In-situ polymerized coating modified ultra-high nickel ternary materials, their preparation methods and applications

Abstract

This invention belongs to the field of battery materials, specifically relating to a method for preparing an in-situ polymerized coated modified ultra-high nickel ternary material. The method involves obtaining a coating solution containing monomer A, monomer B, and additive C; placing the ultra-high nickel ternary material in the coating solution, followed by a first-stage polymerization at temperature T1 and a second-stage polymerization at temperature T2 to obtain the in-situ polymerized coated modified ultra-high nickel ternary material; monomer A is a monomer having the structure of Formula 1; monomer B is obtained by a Michael addition reaction between a polyetheramine and a compound of Formula 2; additive C is a lithium-containing compound that is difficult to dissolve in the electrolyte; wherein the weight ratio of additive C to the total monomers is 0.003–0.02:1; 40℃≤T1<T2≤100℃. This invention also includes the material obtained by the above preparation method and its applications. The material of this invention exhibits excellent fast charging and high-temperature stability.

Description

Technical Field

[0001] This invention belongs to the field of high-energy battery materials technology, specifically relating to an in-situ polymer-modified ultra-high nickel ternary material, its preparation method, and its applications. Background Technology

[0002] Lithium-ion batteries currently dominate the electric vehicle market. High-nickel ternary layered oxides (LiNi) x Co y Mn z O2 (NCM) possesses advantages such as high discharge specific capacity, low cost, and environmental friendliness, and is considered the most advanced cathode material for lithium-ion batteries. Ultra-high nickel cathodes obtained by increasing the nickel content in NCM cathodes can achieve higher energy density in lithium-ion batteries. However, increasing the nickel content exacerbates a series of serious problems in NCM cathodes, such as irreversible structural phase transitions, microcrack formation, and Li-C. + / Ni 2 + Disorders, ultimately leading to a sharp increase in the risk of surface structure degradation and even thermal runaway. The instability of NCM cathode structures is mainly attributed to... Local stresses generated by rapid anisotropic lattice strain during the phase transition. These local stresses, released along grain boundaries, lead to mechanical fatigue and microcrack formation in the bulk structure. The electrolyte then permeates into the cathode particles and reacts with the exposed fresh surface, initiating a continuous irreversible phase transition and slowing down lithium-ion intercalation kinetics. Oxygen vacancies formed by lattice oxygen escape ultimately lead to Li-ion... + / Ni 2+ Disorders, dissolution of transition metals, and formation of rock salt phases.

[0003] Many NCM cathode modification strategies have been developed, such as elemental doping, surface coating, and core-shell structure design. Among these, surface coating is an effective optimization method to directly improve the surface chemical and structural stability of cathode materials. Surface coatings are expected to reduce side reactions between the cathode and the electrolyte and mitigate the dissolution of transition metals (TM) by hydrofluoric acid (HF) erosion. However, conventional metal oxide materials hinder lithium-ion transport and lack the strong mechanical properties to cope with the considerable volume changes that occur during the H2-H3 transition of the cathode, thus failing to maintain the integrity of the coating layer and the cathode body. Therefore, developing a coating layer that can effectively prevent electrolyte erosion, accelerate lithium-ion transport, and possess certain mechanical stability to maintain the stability of the coating layer itself and the cathode structure during long-term cycling is of great significance for expanding the application of ultra-high nickel ternary cathode materials. Summary of the Invention

[0004] To overcome the interface and structural stability problems of ultra-high nickel cathodes, the present invention aims to provide a method for preparing in-situ polymerized coating modified ultra-high nickel ternary materials, which aims to prepare modified high nickel cathode active materials with excellent interface stability, resistance to electrolyte erosion, and good fast charging and stability.

[0005] The second objective of this invention is to provide an in-situ polymerized coated modified ultra-high nickel ternary material prepared by the aforementioned method and its applications.

[0006] A third objective of this invention is to provide a battery comprising the aforementioned in-situ polymerized coated modified ultra-high nickel ternary material.

[0007] Due to surface Ni 4+ Excessive nickel content leads to an unstable chemical environment on the surface of the high-nickel cathode, hindering the development of highly catalytically active Ni. 4+ This can cause the organic electrolyte system to decompose, producing gases such as CO2, CO, and H2. Simultaneously, because the surface of a high-nickel cathode typically has more residual lithium, this residual lithium reacts with the electrolyte to form a thicker CEI layer, increasing the lithium-ion transport path and slowing down the lithium-ion transport rate. To address this problem, this invention, after in-depth research, provides the following solution:

[0008] A method for preparing an in-situ polymerized coated modified ultra-high nickel ternary material involves obtaining a coating solution containing monomer A, monomer B, and additive C; placing the ultra-high nickel ternary material in the coating solution; then performing a first-stage polymerization at temperature T1 and a second-stage polymerization at temperature T2 to obtain the in-situ polymerized coated modified ultra-high nickel ternary material.

[0009] The monomer A is a monomer having the structure of Formula 1;

[0010]

[0011] R1 can be a saturated carbon chain, a saturated carbon ring, an unsaturated carbon ring, a carbon chain with a carbon ring, or a carbon chain with an unsaturated carbon ring.

[0012] The monomer B is obtained by Michael addition reaction of polyetheramine and compound of formula 2;

[0013]

[0014] R2 is a C1 to C6 alkyl group;

[0015] Additive C is a lithium-containing compound that is difficult to dissolve in conventional electrolytes; wherein, the weight ratio of the total monomers of additive C is 0.003 to 0.02:1.

[0016] 40℃≤T1<T2≤100℃.

[0017] This invention innovatively employs monomers A and B, along with additive C, to perform a two-stage in-situ polymerization of ultra-high nickel ternary materials. This allows for the in-situ formation of a coating layer on the surface of the ultra-high nickel ternary material that exhibits interfacial stability while also providing excellent mechanical properties and ion conductivity. Research in this invention demonstrates that the material prepared by this method possesses a stable electrolyte / cathode interface and exhibits excellent fast-charging and high-temperature cycling stability.

[0018] In this invention, in Formula 1, R1 is a saturated carbon chain of C1 to C10, a cyclohexane ring, a cyclohexane ring with a carbon chain, or a benzene ring.

[0019] Preferably, the monomer A is at least one of formula 1-a, formula 1-b, and formula 1-c;

[0020]

[0021] Preferably, monomer A is a composite monomer of formula 1-a and formula 1-c; further, the weight ratio of the two is 0.5 to 2:1. Research in this invention shows that the preferred monomer A can synergistically enhance the fast charging and high-temperature stability of the material.

[0022] In this invention, the polyetheramine can be a conventional polyetheramine in the industry. For example, it can be a conventional polyether polymer with a -NH2 terminal. The molecular weight of the polyetheramine is not particularly required; for example, it can be 200–2500, more preferably 350–450. Specifically, it can be P108071 polyetheramine D-230, P108072 polyetheramine D-400, or P108073 polyetheramine D-2000 provided by Aladdin Reagents.

[0023] In this invention, the molar ratio of -NCO in monomer A to -NH2 in monomer B is 0.9 to 1.1:1.

[0024] In this invention, the additive C includes at least one of lithium difluorophosphate, lithium bis(oxalato)borate, lithium trifluoromethanesulfonate, lithium difluoro(oxalato)borate, and lithium difluoro(bis(oxalato)borate).

[0025] Preferably, additive C is a composite of lithium difluorophosphate and lithium difluorooxalate borate; further, the weight ratio of lithium difluorophosphate to lithium difluorooxalate borate is 0.5 to 2:1. This invention demonstrates that the preferred additive C can synergistically enhance the fast charging and high-temperature stability of the material.

[0026] Preferably, the weight ratio of additive C to total monomers is 0.005 to 0.01:1.

[0027] Preferably, the coating solution is 1 to 10% of the weight of the ultra-high nickel ternary material.

[0028] The mixture of ultra-high nickel ternary material and coating liquid also contains a dispersant, which includes at least one of acetone and ethanol.

[0029] Preferably, the volume weight ratio of the dispersant to ultra-high nickel ternary material is 10-30 ml / g.

[0030] In this invention, the high-nickel ternary material is an ultra-high-nickel ternary material with a nickel content of more than 70 mol% of the total transition metals; preferably, it is at least one of 8-series ultra-high-nickel material and 9-series ultra-high-nickel material; further, it can be at least one of NCM811 and NCM90.

[0031] In this invention, ultra-high nickel ternary materials are encapsulated in a coating solution, followed by in-situ polymerization of the two stages. This achieves synergy, optimizes the structure of the in-situ polymerization, improves its interface and mechanical properties, further enhances its active ion transport capability, and thus synergistically improves its fast charging and long-cycle stability.

[0032] In this invention, the temperature T1 is 60–80°C;

[0033] Preferably, the holding time t1 at temperature T1 is 0.5 to 1.5 hours;

[0034] Preferably, the temperature T2 is 70–90°C;

[0035] Preferably, the heat preservation time t2 at temperature T2 is 6 to 12 hours;

[0036] In this invention, the preparation of the coating liquid and the first and second polymerization stages can be carried out under an inert atmosphere; the inert atmosphere is, for example, at least one of nitrogen and argon.

[0037] The present invention also provides an in-situ polymerized coated modified ultra-high nickel ternary material prepared by the aforementioned preparation method.

[0038] The preparation method described in this invention can endow the prepared material with special physicochemical properties, and the material prepared by the method has both excellent fast charging and long-range cycling performance.

[0039] The present invention also provides an application of the aforementioned in-situ polymerized coating modified ultra-high nickel ternary material, which is combined with a negative electrode, a separator and an electrolyte to assemble a lithium-ion battery.

[0040] The application described in this invention allows the in-situ polymerized coated modified ultra-high nickel ternary material to be used as a positive electrode active material, thereby producing the desired lithium-ion battery based on existing conventional principles and methods.

[0041] The present invention also provides a composite cathode material, comprising a cathode active material, a conductive agent and a binder, wherein the cathode active material comprises the in-situ polymerized coated modified ultra-high nickel ternary material described in the present invention as the cathode active material.

[0042] In the positive electrode active material of the present invention, the content of the in-situ polymerized coated modified ultra-high nickel ternary material used as the positive electrode active material is above 50 wt.%, and more specifically above 80 wt.%.

[0043] In this invention, the conductive agent and the binder can both be conventional components in the industry.

[0044] In this invention, the weight ratio of the positive electrode active material, the conductive agent, and the binder in the composite positive electrode material can be 7-9.5:0.1-1.5:0.1-1.5.

[0045] The present invention also provides a positive electrode for a lithium-ion battery, comprising a current collector and a positive electrode material composited on the surface of the current collector, wherein the positive electrode material is the positive electrode active material described in the present invention.

[0046] The present invention also provides a lithium-ion battery, including a cell and an electrolyte for soaking the cell, wherein the cell includes a positive electrode, a separator and a negative electrode sequentially laminated, and the positive electrode is laminated with an in-situ polymerized modified ultra-high nickel ternary material prepared by the preparation method.

[0047] Beneficial effects

[0048] This invention utilizes monomers A and B, along with additive C, to perform two-stage in-situ polymerization on ultra-high nickel ternary materials. This optimizes the in-situ polymerization network structure, improves the interface structure, mechanical properties, and ion conductivity, and enhances its tolerance in electrolytes. Consequently, it synergistically improves the fast-charging and high-temperature cycling stability of these materials.

[0049] This invention also shows that optimizing and controlling the composition of monomer A, monomer B, and additive C, as well as the in-situ polymerization process, can further optimize the polymerization network and interface structure, and further improve its fast charging and high-temperature cycling stability. Attached Figure Description

[0050] Figure 1 The XRD patterns are of the samples prepared in Example 1, Example 2A, Example 3A and Example 4A.

[0051] Figure 2 SEM images of the samples prepared in Example 1, Example 2A, Example 3A and Example 4A.

[0052] Figure 3 This is a TEM image of Example 1 group.

[0053] Figure 4 This is a 4C / 100-cycle diagram for Example 1;

[0054] Figure 5 The diagram shows the 50℃ / 100 cycles of Example 1. Detailed Implementation

[0055] The following embodiments are intended to further illustrate the present invention, and are not intended to limit the scope of protection of the present invention. All materials involved in the following embodiments are commercially available.

[0056] The polyetheramine described herein can be, for example, a component of formula 3. It can be obtained using conventional methods. In this invention, the polyetheramine can be purchased from Aladdin Company.

[0057] In this invention, monomer B can be obtained by a conventional Michael addition reaction of polyetheramine and formula 2. For example, optionally, polyetheramine is stirred under a nitrogen atmosphere, and then formula 2 is slowly added to polyetheramine at 20-50°C. After the addition is complete, the temperature is raised to 90-100°C to carry out the Michael addition reaction (reaction time, for example, 12-20 h) to obtain monomer B, wherein the molar ratio of polyetheramine (calculated as -NH2) to formula 2 is 1:1-3.

[0058] As an alternative, monomer B1, as described in the following example, is obtained by Michael addition reaction of formula 3A (polyetheramine D-230 with brand name P108071 and molecular weight of 230) and formula 2-A (compound of formula 2 with R2 being ethyl).

[0059] As an alternative, monomer B2, as described in the following example, is obtained by Michael addition reaction of formula 3B (polyetheramine D-400 with brand name P108072 and molecular weight of 400) and formula 2-A (a compound of formula 2 with R2 being ethyl).

[0060] As an alternative, the monomer B3 described in the following example is obtained by Michael addition reaction of formula 3C (polyetheramine D-2000 with brand name P108073 and molecular weight of 2000) and formula 2-A (compound of formula 2 with R2 being ethyl).

[0061] Example 1

[0062] (1) Mix 2g of monomer A (Formula 1-a) and monomer B (in this case, monomer B1) in a 1:1 molar ratio of -NCO and -NH2 contained therein, and add 0.01g of additive C (lithium difluorophosphate). Stir the mixture together at 30°C and 100rpm in a magnetic stirrer for 1h to obtain the mixture. Stirring is carried out under an argon atmosphere.

[0063] (2) 2g of 9-series ultra-high nickel material NCM90 was dispersed in 25ml of acetone, and then 0.02g of the mixture in step (1) was added. After mixing, the mixture was preheated at temperature T1 (60℃) for t1 (0.5h), and then preheated at temperature T2 (80℃) for t2 (6h) to obtain in-situ coated cathode material.

[0064] The positive electrode material obtained in Example 1 was configured into a positive electrode sheet according to the ratio of positive active material: PVDF: super P of 8:1:1, and assembled into a 2016 type button lithium-ion battery (the separator is a PP separator, and the electrolyte is 1M concentration LiTFSI lithium salt + (DOL:DME = 1:1 volume ratio solvent)). Charge and discharge tests were conducted in the voltage range of 3.0-4.3V, and a lithium metal sheet was used as the negative electrode of the battery.

[0065] High-rate testing: The test was conducted at a high rate of 4C at a temperature of 30℃. The battery was cycled at 4.0C, with 200mA / g at 1C. The test conditions were as follows: the battery was first activated at 0.1C for 5 cycles, then at 0.5C for 2 cycles, and then cycled at 4.0C and 30℃ for 100 cycles. The test results are shown in Table 1.

[0066] High-temperature test: The test was conducted at a high temperature of 50℃. The battery was cycled at 1.0C (200 mA / g). The test conditions were as follows: the battery was first activated at 0.1C for 5 cycles, then activated at 0.5C for 2 cycles, and then cycled 100 times at 1.0C and 50℃. The test results are shown in Table 2.

[0067] Example 2

[0068] Compared to Example 1, the only difference is that monomer A is changed, and the experimental groups are as follows:

[0069] Group A: Monomer A is formula 1-b;

[0070] Group B: Monomer A is formula 1-c;

[0071] Group C: Monomer A is a combination of formula 1-a and 1-c in equal weight proportions;

[0072] Control group A: Monomer A was replaced with

[0073] All other operations and parameters are the same as in Example 1.

[0074] Example 3

[0075] Compared to Example 1, the only difference is that monomer B was changed, and the experimental groups were as follows:

[0076] Group A: Replace monomer B with monomer B2;

[0077] Group B: Replace monomer B with monomer B3;

[0078] Control group A: Monomer B is pentamethylenediamine;

[0079] All other operations and parameters are the same as in Example 1.

[0080] Example 4

[0081] Compared with Example 1, the only difference is that additive C is changed; all other operations and parameters are the same as in Example 1. The experimental groups are as follows:

[0082] Group A: Additive C is lithium difluorobis(oxalato)borate;

[0083] Group B: Additive C is lithium difluorooxalate borate.

[0084] Group C: Additive C is a weight combination of lithium difluorophosphate and lithium difluorooxalate borate.

[0085] Control group A: Additive C was replaced with an equal amount of lithium hexafluorophosphate;

[0086] Control group B: Additive C was replaced with an equal amount of lithium bis(trifluoromethanesulfonylimide).

[0087] All other operations and parameters are the same as in Example 1.

[0088] Example 5

[0089] Compared to Example 1, the only difference is that the weight ratio of additive C to total monomers was changed, and the experimental groups were as follows:

[0090] Group A: The weight ratio of additive C to total monomers is 0.01:1;

[0091] Group B: The weight ratio of additive C to total monomers is 0.015:1;

[0092] Control group A: The amount of additive C added was 0;

[0093] All other operations and parameters are the same as in Example 1.

[0094] Example 6

[0095] Compared with Example 1, the only difference is that the polymerization conditions are changed: T1 is 70°C and t1 is 1.0H; T2 is 85°C and t2 is 8H. All other operations and parameters are the same as in Example 1.

[0096] Example 7

[0097] Compared with Example 1, the only difference is that the positive electrode active material is changed to NCM811, and all other operations and parameters are the same as in Example 1.

[0098] Comparative Example 1

[0099] Compared with Example 1, the only difference is that no in-situ coating modification treatment was performed. That is, the mixture in step 1 was directly preheated at temperature T1 (60°C) for t1 (0.5h), and then reacted at temperature T2 (80°C) for t2 (6h) to obtain product a. Then, 0.02g of product a was mixed with 25ml of acetone solution containing 2g of 9-series ultra-high nickel material NCM90. After mixing evenly, the acetone was allowed to evaporate to obtain the active material.

[0100] All other operations and parameters are the same as in Example 1, and the results are shown in Table 1.

[0101] Comparative Example 2

[0102] Compared with Example 1, the only difference is that in step 1, the coating solution lacks additive C, and the solution containing monomers A and B is preheated at temperature T1 (60°C) for t1 (0.5 h), and then reacted at temperature T2 (80°C) for t2 (6 h) to obtain product b.

[0103] In step 2, 2g of NCM90, 0.02g of product b and 0.01g of additive C are mixed and slurried in 25mL of acetone, and then the acetone is removed to obtain the active material.

[0104] All other operations and parameters are the same as in Example 1, and the results are shown in Table 1.

[0105] Comparative Example 3

[0106] Compared with Example 1, the only difference is that polymerization is carried out at a single temperature T1, that is, the temperature of temperature T2 is set to be the same as that of temperature T1. All other operations and parameters are the same as in Example 1.

[0107] Comparative Example 4

[0108] Compared with Example 1, the only difference is that polymerization is carried out at a single temperature T2, that is, the temperature T1 is set to be the same as the temperature T2. All other operations and parameters are the same as in Example 1.

[0109] The positive electrode active materials obtained in Examples 1, 2-A, 3-A, and 4-A were tested and analyzed using X-ray diffraction (XRD), and their XRD patterns were obtained, as shown below. Figure 1 As shown. By Figure 1 It can be seen that the coated material obtained by the coating modification strategy adopted in this invention still has the characteristic peaks of standard NCM90 material. This indicates that the modification strategy does not damage the ultra-high nickel cathode structure with poor stability due to high nickel content. The coating material and coating method are mild and effective.

[0110] The cathode materials obtained in Example 1, Example 2-A, Example 3-A, and Example 4-A were tested and analyzed using scanning electron microscopy (SEM), and their SEM images were obtained, as shown below. Figure 2 As shown in the figure, all samples have a perfect spherical shape.

[0111] Combination Figure 3 An amorphous layer can be observed on the surface of Example 1, which is attributed to the polymer coating layer.

[0112] Table 1. Comparison of electrochemical performance of the cathode materials prepared in the examples and comparative examples (tested at 30°C, first charge-discharge at 0.1C, followed by cycling at 4.0C).

[0113]

[0114]

[0115] Table 2 Comparison of electrochemical performance of the cathode materials prepared in the examples and comparative examples (tested at 50°C, first charge-discharge at 0.1C, followed by cycling at 1.0C).

[0116]

[0117]

[0118] As can be seen from the present invention, the method described in the present invention can achieve excellent performance, and under preferred conditions, even better performance can be obtained.

Claims

1. A method for preparing an in-situ polymerized coated ultra-high nickel ternary material, characterized in that, A coating solution containing monomer A, monomer B and additive C is obtained; an ultra-high nickel ternary material is placed in the coating solution, and then a first-stage polymerization is carried out at temperature T1, followed by a second-stage polymerization at temperature T2, to obtain the in-situ polymerized coated modified ultra-high nickel ternary material. The monomer A is a monomer having the structure of Formula 1; Formula 1 R1 can be a saturated carbon chain, a saturated carbon ring, an unsaturated carbon ring, a carbon chain with a carbon ring, or a carbon chain with an unsaturated carbon ring. The monomer B is obtained by Michael addition reaction of polyetheramine and compound of formula 2; Formula 2 R2 is a C1-C6 alkyl group; Additive C is a lithium-containing compound that is difficult to dissolve in the electrolyte; wherein, the weight ratio of additive C to the total monomer is 0.003~0.02:

1. 40℃≤T1<T2≤100℃.

2. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary materials as described in claim 1, characterized in that, In Formula 1, R1 is a saturated carbon chain of C1 to C10, a cyclohexane ring, a cyclohexane ring with a carbon chain, or a benzene ring.

3. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 1, characterized in that, The monomer A is at least one of formula 1-a, formula 1-b, and formula 1-c; Formula 1-a Formula 1-b Equation 1-c.

4. The preparation method of the in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 3, characterized in that, Monomer A is a composite monomer of formula 1-a and formula 1-c.

5. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 1, characterized in that, The molar ratio of -NCO in monomer A to -NH2 in monomer B is 0.9~1.1:

1.

6. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 1, characterized in that, The additive C includes at least one of lithium difluorophosphate, lithium bis(oxalato)borate, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, and lithium difluorobis(oxalato)borate.

7. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 6, characterized in that, Additive C is a composite additive of lithium difluorophosphate and lithium difluorooxalate borate.

8. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 6, characterized in that, Additive C has a total monomer weight ratio of 0.005~0.01:

1.

9. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 1, characterized in that, The coating solution is 1 to 10% of the weight of the ultra-high nickel ternary material.

10. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 1, characterized in that, The mixture of ultra-high nickel ternary material and coating liquid also contains a dispersant, which includes at least one of acetone and ethanol.

11. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 10, characterized in that, The dispersant is an ultra-high nickel ternary material with a volume weight ratio of 10~30ml / g.

12. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 1, characterized in that, High-nickel ternary materials are ultra-high-nickel ternary materials in which the nickel content accounts for more than 70 mol% of the total transition metals.

13. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 12, characterized in that, High-nickel ternary materials are at least one of the 8-series ultra-high nickel materials and the 9-series ultra-high nickel materials.

14. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 1, characterized in that, The temperature T1 is 60~80℃.

15. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 1, characterized in that, The heat preservation time t1 at temperature T1 is 0.5~1.5h.

16. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 1, characterized in that, The temperature T2 is 70~90℃.

17. The method for preparing in-situ polymerized coated modified ultra-high nickel ternary material as described in claim 1, characterized in that, The heat preservation time t2 at temperature T2 is 6~12h.

18. An in-situ polymerized coated modified ultra-high nickel ternary material prepared by the preparation method according to any one of claims 1 to 17.

19. An application of the in-situ polymerized coated modified ultra-high nickel ternary material according to claim 18, characterized in that, By combining it with the negative electrode, separator, and electrolyte, a lithium-ion battery is obtained.

20. A lithium-ion battery, comprising a cell and an electrolyte soaking the cell, wherein, The battery cell comprises a positive electrode, a separator, and a negative electrode sequentially composited, characterized in that the positive electrode contains an in-situ polymerized coated modified ultra-high nickel ternary material prepared by the preparation method according to any one of claims 1 to 17.

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