Epoxydized natural rubber coated lithium battery cathode active material, method of making and use thereof

Abstract

The application provides an epoxy natural rubber coated lithium battery positive electrode active material and a preparation method and application thereof, and comprises the following steps: 1) dissolving epoxy natural rubber in toluene and adding dicumyl peroxide (DCP) for dissolving; 2) taking the solution prepared in step 1), adding positive electrode active material particles, and heating and stirring; 3) carrying out vulcanization treatment on the material obtained in step 2). The epoxy natural rubber is used as a coating layer of the positive electrode active material particles, can inhibit the volume expansion of the positive electrode active material and the harmful side reaction between the electrode and the electrolyte in the charging and discharging process of the lithium battery. Under the coating of the epoxy natural rubber, the positive electrode active material after coating can have very good cycle stability under the condition of high rate, compared with the traditional electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to an epoxy natural rubber coated lithium battery positive electrode active material and a preparation method and application thereof. BACKGROUND

[0002] The energy development of human society, the social reserve multifunctionalization, and the new energy industry are in an unprecedented development period. As a core component widely used in the new energy industry, the lithium ion battery has low production and maintenance cost, is environment-friendly, has a long service life, and has many other advantages. The positive electrode active material of the lithium ion battery provides Li + for the lithium intercalation compound between the positive and negative electrodes and helps form a solid electrolyte interface (SEI) film. The new ternary positive electrode active material has excellent discharge specific capacity and charge / discharge rate. However, the microcracks, transition metal dissolution, lithium-nickel mixing, and phase change of the high-nickel ternary positive electrode active material in the cycle process can cause a series of adverse side reactions, which can seriously affect the service life of the lithium ion battery.

[0003] Surface modification by coating is an effective solution to the parasitic reaction at the interface between the positive electrode active material and the electrolyte. This surface coating forms an artificial physical barrier on the surface of the electrochemically active positive electrode particles to act as a protective passivation film to prevent direct contact between the positive electrode active material and the electrolyte. It not only enriches the electrochemical performance of the nickel-rich NCM material, improves the structural integrity and thermal stability of the NCM, but also stabilizes the interface between the electrode and the electrolyte, preventing the NCM surface phase from changing from a layered structure to a rock salt or disordered spinel structure. Polymer coating materials have more varieties and unique properties than inorganic coating materials. They form a surface film with high ionic conductivity on the surface of the NCM, helping to improve the charge transfer at the positive electrode / electrolyte interface. Due to the flexibility of the polymer itself, it can better adapt to the volume change of the cathode material during the cycle process and more effectively reduce the formation of microcracks on the surface of the NCM. SUMMARY

[0004] The application uses epoxy natural rubber to coat the surface of the lithium battery positive electrode active material. Through vulcanization treatment, a network structure that inhibits the generation of microcracks of the positive electrode active material particles during the charge / discharge process is generated in situ on the surface of the positive electrode active material, thereby prolonging the cycle life of the battery.

[0005] To achieve the above purpose, the application provides a method for coating a positive electrode active material with epoxy natural rubber, comprising the following steps:

[0006] 1) Dissolve the epoxy natural rubber in toluene and add dicumyl peroxide (DCP) for dissolution;

[0007] 2) Take the solution prepared in step 1), add positive electrode active material particles, and heat and stir;

[0008] 3) Perform vulcanization treatment on the material in step 2).

[0009] According to an embodiment of the present application, the mass ratio of dicumyl peroxide to epoxidized natural rubber in step 1) is (0.001-0.1):1, for example (0.005-0.08):1, such as 0.01:1.

[0010] According to an embodiment of the present application, the epoxidation degree of the epoxidized natural rubber in step 1) is 10-60%, for example 20-60%, such as 50%.

[0011] According to an embodiment of the present application, the epoxidized natural rubber in step 1) is a high-performance rubber obtained by epoxidation modification of natural rubber. Due to the addition of polar epoxy groups, the polarity of the natural rubber molecules and the intermolecular interaction force are enhanced.

[0012] According to an embodiment of the present application, in step 2), the positive electrode active material is a ternary positive electrode active material (NCM), lithium iron phosphate, lithium cobaltate, lithium manganate, a lithium-rich manganese-based positive electrode active material, and is preferably NCM622.

[0013] According to an embodiment of the present application, the mass ratio of the positive electrode active material particles added in step 2) to the epoxidized natural rubber in step 1) is 1:(0.001-0.05), for example 1:(0.005-0.02), 1:(0.008-0.012), 1:(0.009-0.011), such as 1:0.01, 1:0.005, or 1:0.02.

[0014] According to an embodiment of the present application, in step 2), the heating and stirring is performed at 35-50°C for 1-12 hours.

[0015] According to an embodiment of the present application, after the stirring in step 2) is completed, ultrasonic treatment is performed for more than 10 minutes, for example 30 minutes.

[0016] According to an embodiment of the present application, after the stirring in step 2) is completed, rotary evaporation treatment is also performed, and the rubber is uniformly coated on the surface of the positive electrode particles by continuously rotating and evaporating.

[0017] According to an embodiment of the present application, after the coating in step 2) is completed, drying treatment is also performed. The dried material is then vulcanized in a flat vulcanization instrument, thereby preparing a positive electrode active material coated with epoxidized natural rubber having a network structure.

[0018] According to an embodiment of the present application, the vulcanization treatment in step 3) is performed in a flat vulcanization instrument.

[0019] According to the embodiment of the present application, the vulcanization treatment in step 3) is heating at 100-180°C for 1-30 minutes.

[0020] In a preferred embodiment, the epoxy natural rubber coated positive active material is prepared by the following steps:

[0021] S1) A certain amount of epoxy natural rubber latex is washed in anhydrous ethanol, then dried, and after drying, plasticized in a plasticizer for 30-50 times;

[0022] S2) The epoxy natural rubber dried and plasticized in step 1) is added to toluene for dissolution; after complete dissolution, dicumyl peroxide is added and continued to be dissolved;

[0023] S3) The positive active material is placed in the epoxy natural rubber solution containing dicumyl peroxide in step S2), stirred at 35-50°C, and then ultrasonicated;

[0024] S4) Rotary evaporation treatment is carried out in a rotary evaporator; then the positive active material is continuously dried in a blast oven and a vacuum oven;

[0025] S5) The dried positive active material is heated at 100-180°C for more than 1 minute for vulcanization treatment, to obtain an epoxy natural rubber coated positive active material containing a reticular structure.

[0026] The present application also provides the epoxy natural rubber coated positive active material prepared by the above-mentioned method.

[0027] The present application also provides the use of the epoxy natural rubber coated positive active material prepared by the above-mentioned method as a lithium battery positive electrode material.

[0028] Advantages of the present application

[0029] The present application uses a rotary evaporator to perform in-situ coating, because the solution continuously rotates and flows during the coating process, so that the coating material is maximized on the positive active material. The preparation process of the present application is simple, and good coating effect can be achieved. At the same time, the method has not strict requirements for the positive electrode material. Because of the plasticizing treatment, the epoxidized natural rubber can be well dissolved in toluene. And, the epoxidized natural rubber itself has very good mechanical properties, and the mechanical properties of the epoxidized natural rubber after vulcanization treatment are greatly improved. Selecting epoxidized natural rubber as the coating layer can inhibit the volume expansion of the positive active material and the harmful side reaction between the electrode and the electrolyte during the charging and discharging process of the lithium battery. Under the coating of the epoxidized natural rubber, the positive active material can have very good cycle stability under high rate conditions compared with the traditional electrode material. Compared with the inorganic material coating method, the epoxidized natural rubber used in the present application has better flexibility, and has the advantages of wide source, low cost, simple operation, suitable for large-scale industrial production and easy to realize commercialization.

[0030] The epoxidized natural rubber used in the present application not only retains the high elasticity, high wear resistance and stress-induced crystallization characteristics of the epoxidized natural rubber after coating, but also greatly improves the wet skid resistance, oil resistance, air tightness, adhesion and compatibility with fillers, etc. It has broad application prospects. Through heating and vulcanization treatment, the epoxidized natural rubber is converted from a linear structure to a high-elasticity network structure, which casts a soft protective layer for the positive active material. Compared with the sulfur vulcanization method commonly used, the selected dicumyl peroxide vulcanization method produces latex with good stability, less non-rubber components and high elongation. The bond energy of the C-C bond produced by vulcanization is greater than that of the single sulfur, double sulfur and polysulfide bond produced by the sulfur vulcanization system. At the same time, the structure of the epoxidized natural rubber has very rich structure designability, which makes the performance improvement of the coating layer have unlimited possibilities.

[0031] In summary, for the positive active material, the improvement of the coating layer includes: (1) The coating layer exerts a counteracting force on the volume expansion of the active particles, disperses the mechanical stress inside the positive material particles, thereby reducing the generation of microcracks on the surface of the active particles. (2) The flexible network formed by the coating layer not only inhibits the crushing of the positive active material, but also reduces the contact area between the electrolyte and the positive active material, thereby inhibiting the harmful side reaction between the positive active material and the electrolyte. (3) The coating layer has certain electron and ion conductivity, which not only serves as a surface chemical modifier for ion charge transfer at the cathode / electrolyte interface, but also does not affect the discharge specific capacity of the positive active material itself. (4) The coating material is derived from natural materials, which is cheap and easy to obtain. This coating process adheres to the green and environmental protection concept of battery energy. Therefore, the epoxidized natural rubber with structure designability used as the coating layer makes the performance of the positive active material have a lot of optimization space. Attached Figure Description

[0032] Figure 1 This is a high-magnification scanning electron microscope image of unmodified pure NCM622.

[0033] Figure 2 This is a high-magnification scanning electron microscope image of NCM622 coated with 0.5 wt% epoxidized natural rubber in Example 2.

[0034] Figure 3 This is a high-magnification scanning electron microscope image of NCM622 coated with 1 wt% epoxidized natural rubber in Example 1.

[0035] Figure 4 This is a high-magnification scanning electron microscope image of NCM622 coated with 2wt% epoxidized natural rubber in Example 3.

[0036] Figure 5 The specific capacity-voltage curves are as follows: the unmodified pure NCM622 in Comparative Example 1 is assembled into a full cell, activated at a cutoff voltage of 2.5-4.3V and a current density of 0.2C, and the specific capacity-voltage curves are shown at a current density of 0.5C.

[0037] Figure 6 In Example 2, NCM622 coated with 0.5 wt% epoxidized natural rubber was assembled into a full cell and activated at a cutoff voltage of 2.5-4.3V and a current density of 0.2C. The specific capacity-voltage curves at a current density of 0.5C are shown.

[0038] Figure 7 The NCM622 cells coated with 1 wt% epoxidized natural rubber in Example 1 were assembled into a full cell, activated at a cutoff voltage of 2.5-4.3V and a current density of 0.2C, and the specific capacity-voltage curves were obtained at a current density of 0.5C.

[0039] Figure 8 The NCM622 cells coated with 2wt% epoxidized natural rubber in Example 3 were assembled into a full cell and activated at a cutoff voltage of 2.5-4.3V and a current density of 0.2C. The specific capacity-voltage curves were obtained at a current density of 0.5C.

[0040] Figure 9 This is a schematic diagram showing the long-cycle performance test results of the unmodified pure NCM622 assembled into a full cell in Comparative Example 1, at a cutoff voltage of 2.5-4.3V and a current density of 0.5C.

[0041] Figure 10is the long cycle performance test result of the full battery assembled by 0.5wt% epoxidized natural rubber coated NCM622 in Example 2 at a cutoff voltage of 2.5-4.3V and a current density of 0.5C.

[0042] Figure 11 is the long cycle performance test result of the full battery assembled by 1wt% epoxidized natural rubber coated NCM622 in Example 1 at a cutoff voltage of 2.5-4.3V and a current density of 0.5C.

[0043] Figure 12 is the long cycle performance test result of the full battery assembled by 2wt% epoxidized natural rubber coated NCM622 in Example 3 at a cutoff voltage of 2.5-4.3V and a current density of 0.5C.

[0044] Figure 13 is the long cycle performance test result comparison diagram of the full battery assembled by unmodified pure NCM622 and NCM622 with different coating amounts in Comparative Example 1 at a cutoff voltage of 2.5-4.3V and a current density of 0.5C.

[0045] Figure 14 is the specific capacity-voltage curve of the full battery assembled by unmodified pure NCM622 in Comparative Example 1 at a cutoff voltage of 2.5-4.3V, activated at a current density of 0.2C, and a current density of 1C.

[0046] Figure 15 is the specific capacity-voltage curve of the full battery assembled by 1wt% epoxidized natural rubber coated NCM622 in Example 1 at a cutoff voltage of 2.5-4.3V, activated at a current density of 0.2C, and a current density of 1C.

[0047] Figure 16 is the long cycle performance test result comparison diagram of the full battery assembled by unmodified pure NCM622 in Comparative Example 1 and 1wt% epoxidized natural rubber coated NCM622 in Example 1 at a cutoff voltage of 2.5-4.3V and a current density of 1C.

[0048] Figure 17 is the high-magnification scanning electron microscope photo of the ion beam section of unmodified pure NCM622 in Comparative Example 1 after 500 cycles at a 1C rate.

[0049] Figure 18 is the high-magnification scanning electron microscope photo of the ion beam section of 1wt% epoxidized natural rubber coated NCM622 in Example 1 after 500 cycles at a 1C rate.

[0050] Figure 19is the TEM image of the coating layer of 1 wt% epoxy natural rubber coated NCM622 in Example 1.

[0051] Figure 20 is the EDS element distribution map of 1 wt% epoxy natural rubber coated NCM622 in Example 1.

[0052] Figure 21 is the comparison of stress-strain curves before and after the vulcanization of epoxy natural rubber.

[0053] Figure 22 is the schematic diagram of the test results of long cycle performance at a current density of 0.5C of the full battery assembled by 1 wt% epoxy natural rubber coated NCM622 without vulcanization in Comparative Example 1, at a cutoff voltage of 2.5-4.3V and a current density of 0.2C. DETAILED DESCRIPTION

[0054] The method of the present application is described below by specific examples, but the present application is not limited thereto, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application. The experimental methods described in the following examples are conventional methods, unless otherwise specified; and the reagents and materials described are commercially available, unless otherwise specified.

[0055] The present application provides a method for in-situ coating based on lithium battery cathode active material, specifically comprising the following steps:

[0056] 1) A certain amount of epoxidized natural rubber latex is washed multiple times in anhydrous ethanol, and then dried. After drying, plasticize the rubber in a plasticizer for 30-50 times.

[0057] 2) Weigh 50 mg of dried and plasticized epoxidized natural rubber, add 20 ml of toluene, and dissolve. After complete dissolution, add 0.5 mg of dicumyl peroxide and continue to dissolve and treat.

[0058] 3) Weigh 500 mg of NCM622 cathode active material and place it in the epoxidized natural rubber solution containing dicumyl peroxide. Stir at 40 degrees for 3 hours, and then ultrasonic for half an hour.

[0059] 4) Perform rotary evaporation treatment in a rotary evaporator; then continue to dry the cathode active material in a forced air oven and a vacuum oven.

[0060] 5) Dry the cathode active material and heat it at 160 degrees for 12 minutes for vulcanization treatment. Finally, we get the NCM622 cathode active material coated with epoxidized natural rubber containing a network structure.

[0061] The in-situ coating method of the epoxidized natural rubber provided by the application is simple to operate, can form a coating layer on the positive active material well, and through further vulcanization treatment, the mechanical strength of the prepared epoxidized natural rubber is good, the coating layer formed on the surface of the positive active material can inhibit the volume expansion problem of the positive active material in the charging and discharging process, reduce the harmful side reaction of the positive electrode / electrolyte interface, and greatly prolong the cycle life of the lithium battery in the charging and discharging process.

[0062] The coating layer in the application can maintain good stability of the positive active material in a long-term high-rate cycle process. In addition, due to the designability of the structure of the epoxidized natural rubber, the performance of the coating layer has a lot of room for improvement. Moreover, the method is simple in process and can be well utilized in industrial production.

[0063] The technical solutions of the application will be further described below in combination with specific embodiments.

[0064] Preparation Example 1

[0065] A certain amount of epoxidized natural rubber latex (epoxidation degree is 50%, average molecular weight is about 350,000) is washed multiple times in anhydrous ethanol and dried. Then, the epoxidized natural rubber is prepared by plasticizing in a plasticizer for 30 times. The stress-strain curve comparison chart of the epoxidized natural rubber before and after vulcanization is shown in FIG. 1. Figure 21 As can be seen from FIG. 1, the mechanical properties of the epoxidized natural rubber after vulcanization treatment are obviously improved compared with the epoxidized natural rubber without vulcanization treatment. Figure 21

[0066] Example 1

[0067] (1) Preparation of 1wt% epoxidized natural rubber coated NCM622 positive active material

[0068] 500mg of NCM622 positive active material is weighed and placed in a coating solution containing 5mg of epoxidized natural rubber (the preparation process of the coating solution is as follows: 50mg of dried and plasticized epoxidized natural rubber is weighed, 20ml of toluene is added, and dissolved. After complete dissolution, 0.05mg of dicumyl peroxide is added and continues to be dissolved and treated). Stirring is carried out at 40 degrees for 3 hours, and then ultrasonic treatment is carried out for half an hour.

[0069] Rotary evaporation treatment is carried out in a rotary evaporator; then the positive active material is continuously dried in a blast oven and a vacuum oven.

[0070] The dried positive active material is heated at 160 degrees for 12 minutes for vulcanization treatment. Finally, the epoxidized natural rubber coated NCM622 positive active material with a network structure is obtained. From Figure 3 ​The scanning electron microscope photos show that the 1wt% epoxidized natural rubber is successfully coated on the surface of NCM622 particles.

[0071] (ii) Assembly of full battery and performance study

[0072] Lithium sheet was used as the negative electrode of the full battery, and the 1wt% epoxidized natural rubber coated NCM622 positive electrode active material prepared in step (i) was added with conductive carbon black (ketjen black). The slurry coating was prepared with a mass ratio of positive electrode active material: conductive carbon black: pvdf of 8: 1: 1, and the obtained electrode sheet was vacuum dried as a positive electrode. The full battery was assembled using PP separator, foam nickel and LiPF6 electrolyte containing 2% VC+EC / DEC / DMC mixed solvent. The surface capacity of the 1wt% epoxidized natural rubber coated NCM622 positive electrode material was about 3mAh cm -2 , the test cut-off voltage was 2.5-4.3V, the test temperature was 25℃, the current density was 0.2C activated for five cycles, and the cycle was carried out at a current density of 0.5C. Figure 11 The reversible capacity of the full battery was cycled for 300 cycles, and the specific capacity was still maintained at 150mAh g -1 . Figure 7 The charge-discharge curve was shown, and it could be seen that the charge-discharge reversibility was good and the polarization was small. Figure 19 The transmission electron microscope photo of the coating layer of 1wt% epoxidized natural rubber coated NCM622. Figure 20 The EDS element distribution map of 1wt% epoxidized natural rubber coated NCM622 particles was shown, and it could be seen that the C and O elements were uniformly distributed on the NCM622 particles, indicating that the epoxidized natural rubber coated NCM622 particles were successfully prepared.

[0073] Comparative Example 1

[0074] The other conditions were the same as in Example 1, except that uncoated NCM622 positive electrode active material was used.

[0075] From Figure 9 it can be seen that the reversible capacity of the assembled full battery was cycled for 300 cycles, and the capacity was maintained at 100mAh g -1 . Since it has no epoxidized natural rubber coating layer, during the cycle process of the full battery, the positive electrode active material will produce a series of side reactions such as more serious microcracks, transition metal dissolution, lithium-nickel mixing and phase transition from layered to rock salt or disordered spinel structure, which are not conducive to the service life of lithium ion battery, eventually leading to battery failure. Compared with Figure 17 uncoated pure NCM622 in Figure 18The high magnification scanning electron microscope photo of the ion beam cross section of the 1wt% coated NCM622 positive electrode particles after 500 cycles at 1C rate, the protective effect of the coating layer on pure NCM622 can be directly observed.

[0076] Example 2

[0077] The other conditions are the same as example 1, the difference is that the coating solution containing 2.5g epoxidized natural rubber is selected in step 1). In Figure 2 The scanning electron microscope photo of the 0.5wt% epoxidized natural rubber coated NCM622 particles can be observed. From Figure 2 It can be seen that the 0.5wt% epoxidized natural rubber is successfully coated on the surface of NCM622 particles.

[0078] From Figure 10 It can be seen that the reversible capacity of the assembled full cell is cycled for 300 cycles, and the capacity is still maintained at 113mAh g -1 . Figure 6 The charge-discharge curve thereof is shown.

[0079] Example 3

[0080] The difference from example 1 is that the coating solution containing 10g epoxidized natural rubber is selected in step 1). In Figure 4 The scanning electron microscope photo of the 2wt% epoxidized natural rubber coated NCM622 particles can be observed. From Figure 4 It can be seen that the 2wt% epoxidized natural rubber is successfully coated on the surface of NCM622 particles.

[0081] From Figure 12 It can be seen that the reversible capacity of the full cell is cycled for 300 cycles, and the capacity is maintained at 117mAh g -1 , Figure 8 The charge-discharge curve thereof is shown.

[0082] Comparative Example 2

[0083] Referring to the method in example 1, the difference from example 1 is that no vulcanization treatment is performed, and the unvulcanized 1wt% epoxidized natural rubber coated NCM622 is prepared. According to the method in example 1, it is assembled into a battery, activated at a cutoff voltage of 2.5-4.3V and a current density of 0.2C, and the long cycle performance test result at a current density of 0.5C is shown in Figure 22 The results show that the reversible capacity of the battery assembled by the unvulcanized epoxidized natural rubber coated NCM622 is cycled for 300 cycles, and the specific capacity is 116mAh g -1Therefore, the coating layer of the embodiment 1 of the present application is vulcanized, which can more effectively inhibit the volume expansion of the positive active material and the harmful side reaction between the electrode and the electrolyte during the charging and discharging of the lithium battery, and the positive active material coated by the vulcanized coating layer has obviously better cycle stability than the positive active material coated by the unvulcanized coating layer under the condition of 0.5C rate.

[0084] The above describes the embodiments of the present application. However, the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for coating a positive electrode active material with epoxidized natural rubber, characterized by, Comprising the following steps: 1) Take a certain amount of epoxidized natural rubber latex, wash in anhydrous ethanol, then dry, after drying, plasticize in a plasticizer for 30-50 times; Take the dried and plasticized epoxidized natural rubber and add toluene for dissolution, after complete dissolution, add dicumyl peroxide and continue to dissolve; 2) Take the solution prepared in step 1), add positive electrode active material particles, heat and stir, after stirring, perform rotary evaporation treatment; By continuously rotating evaporation, the epoxidized natural rubber is uniformly coated on the surface of the positive electrode particles; 3) Perform vulcanization treatment on the material obtained in step 2); The mass ratio of the positive electrode active material particles added in step 2) to the epoxidized natural rubber in step 1) is 1:(0.01-0.02).

2. The method of claim 1, wherein, The mass ratio of dicumyl peroxide to epoxidized natural rubber in step 1) is (0.001-0.1):

1.

3. The method according to claim 1 or 2, characterized in that, The epoxidation degree of the epoxidized natural rubber in step 1) is 10-60%.

4. The method according to claim 1 or 2, characterized in that, In step 2), the positive electrode active material is a ternary positive electrode active material, lithium iron phosphate, lithium cobaltate, lithium manganate, or a lithium-rich manganese-based positive electrode active material.

5. The method according to claim 1 or 2, characterized in that, In step 2), the heating and stirring is performed at 35-50°C, and the stirring time is 1-12 hours.

6. The method of claim 1 or 2, wherein, After completing the stirring in step 2), ultrasonic treatment is performed for more than 10 minutes.

7. The method according to claim 1 or 2, characterized in that, The vulcanization treatment in step 3) is performed in a flat vulcanization instrument.

8. The method of claim 7, wherein, The vulcanization treatment in step 3) is heating at 100-180°C for 1-30 minutes.

9. The method of claim 1, wherein, The epoxidized natural rubber-coated positive electrode active material is prepared by the following steps: S1) Take a certain amount of epoxidized natural rubber latex, wash in anhydrous ethanol, then dry, after drying, plasticize in a plasticizer for 30-50 times; S2) Take the dried and plasticized epoxidized natural rubber in step 1) and add toluene for dissolution, after complete dissolution, add dicumyl peroxide and continue to dissolve; S3) Place the positive electrode active material in the epoxidized natural rubber solution containing dicumyl peroxide in step S2), stir at 35-50°C, and then ultrasonic treatment; S4) Perform rotary evaporation treatment in a rotary evaporator; then continue to dry the positive electrode active material in a forced air oven and a vacuum oven; S5) Heat the dried positive electrode active material at 100-180°C for more than 1 minute for vulcanization treatment, to obtain the epoxidized natural rubber-coated positive electrode active material containing a network structure; The mass ratio of the positive electrode active material particles added in step S3) to the epoxidized natural rubber in step S2) is 1:(0.01-0.02).

10. The epoxidized natural rubber-coated positive electrode active material prepared by the method of any one of claims 1-9.

11. Use of the epoxidized natural rubber-coated positive electrode active material prepared by the method of any one of claims 1-9 as a lithium battery positive electrode material.

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