GB2624734A

GB2624734A - Preparation method for closely coated cobalt oxide and use thereof

Info

Publication number: GB2624734A
Application number: GB2310124.9A
Authority: GB
Inventors: Yu Haijun; Xie Yinghao; Li Aixia; Zhang Xuemei; Li Changdong
Original assignee: Hunan Brunp Recycling Technology Co Ltd; Guangdong Brunp Recycling Technology Co Ltd; Hunan Bangpu Automobile Circulation Co Ltd
Current assignee: Hunan Brunp Recycling Technology Co Ltd; Guangdong Brunp Recycling Technology Co Ltd; Hunan Bangpu Automobile Circulation Co Ltd
Priority date: 2022-06-28
Filing date: 2022-09-20
Publication date: 2024-05-29
Also published as: DE112022002441T5; MA65126A1; GB202310124D0; HUP2400047A1; ES3010566A2

Abstract

Disclosed in the present invention are a preparation method for a closely coated cobalt oxide and the use thereof, the preparation method comprising: synthesizing spherical cobalt hydroxide particles by a coprecipitation method; after drying and dehydrating same, uniformly mixing same with zirconium alkyl carboxylate/aluminum alkyl carboxylate and zirconium hydroxide/aluminum hydroxide and coheating the mixture to enable the zirconium alkyl carboxylate/aluminum alkyl carboxylate and zirconium hydroxide/aluminum hydroxide to react with cobalt hydroxide on the surface layers of the particles, so as to tightly attach same to the surfaces of the cobalt hydroxide spherical particles; and finally, performing calcining to remove organic matters so as to form cobalt oxide spherical particles with closely coating layers on the surfaces. By using chemical bonds to connect the coating layers and a base material, the present invention makes the two more closely attached and not prone to pulverization and falling, thus greatly prolonging the service life of the coating layers, and improving cycle performance of the material.

Description

METHOD FOR PREPARING TIGHTLY COATED COBALT OXIDE AND USE

THEREOF

FIELD

100011 The present disclosure relates to the field of precursors of positive electrode material for lithium ion batteries, and in particular to a method for preparing a tightly coated cobalt oxide and use thereof

BACKGROUND

100021 Lithium cobalt oxide electrode material has high specific capacity and good cycle stability, and it is a positive electrode material which is currently widely used in the field of 3C. With the rapid development of 3C electronic products, manufacturers continue to put forward higher requirements for the processing performance and electrochemical performance of lithium cobalt oxide positive electrode materials. Lithium cobalt oxide, as the earliest commercialized positive electrode material for lithium-ion batteries, is still one of the positive electrode materials with the highest compaction density in practical applications. The lithium cobalt oxide has a typical layered structure, in which cobalt ions and lithium ions are alternately distributed in the voids of the close-packed layers formed by oxygen ions. According to the amount of lithium ions that can be extracted from lithium cobalt oxide, the theoretical mass specific capacity of the lithium cobalt oxide is about 274mAhig.

[0003] With the rapid development of fields such as smart electronic devices, there is an urgent need for high-energy-density lithium batteries with long cycle life and high safety. Using positive electrodes with high voltage and high specific capacity is an effective way to improve the energy density of batteries. The lithium cobalt oxide positive electrode material has received extensive attention due to its high theoretical specific capacity, but there are still many problems and challenges on its use at high voltages, especially the problems such as the structural phase change at the interface with the electrolyte, the dissolution of transition metals, the precipitation of oxygen, and the continuous oxidative decomposition of the electrolyte, which severely limit the use of the lithium cobalt oxide positive electrode material in high-energy-density lithium batteries 100041 In view of the above problems, in the prior art, the structural properties and electrochemical properties of the particles can be optimized by forming a coating layer on the surface of the material, so as to improve the corrosion resistance of the material, and reduce the side reaction between the material and the electrolyte. By coating a thin and stable coating layer on the surface of the material, wherein the common coating materials are oxides, fluorides, lithium ion conductors and the like, the coating layer can reduce the contact resistance between the particles, and meanwhile separate the material from the electrolyte, so as to reduce the side reaction between the material and the electrolyte, and prevent the corrosion of the positive electrode material by the HP gas generated by the decomposition of the electrolyte.

[0005] The patent document with a publication number CN103359795A discloses a cobaltosic oxide-covered composite multi-element lithium ion battery positive electrode material precursor and a preparation method thereof; in which the "wet coating + sintering" method is used to obtain a very good and compact cobaltosic oxide coating layer on the surface of the sphere. However, the coating layer is easy to be pulverized and shed off during the long-term cycle, so that the lithium cobalt oxide is re-exposed to the electrolyte to be corroded, which affects the cycle performance of the material.

SUMMARY

[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. Therefore, the present invention provides a method for preparing a tightly coated cobalt oxide and use thereof This method can obtain a layer of tightly-coated cobalt oxide, greatly prolonging the life of the coating layer, and further improving the cycle performance of the material [0007] In one aspect, the present invention provides a method for preparing a tightly-coated cobalt oxide, comprising the following steps: [0008] adding a cobalt salt solution, a sodium hydroxide solution and aqueous ammonia in parallel to a base solution to react, until the reaction material reaches the target particle size, performing ageing on the mixture, then subjecting the resulting mixture to solid-liquid separation

_

to obtain a precipitate, and washing and drying the precipitate to obtain a dry material: 100091 52: adding the dry material and hydroxide to an organic solution of metal carboxylate, heating the mixture to evaporate the solvent, and when the evaporation rate of the solvent reaches more than 90%, heating the mixture to 180-200°C to react; wherein the hydroxide is zirconium hydroxide or aluminum hydroxide, and the organic solution of metal carboxylate is an alcohol solution of zirconium alkylcarboxylate or aluminum alkylcarboxylate; [0010] 53: calcining the product after reaction in step 52 in an oxygen atmosphere to obtain the cobalt oxide.

100111 In some embodiments of the present invention, in step Si, the concentration of the cobalt salt solution is 1.0-2.0 mol/L, and the concentration of the sodium hydroxide solution is 4.0-10.0 mol/L.

[0012] In some embodiments of the present invention, in step SI, the concentration of the aqueous ammonia added in parallel is 6.0-12.0 mol/L.

[0013] In some embodiments of the present invention, in step SI, the base solution is a mixed solution of sodium hydroxide and aqueous ammonia, the pH of the base solution is 10-11, and the concentration of ammonia is 5.0-10.0 g/L.

[0014] In some embodiments of the present invention, in step Sl, the temperature of the reaction is controlled to be 55-65°C, the pH of the reaction material is controlled to be 10-11, and the concentration of the ammonia is controlled to be 5-10 g/L.

[0015] In some embodiments of the present invention, in step SI, the target particle size of the reaction material is 2.0 pm-15.0 gm.

[0016] In some embodiments of the present invention, in step SI, the duration of the aging is I-2h.

100171 In some embodiments of the present invention, in step Si, the temperature of the drying is 100-120°C, and the duration of the drying is 4-6 h. [0018] In some embodiments of the present invention, in step 52, the ratio of the weight of the dry material to the volume of the organic solution of the metal carboxylate (solid-liquid ratio) is 1 g: (1-5) mL, and the concentration of the metal carboxylate in the organic solution of the metal -3 -carboxylate is 0.1-0.2mol/L.

100191 In some embodiments of the present invention, in step S2, the addition amount of the hydroxide is 1-5% of the weight of the dry material.

[0020] In some embodiments of the present invention, in step S2, the temperature of the heating to evaporate the solvent is 70-80°C.

[0021] In some embodiments of the present invention, in step S2, the duration of the reaction is 15-30 min. [0022] In some embodiments of the present invention, in step S2, the number of carbon atoms in the alkyl segment in the zirconium alkylcarboxylate or the aluminum alkylcarboxylate is 6-10.

100231 In some embodiments of the present invention, in step S3, the temperature of the calcining is 500-750°C.

[0024] In some embodiments of the present invention, in step S3, the duration of the calcining is 2-611 [0025] The present invention also provides application of the method in the preparation of lithium cobalt oxide or lithium ion batteries.

100261 According to a preferred embodiment of the present invention, it has at least the following beneficial effects: [0027] 1. In the present invention, spherical cobalt hydroxide particles are first synthesized by a co-precipitation method, then the spherical cobalt hydroxide particles are dried, dehydrated, and uniformly mixed with zirconium alkylcarboxylate/alumin um alkylcarboxylate and zirconium hydroxide/aluminum hydroxide, then the mixture is co-heated to react with the cobalt hydroxide on the particle surface, so as to closely adhere to the surface of the cobalt hydroxide spherical particles, and finally, the particles are calcined to remove the organic matter to form cobalt oxide spherical particles with a tight coating layer on the surface. The reaction equation thereof is as follows: [0028] In the co-precipitation reaction: [0029] Co2++201-1-->Co (OH)2; [0030] Taking zirconium hydroxide and zirconium alkylcarboxylate as an example, in the co-thermal reaction: 100311 (RnC00)4Zr+4Zr(OH)4->[RnC00-Zr(OH)2-0]4-Zr+4H20; [0032] (RnC00)4Zry4Co(OH)2-0.6C00-Co-0)4-ZrE4H20; [0033] Referring to the above reaction, in the present invention, a Co-O-Zr-O-Co or Co-O-Al-O-Co bond can be formed during the co-thermal reaction in step S2, so that the subsequent zirconium/aluminum and cobalt are closely connected through an oxide bond. The addition of zirconium hydroxide/aluminum hydroxide can increase the zirconium/aluminum content of the coating layer and reduce the cobalt content.

[0034] 2. The coating on the surface of the spherical particles is not pure zirconia/alumina, but cobalt zirconium oxide or cobalt aluminum oxide that formed by the connection between the zirconium/aluminum with the cobalt oxide through chemical bonds on the particle surface. Compared with the traditional coating method, in the present invention, the coating layer and the base material are connected through chemical bonds, making the two adhere to each other more closely, so that the coating layer is not easy to be pulverized and shed off, greatly prolonging the life of the coating layer, and improving the cycle performance of the material. Subsequently in the preparation of positive electrode material of lithium cobalt oxide, due to the zirconia/alumina on the surface of cobalt oxide, the problem of cobalt dissolution in lithium cobalt oxide due to long-term cycle can be prevented, further improving the cycle performance of the material.

BRIEF DESCRIPTION OF DRAWINGS

[0035] The present invention will be further described below in conjunction with the drawings and examples, wherein: [0036] FIG. 1 is the SEM image of the cobalt oxide prepared in Example 1 of the present 25 invention.

DETAILED DESCRIPTION -5 -

[0037] The concept of the present invention and the technical effects produced by the present invention will be clearly and completely described below with reference to the examples, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described examples are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the examples of the present invention, other examples obtained by those skilled in the art without creative efforts are all within the protection scope of the present invention

Example 1

[0038] In this example, a tightly-coated cobalt oxide was prepared. The specific process is: [0039] Step 1 a cobalt sulfate solution with a concentration of 2.0mol/L was prepared; [0040] Step 2: a sodium hydroxide solution with a concentration of 10.0mol/L was prepared as a precipitating agent; [0041] Step 3: an aqueous ammonia w with concentration of 12.0mol/L was prepared as a complexing agent; [0042] Step 4: pure water was added to a reaction kettle to overflow the bottom stirring paddle, then a certain amount of sodium hydroxide solution prepared in step 2 and aqueous ammonia prepared in step 3 were added to the kettle to form a base solution for starting reaction, wherein the pH value of the base solution was 10.5, and the concentration of ammonia was 5, OWL; [0043] Step 5: the cobalt salt solution prepared in step 1, the sodium hydroxide solution prepared in step 2, and the aqueous ammonia prepared in step 3 were added in parallel to the reaction kettle to react. In the reaction kettle, the stirring speed was controlled to be 500r/min, the pH was controlled to be 10.5, the temperature was controlled to be 55°C, and the concentration of ammonia was controlled to be 5g/L; [0044] Step 6: when the D50 of the material in the reaction kettle was detected to reach 15.0 pm, the feeding was stopped, and the material was aged for 2h; 100451 Step 7: the material in the kettle was subjected to solid-liquid separation, and then the obtained precipitate was washed with pure water, and dried at 120°C for 4 hours to obtain a dried material; [0046] Step 8: according to the solid-liquid ratio of lg:5mL, the dried material was added to an ethanol solution of aluminum octoate (CAS No. 6028-57-5) with a concentration of 0.2mol/L, then aluminum hydroxide with an amount of 5% of the weight of the dried material was added to the mixture. The obtained mixture was mixed uniformly, and heated (temperature was 70-80°C) under constant stirring to evaporate the organic solvent, and the organic solvent was recovered. When the organic solvent recovery rate reached more than 90%, the heating on the mixture was strengthened, and when the temperature reached 200°C, the temperature was maintained for 15min; 100471 Step 9: the product obtained in step 8 was calcined at 500°C in an oxygen atmosphere for 6 hours to obtain a tightly-coated cobalt oxide.

Example 2

100481 In this example, a tightly-coated cobalt oxide was prepared. The specific process is: 100491 Step 1 a cobalt nitrate solution with a concentration of 1.5mol/L was prepared; [0050] Step 2: a sodium hydroxide solution with a concentration of 7.0mol/L was prepared as a precipitating agent, [0051] Step 3: an aqueous ammonia with a concentration of 10.0mol/L was prepared as a complexing agent; [0052] Step 4: pure water was added to a reaction kettle to overflow the bottom stirring paddle, then a certain amount of sodium hydroxide solution prepared in step 2 and aqueous ammonia prepared in step 3 were added to the kettle to form a base solution for starting reaction, wherein the pH value of the base solution was 10.8, and the concentration of ammonia was 7g/L; [0053] Step 5: the cobalt salt solution prepared in step 1, the sodium hydroxide solution prepared in step 2, and the aqueous ammonia prepared in step 3 were added in parallel to the reaction kettle to react. In the reaction kettle, the stirring speed was controlled to be 350r/min, the pH was controlled to be 10.8, the temperature was controlled to be 60°C, and the concentration of ammonia was controlled to be 7g/L; 100541 Step 6: when the D50 of the material in the reaction kettle was detected to reach 10.0 pm, the feeding was stopped, and the material was aged for 1.5h; [0055] Step 7: the material in the kettle was subjected to solid-liquid separation, and then the obtained precipitate was washed with pure water, and dried at 110°C for 5 hours to obtain a dried material; [0056] Step 8: according to the solid-liquid ratio of Ig:3mL, the dried material was added to an ethanol solution of zirconium octoate (CAS: 18312-04-4) with a concentration of 0.15mol/L, then zirconium hydroxide with an amount of 3% of the weight of the dried material was added to the mixture. The obtained mixture was mixed uniformly, and heated (temperature was 70-80°C) under constant stirring to evaporate the organic solvent, and the organic solvent was recovered. When the organic solvent recovery rate reached more than 90%, the heating on the mixture was strengthened, and when the temperature reached 190°C, the temperature was maintained for 20min, [0057] Step 9: the product obtained in step 8 was calcined at 650°C in an oxygen atmosphere for 4 hours to obtain a tightly-coated cobalt oxide.

Example 3

100581 In th s example, a tightly-coated cobalt ox de was prepared. The specific process is: [0059] Step 1 a cobalt chloride solution with a concentration of 1.0moUL was prepared; [0060] Step 2: a sodium hydroxide solution with a concentration of 4.0mol/L was prepared as a precipitating agent; [0061] Step 3: an aqueous anunon a with a concentra on of 6.0mol/L was prepared as a complexing agent; [0062] Step 4: pure water was added to a reaction kettle to overflow the bottom stirring paddle, then a certain amount of sodium hydroxide solution prepared in step 2 and aqueous ammonia prepared in step 3 were added to the kettle to form a base solution for starting reaction, wherein the pH value of the base solution was 11, and the concentration of ammonia was 10.0g/L; [0063] Step 5: the cobalt salt solution prepared in step 1, the sodium hydroxide solution prepared in step 2, and the aqueous ammonia prepared in step 3 were added in parallel to the reaction kettle to react. In the reaction kettle, the stirring speed was controlled to be 200r/min, the pH was controlled to be 11, the temperature was controlled to be 65°C, and the concentration of -g -ammonia was controlled to be IOWL; 100641 Step 6: when the D50 of the material in the reaction kettle was detected to reach 5.0 the feeding was stopped, and the material was aged for lh, [0065] Step 7: the material in the kettle was subjected to solid-liquid separation, and then the obtained precipitate was washed with pure water, and dried at 100°C for 6 hours to obtain a dried material; [0066] Step 8: according to the solid-liquid ratio of I g:lmL, the dried material was added to an ethanol solution of zirconium 2-ethylhexanoate (CAS: 2233-42-3) with a concentration of 0.1mon, then zirconium hydroxide with an amount of 1% of the weight of the dried material was added to the mixture. The obtained mixture was mixed uniformly, and heated (temperature was 70-80°C) under constant stirring to evaporate the organic solvent, and the organic solvent was recovered. When the organic solvent recovery rate reached more than 90%, the heating on the mixture was strengthened, and when the temperature reached 180°C, the temperature was maintained for 30min; 100671 Step 9: the product obtained in step 8 was calcined at 750°C in an air atmosphere for 2 hours to obtain a tightly-coated cobalt oxide.

Comparative Example 1 [0068] In this example, a cobalt oxide was prepared, which differs from Example 1 in that aluminum octoate was not added The specific process is: [0069] Step 1. a cobalt sulfate solution with a concentration of 2.0mol/L was prepared; [0070] Step 2: a sodium hydroxide solution with a concentration of 10.0mol/L was prepared as a precipitating agent; [0071] Step 3: an aqueous ammonia with a concentration of 12.0mon was prepared as a complexing agent; [0072] Step 4: pure water was added to a reaction kettle to overflow the bottom stirring paddle, then a certain amount of sodium hydroxide solution prepared in step 2 and aqueous ammonia prepared in step 3 were added to the kettle to form a base solution for starting reaction, wherein the pH value of the base solution was 10.5, and the concentration of ammonia was 5.0g/L; [0073] Step 5: the cobalt salt solution prepared in step 1, the sodium hydroxide solution prepared in step 2, and the aqueous ammonia prepared in step 3 were added in parallel to the reaction kettle to react. In the reaction kettle, the stirring speed was controlled to be 500r/min, the pH was controlled to be 10.5, the temperature was controlled to be 55°C, and the concentration of ammonia was controlled to be 5g/L; [0074] Step 6: when the D50 of the material in the reaction kettle was detected to reach 15.0 Ism, the feeding was stopped, and the material was aged for 2h; [0075] Step 7: the material in the kettle was subjected to solid-liquid separation, and then the obtained precipitate was washed with pure water, and dried at 120°C for 4 hours to obtain a dried material; 100761 Step 8: according to the solid-liquid ratio of lg:5mL, the dried material was added to an ethanol solution, then aluminum hydroxide with an amount of 12.8% of the weight of the dried material was added to the mixture. The obtained mixture was mixed uniformly, and heated (temperature was 70-80°C) under constant stirring to evaporate the organic solvent, and the organic solvent was recovered. When the organic solvent recovery rate reached more than 90%, the heating on the mixture was strengthened, and when the temperature reached 200°C, the temperature was maintained for 15min; 100771 Step 9: the product obtained in step 8 was calcined at 500°C in an oxygen atmosphere for 6 hours to obtain a coated cobalt oxide.

Comparative Example 2 [0078] In this example, a cobalt oxide was prepared, which differs from Example 2 in that zirconium octoate was not added. The specific process is: [0079] Step I a cobalt nitrate solution with a concentration of 1 5mol/L was prepared; [0080] Step 2: a sodium hydroxide solution with a concentration of 7.0mol/L was prepared as a precipitating agent; 100811 Step 3: an aqueous ammonia with a concentration of 10.0mon was prepared as a complexing agent; [0082] Step 4: pure water was added to a reaction kettle to overflow the bottom stirring paddle, then a certain amount of sodium hydroxide solution prepared in step 2 and aqueous ammonia prepared in step 3 were added to the kettle to form a base solution for starting reaction, wherein the pH value of the base solution was 10.8, and the concentration of ammonia was 7g/L; [0083] Step 5: the cobalt salt solution prepared in step 1, the sodium hydroxide solution prepared in step 2, and the aqueous ammonia prepared in step 3 were added in parallel to the reaction kettle to react. In the reaction kettle, the stirring speed was controlled to be 350r/min, the pH was controlled to be 10.8, the temperature was controlled to be 60°C, and the concentration of ammonia was controlled to be 7g/L; [0084] Step 6: when the D50 of the material in the reaction kettle was detected to reach 10.0 gm, the feeding was stopped, and the material was aged for 1.5h; 100851 Step 7: the material in the kettle was subjected to solid-liquid separation, and then the obtained precipitate was washed with pure water, and dried at 110°C for 5 hours to obtain a dried material; [0086] Step 8: according to the solid-liquid ratio of lg:3mL, the dried material was added to an ethanol solution, then zirconium hydroxide with an amount of 14.5% of the weight of the dried material was added to the mixture. The obtained mixture was mixed uniformly, and heated (temperature was 70-80°C) under constant stirring to evaporate the organic solvent, and the organic solvent was recovered. When the organic solvent recovery rate reached more than 90%, the heating on the mixture was strengthened, and when the temperature reached 190°C, the temperature was maintained for 20min; [0087] Step 9: the product obtained in step 8 was calcined at 650°C in an oxygen atmosphere for 4 hours to obtain a coated cobalt oxide.

Comparative Example 3 [0088] In this example, a cobalt oxide was prepared, which differs from Example 3 in that zirconium 2-ethylhexanoate was not added. The specific process is: [0089] Step 1: a cobalt chloride solution with a concentration of 1.0mol/L was prepared; 100901 Step 2: a sodium hydroxide solution with a concentration of 4.0mol/L was prepared as a precipitating agent; [0091] Step 3: an aqueous ammonia with a concentration of 6.0mol/L was prepared as a complexing agent; 100921 Step 4: pure water was added to a reaction kettle to overflow the bottom stirring paddle, then a certain amount of sodium hydroxide solution prepared in step 2 and aqueous ammonia prepared in step 3 were added to the kettle to form a base solution for starting reaction, wherein the pH value of the base solution was 11, and the concentration of ammonia was 10.0g/L; [0093] Step 5: the cobalt salt solution prepared in step 1, the sodium hydroxide solution prepared in step 2, and the aqueous ammonia prepared in step 3 were added in parallel to the reaction kettle to react. In the reaction kettle, the stirring speed was controlled to be 200r/min, the pH was controlled to be 11, the temperature was controlled to be 65°C, and the concentration of ammonia was controlled to be IOWL; 100941 Step 6: when the D50 of the material in the reaction kettle was detected to reach 5.0 pm, the feeding was stopped, and the material was aged for lh; [0095] Step 7: the material in the kettle was subjected to solid-liquid separation, and then the obtained precipitate was washed with pure water, and dried at 100°C for 6 hours to obtain a dried material; [0096] Step 8: according to the solid-liquid ratio of I g:lmL, the dried material was added to an ethanol solution, then zirconium hydroxide with an amount of 3.5% of the weight of the dried material was added to the mixture. The obtained mixture was mixed uniformly, and heated (temperature was 70-80°C) under constant stirring to evaporate the organic solvent, and the organic solvent was recovered. When the organic solvent recovery rate reached more than 90%, the heating on the mixture was strengthened, and when the temperature reached 180°C, the temperature was maintained for 30min; [0097] Step 9: the product obtained in step 8 was calcined at 750°C in an air atmosphere for 2 hours to obtain a tightly-coated cobalt oxide.

Test example

[0098] The cobalt oxides obtained in Examples 1-3 and Comparative Examples 1-3 were respectively mixed with lithium carbonate, wherein the molar ratio of Li:Co was controlled to be 1.06, and the mixture was subjected to high-temperature solid-phase sintering in a push-plate kiln at a sintering temperature of 1000°C for 12h to obtain a lithium cobalt oxide positive electrode material respectively: [0099] The lithium cobalt oxide materials obtained by the examples and the comparative examples served as active material, acetylene black served as a conductive agent, and PVDF served as a binding agent. The active material, the conductive agent and the binding agent were weighed in the ratio of 92:4:4 and mixed, a certain amount of the organic solvent NMP was added to the mixture, then the obtained mixture was stirred and coated on an aluminum foil to form a positive electrode sheet, the negative electrode was made of a metal lithium sheet, and a CR2430 button battery was made in an argon-filled glove box. The battery was subjected to the electrical performance test in a CT2001A blue battery test system. Test conditions: 3.0-4.48V test temperature 25±1°C. The test results are shown in Table 1.

[00100] Table 1

Discharge capacity at 0.1C/4.48V Capacity retention rate for 600 cycles at 0.1C/4.48V mAh/g Example 1 211.2 84.1% Example 2 213.7 83.7% Example 3 210.6 84.2% Comparative Example 1 206.8 75.9% Comparative Example 2 203.9 75.6% Comparative Example 3 205.1 76.7% [00101] It can be seen from Table 1 that the cycle retention rate of the comparative examples was significantly lower than that of the examples, this is because the cobalt oxides obtained in the comparative examples only had a common coating, and their coating layer (zirconia/alumina) -13 -cannot form a tight connection with the cobalt hydroxide base material, so that in the process of long-term cycling, the phenomenon of pulverization and shedding occurs, for which the lithium cobalt oxide is re-exposed to the electrolyte to be corroded, thereby affecting the cycle performance of the material.

[00102] The examples of the present invention have been described in detail above in conjunction with the drawings, but the present invention is not limited to the above-mentioned examples, and various changes can also be made within the scope of knowledge possessed by those of ordinary skill in the art without departing from the spirit of the present invention. Furthermore, the examples of the present invention and features in the examples may be combined with each other without conflict.

Claims

CLAIMSI. A method for preparing a tightly-coated cobalt oxide, comprising the following steps: Si: adding a cobalt salt solution, a sodium hydroxide solution and aqueous ammonia in parallel to a base solution to react, until the reaction material reaches the target particle size, performing ageing on the mixture, then subjecting the resulting mixture to solid-liquid separation to obtain a precipitate, and washing and drying the precipitate to obtain a dry material; S2: adding the dry material and hydroxide to an organic solution of metal carboxylate, heating the mixture to evaporate the solvent, and when the evaporation rate of the solvent reaches more than 90%, heating the mixture to 180-200°C to react; wherein the hydroxide is zirconium hydroxide or aluminum hydroxide, and the organic solution of metal carboxylate is an alcohol solution of zirconium alkyl carboxylate or aluminum alkyl carboxylate; 53: calcining the product after reaction in step S2 in an oxygen atmosphere to obtain the cobalt oxide.
2. The method according to claim 1, wherein in step Si, the concentration of the cobalt salt solution is 1.0-2.0 mol/L, and the concentration of the sodium hydroxide solution is 4.0-10.0 mol/L.
3. The method according to claim 1, wherein in step S 1, the base solution is a mixed solution of sodium hydroxide and aqueous ammonia, the pH of the base solution is 10-11, and the concentration of ammonia is 5.0-10.0 g/L.
4. The method according to claim 1, wherein in step Si, the temperature of the reaction is controlled to be 55-65°C, the pH of the reaction material is controlled to be 10-11, and the concentration of the ammonia is controlled to be 5-10 g/L.
5. The method according to claim 1, wherein in step S2, the ratio of the weight of the dry material to the volume of the organic solution of the metal carboxylate is 1 g: (1-5) mL, and the concentration of the metal carboxylate in the organic solution of the metal carboxylate is 0.1-0.2mol/L.
6. The method according to claim 1, wherein in step S2, the addition amount of the hydroxide is 1-5% of the weight of the dry material.
7. The method according to claim 1, wherein in step S2, the number of carbon atoms in the alkyl segment in the zirconium alkyl carboxylate or the aluminum alkyl carboxylate is 6-10.
8. The method according to claim 1, wherein in step S2, the duration of the reaction is 15-30 min.
9. The method according to claim I, wherein in step 53, the temperature of the calcining is 500-750°C.
10. Use of the method according to any one of claims 1-9 in the preparation of lithium cobalt oxide or lithium ion batteries. -6-