A carbon-coated current collector for improving battery cycle life, its preparation method, positive electrode, and battery.

Abstract

This invention discloses a carbon-coated current collector for improving battery cycle life, its preparation method, a positive electrode sheet, and a battery. The method includes the following steps: mixing 3,3'-diaminobenzidine with carbon black in a concentrated nitric acid solution and heat-treating to obtain modified hydrophilic carbon black; mixing the modified hydrophilic carbon black, polytetrafluoroethylene, and water uniformly, then adding isopropanol and stirring uniformly to obtain a carbon-coated slurry; and forming a carbon coating layer on the current collector using the carbon-coated slurry to obtain a carbon-coated current collector. This invention modifies and composites the carbon-coated slurry with concentrated nitric acid and 3,3'-diaminobenzidine, and uses the carbon-coated slurry to form a carbon coating layer on the current collector to obtain an improved carbon-coated current collector. Lithium-ion batteries assembled using this carbon-coated current collector exhibit excellent cycle stability and a long cycle life.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a carbon-coated current collector for improving battery cycle life, its preparation method, a positive electrode sheet, and a battery. Background Technology

[0002] In recent years, lithium-ion batteries have gradually become a research hotspot due to their advantages such as high specific capacity, high charge-discharge efficiency, good cycle performance, and low cost. With the rapid development of electronic products and new energy vehicle technologies, as well as the widespread application of lithium-ion batteries in military equipment, aerospace, and other fields, higher requirements have been placed on the quality and performance of lithium-ion batteries. Among these, cycle life and cycle stability are particularly important. Cycle life refers to the number of charge-discharge cycles a battery can maintain a certain performance standard; cycle stability refers to whether the electrochemical performance of the battery materials remains stable after multiple charge-discharge cycles.

[0003] Currently, most battery manufacturers have devoted a lot of research to extending the cycle life of batteries, but this mainly focuses on improving the characteristics of the positive and negative electrode active materials to increase the cycle life of batteries, while neglecting the optimization and improvement of other battery components such as the current collector. Summary of the Invention

[0004] This invention provides a carbon-coated current collector and its preparation method, a positive electrode sheet, and a battery, aiming to improve the cycle life of lithium-ion batteries and ensure their cycle stability.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0006] The first aspect of this application provides a method for preparing a carbon-coated current collector to improve battery cycle life, comprising the following steps:

[0007] Step S1: 3,3'-diaminobenzidine and carbon black are mixed in concentrated nitric acid solution and heat-treated to obtain modified hydrophilic carbon black;

[0008] Step S2: Mix the modified hydrophilic carbon black, polytetrafluoroethylene and water evenly, then add isopropanol and stir evenly to obtain the carbon coating slurry;

[0009] Step S3: Form a carbon coating layer on the current collector with the carbon coating slurry to obtain a carbon-coated current collector.

[0010] To optimize the above technical solution, the specific limitations also include:

[0011] Further, in step S1, the mass ratio of 3,3'-diaminobenzidine to carbon black is 1-3:7-8; the concentration of the concentrated nitric acid solution is 7.5-8 mol / L, and the amount of concentrated nitric acid solution used is more than 15 times the mass of carbon black.

[0012] Furthermore, in step S1, the reaction temperature for heat treatment of 3,3'-diaminobenzidine and carbon black in concentrated nitric acid solution is 120-140℃, and the reaction time is 8-18h.

[0013] Further, in step S1, the heat-treated product is filtered, washed, and vacuum dried to obtain modified hydrophilic carbon black; the vacuum drying conditions are: drying in a vacuum drying oven at 75-85℃ for 12-24 hours.

[0014] Further, in step S2, the mass ratio of the modified hydrophilic carbon black to polytetrafluoroethylene and isopropanol is 3.2-4.6:1-1.3:0.4-0.6; the solid content of the carbon coating slurry is 9-13 wt%.

[0015] Further, in step S2, the carbon coating slurry is applied to form a carbon coating layer on the current collector using a coating method. The process conditions are: coating speed 30-60 m / min, single-layer coating density 0.3-0.6 g / m². 2 .

[0016] Preferably, the carbon black used is Vulcan XC-72 carbon black.

[0017] The second aspect of this application provides a carbon-coated current collector for improving battery cycle life prepared by the above method.

[0018] A third aspect of this application provides a positive electrode sheet comprising the aforementioned carbon-coated current collector for improving battery cycle life.

[0019] A fourth aspect of this application provides a battery comprising the aforementioned positive electrode.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention modifies and composites a carbon-coated slurry with concentrated nitric acid and 3,3'-diaminobenzidine, and uses the slurry to form a carbon coating layer on the current collector, resulting in an improved carbon-coated current collector. Lithium-ion batteries assembled using this carbon-coated current collector exhibit excellent cycle stability and a long cycle life.

[0022] In the preparation of the carbon coating slurry of the present invention, 3,3'-diaminobenzidine and carbon black are first mixed and heat-treated in a concentrated nitric acid solution to obtain modified hydrophilic carbon black. The modified hydrophilic carbon black of this application has several advantages:

[0023] Concentrated nitric acid solution can improve the hydrophilicity of carbon fiber surface, and its strong oxidizing effect can also enhance its surface polarity, increase the oxygen functional groups and specific surface area of ​​carbon fiber surface, and improve the chemical application effect of carbon fiber.

[0024] The formation of modified hydrophilic carbon black is conducive to expanding the interlayer spacing of carbon black molecules, thereby enhancing the adsorption and capacity of carbon black molecules for ions, enabling carbon black to obtain higher ionic conductivity and faster ion diffusion rate.

[0025] The composite modification with 3,3'-diaminobenzidine increases the active sites on the modified hydrophilic carbon black molecules, allowing the modified hydrophilic carbon black to react more fully with the cathode material on the cathode sheet. This enhances the bonding force between the carbon coating slurry and the cathode material, forming a stable polymer chain, which optimizes the cycle stability and cycle life of the manufactured battery.

[0026] In the preparation of the carbon coating slurry of the present invention, modified hydrophilic carbon black, polytetrafluoroethylene and water are mixed and then isopropanol is added to obtain the carbon coating slurry. The addition of an appropriate proportion of polytetrafluoroethylene mainly plays a binding role, increasing the viscosity of the slurry so that it can be better coated on aluminum foil. An appropriate proportion of isopropanol can increase the wettability of the slurry, so that the slurry is not viscous or solid, and enhance its fluidity. The addition of isopropanol at the end can avoid the star spots and gray spots that are easy to be generated on the film surface during the coating process, so that the film surface is smoother and more even.

[0027] The carbon black preferred in this invention is Vulcan XC-72 carbon black because it has a finer particle size, good dispersibility, and can improve surface smoothness and maintain the mechanical properties of the polymer. Therefore, its composite modification effect with 3,3'-diaminobenzidine is better, and it can better promote the optimization of battery cycle stability and cycle life. Attached Figure Description

[0028] Figure 1 : A schematic diagram of the preparation process of the carbon-coated current collector for improving battery cycle life according to the present invention. Detailed Implementation

[0029] The present invention will be further described in detail below through embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0031] For the sake of brevity, this article only discloses some numerical values ​​and the range of options. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range. Similarly, any upper limit can be combined with any other upper limit to form an unspecified range; the options in the range of options can also be combined arbitrarily.

[0032] Unless otherwise stated, the terms used in this application have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art.

[0033] This application provides a method for preparing a carbon-coated current collector to improve battery cycle life, such as... Figure 1 As shown, it includes the following steps:

[0034] Step S1: 3,3'-diaminobenzidine and carbon black are mixed in concentrated nitric acid solution and heat-treated to obtain modified hydrophilic carbon black;

[0035] Step S2: Mix the modified hydrophilic carbon black, polytetrafluoroethylene and water evenly, then add isopropanol and stir evenly to obtain the carbon coating slurry;

[0036] Step S3: Form a carbon coating layer on the current collector with carbon coating slurry to obtain a carbon-coated current collector.

[0037] In some embodiments, in step S1, the mass ratio of 3,3'-diaminobenzidine to carbon black is 1-3:7-8; and the concentration of the concentrated nitric acid solution is 7.5-8 mol / L.

[0038] The amount of concentrated nitric acid used is excessive, and the amount of concentrated nitric acid solution used is more than 15 times the mass of carbon black. Preferably, the amount of concentrated nitric acid solution used is about 20 times the mass of carbon black.

[0039] In some embodiments, in step S1, the reaction temperature of the heat treatment of mixing 3,3'-diaminobenzidine and carbon black in concentrated nitric acid solution is 120-140°C, and the reaction time is 8-18 hours.

[0040] In some embodiments, in step S1, the heat-treated product is filtered, washed, and vacuum dried to obtain modified hydrophilic carbon black; the vacuum drying conditions are: drying in a vacuum drying oven at 75-85°C for 12-24 hours.

[0041] Washing and filtration are performed using pure water, with excess pure water used for multiple washing and filtration processes.

[0042] In some embodiments, in step S2, the mass ratio of modified hydrophilic carbon black to polytetrafluoroethylene and isopropanol is 3.2-4.6:1-1.3:0.4-0.6; and the solid content of the carbon coating slurry is 9-13 wt%.

[0043] In some embodiments, in step S2, the carbon coating slurry is applied to form a carbon coating layer on the current collector using a coating method. The process conditions are: coating speed 30-60 m / min, and single-layer coating surface density 0.3-0.6 g / m². 2 .

[0044] The present application enables the carbon coating slurry to form a carbon coating layer on the current collector. The carbon-coated current collector is not limited to the above coating method, but can also be produced by spraying, transfer and other optional methods.

[0045] Preferably, Vulcan XC-72 carbon black is used.

[0046] This application also provides a carbon-coated current collector for improving battery cycle life prepared by the above method.

[0047] This application also provides a positive electrode sheet comprising the aforementioned carbon-coated current collector for improving battery cycle life.

[0048] This application also provides a battery comprising the aforementioned positive electrode.

[0049] In some implementations, the battery fabrication process is as follows:

[0050] Preparation of negative electrode sheet: The negative electrode slurry is evenly coated on the negative electrode current collector, and the solvent of the slurry spread on the substrate is removed by drying and heating in an oven, so that the solid material is well adhered to the substrate to obtain the negative electrode material. Then, the corresponding rolling, slitting, die cutting, drying, and tab welding and coating are carried out to finally obtain the corresponding negative electrode sheet.

[0051] Preparation of positive electrode sheet: The positive electrode slurry is coated onto the carbon-coated current collector prepared in this application. The slurry solvent spread on the substrate is removed by drying and heating in an oven, so that the solid material is well adhered to the substrate to prepare the positive electrode material. Then, the corresponding rolling, slitting, die cutting, drying and tab welding and coating are carried out to finally obtain the corresponding positive electrode sheet.

[0052] Battery fabrication: The positive electrode, negative electrode, and separator are wound or stacked in a specific order (positive electrode - separator - negative electrode - separator) to form the initial structure of the battery cell. The wound or stacked battery cell is then placed into a battery casing. Next, the battery casing is sealed to ensure a tight seal between the battery cell and the casing. Finally, electrolyte is injected into the battery casing to provide the medium for ion conduction.

[0053] The preparation of the negative electrode slurry, positive electrode slurry, and electrolyte can be carried out using various optional methods in this field, without any restrictions.

[0054] In the following specific embodiments, the negative electrode current collector is copper foil, but the application of the solution in this application is not limited to this.

[0055] The technical solution of the present invention will be further described in detail below with reference to specific embodiments:

[0056] Example 1:

[0057] Preparation of a carbon-coated current collector, positive electrode, and battery:

[0058] (1) The preparation process of carbon-coated current collector includes the following processes:

[0059] Step S1: Preparation of modified hydrophilic carbon black: 140g of Vulcan XC-72 carbon black and 20g of 3,3'-diaminobenzidine were mixed and added to 2800g of 67wt% concentrated nitric acid. The mixture was heated in an oil bath at 140℃ for 10h. After filtration and washing with pure water, the mixture was dried under vacuum at 80℃ to obtain the modified hydrophilic carbon black.

[0060] Step S2: Preparation of coating slurry: Mix 120g of modified hydrophilic carbon black, 30g of polytetrafluoroethylene and deionized water evenly, add 13g of isopropanol, stir evenly, and obtain a coating slurry with a solid content of 9.2wt%.

[0061] Step S3: Preparation of carbon-coated aluminum foil: Coating slurry is applied to the surface of the aluminum foil (coating speed 50 m / min, single-layer coating density 0.75 g / m²). 2 After drying (at a temperature of 80°C), carbon-coated aluminum foil is obtained, which is a carbon-coated current collector.

[0062] (2) The preparation process of the positive electrode and the battery includes the following processes:

[0063] Step 1: Preparation of negative electrode sheet: Graphite, styrene-butadiene rubber, carboxymethyl cellulose, conductive agent and pure water are mixed evenly to obtain negative electrode slurry (the mass ratio of graphite, styrene-butadiene rubber, carboxymethyl cellulose, conductive agent and pure water is 93.2:1.6:2.3:2.7:2.08). The negative electrode slurry is coated on copper foil, baked at 140℃ for 10h, and rolled to compact to obtain negative electrode sheet (compacted density is 1.23g / cc).

[0064] Step 2: Preparation of the positive electrode sheet: The ternary active material NCM811, conductive agent, polyvinylidene fluoride and N-methylpyrrolidone are mixed evenly to obtain a positive electrode slurry (the mass ratio of ternary active material NCM811, conductive agent, polyvinylidene fluoride and N-methylpyrrolidone is 91:4.2:4.4:2.53); the positive electrode slurry is coated on the prepared carbon-coated current collector, baked at 140℃ for 10h, and rolled to compact to obtain a positive electrode sheet (compacted density is 2.35g / cc);

[0065] Step 3: Preparation of electrolyte: Ethylene carbonate and methyl ethyl carbonate are mixed evenly at a volume ratio of 3:7, and lithium hexafluorophosphate is added and mixed evenly to obtain an electrolyte with a concentration of 0.5 mol / L.

[0066] Step 4: Battery fabrication: The anode sheet, cathode sheet, and separator (PE film) are wound or stacked in a certain order (positive electrode sheet - separator - negative electrode sheet - separator) to form the preliminary structure of the battery cell; then the wound or stacked battery cell is placed into the battery case; next, the battery case is sealed to ensure the airtightness between the battery cell and the battery case; finally, electrolyte is injected into the battery case to provide a medium for ion conduction, and finally a lithium-ion battery is assembled.

[0067] Example 2:

[0068] Compared with Example 1, in step S1 of Example 2, the mass ratio of Vulcan XC-72 carbon black and 3,3'-diaminobenzidine is 7:1.5, and the other steps are the same as in Example 1.

[0069] Example 3:

[0070] Compared with Example 1, in step S1 of Example 3, the mass ratio of Vulcan XC-72 carbon black and 3,3'-diaminobenzidine is 7:2, and the other steps are the same as in Example 1.

[0071] Example 4:

[0072] Compared with Example 1, in step S1 of Example 4, the mass ratio of Vulcan XC-72 carbon black and 3,3'-diaminobenzidine is 7:2.5, and the other steps are the same as in Example 1.

[0073] Example 5:

[0074] Compared with Example 1, in step S1 of Example 5, the mass ratio of Vulcan XC-72 carbon black and 3,3'-diaminobenzidine is 7:3, and the other steps are the same as in Example 1.

[0075] Comparative Example 1:

[0076] Compared with Example 1, Comparative Example 1 replaced concentrated nitric acid in step S1 with acetic acid, while the other steps were the same as in Example 1.

[0077] Comparative Example 2:

[0078] Compared with Example 1, 3,3'-diaminobenzidine was not added in step S1 of Comparative Example 2, while the other steps were the same as in Example 1.

[0079] Comparative Example 3:

[0080] Compared with Example 1, in step S1 of Comparative Example 3, Vulcan XC-72 carbon black was not modified and pretreated, but used directly. Other steps were the same as in Example 1.

[0081] Comparative Example 4:

[0082] Compared with Example 1, in step S1 of Comparative Example 4, the mass ratio of Vulcan XC-72 carbon black and 3,3'-diaminobenzidine was 7:4, and the other steps were the same as in Example 1.

[0083] Comparative Example 5:

[0084] Compared with Example 1, in Comparative Example 5, the mass ratio of Vulcan XC-72 carbon black and 3,3'-diaminobenzidine in step S1 was 7:6, and the other steps were the same as in Example 1.

[0085] The manufacturers of all raw materials involved in this invention are not subject to any special restrictions. Exemplary examples include: carbon black: Vulcan XC-72 (imported from the USA), purchased from Suzhou Shengernuo Technology Co., Ltd.; 3,3'-diaminobenzidine, purchased from Sinopharm Chemical Reagent Co., Ltd.; aluminum foil: 12μm thick, grade H18-1100, purchased from Shenzhen Honglei Metal Materials Co., Ltd.; positive electrode active material: lithium iron phosphate, Defang Nano DF5F; binder: polytetrafluoroethylene and polyvinylidene fluoride, purchased from Shanghai Huaheng Hui New Material Technology Co., Ltd.; conductive agent: conductive carbon black SUPER P. Li (Swiss Temico), purchased from Guangdong Lvwei New Material Technology Co., Ltd.; Copper foil: T2 purple copper foil, 8μm thick, purchased from Shandong Huiya Metal Technology Co., Ltd.; Battery casing: Model CR2032, purchased from Taizhou Yajun Battery Materials Co., Ltd.; Separator: PE film, 20μm thick, purchased from Dongguan Xuecheng Plastic Products Co., Ltd.; Lithium sheet: purchased from Dongguan Liren New Material Technology Co., Ltd.; Gasket: 304 stainless steel round sheet, purchased from Wuxi Yiri New Material Technology Co., Ltd.; Spring: Item No. 2032, purchased from Xinghua Benote Battery Materials Co., Ltd.

[0086] Battery assembly: Lithium iron phosphate, polyvinylidene fluoride, conductive agent and N-methylpyrrolidone are mixed evenly to obtain a positive electrode slurry (the total solid content of the positive electrode slurry is 45%); the positive electrode slurry is coated on the surface of the carbon-coated current collector obtained in the examples and comparative examples, vacuum dried at 110°C for 18 hours, and rolled to compact to obtain a positive electrode sheet; in an inert gas atmosphere, the button cell is assembled in the following order: battery case - placing positive electrode sheet - adding electrolyte - placing separator - adding electrolyte - placing lithium sheet - placing spacer spring - battery case.

[0087] The button cell was tested using the Wuhan Landian testing system (CT3002A) for cycle life and stability. Specifically, a constant current charge-discharge test was conducted at different current densities (0.1, 0.5, 1, 2, 4 A g). -1 Perform cyclic testing with the voltage cutoff range set to 1.8-4.1V.

[0088] Cycle life: Start the test equipment and begin the constant current charge-discharge test. Charge test: Under the specified test ambient temperature, initially charge the battery until the specified charging cut-off voltage is reached. Discharge test: Discharge the battery at the specified discharge current until the specified discharge cut-off voltage is reached. Cycle test: Perform multiple charge-discharge cycle tests on the battery following the above steps. The number of cycles is typically set to 3000.

[0089] Cycle capacity retention: During the cycle test, the corresponding charge / discharge capacity for each cycle is recorded. The specific calculation formula is: Capacity retention = (Terminal capacity / Initial capacity) × 100%. Initial capacity: Refers to the rated capacity of the battery during the test (i.e., the first charge-discharge cycle). Termination capacity: Refers to the remaining capacity of the battery at the end of a specific cycle after a certain number of charge-discharge cycles.

[0090] The results of the experiments conducted on each embodiment and comparative example are shown in Table 1:

[0091] Table 1 Comparison of Cyclic Performance Test Results of Each Example and Comparative Example

[0092] Cycle life / capacity retention <![CDATA[0.2A g -1 ]]> <![CDATA[1A g -1 ]]> <![CDATA[4A g -1 ]]> Example 1 1200 cycles (96.4%) 1000 cycles (95.1%) 920 cycles (93.7%) Example 2 1400 cycles (98.1%) 1240 cycles (96.8%) 1080 cycles (95.1%) Example 3 1160 cycles (95.6%) 970 cycles (94.2%) 910 cycles (93.7%) Example 4 1000 cycles (94.2%) 870 cycles (92.7%) 840 cycles (90.6%) Example 5 950 cycles (93.4%) 750 cycles (91.9%) 680 cycles (89.7%) Comparative Example 1 400 cycles (86.1%) 300 cycles (83%) 200 cycles (79.9%) Comparative Example 2 670 cycles (91%) 620 cycles (87%) 515 cycles (84%) Comparative Example 3 400 cycles (85.4%) 300 cycles (80.9%) 220 cycles (70.1%) Comparative Example 4 800 cycles (75.4%) 690 cycles (70.9%) 540 cycles (62.1%) Comparative Example 5 609 cycles (65.4%) 502 cycles (60.9%) 420 cycles (54.1%)

[0093] Based on the experimental data in Table 1 above, and through analysis and research, the following conclusions can be drawn:

[0094] In Comparative Example 1, concentrated nitric acid in step S1 was replaced with acetic acid. The strong oxidizing effect of concentrated nitric acid on carbon black was lost, and the modifying effect of acetic acid on carbon black was weak. Under these circumstances, even if 3,3'-diaminobenzidine was introduced, the performance of the prepared battery was still poor.

[0095] In Comparative Example 2, no 3,3'-diaminobenzidine was added in step S1, and only concentrated nitric acid was present to modify the carbon black. Although the data was slightly better than that of Comparative Example 1, the battery prepared by this method still could not reach a better cycle performance level.

[0096] In Comparative Example 3, Vulcan XC-72 carbon black was not modified or pretreated in step S1 and was used directly. The result was similar to that of Comparative Example 1.

[0097] In Comparative Examples 4 and 5, the mass ratio of Vulcan XC-72 carbon black to 3,3'-diaminobenzidine was 7:4 and 7:6, respectively. The carbon coating slurry prepared in this ratio exhibited sedimentation during the coating process, which was detrimental to coating. Furthermore, the applied coating gradually detached over time, resulting in lower performance of the carbon-coated aluminum foil current collector, ultimately leading to decreased cycle stability and a higher risk of short circuits in the assembled lithium-ion battery. Therefore, the mass ratio of Vulcan XC-72 carbon black to 3,3'-diaminobenzidine must be greater than 2.

[0098] This invention uses concentrated nitric acid solution to modify carbon black. The strong oxidizing effect of concentrated nitric acid can change the properties of carbon black molecules, increase the pore spacing and interlayer spacing of carbon black molecules, enhance its surface polarity, increase the oxygen functional groups and specific surface area on the carbon fiber surface, and improve the chemical application effect of carbon fiber.

[0099] Concentrated nitric acid provides more favorable conditions for the chemical polymerization reaction of 3,3'-diaminobenzidine and carbon black; and the introduction of 3,3'-diaminobenzidine can increase the active sites on the modified hydrophilic carbon black molecules, so that the modified hydrophilic carbon black can react more fully with the positive electrode material on the positive electrode sheet. The bonding force between the carbon coating slurry and the positive electrode material is enhanced, forming a stable polymer chain, which improves the cycle stability and cycle life of the battery.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a carbon-coated current collector to improve battery cycle life, characterized in that, Includes the following steps: Step S1: 3,3'-diaminobenzidine and carbon black are mixed in concentrated nitric acid solution and heat-treated to obtain modified hydrophilic carbon black; Step S2: Mix the modified hydrophilic carbon black, polytetrafluoroethylene and water evenly, then add isopropanol and stir evenly to obtain the carbon coating slurry; Step S3: Form a carbon coating layer on the current collector with the carbon coating slurry to obtain a carbon-coated current collector.

2. The method for preparing the carbon-coated current collector for improving battery cycle life according to claim 1, characterized in that: In step S1, the mass ratio of 3,3'-diaminobenzidine to carbon black is 1-3:7-8; the concentration of the concentrated nitric acid solution is 7.5-8 mol / L, and the amount of concentrated nitric acid solution used is more than 15 times the mass of carbon black.

3. The method for preparing the carbon-coated current collector for improving battery cycle life according to claim 1, characterized in that: In step S1, the reaction temperature for heat treatment of 3,3'-diaminobenzidine and carbon black mixed in concentrated nitric acid solution is 120-140℃, and the reaction time is 8-18h.

4. The method for preparing the carbon-coated current collector for improving battery cycle life according to claim 1, characterized in that: In step S1, the heat-treated product is filtered, washed, and vacuum dried to obtain modified hydrophilic carbon black; the vacuum drying conditions are: drying in a vacuum drying oven at 75-85℃ for 12-24 hours.

5. The method for preparing a carbon-coated current collector to improve battery cycle life according to claim 1, characterized in that: In step S2, the mass ratio of the modified hydrophilic carbon black to polytetrafluoroethylene and isopropanol is 3.2-4.6:1-1.3:0.4-0.6; The solid content of the carbon coating slurry is 9-13 wt%.

6. The method for preparing the carbon-coated current collector for improving battery cycle life according to claim 1, characterized in that: In step S2, the carbon coating slurry is applied to the current collector to form a carbon coating layer using a coating method. The process conditions are: coating speed 30-60 m / min, and single-layer coating density 0.3-0.6 g / m². 2 .

7. The method for preparing the carbon-coated current collector for improving battery cycle life according to claim 1, characterized in that: The carbon black used is Vulcan XC-72 carbon black.

8. A carbon-coated current collector for improving battery cycle life prepared by the method of any one of claims 1-7.

9. A positive electrode plate, characterized in that: It includes the carbon-coated current collector for improving battery cycle life as described in claim 8.

10. A battery, characterized in that: It includes the positive electrode sheet as described in claim 9.

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