Cobaltosic oxide, preparation method and application thereof, lithium cobalt oxide positive electrode material and lithium ion battery

Abstract

The invention relates to the technical field of new energy, and discloses cobaltosic oxide, a preparation method and application thereof, a lithium cobalt oxide positive electrode material and a lithium ion battery. Firstly, a cobalt source is heated to a first calcination temperature in an oxygen-enriched environment at a first heating rate and is subjected to heat preservation for 5-10 h, and a first calcination product is obtained; the preparation method comprises the following steps: calcining a cobalt source in a first-stage calcining process at a first-stage calcining temperature, heating a first-stage calcining product to a second calcining temperature at a second heating rate in an oxygen-enriched environment, keeping the temperature for 1-3 hours, and naturally cooling to obtain the cobaltosic oxide, thereby obtaining the cobaltosic oxide through two-stage calcining and using relatively low temperature and heating rate in the first-stage calcining process. The low temperature and the low temperature rise rate are used for ensuring that part of cobaltosic oxide particles obtained through decomposition cannot grow too large, cobaltosic oxide is rapidly formed through the obviously-improved temperature rise rate and the higher calcination temperature in the second-stage calcination process, and then small-particle-size cobaltosic oxide is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy, in particular to tricobalt tetroxide and a preparation method and use thereof, lithium cobaltate cathode material and lithium ion battery. BACKGROUND

[0002] With the development of science and technology, lithium ion batteries have been applied to various devices, such as unmanned aerial vehicles, mobile phones, computers, new energy vehicles, etc. However, with the development of society and the increasing demand of people, higher performance is required for the device, and the most important factor affecting the performance of the device is the fast charge-discharge rate of the battery. The faster the fast charge-discharge is, the higher the rate is, and the device can have higher operating performance. Therefore, the research and development of lithium ion batteries with higher rate has become the mainstream of current lithium ion batteries. Among lithium ion batteries, the material with the best rate performance is lithium cobaltate material. The rate performance of the current lithium cobaltate material is related to the primary particle size of the material itself and the interface impedance of the material itself. The interface impedance of the material is difficult to continue to reduce, and no matter what material is coated, it will easily lead to an increase in the interface impedance of the material. Therefore, the mainstream improvement direction of the research and development personnel is to reduce the primary particle size of the material. The only way to reduce the primary particle size is to use small particle size precursors in the precursor;

[0003] Tricobalt tetroxide is a precursor of lithium cobaltate material, and its preparation methods are various, including hydrothermal method, solvothermal method, precipitation method, sol-gel method, microemulsion method, spray pyrolysis method, electrochemical method and high-temperature solid phase method. Among them, the high-temperature solid phase method is the most commonly used method in actual production process because of its easy control of reaction conditions, low cost, large output, simple manufacturing process, good filling property of the prepared powder and other advantages. However, the powder particles prepared by the method are often rough, have uneven particle size distribution and are too large in size.

[0004] Chinese patent application 200710156482.X discloses a preparation method of tricobalt tetroxide for batteries. The scheme uses cobalt ore as cobalt raw material, controls the synthesis of the precursor by using the crystallization theory to separate the generation and growth of the crystal nucleus, and uses complex-homogeneous precipitation method to prepare monodisperse and near-spherical precursors. The precursors are subjected to thermal decomposition to obtain tricobalt tetroxide for batteries with high purity, good flowability, uniform and controllable particle size, high tap density and near-spherical shape. However, the scheme does not attempt to use multiple calcination methods to control the particle size of tricobalt tetroxide, and the scheme uses precipitation + thermal decomposition method to prepare tricobalt tetroxide.

[0005] Li Ying, Zhao Hua, Li Bentao, Huang Hui, Mao Ruzeng, et al. in China Powder Technology disclosed "Influence of Calcination Temperature and Heating Rate on Particle Size of Ferrite Powder", which pointed out that: "When the calcination program is to rapidly heat to 850℃ within 1h and then keep for 7h, the prepared ferrite particles are coarse, irregular in shape, and in agglomeration state, with a particle size of several hundred microns. When the calcination program is divided into two steps, the first step is to heat to 400℃ within 2h and keep for 2h, and the second step is to heat from 400℃ to 850℃ within 2h and keep for 2h, the prepared ferrite particles are smaller and more uniform in size, as shown in FIG. 1. It can be seen that the product obtained by step heating is smaller and more uniform than that obtained by rapid heating. The reason is that the ferrite gel has basically completed the first stage of dehydration after being dried at 120℃ in the oven for 4h, so the calcination process in the microwave muffle furnace is mainly the ash forming process. If the heating rate is too large, the drastic change of temperature will seriously affect the particle size and uniformity of the ferrite product." Figure 2

[0006] It can be seen that the document points out that multi-stage calcination can reduce the particle size of metal oxide and improve the uniformity of the particle size, but further observation of the scheme shows that it also points out that: "The smaller the heating rate, the smaller the particle size of the product, and the better the uniformity of the sample, therefore, the multi-step heating program is more suitable for the preparation of ferrite powder." It can be seen that the document points out that the more the calcination gradient, the smaller the heating rate, and the smaller the particle size of the product.

[0007] The problem to be solved by the present application is: how to provide a preparation method of small particle size of cobalt oxide based on solid phase method. SUMMARY

[0008] The purpose of the present application is to provide a preparation method of cobalt oxide, which is based on the optimization of the preparation method of cobalt oxide based on high-temperature solid phase method, by adjusting the calcination temperature, heating rate and calcination temperature and other parameters, so as to further reduce the particle size of cobalt oxide, and then obtain small particle size of lithium cobalt oxide material to facilitate the preparation of high rate lithium ion battery.

[0009] Unless otherwise specified in the present application: nM represents nanomole per liter, μM represents micromole per liter, mM represents millimole per liter, and M represents mole per liter;

[0010] In order to achieve the above purpose, the present application discloses a preparation method of cobalt oxide, comprising the following steps:

[0011] Step 1: heating the cobalt source to a first calcination temperature at a first heating rate in an oxygen-rich environment and keeping for 5-10h to obtain a first calcination product;

[0012] ​Step 2: heating the product of Step 1 to a second calcination temperature at a second heating rate in an oxygen-rich environment for 1-3 h, and then naturally cooling to obtain the cobaltic tetraoxide;

[0013] wherein the second heating rate is greater than or equal to 1.5 times the first heating rate;

[0014] the second calcination temperature is greater than or equal to 2.5 times the first calcination temperature.

[0015] Preferably, the first heating rate is 5-10℃ / min, the second heating rate is 10-25℃ / min, and the second heating rate is greater than or equal to 1.5 times the first heating rate;

[0016] the first calcination temperature is 300-400℃, the second calcination temperature is 1000-1200℃, and the second calcination temperature is greater than or equal to 2.5 times the first calcination temperature;

[0017] the holding time in Step 1 is greater than or equal to 2 times the holding time in Step 2.

[0018] Preferably, the cobalt source is selected from at least one of cobaltous hydroxide, cobalt sulfate, cobalt chloride, and cobalt carbonate.

[0019] In addition, the application also discloses a cobaltic tetraoxide prepared by the preparation method of the cobaltic tetraoxide.

[0020] In addition, the application also discloses the use of the cobaltic tetraoxide as described above for preparing a lithium cobalt oxide positive electrode material.

[0021] In addition, the application also discloses a lithium cobalt oxide positive electrode material, which is prepared by calcining a cobaltic tetraoxide as described above and a lithium source, wherein the lithium source is selected from at least one of lithium carbonate, lithium chloride, lithium hexafluorophosphate, and lithium hydroxide.

[0022] Preferably, the lithium cobalt oxide positive electrode material is coated with a coating layer, and the coating layer is obtained by coating cobalt hydroxide and / or titanium oxide onto the surface of the lithium cobalt oxide.

[0023] Preferably, the preparation method of the lithium cobalt oxide positive electrode material comprises the following steps:

[0024] Step A1: mixing the cobaltic tetraoxide as the cobalt source with a lithium source, and then calcining at 700-800℃ for 0.8-1.2 h, and then continuing to calcine at 900-990℃ for 9-11 h, and then naturally cooling to room temperature to obtain the lithium cobalt oxide;

[0025] Step A2: mixing the lithium cobalt oxide prepared in Step 1 with cobalt hydroxide and / or titanium oxide, and calcining at 850-900℃ for 8-9 h to obtain the lithium cobalt oxide positive electrode material with a coating layer on the surface.

[0026] The cobalt oxyhydroxide is added in an amount of 0.05-0.15% of the total mass of the lithium cobaltate prepared in step A1;

[0027] The titanium oxide is added in an amount of 3.0-3.5% of the total mass of the lithium cobaltate prepared in step A1.

[0028] In addition, the present application also discloses a lithium ion battery, whose positive electrode material is prepared by using the above-mentioned tricobalt tetroxide as a cobalt source.

[0029] The present application has the following beneficial effects: the present application uses two-stage calcination and a relatively low temperature and heating rate in the first-stage calcination to preliminarily decompose the cobalt source, and the low temperature and heating rate are used to ensure that the part of the tricobalt tetroxide particles obtained by the decomposition will not grow too large, and then the heating rate is significantly increased and the calcination temperature is higher in the second-stage calcination to make the tricobalt tetroxide quickly form, thereby obtaining small-particle-size tricobalt tetroxide. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The electron microscope image of the tricobalt tetroxide prepared in Example 1;

[0031] Figure 2 The electron microscope image of the tricobalt tetroxide prepared in Comparative Example 1. DETAILED DESCRIPTION

[0032] In the description of the present application, it should be noted that, in the examples, the specific conditions not noted are carried out according to the conventional conditions or the conditions suggested by the manufacturers. The reagents or instruments not noted by the manufacturers are all conventional products that can be obtained by market purchase.

[0033] Preparation of the first part of tricobalt tetroxide

[0034] Example 1

[0035] Step 1: the cobaltous hydroxide is heated to 350℃ at a heating rate of 8℃ / min under an oxygen-rich environment and kept for 9h to obtain a calcination product;

[0036] Step 2: the calcination product is heated to 1100℃ at a heating rate of 16℃ / min under an oxygen-rich environment and kept for 2h, and then naturally cooled to obtain tricobalt tetroxide.

[0037] Example 2

[0038] Step 1: the cobaltous hydroxide is heated to 300℃ at a heating rate of 10℃ / min under an oxygen-rich environment and kept for 10h to obtain a calcination product;

[0039] Step 2: The calcined product is heated to 1200°C at a heating rate of 25°C / min in an oxygen-rich environment and kept at this temperature for 3 hours, and then naturally cooled to obtain cobalt tetroxide.

[0040] Example 3

[0041] Step 1: heating cobalt carbonate to 400°C at a heating rate of 5°C / min in an oxygen-rich environment and maintaining the temperature for 8 hours to obtain a calcined product;

[0042] Step 2: The calcined product is heated to 1000°C at a heating rate of 10°C / min in an oxygen-rich environment and kept at this temperature for 1 hour, and then cooled naturally to obtain cobalt tetroxide.

[0043] Example 4

[0044] Step 1: heating the cobalt source to 350°C at a heating rate of 8°C / min in an oxygen-rich environment and maintaining the temperature for 5 hours to obtain a calcined product;

[0045] Step 2: The calcined product is heated to 1100°C at a heating rate of 16°C / min in an oxygen-rich environment and kept at this temperature for 3 hours, followed by natural cooling to obtain cobalt tetroxide.

[0046] Comparative Example 1

[0047] Step 1: heating cobaltous hydroxide to 350°C at a heating rate of 8°C / min in an oxygen-rich environment and maintaining the temperature for 9 hours to obtain a calcined product;

[0048] Step 2: The calcined product is heated to 1100°C at a heating rate of 10°C / min in an oxygen-rich environment and kept at this temperature for 2 hours, followed by natural cooling to obtain cobalt tetroxide.

[0049] Comparative Example 2

[0050] Step 1: heating cobaltous hydroxide to 350°C at a heating rate of 12°C / min in an oxygen-rich environment and maintaining the temperature for 9 hours to obtain a calcined product;

[0051] Step 2: The calcined product is heated to 1100°C at a heating rate of 16°C / min in an oxygen-rich environment and kept at this temperature for 2 hours, followed by natural cooling to obtain cobalt tetroxide.

[0052] Comparative Example 3

[0053] Step 1: heating cobaltous hydroxide to 350°C at a heating rate of 8°C / min in an oxygen-rich environment and maintaining the temperature for 9 hours to obtain a calcined product;

[0054] Step 2: The calcined product is heated to 700°C at a heating rate of 16°C / min in an oxygen-rich environment and kept at this temperature for 2 hours, followed by natural cooling to obtain cobalt tetroxide.

[0055] Comparative Example 4

[0056] Step 1: heating cobaltous hydroxide to 550°C at a heating rate of 8°C / min in an oxygen-rich environment and maintaining the temperature for 9 hours to obtain a calcined product;

[0057] Step 2: The calcined product is heated to 1100°C at a heating rate of 16°C / min in an oxygen-rich environment and kept at this temperature for 2 hours, followed by natural cooling to obtain cobalt tetroxide.

[0058] Comparative Example 5

[0059] Step 1: heating cobaltous hydroxide to 350°C at a heating rate of 8°C / min in an oxygen-rich environment and maintaining the temperature for 3 hours to obtain a calcined product;

[0060] Step 2: The calcined product is heated to 1100°C at a heating rate of 16°C / min in an oxygen-rich environment and kept at this temperature for 3 hours, followed by natural cooling to obtain cobalt tetroxide.

[0061] Comparative Example 6

[0062] Step 1: heating cobaltous hydroxide to 1100° C. at a heating rate of 8° C. / min in an oxygen-rich environment and maintaining the temperature for 11 hours, followed by natural cooling to obtain cobalt trioxide.

[0063] Comparative Example 7

[0064] Step 1: heating cobaltous hydroxide to 350°C at a heating rate of 8°C / min in an oxygen-rich environment and maintaining the temperature for 6 hours to obtain a calcined product;

[0065] Step 2: The primary calcined product was heated to 725°C at a heating rate of 12°C / min in an oxygen-rich environment and kept at this temperature for 3 h to obtain a secondary calcined product;

[0066] Step 3: The di-calcined product is heated to 1100°C at a heating rate of 16°C / min in an oxygen-rich environment and kept at this temperature for 2 hours, followed by natural cooling to obtain cobalt tetroxide.

[0067] Performance Test 1: The particle sizes of Example 1 and Comparative Examples 1-7 were measured using a laser particle size analyzer, and the micromorphology of cobalt trioxide was observed using a scanning electron microscope. The test results are shown in Table 1:

[0068] Table 1

[0069] Group D50 (pm) Group D50 (pm) Example 1 4.72 Comparative Example 4 5.67 Comparative Example 1 5.38 Comparative Example 5 4.25 Comparative Example 2 5.46 Comparative Example 6 6.34 Comparative Example 3 4.39 Comparative Example 7 4.69

[0070] Observe Table 1 and combine Figures 1-2It can be seen that the particle size of Comparative Examples 1, 2, 4 and 6 is slightly larger than that of Example 1. The reason for this phenomenon can be that the slow heating rate in Step 2 of Comparative Example 1 results in a long time for heating to 1100℃ in Step 2, thereby prolonging the time for the material to be in a heated state, and further increasing the particle size of the cobalt oxide. The reason for the large particle size of Comparative Example 2 can be that the fast heating rate in Step 1 results in a too large temperature change in the first calcination stage, thereby resulting in a large particle size of the cobalt oxide prepared in Comparative Example 2. The reason for the large particle size of Comparative Example 4 can be that the abnormal growth of the crystal grains caused by the high calcination temperature in the first calcination stage. The reason for the large particle size of Comparative Example 6 can be that the continuous growth of the crystal grains caused by the one-step sintering.

[0071] Preparation of the second part of lithium cobalt oxide

[0072] Application Examples 1-11

[0073] The cobalt oxide prepared in Example 1-4 and Comparative Examples 1-7 was mixed with a lithium source at a molar ratio of cobalt to lithium of 1:1.03, and heated to 750℃ at a heating rate of 2.5℃ / min and kept for 1h, and then heated to 970℃ at a heating rate of 2.5℃ / min and kept for 10h, and then naturally cooled to room temperature, to obtain a lithium cobalt oxide material.

[0074] Application Example 12

[0075] The cobalt oxide prepared in Example 1 was mixed with a lithium source at a molar ratio of cobalt to lithium of 1:1.03, and heated to 750℃ at a heating rate of 2.5℃ / min and kept for 1h, and then heated to 970℃ at a heating rate of 2.5℃ / min and kept for 10h, and then naturally cooled to room temperature, to obtain a lithium cobalt oxide material.

[0076] The lithium cobalt oxide material was then mixed with titanium oxide at a mass ratio of 100:3.2 and calcined at 900℃ for 8h to obtain a lithium cobalt oxide positive electrode material with a coating layer on the surface.

[0077] Application Example 13

[0078] The cobalt oxide prepared in Comparative Example 1 was mixed with a lithium source at a molar ratio of cobalt to lithium of 1:1.03, and heated to 750℃ at a heating rate of 2.5℃ / min and kept for 1h, and then heated to 970℃ at a heating rate of 2.5℃ / min and kept for 10h, and then naturally cooled to room temperature, to obtain a lithium cobalt oxide material.

[0079] The lithium cobalt oxide material was then mixed with titanium oxide at a mass ratio of 100:3.2 and calcined at 900℃ for 8h to obtain a lithium cobalt oxide positive electrode material with a coating layer on the surface.

[0080] Application Example 14

[0081] The cobalt tetraoxide prepared in Example 1 was mixed with a lithium source in a molar ratio of cobalt to lithium of 1:1.03, and heated to 750°C at a heating rate of 2.5°C / min and held for 1 h, and then heated to 970°C at a heating rate of 2.5°C / min and held for 10 h, and then naturally cooled to room temperature, to obtain a lithium cobaltate material;

[0082] The lithium cobaltate material was then mixed with cobalt oxyhydroxide in a mass ratio of 100:0.1 and calcined at 900°C for 8 h to obtain a lithium cobaltate positive electrode material with a coating layer on the surface.

[0083] Application Example 15

[0084] The cobalt tetraoxide prepared in Example 1 was mixed with a lithium source in a molar ratio of cobalt to lithium of 1:1.03, and heated to 700°C at a heating rate of 2.5°C / min and held for 1.2 h, and then heated to 990°C at a heating rate of 2.5°C / min and held for 9 h, and then naturally cooled to room temperature, to obtain a lithium cobaltate material;

[0085] The lithium cobaltate material was then mixed with titanium oxide in a mass ratio of 100:3.2 and calcined at 850°C for 8.5 h to obtain a lithium cobaltate positive electrode material with a coating layer on the surface.

[0086] Application Example 16

[0087] The cobalt tetraoxide prepared in Example 1 was mixed with a lithium source in a molar ratio of cobalt to lithium of 1:1.03, and heated to 800°C at a heating rate of 2.5°C / min and held for 0.8 h, and then heated to 900°C at a heating rate of 2.5°C / min and held for 11 h, and then naturally cooled to room temperature, to obtain a lithium cobaltate material;

[0088] The lithium cobaltate material was then mixed with titanium oxide in a mass ratio of 100:3.2 and calcined at 870°C for 9 h to obtain a lithium cobaltate positive electrode material with a coating layer on the surface.

[0089] Application Example 17

[0090] The cobalt tetraoxide prepared in Example 1 was mixed with a lithium source in a molar ratio of cobalt to lithium of 1:1.03, and heated to 750°C at a heating rate of 2.5°C / min and held for 1 h, and then heated to 970°C at a heating rate of 2.5°C / min and held for 10 h, and then naturally cooled to room temperature, to obtain a lithium cobaltate material;

[0091] The lithium cobaltate material was then mixed with cobalt oxyhydroxide and titanium oxide in a mass ratio of 100:0.1:3.1 and calcined at 900°C for 8 h to obtain a lithium cobaltate positive electrode material with a coating layer on the surface.

[0092] Performance test 2: lithium cobaltate battery performance test:

[0093] The prepared electrolyte was injected into the soft package battery with lithium cobaltate and graphite carbon as positive and negative electrodes prepared in the above application examples. After the injection was completed, packaging, storage, formation, secondary packaging, and capacity distribution processes were performed to obtain lithium ion batteries. Subsequently, the electrochemical performance of the lithium ion batteries was detected, and the test results are shown in Table 2:

[0094] Table 2

[0095]

[0096] Result analysis:

[0097] 1. Further observation of application examples 1-4 shows that when application examples 1-4 use cobalt tetraoxide prepared by examples 1-4 to prepare lithium cobaltate, the rate performance of application examples 1-3 is relatively close when the prepared lithium cobaltate material is applied to the positive material. However, after significantly adjusting the heating rate, calcination temperature, and holding time in comparative example 1-5, the rate performance of the lithium cobaltate material prepared in application examples 5-9 all decreased to varying degrees. Among them, application examples 5-6 and application examples 8, application example 10 in application examples 5-9 may cause a decrease in rate performance due to the large particle size of cobalt tetraoxide. The reason for the large particle size of cobalt tetraoxide in application example 8 may be that the excessively high first calcination temperature causes the crystal grains to start uncontrollable growth during the first calcination stage;

[0098] And application example 7 and application example 9 are more likely to be caused by the insufficient reaction of the material due to the excessively low second calcination temperature and excessively short first calcination time, resulting in cobalt tetraoxide containing more cobalt hydroxide impurities;

[0099] In addition, as observed in application example 11, although application example 11 uses three-stage calcination, the rate performance of the lithium cobaltate material prepared from the cobalt tetraoxide prepared by application example 11 does not show a significant difference from application example 1, indicating that the performance of the cobalt tetraoxide prepared by the two is relatively close.

[0100] 2. As observed in application examples 1, 5, and 12, 13, when further coating titanium oxide on the surface of the lithium cobaltate material, the rate performance of application examples 12-13 is further improved compared to application examples 1 and 5, indicating that the coating of titanium oxide helps to improve the rate performance of the lithium cobaltate material;

[0101] At the same time, the rate performance of application example 12 is improved by 3.89 compared to application example 1;

[0102] And the rate performance of application example 13 is only improved by 2.02 compared to application example 5;

[0103] Therefore, the lithium cobaltate prepared from the cobalt tetraoxide material of Example 1 is more advantageous in the subsequent coating process. It can be seen that, under the condition of the same kind and the same mass of the coating material, the lithium cobaltate prepared from the cobalt tetraoxide material of Example 1 has better rate performance.

[0104] 3. It can be seen from the application examples 12, 14 and 17 that, when the coating material is a mixture of titanium oxide and cobalt oxyhydroxide, the rate performance is better than that of any of the application examples 12 and 14. It can be seen that there is a synergistic effect between titanium oxide and cobalt oxyhydroxide to further improve the rate performance of the lithium cobaltate material.

[0105] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods and shall be included in the protection scope of the present application.

Claims

1. A method for preparing cobalt trioxide, characterized in that: The following steps are involved: Step 1: heating the cobalt source to a first calcination temperature at a first heating rate in an oxygen-rich environment and maintaining the temperature for 5 to 10 hours to obtain a calcined product; Step 2: heating the calcined product to a second calcination temperature at a second heating rate in an oxygen-rich environment and maintaining the temperature for 1 to 3 hours, and then naturally cooling to obtain cobalt trioxide; The second heating rate is greater than or equal to 1.5 times the first heating rate; The second calcination temperature is greater than or equal to 2.5 times the first calcination temperature.

2. The method for preparing cobalt trioxide according to claim 1, wherein The first heating rate is 5 to 10°C / min, the second heating rate is 10 to 25°C / min, and the second heating rate is greater than or equal to 1.5 times the first heating rate; The first calcination temperature is 300° C. to 400° C., the second calcination temperature is 1000° C. to 1200° C., and the second calcination temperature is greater than or equal to 2.5 times the first calcination temperature; The holding time in step 1 is greater than or equal to 2 times the holding time in step 2.

3. The method for preparing cobalt trioxide according to claim 1, wherein The cobalt source is selected from at least one of cobaltous hydroxide, cobalt sulfate, cobalt chloride and cobalt carbonate.

4. A cobalt trioxide, characterized in that The cobalt trioxide is prepared by the preparation method of any one of claims 1 to 3.

5. Use of the cobalt trioxide as claimed in claim 4 in preparing lithium cobaltate positive electrode materials.

6. A lithium cobalt oxide positive electrode material, characterized in that The cobalt tricobalt tetroxide according to claim 4 is co-calcined with a lithium source, wherein the lithium source is selected from at least one of lithium carbonate, lithium chloride, lithium hexafluorophosphate, and lithium hydroxide.

7. The lithium cobalt oxide positive electrode material according to claim 6, characterized in that The surface of the lithium cobalt oxide positive electrode material is coated with a coating layer, and the coating layer is obtained by coating cobalt oxyhydroxide and / or titanium oxide on the surface of the lithium cobalt oxide.

8. The lithium cobalt oxide positive electrode material according to claim 7, characterized in that The preparation method of the lithium cobalt oxide positive electrode material comprises the following steps: Step A1: Cobalt trioxide is used as a cobalt source and mixed with a lithium source, then heated to 700-800° C. and calcined for 0.8-1.2 hours, then further heated to 900-990° C. and calcined for 9-11 hours, and naturally cooled to room temperature to obtain lithium cobalt oxide; Step A2: mixing the lithium cobalt oxide prepared in step 1 with cobalt oxyhydroxide and / or titanium oxide, and calcining the mixture at 850-900° C. for 8-9 hours to obtain a lithium cobalt oxide positive electrode material having a coating layer on the surface; The amount of cobalt oxyhydroxide added is 0.05-0.15% of the total mass of the lithium cobaltate prepared in step A1; The amount of titanium oxide added is 3.0-3.5% of the total mass of the lithium cobalt oxide prepared in step A1.

9. A lithium-ion battery, characterized in that: The positive electrode material is prepared by using the cobalt trioxide as claimed in claim 4 as a cobalt source.

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