阅读说明：本技术 一种4.7v级钴酸锂正极材料及其制备方法及相应电池 (4.7V-grade lithium cobaltate positive electrode material, preparation method thereof and corresponding battery ) 是由 徐蕾 于 2021-08-26 设计创作，主要内容包括：一种4.7V级钴酸锂正极材料及其制备方法及相应电池,属于锂离子电池技术领域。正极材料为核壳结构,核心为钴酸锂；壳层为稀土金属掺杂的钴酸锂,且稀土金属离子取代的是Li～(+)的位置,掺杂深度为钴酸锂表面1～200nm；稀土金属离子具有4f轨道。制备方法包括以下步骤：(1)取稀土金属源、钴源和锂源按比例配制,形成混合料；(2)将混合料于800～1200℃煅烧4～24小时,得到一次煅烧产物；(3)将一次煅烧产物破碎后于800～1200℃二次煅烧4～24小时,得到钴酸锂粗产物；(4)将钴酸锂粗产物破碎得到成品。本发明的正极材料在4.7V充电截止电压下首次可逆容量高达240.1mAh/g,且循环稳定性良好。(A4.7V-grade lithium cobaltate anode material, a preparation method thereof and a corresponding battery belong to the technical field of lithium ion batteries. The anode material is of a core-shell structure, and the core is lithium cobaltate; the shell layer is rare earth metal doped lithium cobaltate, and the rare earth metal ions replace Li + The doping depth of the position (1) is 1-200 nm of the surface of the lithium cobaltate; the rare earth metal ion has a 4f orbital. The preparation method comprises the following steps: (1) preparing a rare earth metal source, a cobalt source and a lithium source according to a proportion to form a mixture; (2) calcining the mixture at 800-1200 ℃ for 4-24 hours to obtain a primary calcined product; (3) will be provided withCrushing the primary calcined product, and then calcining for 4-24 hours at 800-1200 ℃ for the second time to obtain a crude lithium cobaltate product; (4) and crushing the crude lithium cobaltate product to obtain a finished product. The first reversible capacity of the anode material is up to 240.1mAh/g under the charge cut-off voltage of 4.7V, and the cycling stability is good.)

1. A4.7V-grade lithium cobaltate positive electrode material is characterized in that the positive electrode material is of a core-shell structure, and the core is lithium cobaltate; the shell layer is rare earth metal doped lithium cobaltate, and the rare earth metal ions replace Li⁺The doping depth of the position (1) is 1-200 nm of the surface of the lithium cobaltate; the rare earth metal ions have a 4f orbital.

2. The lithium cobaltate positive electrode material according to claim 1, wherein the rare earth metal accounts for 0.1-10% by weight of the positive electrode material.

3. The lithium cobaltate cathode material according to claim 1, wherein the rare earth metal is one or more of europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

4. The lithium cobaltate positive electrode material according to claim 1, wherein the working voltage of the positive electrode material is 2.5V-4.7V.

5. The method for preparing a lithium cobaltate positive electrode material according to any one of claims 1 to 4, comprising the steps of:

(1) preparing a rare earth metal source, a cobalt source and a lithium source according to a proportion to form a mixture;

(2) calcining the mixture at 800-1200 ℃ for 4-24 hours to obtain a primary calcined product;

(3) crushing the primary calcined product, and then calcining for 4-24 hours at 800-1200 ℃ for the second time to obtain a crude lithium cobaltate product;

(4) and crushing the crude lithium cobaltate product to obtain a 4.7V-grade lithium cobaltate cathode material finished product.

6. The method according to claim 5, wherein the lithium source and the cobalt source are prepared in a molar ratio of 1-1.2: 1 in step (1).

7. The method according to claim 5, wherein the rare earth metal source of step (1) is one or more of the elements, oxides, chlorides, carbonates, nitrates, sulfates, acetates, oxalates, and phosphates of europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; the cobalt source is one or more of oxide, hydroxide, chloride, nitrate, sulfate, carbonate, acetate, oxalate and phosphate of cobalt; the lithium source is one or more of oxides, hydroxides, nitrates, carbonates, oxalates, acetates and citrates of lithium.

8. The method according to claim 5, wherein the rare earth metal source in step (1) is an aqueous or ethanolic solution of soluble salts of europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, and the source is Co₃O₄Powder, the lithium source being Li₂CO₃Powder; the method for forming the mixture is to mixCo₃O₄Adding the powder into the aqueous solution or ethanol solution, heating and stirring until the solvent is completely volatilized to obtain the rare earth metal source and Co₃O₄And then mixing the solid mixture with Li₂CO₃And (4) uniformly mixing the powder.

9. The method according to claim 5, wherein the temperature increase rate before the calcination in the steps (2) and (3) is 0.1-10 ℃/min.

10. A lithium ion battery comprises a positive electrode, a diaphragm, a negative electrode, an electrolyte and a battery shell, and is characterized in that the positive electrode adopts the lithium cobaltate positive electrode material of any one of claims 1 to 4.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and relates to a 4.7V-grade lithium cobaltate positive electrode material, a preparation method thereof and a corresponding battery.

Background

Lithium ion batteries are widely used in the fields of consumer electronics, electric vehicles, aerospace and the like due to their advantages of high energy density and power density, long cycle life, no memory effect, environmental friendliness and the like. With the rapid development of the internet industry and the arrival of the 5G era, the cruising demand of people on mobile terminals (such as smart phones, VR glasses, unmanned aerial vehicles, small robots and the like) is higher and higher. As a power core component of a mobile terminal, the energy density of a lithium ion battery has become a core of consumer appeal. The lithium ion battery comprises a positive electrode, a negative electrode, electrolyte, a diaphragm and a battery package. The most critical component affecting energy density is the lithium storage capacity of the positive and negative electrode materials. So far, the energy of the traditional graphite cathode has been exerted to the utmost, while the energy of the cathode material is exerted to a relatively small extent.

Lithium cobaltate has high tap density, high voltage and stable cycle performance, and has become a poor choice for the anode material of the battery of consumer electronics products. Lithium cobaltate has a theoretical capacity of 274 mAh/g, but in practice it usually only gives a capacity of around 160 mAh/g, since the charge cut-off voltage is set at around 4.35V. When the charge is cut off to increase the voltage, more lithium ions are extracted, i.e., higher capacity is exerted. For example, by setting the charge cut-off voltage to 4.7V, a specific capacity of about 240 mAh/g can be exhibited, which is close to 88% of the theoretical capacity. However, CoO due to the large amount of lithium ion deintercalation₂The layers are supported only by electrostatic force, so that on one hand, expansion and contraction of c-axis crystal lattices are caused, and lattice distortion and crystal plane slippage are caused; on the other hand, Co due to the deintercalation of lithium ions³⁺Is oxidized into Co⁴⁺Highly active Co⁴⁺Will react with the carbonate electrolyte, leading to decomposition of the electrolyte and CO₂Etc. generation of gases. The generation of gas can cause the cell to bulge and the process is an exothermic reaction, which can lead to explosion of the cell in severe cases. Furthermore, Co⁴⁺The participation in the reaction leads to irreversible dissolution of Co, thereby destroying CoO₂The structure of the layer seriously affects the reversible capacity exertion of the battery.

Chinese invention application with publication number CN103618081A discloses a high-voltage high-capacity lithium ion battery positive electrode material, which contains cobalt source substance, lithium source substance, dopant M and coating material, wherein Li: the molar ratio of Co is 0.95-1.2, the doping amount of the doping agent M is 0.01-10 wt%, and the total doping amount of the coating material is 0.01-20 wt%. The highest operating voltage of this prior art is only 4.5V.

The Chinese invention application with the publication number of CN105406036A discloses a high-voltage lithium cobaltate cathode material of a lithium ion battery and a preparation method thereof, the material consists of a doped lithium cobaltate matrix and a coating on the surface of the doped lithium cobaltate matrix, and the general formula of the doped lithium cobaltate matrix is Li_xCo_1-yM_yO_2-zN_zThe general formula of the coating is LiNi_x’Co_y’Al_z’O₂(ii) a The preparation method comprises the following steps: firstly, obtaining lithium cobaltate matrix Li through one-time sintering_xCo_1-yM_yO_2-zN_zThen the Ni-coated surface is prepared by liquid-phase coprecipitation reaction_x’Co_y’Al_z’(OH)₂And finally, sintering the precursor of the lithium cobaltate positive electrode material for the second time to obtain the high-voltage lithium cobaltate positive electrode material. The highest operating voltage of this prior art is only 4.5V.

The Chinese invention application with the publication number of CN109461891A discloses a high-voltage lithium cobaltate material and a preparation method thereof, belonging to the field of lithium ion battery anode materials. The material has a core-shell structure, the inner core is gradient nickel-manganese doped lithium cobaltate particles, and the shell is in-situ generated spinel LiNi doped with rare earth_0.5Mn_1.5O₄And (4) coating. The maximum operating voltage described in the drawings of this prior art specification is 4.6V.

The chinese patent application with publication number CN110299518A discloses a high-voltage lithium cobalt oxide positive electrode material, a preparation method and a lithium ion secondary battery, wherein the high-voltage lithium cobalt oxide positive electrode material is of a multi-stage core-shell structure and comprises from inside to outside: alpha-NaFeO₂The lithium cobaltate core structure comprises a structure lithium cobaltate core layer, a composite doping layer and a functional shell layer. The working voltage range of the prior art is 3.0-4.6V.

When developing 4.7V grade lithium cobaltate anode material, on one hand, the method needs to be carried outThe use of suitable methods to mitigate lattice distortion and crystal plane slip is considered; on the other hand, it is also necessary to lower the valence of Co, and to reduce Co⁴⁺The formation of (2) is carried out to improve the cycling stability and the safety performance of the battery, and finally the application of the lithium ion battery with higher energy density is realized.

Disclosure of Invention

Aiming at the problem of low capacity of the existing lithium cobaltate cathode material, the invention aims to provide a 4.7V-grade lithium cobaltate cathode material, a preparation method thereof and a corresponding battery, which have stable cycle performance while improving the charge cut-off voltage to realize high capacity. The 4.7V-grade lithium cobaltate positive electrode material is a lithium cobaltate positive electrode material with the working voltage of 4.7V. The purpose of the invention is realized by the following technical scheme.

A4.7V-grade lithium cobaltate positive electrode material is characterized in that the positive electrode material is of a core-shell structure, and the core is lithium cobaltate; the shell layer is rare earth metal doped lithium cobaltate, and the rare earth metal ions replace Li⁺The doping depth of the position (1) is 1-200 nm of the surface of the lithium cobaltate; the rare earth metal ions have a 4f orbital.

Among lanthanides, rare earth metal ions have a unique 4f orbital. Due to the dispersive nature of the 4f electron, its shielding effect on the nucleus is weak, and therefore, as the number of 4f electrons increases, the ionic radius of the lanthanide gradually decreases, which is known as "lanthanide contraction". And the rare earth metal ions containing more than or equal to 7 electrons with 4f have more proper ionic radius, namely closer to the radius of lithium ions, so that the rare earth metal ions are more suitable to be doped in the position of lithium cobaltate for replacing Li, and the stability of the lithium cobaltate under high voltage is improved. The rare earth elements with 4f electrons or more include europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

The performance degradation of lithium cobaltate is mainly attributed to the structural damage, which is diffused from the outside to the inside. Therefore, surface doping can play a critical role in stabilizing the lithium cobaltate structure. In addition, doping of + 3-valent rare earth ions into the lithium cobaltate bulk phase inevitably causes reduction in the valence state of Co, thereby reducing highly active Co⁴⁺In the above-described manner, the formation of (2),the surface of the material is stabilized. Furthermore, the doping of rare earth ions in the lithium layer relieves the CoO of lithium cobaltate in a high delithiation state₂The lattice distortion caused by the electrostatic interaction of the layers improves the structural stability of the lithium cobaltate under high voltage, so that the lithium cobaltate material can maintain high capacity and good cycle performance under the high voltage of 4.7V.

Compared with the prior art, the 4.7V-grade lithium cobaltate cathode material provided by the invention mostly adopts a multi-grade core-shell structure of a coating layer, a doping layer and lithium cobaltate, and only needs the doping layer and the core-shell structure of the lithium cobaltate; doping with rare earth metal ions having 4f orbitals, substituting Li with rare earth metal ions⁺The position of (2) and the control of the doping depth are the key points for obtaining the 4.7V grade lithium cobaltate cathode material with high capacity and cycling stability.

Further, the weight of the rare earth metal accounts for 0.1-10% of the weight of the positive electrode material.

Further, the rare earth metal is one or more of europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

Further, the working voltage of the anode material is 2.5-4.7V.

The invention provides a preparation method of a 4.7V-grade lithium cobaltate positive electrode material, which is used for relieving the negative influence of performance deterioration caused by lattice strain of lithium cobaltate in a high lithium removal state, so that the lithium cobaltate positive electrode material has high capacity and stable cycle performance under the ultrahigh charge cut-off voltage of 4.7V. The method specifically comprises the following steps:

(1) preparing a rare earth metal source, a cobalt source and a lithium source according to a proportion to form a mixture;

(2) calcining the mixture at 800-1200 ℃ for 4-24 hours to obtain a primary calcined product;

(3) crushing the primary calcined product, and then calcining for 4-24 hours at 800-1200 ℃ for the second time to obtain a crude lithium cobaltate product;

(4) and crushing the crude lithium cobaltate product to obtain a 4.7V-grade lithium cobaltate cathode material finished product.

The doping depth of the anode material provided by the invention is 1-200 nm of the surface of lithium cobaltate, and the surface doping depth is controlled by the calcining temperature and time length: under the same calcining temperature, the longer the calcining time is, the deeper the doping is; and under the same calcining time, the higher the calcining temperature is, the deeper the doping is.

Further, the lithium source and the cobalt source in the step (1) are prepared according to a molar ratio of 1-1.2: 1.

Further, the rare earth metal source in the step (1) is one or more of simple substances, oxides, chlorides, carbonates, nitrates, sulfates, acetates, oxalates and phosphates of europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium; the cobalt source is one or more of oxide, hydroxide, chloride, nitrate, sulfate, carbonate, acetate, oxalate and phosphate of cobalt; the lithium source is one or more of oxides, hydroxides, nitrates, carbonates, oxalates, acetates and citrates of lithium.

Further, the rare earth metal source in the step (1) is an aqueous solution or an ethanol solution of soluble salts of europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, and the rare earth metal source is Co₃O₄Powder, the lithium source being Li₂CO₃Powder; the method for forming the mixed material is to mix Co₃O₄Adding the powder into the aqueous solution or ethanol solution, heating and stirring until the solvent is completely volatilized to obtain the rare earth metal source and Co₃O₄And then mixing the solid mixture with Li₂CO₃And (4) uniformly mixing the powder.

Further, the heating rate before the calcination in the steps (2) and (3) is 0.1-10 ℃/min.

The invention also provides a lithium ion battery which comprises an anode, a diaphragm, a cathode, electrolyte and a battery shell, wherein the anode adopts the 4.7V-grade lithium cobalt oxide anode material.

The invention has the following technical effects: the invention provides a universal method for preparing rare earth element surface-doped lithium cobaltate, and the preparation process is simple and is suitable for large-scale industrial production. The 4.7V-grade lithium cobaltate cathode material provided by the invention has the first reversible capacity of 240.1mAh/g under the charge cut-off voltage of 4.7V, and has good cycling stability.

The improvement of the stability can be attributed to the stability of the rare earth ions to the surface structure of lithium cobaltate. Because the performance degradation of lithium cobaltate is mainly attributed to the structural damage, which is diffused from the outside to the inside. Therefore, surface doping can play a critical role in stabilizing the lithium cobaltate structure. In addition, the rare earth ions doped in the lithium layer not only play a role of supporting a layered structure, but also replace the lithium ions with low valence by the rare earth ions with high valence, so that the valence of the surrounding Co can be reduced, and the Co valence in the charging process is reduced⁴⁺Is performed. The universal synthesis method and the excellent electrochemical performance have very important practical significance for realizing the application of the lithium ion battery with higher energy density.

Drawings

FIG. 1 is a schematic structural diagram of the 4.7V grade lithium cobaltate positive electrode material;

FIG. 2 is a schematic diagram of the crystal structure of the 4.7V grade lithium cobaltate cathode material;

FIG. 3 is a scanning electron microscope image of a 4.7V grade lithium cobaltate cathode material provided in example 1 of the present invention;

FIG. 4 is a powder X-ray diffraction pattern of a 4.7V grade lithium cobaltate positive electrode material provided in example 4 of the present invention;

fig. 5 is a cycle performance diagram of the 4.7V grade lithium cobalt oxide positive electrode material provided in example 7 of the present invention at a voltage interval of 3.0 to 4.7V and a current density of 0.1C.

Detailed Description

The present invention will be further described with reference to the accompanying drawings, but the present invention is not limited thereto.

Example 1

Respectively taking Co₃O₄，Li₂CO₃And EuCl₃·6H₂Feeding O according to the molar ratio of Co to Li to Eu of 1:1.05:0.02, and firstly, adding EuCl₃·6H₂Dissolving O in distilled water, and adding Co₃O₄Stirring at 80 deg.C until water is completely evaporated, and mixing with Li₂CO₃Uniformly mixing and placing in a muffle furnace for high-temperature sintering, wherein the sintering process is as follows: to be provided withRaising the temperature rise rate to 1000 ℃ at the speed of 5 ℃/min, preserving the heat for 12 hours, naturally cooling, and collecting a primary sintering product; and (3) crushing the primary sintering product, and then placing the crushed primary sintering product in a muffle furnace for high-temperature sintering, wherein the secondary sintering process comprises the following steps: raising the temperature to 900 ℃ at the heating rate of 5 ℃/min, preserving the heat for 10 hours, naturally cooling, and collecting a secondary sintering product; and crushing the secondary sintered product to obtain a final product.

Example 2

Respectively taking Co₃O₄，Li₂CO₃And Gd (NO)₃)₃·6H₂And feeding O according to the molar ratio of Co to Li to Gd of 1:1.05: 0.02. Gd (NO) first₃)₃·6H₂Dissolving O in distilled water, and adding Co₃O₄Stirring at 80 deg.C until water is completely evaporated, and mixing with Li₂CO₃Uniformly mixing and placing in a muffle furnace for high-temperature sintering, wherein the sintering process is as follows: heating to 1100 deg.C at a rate of 5 deg.C/min, maintaining for 10 hr, naturally cooling, and collecting the primary sintered product; and (3) crushing the primary sintering product, and then placing the crushed primary sintering product in a muffle furnace for high-temperature sintering, wherein the secondary sintering process comprises the following steps: raising the temperature to 1000 ℃ at the heating rate of 5 ℃/min, preserving the heat for 4 hours, naturally cooling, and collecting a secondary sintering product; and crushing the secondary sintered product to obtain a final product.

Example 3

Respectively taking Co₃O₄，Li₂CO₃And Ho₂(SO₄)₃·8H₂Feeding O according to the molar ratio of Co to Li to Ho of 1:1.05: 0.02. Firstly, Ho is put₂(SO₄)₃·8H₂Dissolving O in distilled water, and adding Co₃O₄Stirring at 80 deg.C until water is completely evaporated, and mixing with Li₂CO₃Uniformly mixing and placing in a muffle furnace for high-temperature sintering, wherein the sintering process is as follows: raising the temperature to 1200 ℃ at the heating rate of 5 ℃/min, preserving the heat for 12 hours, naturally cooling, and collecting a primary sintering product; and (3) crushing the primary sintering product, and then placing the crushed primary sintering product in a muffle furnace for high-temperature sintering, wherein the secondary sintering process comprises the following steps: raising the temperature to 1000 ℃ at the heating rate of 5 ℃/min, preserving the heat for 4 hours, naturally cooling, and collecting a secondary sintering product; crushing the secondary sintered product to obtain the final product。

Example 4

Respectively taking Co₃O₄，Li₂CO₃And ErCl₃·6H₂And feeding O according to the molar ratio of Co to Li to Er of 1:1.05: 0.02. First ErCl₃·6H₂Dissolving O in absolute ethyl alcohol, and adding Co₃O₄Stirring at 80 deg.C until absolute ethanol is completely evaporated, and mixing with Li₂CO₃Uniformly mixing and placing in a muffle furnace for high-temperature sintering, wherein the sintering process is as follows: raising the temperature to 1200 ℃ at the heating rate of 5 ℃/min, preserving the temperature for 10 hours, naturally cooling, and collecting a primary sintering product; and (3) crushing the primary sintering product, and then placing the crushed primary sintering product in a muffle furnace for high-temperature sintering, wherein the secondary sintering process comprises the following steps: raising the temperature to 800 ℃ at the heating rate of 5 ℃/min, preserving the heat for 10 hours, naturally cooling, and collecting a secondary sintering product; and crushing the secondary sintered product to obtain a final product.

Example 5

Respectively taking Co₃O₄，Li₂CO₃And Tm (NO)₃)₃·6H₂Feeding O according to the molar ratio of Co to Li to Tm of 1:1.05: 0.05. Tm (NO) first₃)₃·6H₂Dissolving O in absolute ethyl alcohol, and adding Co₃O₄Stirring at 80 deg.C until absolute ethanol is completely evaporated, and mixing with Li₂CO₃Uniformly mixing and placing in a muffle furnace for high-temperature sintering, wherein the sintering process is as follows: raising the temperature to 1200 ℃ at the heating rate of 5 ℃/min, preserving the temperature for 10 hours, naturally cooling, and collecting a primary sintering product; and (3) crushing the primary sintering product, and then placing the crushed primary sintering product in a muffle furnace for high-temperature sintering, wherein the secondary sintering process comprises the following steps: raising the temperature to 800 ℃ at the heating rate of 5 ℃/min, preserving the heat for 10 hours, naturally cooling, and collecting a secondary sintering product; and crushing the secondary sintered product to obtain a final product.

Example 6

Respectively taking Co₃O₄，Li₂CO₃And Yb₂(CO₃)₃·xH₂And feeding O according to the molar ratio of Co to Li to Yb of 1:1.05: 0.02. First Yb₂(CO₃)₃·xH₂Dissolving O in absolute ethyl alcohol, and adding Co₃O₄Stirring at 80 deg.C until absolute ethanol is completely evaporated, and mixing with Li₂CO₃Uniformly mixing and placing in a muffle furnace for high-temperature sintering, wherein the sintering process is as follows: raising the temperature to 1000 ℃ at the heating rate of 5 ℃/min, preserving the temperature for 10 hours, naturally cooling, and collecting a primary sintering product; and (3) crushing the primary sintering product, and then placing the crushed primary sintering product in a muffle furnace for high-temperature sintering, wherein the secondary sintering process comprises the following steps: raising the temperature to 1000 ℃ at the heating rate of 5 ℃/min, preserving the heat for 10 hours, naturally cooling, and collecting a secondary sintering product; and crushing the secondary sintered product to obtain a final product.

Example 7

Respectively taking Co₃O₄，Li₂CO₃And Lu (NO)₃)₃·xH₂Feeding O according to the molar ratio of Co to Li to Lu of 1:1.05:0.02, and firstly feeding Lu (NO)₃)₃·xH₂Dissolving O in absolute ethyl alcohol, and adding Co₃O₄Stirring at 80 deg.C until absolute ethanol is completely evaporated, and mixing with Li₂CO₃Uniformly mixing and placing in a muffle furnace for high-temperature sintering, wherein the sintering process is as follows: heating to 1100 deg.C at a rate of 5 deg.C/min, maintaining for 10 hr, naturally cooling, and collecting the primary sintered product; and (3) crushing the primary sintering product, and then placing the crushed primary sintering product in a muffle furnace for high-temperature sintering, wherein the secondary sintering process comprises the following steps: raising the temperature to 800 ℃ at the heating rate of 5 ℃/min, preserving the heat for 10 hours, naturally cooling, and collecting a secondary sintering product; and crushing the secondary sintered product to obtain a final product.

The products obtained in examples 1 to 7 were subjected to various kinds of characterization, and the data in the following randomly selected examples are illustrated:

fig. 1 is a schematic structural diagram of the 4.7V-grade lithium cobalt oxide positive electrode material, and it can be seen from the schematic diagram that the rare earth metal ion-doped lithium cobalt oxide is a core-shell structure, the inner layer is a lithium cobalt oxide core, and the outer layer is a lithium cobalt oxide layer doped with rare earth metal ions.

FIG. 2 is a schematic diagram of the crystal structure of the 4.7V grade lithium cobaltate positive electrode material, wherein the lithium cobaltate is CoO₂A layered structure of layers alternately stacked with Li layers, each Co atom coordinated with 6O atoms to form CoO₆Octahedron, Co in the center of the octahedron and O at the 6 top of the octahedronPoint, Li⁺The ions being replaced by rare earth ions of slightly larger radius, which enable adjacent CoO to be amplified₂Interlayer spacing between layers, which favors Li⁺The transmission of ions; the electrochemically inert rare earth metal ions can play a role in supporting CoO in a high delithiation state₂The effect of the layer relieves the phenomena of lattice distortion and crystal face slip, thereby improving the high-voltage cycle stability.

Fig. 3 is a scanning electron microscope image of the 4.7V grade lithium cobaltate cathode material provided in example 1, wherein the image shows that the cathode material has a blocky morphology and a smooth surface, which indicates that the rare earth metal ions are uniformly doped on the surface.

Fig. 4 is an X-ray diffraction pattern of the 4.7V-grade lithium cobaltate positive electrode material of example 4, all diffraction peaks correspond to those of lithium cobaltate, and no impurity peak appears, indicating successful doping.

Fig. 5 is a graph showing the cycle performance of the 4.7V grade lithium cobaltate positive electrode material provided in example 7 in a voltage interval of 3.0 to 4.7V and a current density of 0.1C, wherein the lithium cobaltate can not only exert high capacity but also have stable cycle performance under high voltage.