Preparation method of anode material for improving cycle performance of sodium battery

Abstract

The application discloses a preparation method of a negative electrode material for improving cycle performance of a sodium battery, and relates to the technical field of battery preparation. The method comprises the following steps: a sodium battery negative electrode material is prepared through ball milling calcination and hydrothermal synthesis, and the prepared negative electrode material is mixed with an adhesive and modified carbon black, stirred uniformly, coated on an aluminum foil with a thickness of 12-15 mu m, dried, and then rolled at 120-150 DEG C for 12-15 h to obtain a negative electrode sheet. The sodium battery negative electrode material is prepared through ball milling calcination and hydrothermal synthesis, and the adhesive with a three-dimensional cross-linked structure is obtained through modification, so that the mechanical performance and electrochemical stability of the adhesive are remarkably improved. In addition, in order to improve the compatibility of the conductive carbon black and the adhesive, polyamide acid segments are introduced on the surface of the conductive carbon black, so that the conductivity and structural stability of the electrode are enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery preparation, in particular to a preparation method of a negative electrode material for improving the cycle performance of a sodium battery. BACKGROUND

[0002] With the increasing demand for renewable energy worldwide, the scarcity of traditional energy and the limited nature of lithium resources have become pressing problems. To address these challenges, sodium battery technology, which is less costly and more abundant in resources, has gradually become a research hotspot in the academic community. Unlike lithium batteries, the negative electrode material of sodium batteries needs to have a larger interlayer spacing and a lower volume expansion coefficient to accommodate the insertion and extraction of sodium ions. Red phosphorus, as a highly potential negative electrode material for sodium-ion batteries, has a theoretical capacity of 2596mAh·g⁻¹, showing significant advantages. However, red phosphorus faces two major problems in practical applications: first, its poor electrical conductivity limits the rate of electrochemical reactions; second, during the charging and discharging process, red phosphorus undergoes significant volume changes, leading to the destruction of the electrode structure and rapid capacity decay.

[0003] In addition, the battery binders in the prior art have significant defects, especially in terms of cycle performance. The mechanical properties and electrochemical stability of traditional binders are poor, and they cannot effectively inhibit the volume expansion of electrode materials during the charging and discharging process, leading to gradual destruction of the electrode structure, accelerated capacity decay, and significantly shortened cycle life. At the same time, the compatibility between the conductive agent and the binder is poor, which not only reduces the electrical conductivity of the electrode, but also affects the overall structural stability of the electrode, further exacerbating the deterioration of the cycle performance.

[0004] In summary, in order to solve the above problems, the present application provides a negative electrode material for improving the cycle performance of a sodium battery. SUMMARY

[0005] The present application aims to provide a preparation method of a negative electrode material for improving the cycle performance of a sodium battery to solve the problems in the prior art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] A preparation method of a negative electrode material for improving the cycle performance of a sodium battery, comprising the following steps:

[0008] Step 1: mechanically mix red phosphorus and sulfurized polyacrylonitrile, then perform ball milling treatment, and then transfer into a tube furnace, introduce argon gas, calcine at 300-350℃ for 10-12h to obtain a red phosphorus-sulfurized polyacrylonitrile sample;

[0009] Step 2: Dissolve the red phosphorus-sulfurized polyacrylonitrile sample in pure water, then add a small amount of MXene, stir until uniform, bake at 180-200℃ for 16-18h, and finally obtain the modified negative electrode material after filtration, washing, and drying.

[0010] More preferably, the mass ratio of red phosphorus to sulfurized polyacrylonitrile is (60-65):1; and the mass ratio of red phosphorus to small MXene is (20-22):1.

[0011] More preferably, during the baking process, the heating rate is 40-45℃ / min, and the annealing rate is 10-15℃ / min.

[0012] A method for preparing a negative electrode sheet, comprising the following steps: mixing the above-mentioned negative electrode material with an adhesive and modified carbon black, stirring until uniform, then coating on a 12-15μm aluminum foil, drying and rolling, drying at 120-150℃ for 12-15h to obtain a negative electrode sheet.

[0013] More preferably, the mass ratio of the negative electrode material, adhesive, and modified carbon black is (8-9):1:1.

[0014] More preferably, the preparation process of the adhesive is as follows:

[0015] S1: Under a protective atmosphere, add diamino diphenyl ether to N-methyl pyrrolidone, stir several times until completely dissolved, then add 4,4'-oxydiphthalic anhydride in batches, react at 0-5℃ for 4-6h to obtain anhydride-terminated polyamic acid;

[0016] S2: Mix 2,4-diaminobutyric acid, anhydrous sodium carbonate, and deionized water, mechanically stir until uniform, slowly add cyanuric chloride solution at 0-5℃, dropwise complete within 2-3h, continue stirring for 6-8h, filter, wash, and recrystallize to obtain triaminocarboxylic acid triazine;

[0017] S3: Add triaminocarboxylic acid triazine to N-methyl pyrrolidone, dissolve completely, then slowly add to the anhydride-terminated polyamic acid at 0-5℃, react for 3-4h, after the reaction is complete, continue to add N-methyl pyrrolidone for dilution to obtain the adhesive.

[0018] More preferably, the anhydride-terminated polyamic acid comprises the following substances: 5-8 parts by weight of diamino diphenyl ether, 40-50 parts by weight of N-methyl pyrrolidone, and 7.5-12 parts by weight of 4,4'-oxydiphthalic anhydride.

[0019] The triaminocarboxylic acid triazine comprises the following components: 35-40 parts of 2,4-diaminobutyric acid, 40-42 parts of anhydrous sodium carbonate, 300-320 parts of deionized water, and 18-20 parts of cyanuric chloride solution; wherein the mass fraction of the cyanuric chloride solution is 8-10 wt%, and the solvent is dioxane;

[0020] The adhesive raw material comprises the following components: 0.5-0.8 parts of triaminocarboxylic acid triazine, 50-55 parts of N-methylpyrrolidone, and 30-35 parts of acid anhydride-terminated polyamide acid; wherein the solid content of the adhesive is 6-8 wt%.

[0021] More preferably, the preparation process of the modified carbon black is as follows: (1) uniformly dispersing conductive carbon black in ethanol, adjusting the pH to 6-6.5, adding gamma-aminopropyl triethoxysilane dropwise, heating to 60-70 DEG C, and reacting for 3-4 h to obtain aminated carbon black; (2) mixing the aminated carbon black with acid anhydride-terminated polyamide acid, and reacting for 4-5 h at 0-5 DEG C to obtain modified carbon black.

[0022] More preferably, the mass ratio of the conductive carbon black to gamma-aminopropyl triethoxysilane is (9-10):1; and the mass ratio of the aminated carbon black to acid anhydride-terminated polyamide acid is 1:(2-3).

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] The sodium battery negative electrode material is prepared by ball milling and calcination and hydrothermal synthesis, and a binder with a three-dimensional cross-linked structure is obtained by modification, which significantly improves the mechanical properties and electrochemical stability; in addition, in order to improve the compatibility of conductive carbon black and the binder, polyamide acid segments are introduced on the surface of the conductive carbon black, which enhances the conductivity and structural stability of the electrode.

[0025] Firstly, the scheme forms P-S bonds between red phosphorus and sulfidized polyacrylonitrile through ball milling and calcination, significantly improves the conductivity of red phosphorus, and constructs a stable electrode structure, effectively alleviates the volume expansion problem in the charging and discharging process, and improves the cycle stability; further, the calcined sample is compounded with few-layer MXene through hydrothermal synthesis to form P-C bonds, which enhances the contact properties of red phosphorus and MXene, stabilizes the material structure, and realizes high-stable cycle performance; in addition, the large interlayer spacing of MXene provides a fast channel for sodium ion transmission, further improving the kinetic performance of the electrode.

[0026] Secondly, by reacting triaminocarboxylic acid triazine with anhydride-terminated polyamic acid, a binder system with three-dimensional cross-linked structure is formed, which significantly improves its performance. The three-dimensional cross-linked structure endows the binder with excellent mechanical strength and flexibility, effectively inhibits the volume expansion of the electrode material during charging and discharging, and reduces the pulverization and shedding. At the same time, the obtained binder system contains more carboxyl groups, which effectively enhances the interfacial bonding force between the binder and the electrode material, improves the structural stability of the electrode, and helps to maintain the integrity of the electrode during long cycle process. In addition, the three-dimensional network structure of the binder provides a continuous channel for ion transport, optimizing the electrode kinetics performance;

[0027] Thirdly, by introducing polyamic acid segments on the surface of conductive carbon black, the interfacial bonding between conductive carbon black and binder is improved, the interfacial defects are reduced, and the overall structural stability of the electrode is improved. At the same time, the introduction of polyamic acid segments makes the conductive carbon black more uniformly dispersed in the electrode material, forming a continuous and efficient conductive network, which improves the conductivity and charge transport efficiency of the electrode. DETAILED DESCRIPTION

[0028] Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0029] It should be noted that the following parts are parts by weight, and there is no special restriction on the purchase manufacturers of all raw materials involved in the present application. Exemplarily, in the following examples, the diamine-based diphenyl ether has a CAS of 101-80-4; 4,4'-oxybisphthalic anhydride has a CAS of 1823-59-2; 2,4-diaminobutyric acid has a CAS of 305-62-4; and cyanuric chloride has a CAS of 108-77-0.

[0030] Example 1: A preparation method of a negative electrode material for improving the cycle performance of a sodium battery, comprising the following steps:

[0031] Step 1: Red phosphorus and sulfurized polyacrylonitrile are mechanically mixed and then subjected to ball milling treatment, and then transferred into a tube furnace, argon is introduced, calcined at 300℃ for 10h, and a red phosphorus-sulfurized polyacrylonitrile sample is obtained;

[0032] Step 2: The red phosphorus-sulfurized polyacrylonitrile sample is dissolved in pure water, then a few-layer MXene is added, stirred uniformly, baked at 180℃ for 16h, and finally filtered, washed and dried to obtain a modified negative electrode material; wherein the mass ratio of red phosphorus to sulfurized polyacrylonitrile is 65:1; the mass ratio of red phosphorus to few-layer MXene is 22:1;

[0033] A preparation method of a negative electrode sheet, comprising the following steps: mixing the above-mentioned negative electrode material with an adhesive and modified carbon black, stirring uniformly, then coating on a 12 mu m aluminum foil, drying and rolling after drying, drying at 120 DEG C for 12 hours to obtain the negative electrode sheet; the mass ratio of the negative electrode material, the adhesive and the modified carbon black is 8:1:1;

[0034] The preparation process of the adhesive is as follows:

[0035] S1: 5 parts of diamino diphenyl ether are added to 40 parts of N-methyl pyrrolidone under nitrogen, and stirred multiple times until completely dissolved, then 7.5 parts of 4,4'-oxydiphthalic anhydride are added in batches, reacted at 0 DEG C for 4 hours to obtain an anhydride-terminated polyamic acid;

[0036] S2: 35 parts of 2,4-diaminobutyric acid, 40 parts of anhydrous sodium carbonate and 300 parts of deionized water are mixed and mechanically stirred uniformly, 18 parts of cyanuric chloride solution is slowly added dropwise at 0-5 DEG C, and the addition is completed within 2 hours, and stirring is continued for 6 hours, then filtered, washed and recrystallized to obtain triaminocarboxylic acid triazine;

[0037] S3: 0.5 parts of triaminocarboxylic acid triazine is added to 45 parts of N-methyl pyrrolidone, and after being fully dissolved, it is slowly added dropwise into 30 parts of anhydride-terminated polyamic acid at 0 DEG C, and reacted for 3 hours, then 6 parts of N-methyl pyrrolidone is continuously added for dilution to obtain the adhesive;

[0038] The preparation process of the modified carbon black is as follows:

[0039] (1) 9 parts of conductive carbon black is uniformly dispersed in ethanol, the pH is adjusted to 6, 1 part of gamma-aminopropyl triethoxysilane is added dropwise, the temperature is raised to 60 DEG C, and the reaction is carried out for 3 hours to obtain aminated carbon black; (2) 1 part of aminated carbon black is mixed with 2 parts of anhydride-terminated polyamic acid, and the reaction is carried out at 0 DEG C for 4 hours to obtain the modified carbon black.

[0040] Example 2: substantially the same as example 1, the difference is that the mass ratio of red phosphorus material to sulfurized polyacrylonitrile is 55:1.

[0041] Example 3: substantially the same as example 1, the difference is that the mass ratio of red phosphorus material to sulfurized polyacrylonitrile is 60:1.

[0042] Example 4: substantially the same as example 1, the difference is that the mass ratio of red phosphorus material to sulfurized polyacrylonitrile is 70:1.

[0043] Example 5: substantially the same as example 1, the difference is that the mass ratio of red phosphorus material to sulfurized polyacrylonitrile is 75:1.

[0044] Example 6: substantially the same as Example 1, except that the mass ratio of red phosphorus material to few-layer MXene is 18:1.

[0045] Example 7: substantially the same as Example 1, except that the mass ratio of red phosphorus material to few-layer MXene is 20:1.

[0046] Example 8: substantially the same as Example 1, except that the mass ratio of red phosphorus material to few-layer MXene is 24:1.

[0047] Example 9: substantially the same as Example 1, except that the mass ratio of red phosphorus material to few-layer MXene is 26:1.

[0048] Comparative Example 1: substantially the same as Example 1, except that no sulfurized polyacrylonitrile is introduced.

[0049] Comparative Example 2: substantially the same as Example 1, except that no few-layer MXene material is introduced.

[0050] Comparative Example 3: substantially the same as Example 1, except that a traditional red phosphorus material is used as the positive electrode material.

[0051] Comparative Example 4: substantially the same as Example 1, except that PVDF is used, and the conductive carbon black is not modified, as follows:

[0052] Step 1: red phosphorus and sulfurized polyacrylonitrile are mechanically mixed and then ball milled, and then transferred into a tube furnace, argon is introduced, calcined at 300°C for 10h, to obtain a red phosphorus-sulfurized polyacrylonitrile sample;

[0053] Step 2: the red phosphorus-sulfurized polyacrylonitrile sample is dissolved in pure water, then few-layer MXene is added, stirred uniformly, baked at 180°C for 16h, and finally filtered, washed, and dried to obtain a modified negative electrode material; wherein the mass ratio of red phosphorus to sulfurized polyacrylonitrile is 65:1; the mass ratio of red phosphorus to few-layer MXene is 22:1;

[0054] A method for preparing a negative electrode sheet, comprising the following steps: 0.5 parts of white powder PVDF (the molecular weight of PVDF is 500,000) is weighed and dissolved in 15 parts of N-methyl pyrrolidone, and stirred uniformly, the above-mentioned negative electrode material and conductive carbon black are added and stirred uniformly, then coated on a 12μm aluminum foil, dried and rolled, dried at 100°C for 2h, to obtain a negative electrode sheet; the mass ratio of negative electrode material, adhesive, and conductive agent is 8:1:1.

[0055] Comparative Example 5: substantially the same as Example 1, except that the conductive carbon black is not modified, as follows:

[0056] Step 1: red phosphorus and sulfidized polyacrylonitrile are mechanically mixed and then ball milled, and then transferred into a tube furnace, argon is introduced, calcined at 300 DEG C for 10h, to obtain a red phosphorus-sulfidized polyacrylonitrile sample;

[0057] Step 2: the red phosphorus-sulfidized polyacrylonitrile sample is dissolved in pure water, then a few-layer MXene is added, stirred uniformly, baked at 180 DEG C for 16h, and finally filtered, washed and dried to obtain a modified negative electrode material; wherein the mass ratio of red phosphorus and sulfidized polyacrylonitrile is 65:1; the mass ratio of red phosphorus and few-layer MXene is 22:1;

[0058] A preparation method of a negative electrode sheet, comprising the following steps: mixing the above-mentioned negative electrode material with an adhesive and conductive carbon black, stirring uniformly, then coating on a 12 mu m aluminum foil, drying and rolling, drying at 120 DEG C for 12h to obtain a negative electrode sheet; the mass ratio of negative electrode material, adhesive and conductive carbon black is 8:1:1;

[0059] The preparation process of the adhesive is as follows:

[0060] S1: 5 parts of diamino diphenyl ether are added to 40 parts of N-methyl pyrrolidone under nitrogen, and stirred several times until completely dissolved, then 7.5 parts of 4,4'-oxybisphthalic anhydride are added in batches, reacted at 0 DEG C for 4h to obtain an anhydride-terminated polyamic acid;

[0061] S2: 35 parts of 2,4-diaminobutyric acid, 40 parts of anhydrous sodium carbonate and 300 parts of deionized water are mixed and mechanically stirred uniformly, 18 parts of cyanuric chloride solution is slowly added at 0-5 DEG C, and the addition is completed within 2h, and stirring is continued for 6h, then filtered, washed and recrystallized to obtain a triaminocarboxylic acid triazine;

[0062] S3: 0.5 parts of triaminocarboxylic acid triazine is added to 45 parts of N-methyl pyrrolidone, fully dissolved, then slowly added to 30 parts of anhydride-terminated polyamic acid at 0 DEG C, reacted for 3h, after the reaction is completed, 6 parts of N-methyl pyrrolidone is continuously added for dilution to obtain the adhesive.

[0063] Comparative Example 6: basically the same as Example 1, the difference is that triaminocarboxylic acid triazine is not introduced, and the rest is the same, as follows:

[0064] Step 1: red phosphorus and sulfidized polyacrylonitrile are mechanically mixed and then ball milled, and then transferred into a tube furnace, argon is introduced, calcined at 300 DEG C for 10h, to obtain a red phosphorus-sulfidized polyacrylonitrile sample;

[0065] Step 2: the red phosphorus-sulfurized polyacrylonitrile sample is dissolved in pure water, then a small amount of MXene is added, stirred uniformly, baked at 180℃ for 16h, and finally obtained by filtering, washing, and drying to obtain the modified negative electrode material; wherein the mass ratio of red phosphorus and sulfurized polyacrylonitrile is 65:1; the mass ratio of red phosphorus and small amount of MXene is 22:1;

[0066] A preparation method of a negative electrode tab, comprising the following steps: mixing the above-mentioned negative electrode material with a binder and modified conductive carbon black, stirring uniformly, then coating on a 12μm aluminum foil, drying and rolling, drying at 120℃ for 12h to obtain a negative electrode tab; the mass ratio of the negative electrode material, the binder and the modified carbon black is 8:1:1;

[0067] The preparation process of the binder is as follows:

[0068] S1: under nitrogen, 5 parts of diamino diphenyl ether are added to 40 parts of N-methyl pyrrolidone, stirred several times until completely dissolved, then 7.5 parts of 4,4'-oxydiphthalic anhydride are added in batches, reacted at 0℃ for 4h to obtain anhydride-terminated polyamic acid, which is used as a binder;

[0069] The preparation process of the modified carbon black is as follows:

[0070] (1) 9 parts of conductive carbon black are uniformly dispersed in ethanol, the pH is adjusted to 6, 1 part of γ-aminopropyl triethoxysilane is added dropwise, the temperature is raised to 60℃, and the reaction is carried out for 3h to obtain aminated carbon black; (2) 1 part of aminated carbon black is mixed with 2 parts of anhydride-terminated polyamic acid, reacted at 0℃ for 4h to obtain modified carbon black.

[0071] Performance test:

[0072] Preparation of positive electrode tab: the positive electrode active material is selected as NaFePO4 material, the binder is selected as PVDF (Sabic 5130), and the conductive agent is selected as SuperP (Switzerland Timi Gao); stirring and mixing according to the ratio of active material: binder: conductive agent = 8:1:1, coating on a 12um aluminum foil after uniform mixing, drying and rolling, then drying in a vacuum drying oven at 120℃ for 12h.

[0073] Assembly of soft package battery:

[0074] The negative electrode tab obtained by the examples and comparative examples and the above-mentioned positive electrode tab are obtained by the steps of rolling, die cutting, lamination, entering the shell, packaging, formation, and capacity sorting, etc. to obtain a 3.1Ah soft package battery.

[0075] Test experiment one: using a soft package battery charge-discharge tester (Xinwei) to test the soft package battery at 0.5C for 100 cycles, 300 cycles and 500 cycles, the voltage range is 1.8-4.0V, and the results are shown in the following table:

[0076] Table I

[0077]

[0078] Test Experiment Two: The negative electrode materials obtained from Example 1 and Comparative Examples 4-6 were cut into 50x20mm rectangular samples, 3M tape was used to adhere the samples to an aluminum plate, and 3M tape was adhered to the surface of the negative electrode sheet, a universal testing machine was used to pull down the tape at a speed of 10mm / min and the peeling data was recorded, and the obtained data is shown in the following table: -1

[0079] Table II

[0080]

[0081] Conclusion: The sodium battery negative electrode material, the three-dimensional cross-linked structure binder and the polyamide acid chain segment introduced on the surface of the conductive carbon black in the application significantly improve the mechanical properties and electrochemical stability of the battery, which meets the actual application. Among them, Example 1 is the best embodiment, and the cycle performance and adhesion strength are the highest;

[0082] Comparative Example 1 lacks sulfurized polyacrylonitrile, resulting in poor conductivity of red phosphorus and insufficient stability of electrode structure, and the cycle performance is significantly reduced; Comparative Example 2 lacks a few layers of MXene, resulting in poor structural stability of the composite material, reduced ion transmission efficiency, and reduced cycle performance; Comparative Example 3 has the worst cycle performance due to poor conductivity and volume expansion of the traditional red phosphorus material; In Comparative Example 4, the mechanical properties and electrochemical stability of the PVDF binder are poor, which cannot effectively inhibit the volume expansion of the electrode material, resulting in gradual destruction of the electrode structure and accelerated capacity decay; In Comparative Example 5, the conductive carbon black is not modified, resulting in poor compatibility between the conductive carbon black and the binder, and the conductivity and structural stability of the electrode are reduced; In Comparative Example 6, triaminocarboxylic acid triazine is not introduced, resulting in the absence of a three-dimensional cross-linked structure of the binder, insufficient mechanical strength and flexibility of the binder, and the inability to effectively inhibit the volume expansion of the electrode material, resulting in reduced electrode structural stability and significantly reduced cycle performance.

[0083] Finally, it should be noted that: the above only describes the preferred embodiments of the application and is not intended to limit the application, although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements for some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.​

Claims

1. A method for preparing a negative electrode material for improving the cycle performance of a sodium battery, characterized by: The following steps are involved: Step 1: Red phosphorus and polyacrylonitrile sulfide are mechanically mixed and ball-milled, and then transferred to a tube furnace, introduced with argon gas, and calcined at 300-350°C for 10-12 hours to obtain a red phosphorus-polyacrylonitrile sulfide sample; Step 2: Dissolve the red phosphorus-sulfurized polyacrylonitrile sample in pure water, then add a few-layer MXene, stir evenly, bake at 180-200°C for 16-18 hours, and finally filter, wash, and dry to obtain the negative electrode material; The mass ratio of the red phosphorus to the sulfide polyacrylonitrile is (60-65):1; the mass ratio of the red phosphorus to the few-layer MXene is (20-22):

1.

2. The method for preparing a negative electrode material for improving the cycle performance of a sodium battery according to claim 1, characterized in that: During the baking process, the heating rate is 40-45°C / min, and the annealing rate is 10-15°C / min.

3. A negative electrode material, characterized in that: The negative electrode material is obtained by the preparation method according to claim 1.

4. A method for preparing a negative electrode sheet, characterized in that: The method comprises the following steps: mixing the negative electrode material according to claim 3 with a binder and modified carbon black, stirring the mixture evenly, coating the mixture on a 12-15 μm aluminum foil, drying the mixture and rolling the mixture, and drying the mixture at 120-150° C. for 12-15 hours to obtain a negative electrode sheet.

5. The method for preparing a negative electrode sheet according to claim 4, wherein: The mass ratio of the negative electrode material, the binder and the modified carbon black is (8-9):1:

1.

6. The method for preparing a negative electrode sheet according to claim 4, wherein: The preparation process of the adhesive is: S1: Under a protective atmosphere, diaminodiphenyl ether was added to N-methylpyrrolidone and stirred several times until completely dissolved. Then, 4,4'-oxydiphthalic anhydride was added in batches and reacted at 0-5°C for 4-6 hours to obtain anhydride-terminated polyamic acid; S2: 2,4-diaminobutyric acid, anhydrous sodium carbonate, and deionized water are mixed and mechanically stirred until uniform. Cyanuric chloride solution is slowly added dropwise at 0-5°C within 2-3 hours. The mixture is stirred for 6-8 hours, filtered, washed, and recrystallized to obtain triaminocarboxylic acid triazine. S3: Add triaminocarboxylic acid triazine to N-methylpyrrolidone, fully dissolve it, and then slowly drip it into the anhydride-terminated polyamic acid at 0-5°C for 3-4 hours. After the reaction is completed, continue to add N-methylpyrrolidone for dilution to obtain an adhesive.

7. The method for preparing a negative electrode sheet according to claim 6, wherein: The anhydride-terminated polyamic acid comprises the following substances: 5-8 parts by weight of diaminodiphenyl ether, 40-50 parts by weight of N-methylpyrrolidone, and 7.5-12 parts by weight of 4,4'-oxydiphthalic anhydride; The triaminocarboxylic acid triazine comprises the following substances: 35-40 parts by weight of 2,4-diaminobutyric acid, 40-42 parts of anhydrous sodium carbonate, 300-320 parts of deionized water, and 18-20 parts of cyanuric chloride solution; wherein the mass fraction of the cyanuric chloride solution is 8-10wt%, and the solvent is dioxane; The adhesive raw materials include the following substances: 0.5-0.8 parts of triaminocarboxylic acid triazine, 50-55 parts of N-methylpyrrolidone, and 30-35 parts of anhydride-terminated polyamic acid, in parts by weight; wherein the solid content of the adhesive is 6-8wt%.

8. The method for preparing a negative electrode sheet according to claim 4, wherein: The preparation process of the modified carbon black is as follows: (1) conductive carbon black is uniformly dispersed in ethanol, the pH is adjusted to 6-6.5, γ-aminopropyltriethoxysilane is added dropwise, the temperature is raised to 60-70°C, and the reaction is carried out for 3-4 hours to obtain amino carbon black; (2) the amino carbon black is mixed with anhydride-terminated polyamic acid, and the mixture is reacted at 0-5°C for 4-5 hours to obtain modified carbon black.

9. The method for preparing a negative electrode sheet according to claim 8, wherein: The mass ratio of the conductive carbon black to γ-aminopropyltriethoxysilane is (9-10):1; the mass ratio of the amination carbon black to the anhydride-terminated polyamic acid is 1:(2-3).

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