Modified positive electrode material, preparation method therefor, and application thereof

Abstract

A preparation method for a modified positive electrode material comprises the following steps: (1) mixing tungsten disulfide with a tannic acid solution, performing ultrasonic treatment, and separating to obtain a TA-WS2 nanosheet solution; (2) performing corona discharge treatment on the positive electrode material, then mixing the positive electrode material with a solvent to obtain a positive electrode material solution, and mixing the positive electrode material solution with the TA-WS2 nanosheet solution to obtain a mixed solution; and (3) performing solid-liquid separation treatment on the mixed solution, and performing calcination treatment on the obtained solid material to obtain the modified positive electrode material. By means of preparing nanoparticles with strong electronegativity and making the particles of the positive electrode material charged, the nanoparticles with strong electronegativity are uniformly and spontaneously loaded on the charged particles by utilising the acting force between the nanoparticles with strong electronegativity and the electrons, and finally a uniform coating layer is formed on the surface of the positive electrode material by means of calcination.

Description

A modified positive electrode material and its preparation method and application Technical Field

[0001] The present disclosure belongs to the technical field of battery materials and relates to a modified positive electrode material and a preparation method and application thereof. Background Art

[0002] As one of the most important products in the battery industry, lithium-ion batteries are experiencing rapid growth with the expansion of the new energy vehicle and energy storage markets, making them a key future development area in the secondary battery industry. Lithium-ion secondary batteries offer advantages such as high operating voltage, high capacity, compact size, light weight, and long cycle life, making them widely used in portable electronics, electric bicycles, electric vehicles, and energy storage. Cathode materials, a key factor influencing the performance and application of lithium-ion batteries, have attracted considerable attention from researchers worldwide in recent years, leading to rapid development.

[0003] Currently developed cathode materials for lithium-ion batteries are primarily classified into three categories based on their structure: hexagonal layered cathode materials, represented by lithium cobalt oxide (LiCoO2), ternary nickel cobalt manganese oxide (NCM), and nickel cobalt aluminum oxide (NCA), belonging to the R-3m space group; spinel cathode materials, represented by lithium manganese oxide (LiMn2O4), belonging to the Fd-3m space group; and polyanion cathode materials, such as lithium iron phosphate (LiFePO4), lithium iron silicate (Li2FeSiO4), and lithium vanadium phosphate (LiVPO4), with an olivine structure. Despite continuous development, cathode materials still face challenges such as poor structural stability, cation mixing, transition metal dissolution, voltage decay, poor rate and high-temperature performance, and low initial coulombic efficiency.

[0004] CN110429275A discloses a method for preparing a carbon-coated ternary positive electrode material and a carbon-coated ternary positive electrode material; the method for preparing the carbon-coated ternary positive electrode material comprises subjecting a dried ternary positive electrode material, an organic carbon source and an organic solvent complex to heat treatment at a temperature of 240-350°C.

[0005] CN103474628A discloses a preparation method of a carbon-coated ternary positive electrode material and the carbon-coated ternary positive electrode material. The preparation method includes the following steps: S1, preparing a ternary positive electrode material precursor using nickel salt, cobalt salt and manganese salt as raw materials; S2, preparing a conductive carbon dispersion system: dispersing conductive carbon in water containing an organic carbon source; S3, adding the ternary positive electrode material precursor and a lithium compound to the conductive carbon dispersion system, mixing them evenly, to obtain a mixture; S4, drying the mixture under vacuum conditions; S5, high-temperature treating the dried mixture under closed conditions or in an inert gas-protected atmosphere to obtain a carbon-coated ternary positive electrode material.

[0006] The above scheme produces a coated positive electrode material, but the coating layer has a poor bonding effect with the positive electrode material and is easily detached, thereby leading to a problem of reduced cycle performance of the material.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of the present disclosure is to provide a modified positive electrode material and its preparation method and application. The present disclosure prepares nanoparticles with strong electronegativity and charges the positive electrode material particles at the same time. The interaction between the strongly electronegative nanoparticles and electrons is utilized to make the strongly electronegative nanoparticles uniformly and spontaneously loaded on the charged particles. Finally, a uniform coating layer is formed on the surface of the positive electrode material through calcination.

[0010] To achieve this purpose, the present disclosure adopts the following technical solutions:

[0011] In a first aspect, the present disclosure provides a method for preparing a modified positive electrode material, the preparation method comprising the following steps:

[0012] (1) Tungsten disulfide and tannic acid (TA) solution were mixed and ultrasonically treated to obtain TA-WS2 nanosheet solution;

[0013] (2) performing corona discharge treatment on the positive electrode material and mixing it with a solvent to obtain a positive electrode material solution, and mixing the positive electrode material solution with a TA-WS2 nanosheet solution to obtain a mixed solution;

[0014] (3) performing solid-liquid separation on the mixed solution, and calcining the obtained solid material to obtain the modified positive electrode material.

[0015] The present invention pre-prepares TA-WS2 nanosheets with strong electronegativity. The unique layered structure of the two-dimensional TA-WS2 nanosheets and the large interlayer spacing allow lithium ions to be freely embedded and extracted. At the same time, WS2 has the advantages of high electrical conductivity, excellent high and low temperature resistance, and high capacitance density, which increases the stability, capacity and service life of lithium-ion batteries. The positive electrode material particles are charged using corona discharge technology. Based on the interaction between the strongly electronegative nanoparticles and the negative charges, the TA-WS2 nanosheets are spontaneously and evenly coated on the surface of the ternary positive electrode material. Finally, by carbonizing TA, the positive electrode material and WS2 are simultaneously carbon-coated. While solving the expansion problem of tungsten disulfide during the charge and discharge process, it can buffer the volume expansion of the battery structure and improve the cycle stability and high rate capability. At the same time, by coating the carbon layer on the surface of the positive electrode material, the electrical conductivity of tungsten disulfide is increased, thereby improving the charge and discharge efficiency of the battery, improving the battery life and performance, and improving the stability and safety of the battery.

[0016] In one embodiment, the solvent in the tannic acid solution in step (1) comprises any one of ultrapure water, ethanol, methanol, acetone or ethyl acetate, or a combination of at least two thereof.

[0017] In one embodiment, the concentration of the tannic acid solution is (0.2-10) g / L, for example, 0.2 g / L, 1 g / L, 2 g / L, 5 g / L or 10 g / L.

[0018] In one embodiment, the mass ratio of tungsten disulfide to tannic acid in the tannic acid solution is (1-5):(1-5), for example: 1:5, 1:2, 1:1, 2:1 or 5:1.

[0019] In one embodiment, the power of the ultrasonic treatment in step (1) is 200-600W, for example, 200W, 300W, 400W, 500W or 600W.

[0020] In one embodiment, the ultrasonic treatment time is 1 to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours.

[0021] In one embodiment, the separation method in step (1) includes centrifuging the suspension after ultrasonic treatment, taking the supernatant, and obtaining a TA-WS2 nanosheet solution.

[0022] In one embodiment, the solvent in step (2) comprises any one of ultrapure water, ethanol, methanol, acetone or ethyl acetate, or a combination of at least two thereof.

[0023] In one embodiment, the mass ratio of the positive electrode material to the TA-WS2 nanosheets is 1:(0.1-1), for example: 1:0.1, 1:0.3, 1:0.5, 1:0.8 or 1:1, etc., preferably 1:(0.2-0.4).

[0024] In one embodiment, the mass concentration of the positive electrode material in the mixed solution is 20% to 50%, for example, 20%, 25%, 30%, 35% or 50%.

[0025] In one embodiment, the mass concentration of TA-WS2 nanosheets in the mixed solution is 5% to 20%, for example, 5%, 8%, 10%, 15% or 20%.

[0026] In one embodiment, the solid-liquid separation in step (3) comprises filtration.

[0027] In one embodiment, the filtration is followed by drying.

[0028] In one embodiment, the temperature of the calcination treatment in step (3) is 300-500°C, for example, 300°C, 350°C, 400°C, 450°C or 500°C.

[0029] In one embodiment, the calcination atmosphere includes nitrogen.

[0030] In one embodiment, the calcination treatment time is 15 to 60 minutes, for example, 15 minutes, 20 minutes, 30 minutes, 40 minutes or 60 minutes.

[0031] In a second aspect, the present disclosure provides a modified positive electrode material, which is prepared by the method described in the first aspect.

[0032] In a third aspect, the present disclosure provides a positive electrode plate, wherein the positive electrode plate comprises the modified positive electrode material as described in the second aspect.

[0033] In a fourth aspect, the present disclosure provides a lithium-ion battery, comprising the positive electrode sheet as described in the third aspect.

[0034] Compared with the prior art, the present disclosure has the following beneficial effects:

[0035] (1) The present invention pre-prepare highly electronegative TA-WS2 nanosheets. The unique layered structure of the two-dimensional TA-WS2 nanosheets and the large interlayer spacing allow lithium ions to be freely embedded and released. At the same time, WS2 has the advantages of high conductivity, excellent high and low temperature resistance, and high capacitance density, which increases the stability, capacity and service life of lithium-ion batteries. The positive electrode material particles are charged using corona discharge technology. Based on the interaction between the highly electronegative nanoparticles and the negative charge, the TA-WS2 nanosheets are spontaneously and evenly coated on the surface of the ternary positive electrode material. Finally, by carbonizing TA, the positive electrode material and WS2 are simultaneously carbon-coated. While solving the expansion problem of tungsten disulfide during the charge and discharge process, it can buffer the volume expansion of the battery structure and improve the cycle stability and high rate capability. At the same time, by coating the carbon layer on the surface of the positive electrode material, the conductivity of tungsten disulfide is increased, thereby improving the charge and discharge efficiency of the battery, improving the battery life and performance, and improving the stability and safety of the battery.

[0036] (2) The modification method described in this application can be applied to various cathode materials, significantly improving their performance. The modified NCM811 cathode material can maintain a capacity of over 97% after 100 cycles at a 0.1C charge / discharge rate. The modified lithium iron phosphate battery can achieve a discharge capacity of over 149 mAh / g after 200 cycles at room temperature, and over 146 mAh / g after 100 cycles at 66°C. This significantly improves the cycling stability of the material.

[0037] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0039] FIG1 is a SEM image of the modified positive electrode material obtained in Example 1.

[0040] FIG2 is a SEM image of the modified positive electrode material obtained in Comparative Example 1.

[0041] FIG3 is a SEM image of the modified positive electrode material obtained in Comparative Example 2. DETAILED DESCRIPTION

[0042] The technical solution of the present disclosure is further described below through specific implementation methods. It should be understood by those skilled in the art that the embodiments are only used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[0043] Example 1

[0044] This embodiment provides a modified positive electrode material, and the preparation method of the modified positive electrode material is as follows:

[0045] (1) Tannic acid and ethanol were mixed at a mass volume ratio of 1 g:1 L, and WS2 was mixed therein at a mass ratio of tungsten disulfide nanosheets to tannic acid of 2:1. The mixed solution was then ultrasonically treated at 300 W for 2 h, and the suspension after ultrasonic treatment was centrifuged for 30 min. The supernatant was collected to obtain a TA-WS2 nanosheet solution.

[0046] (2) Select 3μm LiNi 0.8 Co 0.1 Mn 0.1 O2 cathode material particles are treated with corona discharge technology to make the particle surface negatively charged; the treated cathode material particles are then mixed evenly with ethanol, and then the TA-WS2 nanosheet solution is added at a mass ratio of 1:0.2 between the cathode material and TA-WS2 to obtain a mixed solution, wherein the mass concentration of the cathode material in the mixed solution is 40%, and the mass concentration of the TA-WS2 nanosheet is 8%;

[0047] (3) The mixed solution was filtered and vacuum dried, and then the material was reacted at 400° C. in a nitrogen atmosphere for 20 minutes to obtain the modified positive electrode material. The SEM image of the modified positive electrode material is shown in FIG1 .

[0048] The obtained modified cathode material was used for LiNi 0.8Co 0.1 Mn 0.1 The positive electrode material for the O2 battery, assembled into finished batteries, demonstrated an initial discharge capacity of 212 mAh / g at 0.1C within a voltage range of 2.75 to 4.3 V, with an initial coulombic efficiency of 86%. The battery was tested at room temperature under 0.1C conditions and cycled 100 times at a 0.1C charge-discharge rate, with a capacity retention rate of 97%.

[0049] Example 2

[0050] This embodiment provides a modified positive electrode material, and the preparation method of the modified positive electrode material is as follows:

[0051] (1) Tannic acid and ethanol were mixed at a mass volume ratio of 1 g:1 L, and WS2 was mixed therein at a mass ratio of 5:1 of tungsten disulfide nanosheets to tannic acid. The mixed solution was then ultrasonically treated at 200 W for 5 h, and the ultrasonically treated suspension was centrifuged for 30 min. The supernatant was collected to obtain a TA-WS2 nanosheet solution.

[0052] (2) 3 μm lithium iron phosphate positive electrode material particles were selected and the surface of the particles was negatively charged by corona discharge technology; the treated positive electrode material particles were then mixed evenly with ethanol, and then the TA-WS2 nanosheet solution was added according to the mass ratio of the positive electrode material to TA-WS2 of 1:0.3 to obtain a mixed solution, in which the mass concentration of the positive electrode material in the mixed solution was 30% and the mass concentration of the TA-WS2 nanosheet was 9%;

[0053] (3) The mixed solution was filtered and vacuum dried, and then the material was reacted at 300° C. in a nitrogen atmosphere for 60 minutes to obtain the modified positive electrode material.

[0054] The obtained modified positive electrode material was used as the positive electrode material of lithium iron phosphate batteries. By assembling the finished batteries, the battery was cycled 200 times at 2.5-3.9V, at a rate of 1C (1C = 170mA / g), and at room temperature, and the discharge specific capacity reached 149mAh / g; in the electrochemical performance test at 66℃, after 100 cycles, the discharge specific capacity reached 146mAh / g.

[0055] Example 3

[0056] This embodiment provides a modified positive electrode material, and the preparation method of the modified positive electrode material is as follows:

[0057] (1) Tannic acid and ethanol were mixed at a mass volume ratio of 1 g:1 L, and WS2 was mixed therein at a mass ratio of tungsten disulfide nanosheets to tannic acid of 1:5. The mixed solution was then ultrasonically treated at 600 W for 1 h, and the ultrasonically treated suspension was centrifuged for 30 min. The supernatant was collected to obtain a TA-WS2 nanosheet solution.

[0058] (2) Select 3μm LiNi 0.8 Co 0.1 Mn 0.1 O2 cathode material particles are treated with corona discharge technology to make the particle surface negatively charged; the treated cathode material particles are then mixed evenly with ethanol, and then the TA-WS2 nanosheet solution is added at a mass ratio of 1:0.4 to obtain a mixed solution. The mass concentration of the cathode material in the mixed solution is 20%, and the mass concentration of the TA-WS2 nanosheet is 8%.

[0059] (3) The mixed solution was filtered and vacuum dried, and then the material was reacted at 500° C. in a nitrogen atmosphere for 15 minutes to obtain the modified positive electrode material.

[0060] The obtained modified cathode material was used for LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode material for the O2 battery, assembled into finished batteries, demonstrated an initial discharge capacity of 214 mAh / g at 0.1C within a voltage range of 2.75 to 4.3 V, with an initial coulombic efficiency of 87%. The battery was tested at room temperature under 0.1C conditions and cycled 100 times at a 0.1C charge-discharge rate, with a capacity retention rate of 97%.

[0061] Example 4

[0062] The only difference between this embodiment and embodiment 1 is that the mass ratio of tungsten disulfide to tannic acid is 8:1, and other conditions and parameters are exactly the same as those in embodiment 1.

[0063] The obtained modified cathode material was used for LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode material for the O2 battery, assembled into finished batteries, demonstrated an initial discharge capacity of 208 mAh / g at 0.1C within a voltage range of 2.75 to 4.3 V, with an initial coulombic efficiency of 84%. The battery was tested at room temperature under 0.1C conditions and cycled 100 times at a 0.1C charge-discharge rate, with a capacity retention rate of 87%.

[0064] Example 5

[0065] The only difference between this embodiment and embodiment 1 is that the mass ratio of tungsten disulfide to tannic acid is 1:8, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0066] The obtained modified cathode material was used for LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode material for the O2 battery, assembled into finished batteries, demonstrated an initial discharge capacity of 204 mAh / g at 0.1C within a voltage range of 2.75 to 4.3 V, with an initial coulombic efficiency of 85%. The battery was tested at room temperature under 0.1C conditions and maintained at 95% capacity after 100 cycles at a 0.1C charge-discharge rate.

[0067] Example 6

[0068] The only difference between this embodiment and Example 1 is that the mass ratio of the positive electrode material to the TA-WS2 nanosheets is 1:0.1, and the other conditions and parameters are exactly the same as those in Example 1.

[0069] The obtained modified cathode material was used for LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode material for the O2 battery, assembled into finished batteries, demonstrated an initial discharge capacity of 210 mAh / g at 0.1C within a voltage range of 2.75 to 4.3 V, with an initial coulombic efficiency of 86%. The battery was tested at room temperature under 0.1C conditions and maintained a capacity retention of 94% after 100 cycles at a 0.1C charge-discharge rate.

[0070] Example 7

[0071] The only difference between this embodiment and Example 1 is that the mass ratio of the positive electrode material to the TA-WS2 nanosheets is 1:0.5, and the other conditions and parameters are exactly the same as those in Example 1.

[0072] The obtained modified cathode material was used for LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode material for the O2 battery, assembled into finished batteries, demonstrated an initial discharge capacity of 213 mAh / g at 0.1C within a voltage range of 2.75 to 4.3 V, with an initial coulombic efficiency of 88%. The battery was tested at room temperature under 0.1C conditions and maintained a capacity retention of 96% after 100 cycles at a 0.1C charge-discharge rate.

[0073] Comparative Example 1

[0074] The only difference between this comparative example and Example 1 is that tannic acid is not added, and the other conditions and parameters are exactly the same as those in Example 1. The SEM image of the obtained modified positive electrode material is shown in FIG2 .

[0075] The obtained modified cathode material was used for LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode material for the O2 battery, assembled into finished batteries, demonstrated an initial discharge capacity of 190 mAh / g at 0.1C within a voltage range of 2.75 to 4.3 V, with an initial coulombic efficiency of 82%. Furthermore, the battery was tested at room temperature under 0.1C conditions, and after 100 cycles at a 0.1C charge-discharge rate, the capacity retention rate was 74%.

[0076] Comparative Example 2

[0077] The only difference between this comparative example and Example 1 is that the positive electrode material is not subjected to corona discharge treatment, and the other conditions and parameters are exactly the same as those in Example 1. The SEM image of the obtained modified positive electrode material is shown in FIG3 .

[0078] The obtained modified cathode material was used for LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode material for the O2 battery, assembled into finished batteries, demonstrated an initial discharge capacity of 208 mAh / g at 0.1C within a voltage range of 2.75 to 4.3 V, with an initial coulombic efficiency of 84%. Testing of the battery at room temperature under 1C conditions revealed a capacity retention rate of 79% after 100 cycles at a 0.1C charge-discharge rate.

[0079] Comparison of Examples 1-3 demonstrates that the modification method described herein can be applied to a variety of cathode materials, significantly improving their performance. The modified NCM811 cathode material exhibited a capacity retention rate exceeding 97% after 100 cycles at a 0.1C charge / discharge rate. The modified lithium iron phosphate battery achieved a discharge capacity exceeding 149 mAh / g after 200 cycles at room temperature, and a discharge capacity exceeding 146 mAh / g after 100 cycles at 66°C. This significantly improves the material's cycling stability.

[0080] By comparing Example 1 with Examples 3-5, it can be seen that in the preparation process of the modified positive electrode material described in the present disclosure, the mass ratio of tungsten disulfide and tannic acid affects its performance. The mass ratio of tungsten disulfide and tannic acid is controlled at 1:5 to 5:1, and the positive electrode material obtained has better performance. If the proportion of tannic acid is too high and the proportion of tungsten disulfide is too low, it will cause waste of resources and will not actually improve the battery performance; if the proportion of tannic acid is too low and the proportion of tungsten disulfide is too high, the nanosheets will be stacked after exfoliation, and stable dispersion cannot be achieved.

[0081] By comparing Example 1 with Examples 6-7, it can be seen that in the preparation process of the modified positive electrode material described in the present disclosure, the mass ratio of the positive electrode material and the TA-WS2 nanosheets will affect its performance. The mass ratio of the positive electrode material and the TA-WS2 nanosheets is controlled at 1:0.2~0.4, and the positive electrode material has better performance. If the addition amount of TA-WS2 nanosheets is too high, it will cause stacking on the surface of the positive electrode material and cannot form a thin and uniform coating layer; if the addition amount of TA-WS2 nanosheets is too low, the positive electrode material cannot be completely coated, resulting in coating defects in the material.

[0082] From the comparison between Example 1 and Comparative Example 1, it can be seen that the addition of tannic acid to the surface carbon coating of WS2 and the positive electrode material in the present invention can reduce the volume expansion problem of WS2 during the charging and discharging process, and at the same time the electrical conductivity of tungsten disulfide is significantly improved; after corona discharge treatment, TA-WS2 can spontaneously form a uniform coating around the positive electrode material.

[0083] From the comparison between Example 1 and Comparative Example 2, it can be seen that without corona discharge treatment, the surface of the positive electrode material does not carry a negative charge, and TA-WS2 cannot spontaneously form around the positive electrode material, resulting in the inability to form a uniform coating layer, resulting in defects on the surface of the positive electrode material, reducing the effective coating rate during long-term circulation, and causing corrosion of the electrolyte.

Claims

1. A method for preparing a modified positive electrode material, the method comprising the following steps: (1) mixing tungsten disulfide and tannic acid solution, and separating to obtain TA-WS2 nanosheet solution after ultrasonic treatment; (2) subjecting the positive electrode material to corona discharge treatment and then mixing it with a solvent to obtain a positive electrode material solution, and mixing the positive electrode material solution with a TA-WS2 nanosheet solution to obtain a mixed solution; (3) performing solid-liquid separation on the mixed solution, and calcining the obtained solid material to obtain the modified positive electrode material.

2. The preparation method according to claim 1, wherein The solvent in the tannic acid solution in step (1) includes any one of ultrapure water, ethanol, methanol, acetone or ethyl acetate, or a combination of at least two of them.

3. The preparation method according to claim 1 or 2, wherein: The concentration of the tannic acid solution is (0.2-10) g / L.

4. The preparation method according to any one of claims 1 to 3, wherein The mass ratio of the tungsten disulfide to the tannic acid in the tannic acid solution is (1-5):(1-5).

5. The preparation method according to any one of claims 1 to 4, wherein: The power of the ultrasonic treatment in step (1) is 200 to 600W.

6. The preparation method according to any one of claims 1 to 5, wherein: The ultrasonic treatment time is 1 to 5 hours.

7. The preparation method according to any one of claims 1 to 6, wherein: The separation method in step (1) includes centrifuging the suspension after ultrasonic treatment, taking the supernatant, and obtaining a TA-WS2 nanosheet solution.

8. The preparation method according to any one of claims 1 to 7, wherein: The solvent in step (2) includes any one of ultrapure water, ethanol, methanol, acetone or ethyl acetate, or a combination of at least two thereof.

9. The preparation method according to any one of claims 1 to 8, wherein: The mass ratio of the positive electrode material to the TA-WS2 nanosheet is 1:(0.1-1).

10. The preparation method according to any one of claims 1 to 8, wherein: The mass ratio of the positive electrode material to the TA-WS2 nanosheet is 1:(0.2-0.4).

11. The preparation method according to any one of claims 1 to 10, wherein: The mass concentration of the positive electrode material in the mixed solution is 20-50%.

12. The preparation method according to any one of claims 1 to 11, wherein: The mass concentration of TA-WS2 nanosheets in the mixed solution is 5-20%.

13. The preparation method according to any one of claims 1 to 12, wherein: The solid-liquid separation in step (3) comprises filtration; Optionally, the filtration is followed by drying.

14. The preparation method according to any one of claims 1 to 13, wherein: The temperature of the calcination treatment in step (3) is 300-500° C. Optionally, the calcination atmosphere includes nitrogen; Optionally, the calcination treatment time is 15 to 60 minutes.

15. A modified positive electrode material, wherein the modified positive electrode material is prepared by the method according to any one of claims 1 to 14. 16 . A positive electrode sheet, comprising the modified positive electrode material according to claim 15 .

17. A lithium ion battery, comprising the positive electrode sheet according to claim 16.

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