A ternary cathode material, its preparation method and application

Abstract

The present disclosure provides a ternary cathode material, a preparation method thereof, and an application. The preparation method includes the following steps: (1) mixing a ternary precursor and a lithium source, and then performing a first-stage sintering treatment to obtain a first-sintered material; (2) after performing a crushing treatment on the first-sintered material obtained in step (1), mixing the crushed first-sintered material with titanium dioxide, and performing a second-stage sintering treatment under light to obtain the ternary cathode material. In the preparation process of the ternary cathode material of the present disclosure, the assistance of light can oxidize divalent nickel to trivalent nickel, and at the same time inhibit the transformation of trivalent nickel into divalent nickel, thereby reducing the nickel-lithium mixing of the material.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of lithium-ion batteries, and relates to a ternary cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the increasing depletion of fossil energy such as coal, natural gas, and petroleum, renewable resources and environmental issues have gradually become the focus of attention of various countries, and new energy vehicles have emerged as the times require. As one of the core components of new energy vehicles, new energy batteries are in urgent need of rapid development to meet the urgent needs of people for their practical applications. As a very important member of the cathode materials for lithium-ion batteries, lithium nickel cobalt manganate has a high discharge specific capacity and is the most promising cathode material for lithium-ion batteries.

[0003] Currently, the lithium nickel cobalt manganate cathode material has not been widely commercialized, mainly because its cycle stability and rate performance are poor. The main reason for its poor cycle stability is that Ni 2+ is difficult to be completely oxidized to Ni 3+ during the synthesis of the ternary cathode material, and the remaining Ni 2+ has a similar ionic radius to Li+ ions. Therefore, Li + / Ni 2+ mixing occurs during the charge and discharge cycle, resulting in a change in the structure of lithium nickel cobalt manganate and thus affecting the cycle stability.

[0004] CN114975915A discloses a high-nickel NCM ternary cathode material coated with ZnO and Li 2 ZnO 2 and its application. By coating ZnO and Li 2 ZnO 2 on the surface of the high-nickel ternary cathode material, the residual alkali and the inherent rock salt phase on the material surface are removed, but the nickel-lithium mixing of the cathode material is relatively high, affecting the performance of the material.

[0005] CN108777291A mixes a strong oxidizing anhydride with a precursor by ball milling, so that the precursor powder is pre-oxidized to reduce nickel-lithium mixing and improve the reversible capacity of the battery. Although it reduces Li + / Ni 2+ mixing to a certain extent, simple coating is difficult to increase the content of Ni 3+ during the synthesis process. Although the pre-oxidation method can increase the content of Ni 3+ in the early stage, it is difficult to inhibit the transformation of Ni 3+ to Ni 2+ in the subsequent synthesis, and the nickel-lithium mixing cannot be further reduced.

[0006] The above - mentioned solutions reduce the Ni - Li mixing by simply coating or preparing hydroxyoxides, but it is difficult to inhibit Ni 3+ in the subsequent synthesis, and the effect of reducing Ni - Li mixing is poor. 2+ The transformation of reduces the Ni - Li mixing with a poor effect. SUMMARY OF THE INVENTION

[0007] The following is an overview of the subject matter described in detail in this document. This overview is not intended to limit the scope of the claims.

[0008] An object of the present disclosure is to provide a ternary cathode material, a preparation method thereof, and an application. In the preparation process of the ternary cathode material of the present disclosure, assisted by light, divalent nickel can be oxidized to trivalent nickel, and at the same time, the transformation of trivalent nickel into divalent nickel can be inhibited, thereby reducing the Ni - Li mixing of the material.

[0009] To achieve this disclosure object, the present disclosure adopts the following technical solutions:

[0010] In a first aspect, an embodiment of the present disclosure provides a preparation method of a ternary cathode material, and the preparation method includes the following steps:

[0011] (1) After mixing a ternary precursor, a titanium source, and a lithium source, perform a first - stage sintering treatment to obtain a first - sintered material;

[0012] (2) After performing a crushing treatment on the first - sintered material obtained in step (1), mix the crushed first - sintered material with titanium dioxide, and perform a second - stage sintering treatment on the first - sintered material obtained in step (1) under light to obtain the ternary cathode material.

[0013] In the preparation process of the ternary cathode material of the embodiment of the present disclosure, after crushing the first - sintered material, the Ni 2+ inside the material is exposed on the material surface. During the second - stage sintering, titanium dioxide is added, and the titanium dioxide is uniformly coated on the material surface. With the assistance of light during the second - stage sintering, it can make Ni 2+ be better oxidized to Ni 3+ , and it can also inhibit Ni 3+ from transforming into Ni 2+ during the synthesis process, improve the electrochemical performance of the material, and reduce the Li - Ni mixing caused by incomplete oxidation of nickel ions and the transformation of nickel ions. At the same time, the ternary cathode material prepared has titanium dioxide coated on its surface, which reduces the direct contact between the cathode material and the electrolyte, reduces the adverse reactions between the two, and improves the cycle stability of the cathode material.

[0014] In one embodiment, the ternary precursor in step (1) includes a ternary nickel - cobalt - manganese precursor.

[0015] In the second - stage sintering of the embodiment of the present disclosure, the ionic equation of the light - induced reaction is as follows:

[0016]

[0017]

[0018] In one embodiment, the lithium source includes lithium hydroxide and / or lithium carbonate.

[0019] In one embodiment, the molar ratio of lithium element in the lithium source to the total metal elements in the ternary precursor in step (1) is (1.01 - 1.05):1, for example: 1.01:1, 1.02:1, 1.03:1, 1.04:1 or 1.05:1, etc.

[0020] In one embodiment, the temperature of the first-stage sintering treatment in step (1) is 450 - 600 °C, for example: 450 °C, 480 °C, 500 °C, 550 °C or 600 °C, etc.

[0021] In one embodiment, the time of the first-stage sintering treatment is 3 - 8 h, for example: 3 h, 4 h, 5 h, 7 h or 8 h, etc.

[0022] In one embodiment, the mass ratio of the material after the first sintering in step (2) to titanium dioxide is 100:(0.2 - 1), for example: 100:0.2, 100:0.4, 100:0.6, 100:0.8 or 100:1, etc.

[0023] In one embodiment, the intensity of the light irradiation in step (2) is 12 - 36 mW / cm 2 , for example: 12 mW / cm 2 , 15 mW / cm 2 , 20 mW / cm 2 , 25 mW / cm 2 , 30 mW / cm 2 or 36 mW / cm 2 etc.

[0024] In one embodiment, the wavelength of the light irradiation is 200 - 380 nm, for example: 200 nm, 250 nm, 300 nm, 350 nm or 380 nm, etc.

[0025] In one embodiment, the temperature of the second-stage sintering treatment in step (2) is 600 - 1000 °C, for example: 600 °C, 700 °C, 800 °C, 900 °C or 1000 °C, etc.

[0026] In one embodiment, the time of the second-stage sintering treatment is 5 - 12 h, for example: 5 h, 6 h, 8 h, 10 h or 12 h, etc.

[0027] In one embodiment, the device for the second-stage sintering treatment includes a rotary kiln.

[0028] In the two-stage sintering process described in the embodiments of the present disclosure, a rotary kiln is used. During the sintering process, titanium dioxide and the crushed first-stage sintered material roll continuously, enabling a better and more uniform photocatalytic reaction, and at the same time, the obtained titanium dioxide coating layer is more uniform.

[0029] As an alternative embodiment of the present disclosure, the preparation method includes the following steps:

[0030] (1) After mixing the ternary precursor and the lithium source, sintering at 450 - 600 °C for 3 - 8 h to obtain the first-stage sintered material;

[0031] (2) After crushing the first-stage sintered material obtained in step (1), mixing the crushed first-stage sintered material with titanium dioxide in a mass ratio of 100:(0.2 - 1), and sintering at 600 - 900 °C for 5 - 12 h under light with a wavelength of 200 - 380 nm and an intensity of 12 - 36 mW / cm 2 to obtain the ternary cathode material.

[0032] In a second aspect, the embodiments of the present disclosure provide a ternary cathode material, which is prepared by the method described in the first aspect. The ternary cathode material includes a core and a titanium dioxide coating layer disposed on the surface of the core, and the titanium dioxide coating layer is anatase titanium dioxide.

[0033] In a third aspect, the embodiments of the present disclosure provide a positive electrode sheet, which includes the ternary cathode material described in the second aspect.

[0034] In a fourth aspect, the embodiments of the present disclosure provide a lithium-ion battery, which includes the positive electrode sheet described in the third aspect.

[0035] The present disclosure has the following beneficial effects:

[0036] (1) During the preparation process of the ternary cathode material of the present disclosure, assisted by light, divalent nickel can be oxidized to trivalent nickel, while suppressing the transformation of trivalent nickel into divalent nickel, thereby reducing the nickel-lithium mixing in the material. Directly using titanium dioxide as the titanium source and performing light irradiation during the first-stage sintering process can make Ni 2+ better oxidized to Ni 3+ .

[0037] (2) The initial discharge specific capacity of the NCM622 type battery prepared from the ternary cathode material by the method described in the present disclosure can reach above 178.04 mAh / g, the discharge specific capacity after 100 cycles can reach above 176 mAh / g, and the capacity retention rate can reach above 98.85%. The initial discharge specific capacity of the NCM811 type battery can reach 213.54 mAh / g, the discharge specific capacity after 100 cycles can reach 209.18 mAh / g, and the capacity retention rate can reach 97.96%. The initial discharge specific capacity of the NCM523 type battery can reach 168.24 mAh / g, the discharge specific capacity after 100 cycles can reach 166.41 mAh / g, and the capacity retention rate can reach 98.91%, showing good electrochemical performance.

[0038] Other aspects will be apparent after reading and understanding the drawings and the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings are used to provide a further understanding of the technical solutions herein, and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solutions herein and do not constitute a limitation to the technical solutions herein.

[0040] Figure 1 It is the SEM diagram of the ternary cathode material described in Example 1 of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] The technical solutions of the present disclosure will be further described below by specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present disclosure and should not be regarded as specific limitations to the present disclosure.

[0042] The ternary precursors used in the embodiments and comparative examples of the present disclosure are all prepared by the following method:

[0043] Example 1

[0044] This example provides a ternary cathode material, and the preparation method of the ternary cathode material is as follows:

[0045] (1) Mix nickel chloride, cobalt chloride, and manganese chloride and dissolve them in water to obtain solution A. The concentration of solution A is 2 mol / L, and the molar ratio of Ni:Co:Mn elements is 6:2:2. Add precipitant solution B and complexing agent solution C to solution A, mix and stir for 2 h, and then age for 12 h. The precipitant solution is sodium hydroxide solution with a concentration of 4 mol / L, and the complexing agent is ammonia water solution with a concentration of 4 mol / L. The volume ratio of solution A to solution B and solution C is 2:3:0.8. After aging, filter, wash, and dry to obtain the ternary precursor;

[0046] (2) Mix the ternary precursor lithium hydroxide, where the molar ratio of lithium element in lithium hydroxide to the total molar amount of nickel, cobalt, and manganese metals in the ternary precursor is 1.02:1, and sinter at 500 °C for 6 h in one stage to obtain the first-stage sintered material;

[0047] (3) After crushing the first-stage sintered material obtained in step (1), mix the crushed first-stage sintered material with titanium dioxide at a mass ratio of 100:0.5, and irradiate the mixture under light with a wavelength of 280 nm and an intensity of 20 mW / cm 2 in a rotary kiln and sinter at 750 °C for 8 h to obtain the ternary cathode material.

[0048] The SEM image of the ternary cathode material is as Figure 1 shown.

[0049] Example 2

[0050] This example provides a ternary cathode material, and the preparation method of the ternary cathode material is as follows:

[0051] (1) Mix nickel chloride, cobalt chloride, and manganese chloride and dissolve them in water to obtain solution A with a concentration of 2 mol / L, where the molar ratio of Ni:Co:Mn elements is 8:1:1. Add precipitant solution B and complexing agent solution C to solution A, mix and stir for 2 h, and then age for 12 h. The precipitant solution is sodium hydroxide solution with a concentration of 4 mol / L, and the complexing agent is ammonia water solution with a concentration of 4 mol / L. The volume ratio of solution A to solution B and solution C is 2:3:0.8. After aging, filter, wash, and dry to obtain the ternary precursor;

[0052] (2) Mix the ternary precursor lithium hydroxide, where the molar ratio of lithium element in lithium hydroxide to the total molar amount of nickel, cobalt, and manganese metals in the ternary precursor is 1.02:1, and sinter the mixture at 500 °C for 6 h in one stage to obtain the first-stage sintered material;

[0053] (3) After crushing the first-stage sintered material obtained in step (1), mix the crushed first-stage sintered material with titanium dioxide at a mass ratio of 100:0.2, and irradiate the mixture under light with a wavelength of 280 nm and an intensity of 36 mW / cm 2 in a rotary kiln and sinter at 750 °C for 8 h to obtain the ternary cathode material.

[0054] Example 3

[0055] This example provides a ternary cathode material, and the preparation method of the ternary cathode material is as follows:

[0056] (1) Mix nickel chloride, cobalt chloride, and manganese chloride and dissolve them in water to obtain solution A with a concentration of 2 mol / L, where the molar ratio of Ni:Co:Mn elements is 5:2:3. Add precipitant solution B and complexing agent solution C to solution A, mix and stir for 2 h, then age for 12 h. The precipitant solution is sodium hydroxide solution with a concentration of 4 mol / L, and the complexing agent is ammonia water solution with a concentration of 4 mol / L. The volume ratio of solution A to solution B and solution C is 2:3:0.8. After aging, filter, wash, and dry to obtain the ternary precursor;

[0057] (2) Mix the ternary precursor and lithium hydroxide, where the molar ratio of lithium element in lithium hydroxide to the total molar amount of nickel, cobalt, and manganese metals in the ternary precursor is 1.02:1. Sinter the mixture at 500 °C for 6 h in one stage to obtain the first-sintered material;

[0058] (3) After crushing the first-sintered material obtained in step (1), mix the crushed first-sintered material with titanium dioxide at a mass ratio of 100:1. Under illumination with a wavelength of 280 nm and an intensity of 12 mW / cm 2 Sinter in a rotary kiln at 750 °C for 8 h to obtain the ternary cathode material.

[0059] Example 4

[0060] This example provides a ternary cathode material, and the preparation method of the ternary cathode material is as follows:

[0061] (1) Mix nickel chloride, cobalt chloride, and manganese chloride and dissolve them in water to obtain solution A with a concentration of 2 mol / L, where the molar ratio of Ni:Co:Mn elements is 6:2:2. Add precipitant solution B and complexing agent solution C to solution A, mix and stir for 2 h, then age for 12 h. The precipitant solution is sodium hydroxide solution with a concentration of 4 mol / L, and the complexing agent is ammonia water solution with a concentration of 4 mol / L. The volume ratio of solution A to solution B and solution C is 2:3:0.8. After aging, filter, wash, and dry to obtain the ternary precursor;

[0062] (2) Mix the ternary precursor and lithium hydroxide, where the molar ratio of lithium element in lithium hydroxide to the total molar amount of nickel, cobalt, and manganese metals in the ternary precursor is 1.02:1. Sinter the mixture at 450 °C for 6.2 h in one stage to obtain the first-sintered material;

[0063] (3) After crushing the first-sintered material obtained in step (1), mix the crushed first-sintered material with titanium dioxide at a mass ratio of 100:0.6. Under illumination with a wavelength of 300 nm and an intensity of 22 mW / cm 2 Sinter the mixture in a rotary kiln at 760 °C for 8 h to obtain the ternary cathode material.

[0064] Example 5

[0065] This example provides a ternary cathode material, and the preparation method of the ternary cathode material is as follows:

[0066] (1) Mix nickel chloride, cobalt chloride, and manganese chloride and dissolve them in water to obtain solution A. The concentration of solution A is 2 mol / L, and the molar ratio of Ni:Co:Mn elements is 6:2:2. Add precipitant solution B and complexing agent solution C to solution A, mix and stir for 2 h, and then age for 12 h. The precipitant solution is sodium hydroxide solution with a concentration of 4 mol / L, and the complexing agent is ammonia water solution with a concentration of 4 mol / L. The volume ratio of solution A to solution B and solution C is 2:3:0.8. After aging, filter, wash, and dry to obtain a ternary precursor;

[0067] (2) Mix the ternary precursor and lithium hydroxide, where the molar amount of lithium element in lithium hydroxide is in a ratio of 1.02:1 to the total molar amount of nickel, cobalt, and manganese metals in the ternary precursor. Sinter the mixture at 500 °C for 6 h in one stage to obtain a first-sintered material;

[0068] (3) After crushing the first-sintered material obtained in step (1), mix the crushed first-sintered material with titanium dioxide in a mass ratio of 100:0.5, and irradiate the mixture in a rotary kiln at 750 °C for 8 h under light with a wavelength of 280 nm and an intensity of 5 mW / cm 2 to obtain the ternary cathode material.

[0069] Example 6

[0070] This example provides a ternary cathode material, and the preparation method of the ternary cathode material is as follows:

[0071] (1) Mix nickel chloride, cobalt chloride, and manganese chloride and dissolve them in water to obtain solution A. The concentration of solution A is 2 mol / L, and the molar ratio of Ni:Co:Mn elements is 6:2:2. Add precipitant solution B and complexing agent solution C to solution A, mix and stir for 2 h, and then age for 12 h. The precipitant solution is sodium hydroxide solution with a concentration of 4 mol / L, and the complexing agent is ammonia water solution with a concentration of 4 mol / L. The volume ratio of solution A to solution B and solution C is 2:3:0.8. After aging, filter, wash, and dry to obtain a ternary precursor;

[0072] (2) Mix the ternary precursor and lithium hydroxide, where the molar amount of lithium element in lithium hydroxide is in a ratio of 1.02:1 to the total molar amount of nickel, cobalt, and manganese metals in the ternary precursor. Sinter the mixture at 500 °C for 6 h in one stage to obtain a first-sintered material;

[0073] (3) After crushing the first-fired material obtained in step (1), the crushed first-fired material is mixed with titanium dioxide in a mass ratio of 100:0.5, and the mixture is sintered in a rotary kiln at 750 °C for 8 h under illumination with a wavelength of 300 nm and an intensity of 50 mW / cm 2 to obtain the ternary cathode material.

[0074] Example 7

[0075] This example provides a ternary cathode material, and the preparation method of the ternary cathode material is as follows:

[0076] (1) Nickel chloride, cobalt chloride, and manganese chloride are mixed and dissolved in water to obtain solution A with a concentration of 2 mol / L, where the molar ratio of Ni:Co:Mn elements is 6:2:2. A precipitant solution B and a complexing agent solution C are added to solution A, and the mixture is stirred for 2 h and then aged for 12 h. The precipitant solution is a sodium hydroxide solution with a concentration of 4 mol / L, and the complexing agent is an ammonia water solution with a concentration of 4 mol / L. The volume ratio of solution A to solution B and solution C is 2:3:0.8. After aging, filtration, washing, and drying are performed to obtain a ternary precursor;

[0077] (2) The ternary precursor and lithium hydroxide are mixed, where the molar amount of lithium element in lithium hydroxide is in a ratio of 1.02:1 to the total molar amount of nickel, cobalt, and manganese metals in the ternary precursor. The mixture is sintered at 500 °C for 6 h in the first stage to obtain a first-fired material;

[0078] (3) After crushing the first-fired material obtained in step (1), the crushed first-fired material is mixed with titanium dioxide in a mass ratio of 100:0.5, and the mixture is sintered in a rotary kiln at 1100 °C for 8 h under illumination with a wavelength of 300 nm and an intensity of 20 mW / cm 2 to obtain the ternary cathode material.

[0079] Comparative Example 1

[0080] The difference between this comparative example and Example 1 is only that the second-stage sintering is not subjected to light treatment, and other conditions and parameters are exactly the same as those in Example 1.

[0081] Performance test:

[0082] The cathode materials obtained in Examples 1-7 and Comparative Example 1 are taken, and a slurry is prepared according to the ratio of cathode material: conductive carbon black: PVDF: N-methylpyrrolidone of 90:5:5:40. The slurry is coated on an aluminum foil sheet, vacuum dried, and roll-pressed to obtain a cathode sheet. Using the cathode sheet as the cathode and a lithium sheet as the anode, a button cell is assembled, and the charge-discharge voltage is set to 3.0-4.3 V. The initial capacity and cycle performance of the battery are tested under 1C conditions, and the test results are shown in Table 1:

[0083] Table 1

[0084]

[0085] As can be seen from Table 1, it can be obtained from Examples 1-4 that for the NCM622 type battery prepared by the ternary cathode material prepared by the method of the present disclosure, the initial discharge specific capacity can reach more than 178.04 mAh / g, the discharge specific capacity can reach more than 176 mAh / g after 100 cycles, and the capacity retention rate can reach more than 98.85%. For the NCM811 type battery, the initial discharge specific capacity can reach 213.54 mAh / g, the discharge specific capacity can reach 209.18 mAh / g after 100 cycles, and the capacity retention rate can reach 97.96%. For the NCM523 type battery, the initial discharge specific capacity can reach 168.24 mAh / g, the discharge specific capacity can reach 166.41 mAh / g after 100 cycles, and the capacity retention rate can reach 98.91%, showing good electrochemical performance.

[0086] From the comparison between Example 1 and Examples 5-6, it can be obtained that during the preparation process of the ternary cathode material of the present disclosure, the light intensity of the second-stage sintering will affect the performance of the prepared ternary cathode material. When the light intensity is controlled at 12-36 mW / cm 2 , the performance of the prepared cathode material is better. If the light intensity is too high, other side reactions of titanium dioxide may be excited. If the light intensity is too low, the reaction rate of hole generation will be reduced.

[0087] From the comparison between Example 1 and Example 7, it can be obtained that the temperature of the second-stage sintering of the present disclosure needs to be controlled within 900 °C. If the sintering temperature is too high, most of the anatase titanium dioxide will transform into rutile titanium dioxide, and the photocatalytic performance will be reduced.

[0088] From the comparison between Example 1 and Comparative Example 1, it can be obtained that during the preparation process of the ternary cathode material of the present disclosure, by using light assistance, Ni 2+ can be better oxidized to Ni 3+ , and it can also inhibit Ni 3+ from transforming into Ni 2+ during the synthesis process, improve the electrochemical performance of the material, and reduce the lithium-nickel mixing caused by incomplete oxidation of nickel ions and the transformation of nickel ions. At the same time, the surface coating of titanium dioxide on the prepared ternary cathode material reduces the direct contact between the cathode material and the electrolyte, reduces the adverse reactions between the two, and improves the cycle stability of the cathode material.

Claims

1. A preparation method of a ternary cathode material, the preparation method comprises the following steps: (1) After mixing a ternary precursor and a lithium source, perform a first-stage sintering treatment to obtain a first-sintered material; (2) After performing a crushing treatment on the first-sintered material obtained in step (1), mix the crushed first-sintered material with titanium dioxide, and perform a second-stage sintering treatment under light to obtain the ternary cathode material; The mass ratio of the first-fired material to titanium dioxide described in step (2) is 100:(0.2 - 1), the intensity of the light is 12 - 36 mW / cm 2 , the wavelength of the light is 200 - 380 nm, and the temperature of the two-stage sintering treatment is 600 - 1000 °C.

2. The preparation method according to claim 1, wherein, the ternary precursor in step (1) comprises a ternary nickel cobalt manganese precursor.

3. The preparation method according to claim 1, wherein, the lithium source comprises lithium hydroxide and / or lithium carbonate.

4. The preparation method according to claim 1, wherein, the molar ratio of lithium element in the lithium source to the total metal elements in the ternary precursor in step (1) is (1.01 - 1.05):

1.

5. The preparation method according to claim 1, wherein, the temperature of the first-stage sintering treatment in step (1) is 450 - 600 °C.

6. The preparation method according to claim 1, wherein, the time of the first-stage sintering treatment is 3 - 8 h.

7. The preparation method according to claim 1, wherein, the time of the second-stage sintering treatment is 5 - 12 h.

8. The preparation method according to claim 1, wherein, the device for the second-stage sintering treatment comprises a rotary kiln.

9. The preparation method according to claim 1, wherein, the preparation method comprises the following steps: (1) After mixing a ternary precursor and a lithium source, sinter at 450 - 600 °C for 3 - 8 h to obtain a first-sintered material; (2) After crushing the first-fired material obtained in step (1), the crushed first-fired material is mixed with titanium dioxide in a mass ratio of 100: (0.2 - 1), and under light with a wavelength of 200 - 380 nm and an intensity of 12 - 36 mW / cm 2 , it is sintered at 600 - 900 °C for 5 - 12 h to obtain the ternary cathode material.

10. A ternary cathode material, the ternary cathode material is prepared by the method according to any one of claims 1 - 9, the ternary cathode material comprises a core and a titanium dioxide coating layer arranged on the surface of the core, and the titanium dioxide coating layer is anatase-type titanium dioxide.

11. A positive electrode sheet, wherein, the positive electrode sheet comprises the ternary cathode material according to claim 10.

12. A lithium-ion battery, wherein, the lithium-ion battery comprises the positive electrode sheet according to claim 11.

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