer, instrument model: bruker D8 Advance, germany.

And (3) testing the content of metal ions in the electrolyte: inductively coupled plasma mass spectrometer (ICP-MS), instrument model: agilent 7700, usa.

Assembly and testing of CR2025 button cells: the final product prepared in the example or the comparative example, acetylene black and polyvinylidene fluoride (PVDF) are prepared into slurry according to the mass ratio of 8:1:1 and coated on an aluminum foil, the aluminum foil loaded with the dried slurry is cut into small round pieces with the diameter of about 1cm by a cutting machine to be used as a positive electrode, a metal lithium piece is used as a negative electrode, Celgard2500 is used as a diaphragm, and 1M carbonate solution is used as electrolyte (wherein, the solvent is carbonic acid with the volume ratio of 1:1: 1)Mixed solution of ethylene ester, methyl ethyl carbonate and dimethyl carbonate, and the solute is LiPF₆) And assembling the button cell CR2025 in an argon atmosphere glove box.

Nickel cobalt manganese hydroxide (Ni)_0.8Co_0.1Mn_0.1(OH)₂) Prepared by a hydroxide coprecipitation method, and the catalyst comprises the following components:

step (1) NiSO₄·6H₂O solid, CoSO₄·7H₂O solid, MnSO₄·H₂210.28g, 28.11g and 16.9g of solid O were weighed out in a molar ratio of Ni to Co to Mn to 8 to 1. Adding three sulfates into 500mL of deionized water, dissolving to form metal ions with the total concentration of 2 mol.L^-1A metal salt solution of (a); weighing 100g of sodium hydroxide, adding 500mL of deionized water to prepare 2 mol.L^-1NaOH solution of (2); 50mL of 30% ammonia water solution is measured, and deionized water is added to prepare 2 mol.L^-1The aqueous ammonia solution I of (1).

Adding 1000mL of deionized water into a reaction kettle as a coprecipitation reaction base solution, wherein stirring and water bath processes are required in the whole reaction stage, the temperature of the water bath is controlled to be 55 ℃, the stirring speed is stabilized at 800r/min, argon protective gas is introduced before the reaction is started to ensure that the whole reaction is carried out in argon atmosphere, pumping an ammonia water solution II with the mass fraction of 30 percent to control the pH value of the base solution to be 11, pumping the metal salt solution, the NaOH solution and the ammonia water solution into a reaction kettle through a peristaltic pump, controlling the feeding speed of the metal salt solution and the ammonia water solution I at 1mL/min, adjusting the feeding speed of the NaOH solution to stabilize the pH value of the reaction at 11, entering an aging stage after the feeding is finished, keeping the original temperature and the original rotating speed, continuously stirring for 2 hours, after the aging is finished, filtering and washing the hot solution, and then putting the precipitate into a vacuum drying oven at 80 ℃ for drying for 24h to finally obtain Ni._0.8Co_0.1Mn_0.1(OH)₂。

Comparative example 1

(1) Mixing Ni_0.8Co_0.1Mn_0.1(OH)₂Mixing the lithium carbonate and the lithium carbonate according to a molar ratio of 1:1.05, adding alcohol, and grinding to be dry to obtain mixed powder 1;

(2) weighing Na₂SO₄Mixing the powder 2 with the mixed powder 1, grinding and uniformly mixing to obtain mixed powder 3, wherein the mass fraction of the mixed powder 2 in the mixed powder 3 is 50%; na in Mixed powder 2₂SO₄The mass fraction of (A) is 100%;

(3) putting the solid powder material 3 into a tube furnace, heating to 600 ℃ at a heating rate of 5 ℃/min in an oxygen atmosphere, and preserving heat for 4h, then heating to 1100 ℃ at a heating rate of 1 ℃/min, and preserving heat for 20h to obtain a solid block material;

(4) and crushing and grinding the solid block material, adding deionized water, stirring for 60min at 40 ℃, performing solid-liquid separation, and fully drying to obtain the single crystal NCM ternary material.

According to the scanning electron microscope result of the final product, the final product is single crystal particles, and the surface is smooth and has no impurities.

According to the electrochemical test results of the final product, the assembled battery has a cut-off voltage in the range of 2.8 to 4.3V, 0.2C (1C 190mAh g ═ g)^-1) After the material is cycled for 100 weeks under magnification, the capacity retention rate of the final product is found to be 74.36%, which indicates that the cycling stability of the material is poor.

The circulated battery is disassembled and the electrolyte is washed out, the percentage content of metal ions in the electrolyte is 237ppm through ICP test, and the metal ions are seriously dissolved, which shows that the side reaction degree between the electrolyte and the interface of the anode material is larger.

Example 1

(1) Mixing Ni_0.8Co_0.1Mn_0.1(OH)₂Mixing with lithium hydroxide according to the molar ratio of 1:1.07, adding alcohol, and grinding to dryness to obtain mixed powder 1;

(2) weighing mixed powder 2 of aluminum nitrate, zirconium carbonate and KCl, mixing the mixed powder with the mixed powder 1, grinding and uniformly mixing to obtain mixed powder 3, wherein the mass fraction of the mixed powder 2 in the mixed powder 3 is 5%; mixing aluminum nitrate and zirconium carbonate in the mixed powder 2 according to a molar ratio of 1:1, wherein the mass fraction of KCl is 20%;

(3) putting the solid powder material 3 into a tube furnace, heating to 500 ℃ at a heating rate of 5 ℃/min in an oxygen atmosphere, and preserving heat for 3h, then heating to 800 ℃ at a heating rate of 1 ℃/min, and preserving heat for 10h to obtain a solid block material;

(4) crushing and grinding the solid block material, adding deionized water, stirring for 10min at 80 ℃, performing solid-liquid separation, and fully drying to obtain an in-situ aluminum lithium zirconate coated monocrystal NCM ternary material;

according to the scanning electron microscope result of the final product, the final product is micron-sized single crystal particles, and the surface of the single crystal particles is coated.

According to the X-ray diffraction result of the final product, the characteristic diffraction peak of the lithium aluminum zirconate exists in the final product, and the existence of the lithium aluminum zirconate coating is proved.

According to the electrochemical test result of the final product, the assembled battery is cycled for 100 weeks at the cut-off voltage of 2.8-4.3V and the 0.2C multiplying power, the capacity retention rate of the final product is found to be 85.47%, which indicates that the cycling stability of the material is improved after the in-situ coating of the lithium aluminum zirconate.

The battery after the circulation is disassembled and the electrolyte is washed out, the percentage content of metal ions in the electrolyte is 132ppm through ICP test, compared with the metal ion dissolution of the material prepared in the comparative example 1, the metal ion dissolution is relieved, and the existence of the coating is helpful for reducing the degree of interface side reaction.

Example 2

(1) Mixing a single-crystal NCM ternary material precursor with a lithium salt according to a molar ratio of 1:1.2, adding alcohol, and grinding to dryness to obtain mixed powder 1;

(2) weighing mixed powder 2 of aluminum nitrate, zirconium carbonate and NaCl, mixing the mixed powder with the mixed powder 1, grinding and uniformly mixing to obtain mixed powder 3, wherein the mass fraction of the mixed powder 2 in the mixed powder 3 is 60%; mixing aluminum nitrate and zirconium carbonate in the mixed powder 2 according to a molar ratio of 1:1, wherein the mass fraction of NaCl is 80%;

(3) putting the solid powder material 3 into a tube furnace, heating to 550 ℃ at a heating rate of 2 ℃/min in an oxygen atmosphere, and preserving heat for 7h, then heating to 950 ℃ at a heating rate of 0.2 ℃/min, and preserving heat for 18h to obtain a solid block material;

(4) crushing and grinding the solid block material, then adding deionized water, stirring for 30min at 50 ℃, carrying out solid-liquid separation, and fully drying to obtain the in-situ aluminum lithium zirconate-coated monocrystal NCM ternary material;

according to the scanning electron microscope result of the final product, the final product is single crystal particles, and the surface of the single crystal particles is coated.

According to the X-ray diffraction result of the final product, the characteristic diffraction peak of the lithium aluminum zirconate exists in the final product, and the existence of the lithium aluminum zirconate coating is proved.

According to the electrochemical test result of the final product, the assembled battery is cycled for 100 weeks at a cut-off voltage of 2.8-4.3V and a multiplying power of 0.2C, and the capacity retention rate of the final product is found to be 90.16%, which indicates that the in-situ coating of the lithium aluminum zirconate can improve the cycling stability of the material.

The battery after circulation is disassembled and the electrolyte is washed out, the percentage content of metal ions in the electrolyte is 72ppm through ICP test, compared with the metal ion dissolution of the material prepared in the comparative example 1, the metal ion dissolution is obviously relieved, and the existence of the coating is helpful for reducing the degree of interface side reaction.

Example 3

(1) Mixing the single-crystal NCM ternary material precursor with lithium salt according to the molar ratio of 1:1.5, adding alcohol, and grinding to dryness to obtain mixed powder 1;

(2) weighing mixed powder 2 of aluminum sulfate and zirconium acetate, mixing the mixed powder with the mixed powder 1, grinding and uniformly mixing to obtain mixed powder 3, wherein the mass fraction of the mixed powder 2 in the mixed powder 3 is 80%; mixing aluminum nitrate and zirconium carbonate in the mixed powder 2 according to a molar ratio of 1: 1;

(3) putting the solid powder material 3 into a tubular furnace, heating to 600 ℃ at a heating rate of 5 ℃/min in an oxygen atmosphere, and preserving heat for 4h, then heating to 1000 ℃ at a heating rate of 1 ℃/min, and preserving heat for 15h to obtain a solid block material;

(4) crushing and grinding the solid block material, then adding deionized water, stirring for 50min at 40 ℃, carrying out solid-liquid separation, and fully drying to obtain the in-situ aluminum lithium zirconate-coated monocrystal NCM ternary material;

according to the scanning electron microscope result of the final product, the final product is micron-sized single crystal particles, and the surface of the single crystal particles is coated.

According to the X-ray diffraction result of the final product, the characteristic diffraction peak of the lithium aluminum zirconate exists in the final product, and the existence of the lithium aluminum zirconate coating is proved.

According to the electrochemical test result of the final product, after the assembled battery is cycled for 100 weeks at a cut-off voltage of 2.8-4.3V and a multiplying power of 0.2C, the capacity retention rate of the final product is found to be 82.64%, which indicates that the formation of excessive lithium aluminum zirconate can cause the surface passivation layer of the material to be thickened, hinder the migration of lithium ions and cause the rapid decay of electrochemical performance.

The battery after circulation is disassembled and the electrolyte is washed out, the percentage content of metal ions in the electrolyte is 69ppm through ICP test, compared with the metal ion dissolution of the material prepared in the comparative example 1, the metal ion dissolution is obviously relieved, and the existence of the coating is helpful for reducing the degree of interface side reaction.

The present invention includes, but is not limited to, the above embodiments, and any equivalent substitutions or partial modifications made under the principle of the spirit of the present invention are considered to be within the scope of the present invention.