Preparation method of dry-method electrode plate and prepared battery

Abstract

The invention relates to the technical field of electrodes, in particular to a preparation method of a dry-method electrode plate and a prepared battery. The composite conductive material is prepared by adding a composite carbon nanotube conductive material, a silver solution, hydrogen iodide, hexadecyl trimethyl ammonium bromide, an aniline monomer, ferric chloride and ammonium persulfate as raw materials. And adding polyvinylpyrrolidone, ethylene glycol, sodium chloride, silver nitrate and the nickel-cobalt-manganese active material to prepare the modified nickel-cobalt-manganese active material. And mixing the modified nickel-cobalt-manganese active material, the composite conductive material and a polytetrafluoroethylene binder, and carrying out low-temperature ball milling, high-temperature pre-fibration and rolling to obtain the self-supporting membrane. And rolling and compounding the self-supporting film and the current collector to obtain the electrode plate. The prepared dry-method electrode plate has good conductivity and cycle performance, so that the dry-method electrode plate has a wide application prospect in the technical field of electrodes.

Description

Technical Field

[0001] The present invention relates to the technical field of electrodes, and specifically to a preparation method of a dry electrode sheet and a battery prepared thereby. Background Art

[0002] In the context of the booming development of modern energy and electronic technologies, dry electrode sheets have demonstrated significant value due to their unique advantages. From the perspective of environmental protection and sustainable development, dry electrode sheets have obvious advantages. In the preparation process of traditional wet electrodes, a large amount of organic solvents are required. The use and treatment of these solvents not only increase costs but also pose potential hazards to the environment. In contrast, the preparation process of dry electrode sheets does not require the use of organic solvents, reducing the emission of volatile organic compounds and the pollution to the environment. In addition, its preparation process is relatively simple and has low energy consumption, meeting the requirements of modern society for green manufacturing and contributing to the sustainable development of the battery industry.

[0003] However, despite the many advantages of dry electrodes in the preparation process, the construction of the internal conductive network is still not perfect. The contact between components such as active materials and conductive agents in the electrode sheet is not tight and uniform enough, resulting in a large resistance to electron conduction. During the charge and discharge process of the battery, electrons are difficult to transmit quickly and smoothly, which limits the overall performance of the battery. Moreover, the poor conductivity also causes more heat to be generated inside the battery, accelerating the aging of battery materials and shortening the service life of the battery. In addition, in terms of cycle performance, due to the problem of unsmooth electron conduction caused by the imperfect conductive network of dry electrodes, active materials cannot participate in the electrochemical reaction evenly. During charging, some active materials may not be able to fully de-lithiate due to untimely electron supply; during discharging, it is difficult to fully intercalate lithium. This uneven reaction process will cause large stresses inside the active materials, leading to changes in their crystal structures and even cracks. As the number of cycles increases, these structural changes will gradually intensify, causing more and more active materials to lose their electrochemical activity and resulting in continuous attenuation of the battery capacity.

[0004] To overcome the defects of the prior art, the present invention provides a preparation method of a dry electrode sheet and a battery prepared thereby. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of a dry electrode sheet and a battery prepared thereby to solve the problems in the prior art.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] A preparation method of a dry electrode sheet, comprising the following steps:

[0008] Step 1: Disperse the composite carbon nanotube conductive material in deionized water, then add sodium dodecylbenzenesulfonate and stir well for 1.0 - 1.5 h to obtain a modified carbon nanotube solution with a concentration of 7 - 9 mg / mL. Add the silver solution to the modified carbon nanotube solution, stir and react at 100 - 110 °C for 4 - 5 h, then add hydrogen iodide and continue to react for 3 - 4 h. After the reaction, perform vacuum drying to obtain the silver-doped carbon nanotube conductive material;

[0009] Step 2: Add the silver-doped carbon nanotube conductive material and cetyltrimethylammonium bromide to 4 / 5 mass parts of deionized water, stir well, then add aniline monomer and stir well to obtain a mixture. Add ferric chloride and ammonium persulfate to 1 / 5 mass parts of deionized water, stir evenly at 0 - 4 °C, then dropwise add the mixture to the above mixture and continue to react at 0 - 4 °C for 6 - 8 h to obtain the composite conductive material;

[0010] Step 3: Mix polyvinylpyrrolidone and ethylene glycol thoroughly to obtain a polyvinylpyrrolidone solution. Mix sodium chloride and ethylene glycol thoroughly to obtain a sodium chloride solution. Dissolve silver nitrate in the polyvinylpyrrolidone solution completely, then add the sodium chloride solution, stir for 5 - 10 min, then add the nickel cobalt manganese active material, stir for 15 - 20 min, and then carry out a closed reaction at 130 - 140 °C for 5 - 6 h to obtain the modified nickel cobalt manganese active material;

[0011] Step 4: Mix the modified nickel cobalt manganese active material, the composite conductive material and the polytetrafluoroethylene binder, and carry out low-temperature ball milling to obtain a mixed material. Place the mixed material in a high-temperature environment of 20 - 50 °C for 1 - 3 h to obtain a pre-fibrillated powder material. Roll press the pre-fibrillated powder material to obtain a self-supporting film. Roll press and laminate the self-supporting film with a current collector to obtain an electrode pole piece.

[0012] Preferably, in Step 1, the preparation process of the composite carbon nanotube conductive material is as follows: Add multi-walled carbon nanotubes to concentrated sulfuric acid, carry out an oil bath reaction at 80 - 90 °C for 20 - 25 h. After the reaction, perform suction filtration, washing and drying to obtain pretreated carbon nanotubes. Disperse the pretreated carbon nanotubes in N,N-dimethylformamide completely. Disperse 1,3,5-benzenetricarboxylic acid and copper nitrate trihydrate in a mixed solvent completely, then mix the two solutions evenly, heat at 90 - 95 °C for 20 - 25 h. After the reaction, carry out cooling, filtration, washing and supercritical carbon dioxide activation treatment to obtain the composite carbon nanotube conductive material;

[0013] The preparation process of the silver solution is as follows: Dissolve silver nitrate in polyethylene glycol to obtain a silver nitrate solution; add polyvinylpyrrolidone and sodium chloride to polyethylene glycol, stir in an oil bath at 130 - 140 °C for 10 - 12 min, then add the silver nitrate solution and continue stirring for 8 - 14 min, and then carry out a sealed reaction at 160 - 170 °C for 7 - 8 h. After the reaction, add methanol and centrifuge repeatedly to obtain a silver solution with a concentration of 3.0 - 3.5 mg / mL.

[0014] Preferably, the mass - to - volume ratio of multi - walled carbon nanotubes to concentrated sulfuric acid is (0.1 - 0.2):8; the reaction mass ratio of pretreated carbon nanotubes, 1,3,5 - benzenetricarboxylic acid, and copper nitrate trihydrate is (0.01 - 0.02):25:50; the reaction mass ratio of silver nitrate, polyvinylpyrrolidone, and sodium chloride is (1.5 - 1.7):3:(10 - 12).

[0015] Preferably, in step one, when preparing the silver - doped carbon nanotube conductive material, the reaction volume ratio of the modified carbon nanotube solution, silver solution, and hydrogen iodide is 10:(3.5 - 4.5):(1 - 2); when preparing the modified carbon nanotube solution, sodium dodecylbenzenesulfonate is 10 - 15 wt% of the carbon nanotube dosage.

[0016] Preferably, in step two, the content of each component of the composite conductive material is: by mass fraction, 0.05 - 0.07 parts of the silver - doped carbon nanotube conductive material, 0.010 - 0.012 parts of cetyltrimethylammonium bromide, 120 - 140 parts of deionized water, 0.02 - 0.03 parts of aniline monomer, 0.03 - 0.04 parts of ferric chloride, and 0.15 - 0.20 parts of ammonium persulfate.

[0017] Preferably, in step three, when preparing the modified nickel - cobalt - manganese active material, the reaction mass ratio of silver nitrate, polyvinylpyrrolidone, sodium chloride, and nickel - cobalt - manganese active material is (1.0 - 1.2):3:(5 - 8):10.

[0018] Preferably, in step four, the content of each component in the mixture is: by mass fraction, 90 - 93% of the modified nickel - cobalt - manganese active material, 3 - 5% of the composite conductive material, and the balance is polytetrafluoroethylene binder.

[0019] Preferably, in step four, the low - temperature ball - milling parameters are: temperature is 2 - 5 °C, rotation speed is 300 - 500 rpm, and ball - milling time is 1 - 2 h; the thickness of the self - supporting film is 100 - 3000 μm.

[0020] The beneficial effects of the present invention:

[0021] The characteristics of the present invention are as follows. In step one, a composite carbon nanotube conductive material is obtained by adding pretreated carbon nanotubes, 1,3,5-benzenetricarboxylic acid, and copper nitrate trihydrate. The MOF material has a high surface area and a rich pore structure, thus providing sufficient space. The composite carbon nanotube conductive material prepared in the present invention constructs a three-dimensional conductive carbon network by introducing carbon nanotubes into the structure of the MOF material. This three-dimensional conductive carbon network can enhance the charge transfer process, thereby effectively reducing the electrochemical polarization. The reduction of electrochemical polarization improves the energy efficiency and charge-discharge efficiency of the battery, and ultimately helps to improve the cycle performance of the battery.

[0022] Then, a silver-doped carbon nanotube conductive material is prepared by adding the composite carbon nanotube conductive material, sodium dodecylbenzenesulfonate, silver solution, and hydrogen iodide. The main component of the silver solution is silver nanowires, which have a unique one-dimensional structure and extremely low resistivity, and are thus widely used in high-performance conductive adhesives. Based on the composite carbon nanotube conductive material, this preparation step intersperses silver nanowires into the structure of the composite carbon nanotube conductive material. In this way, the characteristics of silver nanowires can be fully utilized to construct more conductive pathways in the composite carbon nanotube conductive material and increase its specific surface area, ultimately obtaining a silver-doped carbon nanotube conductive material with more excellent conductive performance.

[0023] The characteristics of the present invention are as follows. In step two, a composite conductive material is prepared using the silver-doped carbon nanotube conductive material, cetyltrimethylammonium bromide, aniline monomer, ferric chloride, and ammonium persulfate as raw materials. This step introduces a polyaniline conductive layer on the surface of the silver-doped carbon nanotube conductive material through a low-temperature oxidative polymerization method. The introduction of the conductive polymer can improve the conductivity of the material and promote the transmission of Li + and electrons. In summary, the present invention is based on the MOF material structure and sequentially introduces conductive carbon, silver nanowires, and conductive polymers. Among them, conductive carbon itself has good conductive performance, the unique one-dimensional structure and extremely low resistivity of silver nanowires provide an efficient channel for electron transmission, and conductive polymers also have certain conductive ability. Therefore, combining the three with the MOF material constructs a rich and efficient conductive network, significantly improving the conductivity of the composite material. In addition, the regular pore structure and stable framework of the MOF material can fix and support the conductive carbon, silver nanowires, and conductive polymers, preventing them from agglomerating or migrating under the action of the external environment. This enables the composite material to maintain stable electrical properties during long-term use, reducing electrical property fluctuations caused by external factors (such as temperature and humidity changes), and improving the reliability and service life of electronic devices.

[0024] The characteristics of the present invention are as follows. In step three, by adding polyvinylpyrrolidone, ethylene glycol, sodium chloride, silver nitrate, and nickel cobalt manganese active material, silver nanowires are introduced onto the surface of the nickel cobalt manganese active material to obtain a modified nickel cobalt manganese active material. After introducing the silver nanowires onto the surface of the nickel cobalt manganese active material, a more efficient conductive network is constructed, making the transmission of electrons inside the material smoother. In battery applications, this modification can reduce the internal resistance of the battery, reduce the loss of energy during transmission, improve the charge-discharge efficiency of the battery, and enable the battery to store and release energy more quickly. In addition, during the charge-discharge process of the battery, the nickel cobalt manganese active material will undergo a certain degree of volume expansion and contraction, which may lead to the destruction of the material structure and the pulverization of particles, thereby affecting the cycle life of the battery. The attachment of silver nanowires to the surface of the nickel cobalt manganese active material can play a certain buffering role, relieve the stress caused by volume changes, reduce the damage to the material structure and the separation between particles, and maintain the integrity and stability of the material structure.

[0025] The characteristics of the present invention are as follows. In step four, the modified nickel cobalt manganese active material, composite conductive material, and polytetrafluoroethylene binder are mixed, and after low-temperature ball milling, high-temperature pre-fibrillation, and rolling, a self-supporting film is obtained. The self-supporting film is roll-compounded with the current collector to obtain an electrode sheet. The dry-process electrode sheet prepared by the present invention has good electrical conductivity and cycle performance, so it has broad application prospects in the field of electrode technology. Specific embodiments

[0026] The following will clearly and completely describe the technical solutions in the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0027] Source of raw materials:

[0028] Multi-walled carbon nanotubes with a tube diameter of 20 nm; polyvinylpyrrolidone provided by Shandong Baihua Chemical Co., Ltd., model K30; nickel cobalt manganese active material, specifically nickel cobalt manganese 811 (NCM811), provided by Hubei Maidehao Chemical Co., Ltd., model MDH; polytetrafluoroethylene binder provided by Quzhou Baimao Technology Co., Ltd., model BM-015; by mass, one part is 1 g.

[0029] Example 1: Step 1: Add multi-walled carbon nanotubes to concentrated sulfuric acid, react in an oil bath at 90 °C for 25 h, and after the reaction, perform suction filtration, washing, and drying to obtain pretreated carbon nanotubes; fully disperse the pretreated carbon nanotubes in N,N-dimethylformamide, fully disperse 1,3,5-benzenetricarboxylic acid and copper nitrate trihydrate in a mixed solvent, then mix the two solutions evenly, heat at 95 °C for 25 h, and after the reaction, perform cooling, filtration, washing, and supercritical carbon dioxide activation treatment to obtain a composite carbon nanotube conductive material; the mass-volume ratio of multi-walled carbon nanotubes to concentrated sulfuric acid is 0.15:8; the reaction mass ratio of pretreated carbon nanotubes, 1,3,5-benzenetricarboxylic acid, and copper nitrate trihydrate is 0.015:25:50;

[0030] Dissolve silver nitrate in polyethylene glycol to obtain a silver nitrate solution; add polyvinylpyrrolidone and sodium chloride to polyethylene glycol, stir in an oil bath at 140 °C for 12 min, then add the silver nitrate solution and continue stirring for 14 min, and then react in a sealed manner at 170 °C for 8 h. After the reaction, add methanol and centrifuge repeatedly to obtain a silver solution with a concentration of 3.2 mg / mL; the reaction mass ratio of silver nitrate, polyvinylpyrrolidone, and sodium chloride is 1.6:3:11;

[0031] Disperse the composite carbon nanotube conductive material in deionized water, then add sodium dodecylbenzenesulfonate, and stir well for 1.5 h to obtain a modified carbon nanotube solution with a concentration of 8 mg / mL; add the silver solution to the modified carbon nanotube solution, stir and react at 110 °C for 5 h, then add hydrogen iodide and continue reacting for 4 h. After the reaction, perform vacuum drying to obtain a silver-doped carbon nanotube conductive material; the reaction volume ratio of the modified carbon nanotube solution, the silver solution, and hydrogen iodide is 10:4.5:1.5; the amount of sodium dodecylbenzenesulfonate is 15 wt% of the amount of carbon nanotubes;

[0032] Step 2: Add 0.07 g of the silver-doped carbon nanotube conductive material and 0.012 g of cetyltrimethylammonium bromide to 96 g of deionized water, stir well, then add 0.03 g of aniline monomer, and stir well to obtain a mixed solution; add 0.04 g of ferric chloride and 0.2 g of ammonium persulfate to 24 g of deionized water, stir evenly at 4 °C, and then dropwise add it to the mixed solution, and continue reacting at 4 °C for 8 h to obtain a composite conductive material;

[0033] Step 3: Mix polyvinylpyrrolidone and ethylene glycol evenly to obtain a polyvinylpyrrolidone solution; mix sodium chloride and ethylene glycol evenly to obtain a sodium chloride solution; fully dissolve silver nitrate in the polyvinylpyrrolidone solution, then add the sodium chloride solution, stir for 10 min, then add nickel cobalt manganese active material, stir for 20 min, and then react in a sealed manner at 140 °C for 6 h to obtain a modified nickel cobalt manganese active material; the reaction mass ratio of silver nitrate, polyvinylpyrrolidone, sodium chloride, and nickel cobalt manganese active material is 1.2:3:6:10;

[0034] Step 4: Mix 93% modified nickel-cobalt-manganese active material, 5% composite conductive material, and 2% polytetrafluoroethylene binder, and obtain a mixed material through low-temperature ball milling; leave the mixed material in a high-temperature environment at 50°C for 3 h to obtain pre-fibrillated powder; roll-press the pre-fibrillated powder to obtain a self-supporting film; roll-press and composite the self-supporting film with a current collector to obtain an electrode sheet; Low-temperature ball milling parameters: temperature is 5°C, rotation speed is 500 rpm, and ball milling time is 2 h; the thickness of the self-supporting film is 200 μm.

[0035] Example 2: Step 1: Add multi-walled carbon nanotubes to concentrated sulfuric acid, react in an oil bath at 85°C for 23 h, and after the reaction, perform suction filtration, washing, and drying to obtain pretreated carbon nanotubes; fully disperse the pretreated carbon nanotubes in N,N-dimethylformamide, fully disperse 1,3,5-benzenetricarboxylic acid and copper nitrate trihydrate in a mixed solvent, then mix the two solutions evenly, heat at 92°C for 23 h, and after the reaction, perform cooling, filtration, washing, and supercritical carbon dioxide activation treatment to obtain a composite carbon nanotube conductive material; the mass-volume ratio of multi-walled carbon nanotubes to concentrated sulfuric acid is 0.15:8; the reaction mass ratio of pretreated carbon nanotubes, 1,3,5-benzenetricarboxylic acid, and copper nitrate trihydrate is 0.015:25:50;

[0036] Dissolve silver nitrate in polyethylene glycol to obtain a silver nitrate solution; add polyvinylpyrrolidone and sodium chloride to polyethylene glycol, stir in an oil bath at 135°C for 11 min, then add the silver nitrate solution and continue stirring for 12 min, and then react in a sealed manner at 165°C for 7.5 h. After the reaction, add methanol and centrifuge repeatedly to obtain a silver solution with a concentration of 3.2 mg / mL; the reaction mass ratio of silver nitrate, polyvinylpyrrolidone, and sodium chloride is 1.6:3:11;

[0037] Disperse the composite carbon nanotube conductive material in deionized water, then add sodium dodecylbenzenesulfonate, and stir well for 1.2 h to obtain a modified carbon nanotube solution with a concentration of 8 mg / mL; add the silver solution to the modified carbon nanotube solution, stir and react at 105°C for 4.5 h, then add hydrogen iodide and continue reacting for 3.5 h. After the reaction, perform vacuum drying to obtain a silver-doped carbon nanotube conductive material; the reaction volume ratio of the modified carbon nanotube solution, the silver solution, and hydrogen iodide is 10:4.5:1.5; sodium dodecylbenzenesulfonate is 15 wt% of the carbon nanotube dosage;

[0038] Step 2: Add 0.07 g of silver-doped carbon nanotube conductive material and 0.012 g of cetyltrimethylammonium bromide to 96 g of deionized water. After sufficient stirring, add 0.03 g of aniline monomer and stir well to obtain a mixed solution. Add 0.04 g of ferric chloride and 0.2 g of ammonium persulfate to 24 g of deionized water, stir evenly at 2 °C, and then dropwise add it to the mixed solution. Continue the reaction at 2 °C for 7 h to obtain a composite conductive material;

[0039] Step 3: Mix polyvinylpyrrolidone and ethylene glycol thoroughly to obtain a polyvinylpyrrolidone solution; mix sodium chloride and ethylene glycol thoroughly to obtain a sodium chloride solution; dissolve silver nitrate completely in the polyvinylpyrrolidone solution, then add the sodium chloride solution, stir for 7 min, and then add nickel cobalt manganese active material. Stir for 17 min and then react in a closed environment at 135 °C for 5.5 h to obtain a modified nickel cobalt manganese active material; the reaction mass ratio of silver nitrate, polyvinylpyrrolidone, sodium chloride, and nickel cobalt manganese active material is 1.2:3:6:10;

[0040] Step 4: Mix 93% of the modified nickel cobalt manganese active material, 5% of the composite conductive material, and 2% of the polytetrafluoroethylene binder, and perform low-temperature ball milling to obtain a mixed material; leave the mixed material in a high-temperature environment at 50 °C for 3 h to obtain a pre-fibrillated powder material; roll press the pre-fibrillated powder material to obtain a self-supporting film; roll press and laminate the self-supporting film with a current collector to obtain an electrode pole piece; low-temperature ball milling parameters: temperature is 4 °C, rotation speed is 400 rpm, and ball milling time is 15 h; the thickness of the self-supporting film is 200 μm.

[0041] Example 3: Step 1: Add multi-walled carbon nanotubes to concentrated sulfuric acid and react in an oil bath at 80 °C for 20 h. After the reaction, perform suction filtration, washing, and drying to obtain pretreated carbon nanotubes; disperse the pretreated carbon nanotubes thoroughly in N,N-dimethylformamide, disperse 1,3,5-benzenetricarboxylic acid and copper nitrate trihydrate thoroughly in a mixed solvent, then mix the two solutions evenly and heat at 90 °C for 20 h. After the reaction, perform cooling, filtration, washing, and supercritical carbon dioxide activation treatment to obtain a composite carbon nanotube conductive material; the mass-volume ratio of multi-walled carbon nanotubes to concentrated sulfuric acid is 0.15:8; the reaction mass ratio of pretreated carbon nanotubes, 1,3,5-benzenetricarboxylic acid, and copper nitrate trihydrate is 0.015:25:50;

[0042] Dissolve silver nitrate in polyethylene glycol to obtain a silver nitrate solution; add polyvinylpyrrolidone and sodium chloride to polyethylene glycol, stir in an oil bath at 130 °C for 10 min, then add the silver nitrate solution and continue stirring for 8 min, and then react in a closed environment at 160 °C for 7 h. After the reaction, add methanol and centrifuge repeatedly to obtain a silver solution with a concentration of 3.2 mg / mL; the reaction mass ratio of silver nitrate, polyvinylpyrrolidone, and sodium chloride is 1.6:3:11;

[0043] Disperse the composite carbon nanotube conductive material in deionized water, then add sodium dodecylbenzenesulfonate and stir well for 1.0 h to obtain a modified carbon nanotube solution with a concentration of 8 mg / mL; add the silver solution to the modified carbon nanotube solution, stir and react at 100 °C for 4 h, then add hydrogen iodide and continue to react for 3 h. After the reaction is completed, vacuum dry to obtain the silver-doped carbon nanotube conductive material; the reaction volume ratio of the modified carbon nanotube solution, silver solution, and hydrogen iodide is 10:4.5:1.5; the amount of sodium dodecylbenzenesulfonate is 15 wt% of the carbon nanotube dosage.

[0044] Step 2: Add 0.07 g of the silver-doped carbon nanotube conductive material and 0.012 g of cetyltrimethylammonium bromide to 96 g of deionized water, stir well, and then add 0.03 g of aniline monomer and stir well to obtain a mixture; add 0.04 g of ferric chloride and 0.2 g of ammonium persulfate to 24 g of deionized water, stir evenly at 0 °C, and then dropwise add it to the mixture, and continue to react at 0 °C for 6 h to obtain the composite conductive material.

[0045] Step 3: Mix polyvinylpyrrolidone and ethylene glycol thoroughly to obtain a polyvinylpyrrolidone solution; mix sodium chloride and ethylene glycol thoroughly to obtain a sodium chloride solution; dissolve silver nitrate in the polyvinylpyrrolidone solution, then add the sodium chloride solution, stir for 5 min, and then add the nickel-cobalt-manganese active material and stir for 15 min, and then react in a closed state at 130 °C for 5 h to obtain the modified nickel-cobalt-manganese active material; the reaction mass ratio of silver nitrate, polyvinylpyrrolidone, sodium chloride, and nickel-cobalt-manganese active material is 1.2:3:6:10.

[0046] Step 4: Mix 93% of the modified nickel-cobalt-manganese active material, 5% of the composite conductive material, and 2% of the polytetrafluoroethylene binder, and perform low-temperature ball milling to obtain a mixed material; leave the mixed material in a high-temperature environment at 20 °C for 1 h to obtain a pre-fibrillated powder material; roll press the pre-fibrillated powder material to obtain a self-supporting film; roll press and laminate the self-supporting film with the current collector to obtain the electrode pole piece; low-temperature ball milling parameters: temperature is 2 °C, rotation speed is 300 rpm, and ball milling time is 1 h; the thickness of the self-supporting film is 200 μm.

[0047] Comparative Example 1: Replace the composite conductive material with a carbon nanotube conductive material, and the rest is the same as in Example 1. The specific steps are as follows: Step 1: Mix polyvinylpyrrolidone and ethylene glycol thoroughly to obtain a polyvinylpyrrolidone solution; mix sodium chloride and ethylene glycol thoroughly to obtain a sodium chloride solution; dissolve silver nitrate in the polyvinylpyrrolidone solution, then add the sodium chloride solution, stir for 10 min, and then add the nickel-cobalt-manganese active material and stir for 20 min, and then react in a closed state at 140 °C for 6 h to obtain the modified nickel-cobalt-manganese active material; the reaction mass ratio of silver nitrate, polyvinylpyrrolidone, sodium chloride, and nickel-cobalt-manganese active material is 1.2:3:6:10.

[0048] Step 2: Mix 93% modified nickel-cobalt-manganese active material, 5% carbon nanotube conductive material, and 2% polytetrafluoroethylene binder, and obtain a mixture through low-temperature ball milling; leave the mixture in a high-temperature environment at 50°C for 3 h to obtain pre-fibrillated powder; roll press the pre-fibrillated powder to obtain a self-supporting film; roll press and composite the self-supporting film with a current collector to obtain an electrode sheet; Low-temperature ball milling parameters: temperature is 5°C, rotation speed is 500 rpm, and ball milling time is 2 h; the thickness of the self-supporting film is 200 μm.

[0049] Comparative Example 2: Remove the modification step of the nickel-cobalt-manganese active material, and the rest is the same as in Example 1. The specific steps are as follows: Step 1: Add multi-walled carbon nanotubes to concentrated sulfuric acid, react in an oil bath at 90°C for 25 h, and after the reaction, obtain pretreated carbon nanotubes through suction filtration, washing, and drying; fully disperse the pretreated carbon nanotubes in N,N-dimethylformamide, fully disperse 1,3,5-benzenetricarboxylic acid and copper nitrate trihydrate in a mixed solvent, then mix the two solutions evenly, heat at 95°C for 25 h, and after the reaction, obtain a composite carbon nanotube conductive material through cooling, filtration, washing, and supercritical carbon dioxide activation treatment; the mass-volume ratio of multi-walled carbon nanotubes to concentrated sulfuric acid is 0.15:8; the reaction mass ratio of pretreated carbon nanotubes, 1,3,5-benzenetricarboxylic acid, and copper nitrate trihydrate is 0.015:25:50;

[0050] Dissolve silver nitrate in polyethylene glycol to obtain a silver nitrate solution; add polyvinylpyrrolidone and sodium chloride to polyethylene glycol, stir in an oil bath at 140°C for 12 min, then add the silver nitrate solution and continue stirring for 14 min, and then react in a closed state at 170°C for 8 h. After the reaction, add methanol and centrifuge repeatedly to obtain a silver solution with a concentration of 3.2 mg / mL; the reaction mass ratio of silver nitrate, polyvinylpyrrolidone, and sodium chloride is 1.6:3:11;

[0051] Disperse the composite carbon nanotube conductive material in deionized water, then add sodium dodecylbenzenesulfonate, and stir well for 1.5 h to obtain a modified carbon nanotube solution with a concentration of 8 mg / mL; add the silver solution to the modified carbon nanotube solution, stir and react at 110°C for 5 h, then add hydrogen iodide and continue reacting for 4 h. After the reaction, perform vacuum drying to obtain a silver-doped carbon nanotube conductive material; the reaction volume ratio of the modified carbon nanotube solution, the silver solution, and hydrogen iodide is 10:4.5:1.5; sodium dodecylbenzenesulfonate is 15 wt% of the carbon nanotube dosage;

[0052] Step 2: Add 0.07 g of silver-doped carbon nanotube conductive material and 0.012 g of cetyltrimethylammonium bromide to 96 g of deionized water. After stirring well, add 0.03 g of aniline monomer and stir thoroughly to obtain a mixed solution. Add 0.04 g of ferric chloride and 0.2 g of ammonium persulfate to 24 g of deionized water, stir evenly at 4 °C, and then dropwise add it to the mixed solution. React at 4 °C for another 8 h to obtain a composite conductive material.

[0053] Step 3: Mix 93% nickel cobalt manganese active material, 5% composite conductive material, and 2% polytetrafluoroethylene binder, and obtain a mixture through low-temperature ball milling. Leave the mixture in a high-temperature environment at 50 °C for 3 h to obtain pre-fibrillated powder. Roll-press the pre-fibrillated powder to obtain a self-supporting film. Roll-press and laminate the self-supporting film with a current collector to obtain an electrode sheet. Low-temperature ball milling parameters: temperature is 5 °C, rotation speed is 500 rpm, and ball milling time is 2 h. The thickness of the self-supporting film is 200 μm.

[0054] Detection test:

[0055] Battery assembly: Use the electrode sheet prepared in the present invention as the positive electrode sheet, and obtain a dry battery cell through a stacking process with a graphite negative electrode sheet and a separator. After encapsulating with an aluminum-plastic film, obtain a lithium-ion battery through processes such as hot pressing, liquid injection, standing, and formation.

[0056] Cycling performance test: At 25 °C, charge the lithium-ion battery at a constant current of 1.0C until the voltage reaches 4.3V, then charge at a constant voltage of 4.3V until the current reaches 0.05C and cut off. After standing for 30 min, discharge at a constant current of 1.0C until the voltage reaches 3.0V to obtain the first-cycle discharge capacity of the battery. Perform multiple cyclic charge and discharge tests on the lithium-ion battery according to the above method until the discharge capacity of the lithium-ion battery decays to 80% of the first-cycle discharge capacity, and record the number of cycles of the battery.

[0057] Positive electrode sheet resistivity test: Select the positive electrode sheet prepared in the present invention, use an ST-2258A type four-probe tester, fix the positive electrode sheet and then conduct the test, and take the average value after testing 5 times. The results are as follows in the table:

[0058] Cycle life (cycles) <![CDATA[Resistivity ( mΩ ·cm)]]> Example 1 1855 375 Example 2 1843 361 Example 3 1821 355 Comparative Example 1 1351 572 Comparative Example 2 1625 486

[0059] Comparative Example 1: The composite conductive material was replaced with a carbon nanotube conductive material, and the rest was the same as in Example 1. It can be seen from the experimental data that, compared with Example 1, the cycle life decreased to 1351 cycles, and the resistivity increased to 572 mΩ·cm. The reason for the analysis is as follows: Based on the MOF material as the basic structure, the present invention introduced conductive carbon, silver nanowires and conductive polymers with good electrical conductivity to construct a rich and efficient conductive network, which greatly improved the electrical conductivity of the composite material. Therefore, after replacing the composite conductive material with a common carbon nanotube conductive material, the electrical conductivity of the electrode sheet decreased significantly, the cycle life decreased, and the resistivity increased.

[0060] Comparative Example 2: The modification step of the nickel cobalt manganese active material was removed, and the rest was the same as in Example 1. It can be seen from the experimental data that, compared with Example 1, the cycle life decreased to 1625 cycles, and the resistivity increased to 486 mΩ·cm. The reason for the analysis is as follows: By introducing silver nanowires onto the surface of the nickel cobalt manganese active material, the modified nickel cobalt manganese active material constructed a more efficient conductive network, making the transmission of electrons inside the material smoother. Therefore, after removing the modification step of the nickel cobalt manganese active material, the electrical conductivity of the electrode sheet decreased significantly, the cycle life decreased, and the resistivity increased.

[0061] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0062] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention 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 perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a dry electrode sheet, characterized in that: The following steps are involved: Step 1: Disperse the composite carbon nanotube conductive material in deionized water, add sodium dodecylbenzene sulfonate, and stir for 1.0-1.5 hours to obtain a 7-9 mg / mL modified carbon nanotube solution; add the silver solution to the modified carbon nanotube solution, stir and react at 100-110° C. for 4-5 hours, then add hydrogen iodide and continue to react for 3-4 hours. After the reaction is completed, vacuum dry to obtain a silver-doped carbon nanotube conductive material; Step 2: Add silver-doped carbon nanotube conductive material and hexadecyltrimethylammonium bromide to 4 / 5 mass parts of deionized water, stir thoroughly, then add aniline monomer, stir thoroughly to obtain a mixed solution; add ferric chloride and ammonium persulfate to 1 / 5 mass parts of deionized water, stir evenly at 0-4°C, then dropwise add to the mixed solution, continue to react at 0-4°C for 6-8h, to obtain a composite conductive material; Step 3: fully mix polyvinyl pyrrolidone and ethylene glycol to obtain a polyvinyl pyrrolidone solution; fully mix sodium chloride and ethylene glycol to obtain a sodium chloride solution; fully dissolve silver nitrate in the polyvinyl pyrrolidone solution, add the sodium chloride solution, stir for 5-10 minutes, then add the nickel-cobalt-manganese active material, stir for 15-20 minutes, and react at 130-140° C. for 5-6 hours to obtain a modified nickel-cobalt-manganese active material; Step 4: Mix the modified nickel-cobalt-manganese active material, the composite conductive material and the polytetrafluoroethylene binder, and obtain a mixture by low-temperature ball milling; place the mixture in a high temperature environment of 20-50°C for 1-3 hours to obtain a pre-fiberized powder; roll the pre-fiberized powder to obtain a self-supporting film; roll-compound the self-supporting film and the current collector to obtain an electrode plate.

2. The method for preparing a dry electrode sheet according to claim 1, characterized in that: In step 1, the preparation process of the composite carbon nanotube conductive material is as follows: adding multi-walled carbon nanotubes to concentrated sulfuric acid, reacting in an oil bath at 80-90°C for 20-25h, filtering, washing, and drying after the reaction to obtain pretreated carbon nanotubes; fully dispersing the pretreated carbon nanotubes in N,N-dimethylformamide, fully dispersing 1,3,5-trimethylbenzenecarboxylic acid and copper nitrate trihydrate in a mixed solvent, and then mixing the two solutions evenly, heating at 90-95°C for 20-25h, cooling, filtering, washing, and supercritical carbon dioxide activation after the reaction to obtain the composite carbon nanotube conductive material; The preparation process of the silver solution is as follows: dissolving silver nitrate in polyethylene glycol to obtain a silver nitrate solution; adding polyvinyl pyrrolidone and sodium chloride to the polyethylene glycol, stirring in an oil bath at 130-140° C. for 10-12 minutes, adding the silver nitrate solution and continuing to stir for 8-14 minutes, and then reacting in a sealed state at 160-170° C. for 7-8 hours, adding methanol after the reaction is completed, and repeatedly centrifuging to obtain a 3.0-3.5 mg / mL silver solution.

3. The method for preparing a dry electrode sheet according to claim 2, characterized in that: The mass volume ratio of multi-walled carbon nanotubes and concentrated sulfuric acid is (0.1-0.2):8; the reaction mass ratio of pretreated carbon nanotubes, 1,3,5-trimethylbenzene carboxylic acid and copper nitrate trihydrate is (0.01-0.02):25:50; the reaction mass ratio of silver nitrate, polyvinyl pyrrolidone and sodium chloride is (1.5-1.7):3:(10-12).

4. The method for preparing a dry electrode sheet according to claim 1, characterized in that: In step 1, when preparing the silver-doped carbon nanotube conductive material, the reaction volume ratio of the modified carbon nanotube solution, the silver solution, and the hydrogen iodide is 10:(3.5-4.5):(1-2); when preparing the modified carbon nanotube solution, the sodium dodecylbenzene sulfonate is 10-15wt% of the amount of the carbon nanotubes.

5. The method for preparing a dry electrode sheet according to claim 1, characterized in that: In step 2, the contents of the components of the composite conductive material are as follows: by mass: 0.05-0.07 parts of silver-doped carbon nanotube conductive material, 0.010-0.012 parts of hexadecyltrimethylammonium bromide, 120-140 parts of deionized water, 0.02-0.03 parts of aniline monomer, 0.03-0.04 parts of ferric chloride, and 0.15-0.20 parts of ammonium persulfate.

6. The method for preparing a dry electrode sheet according to claim 1, characterized in that: In step 3, when preparing the modified nickel-cobalt-manganese active material, the reaction mass ratio of silver nitrate, polyvinyl pyrrolidone, sodium chloride, and nickel-cobalt-manganese active material is (1.0-1.2):3:(5-8):

10.

7. The method for preparing a dry electrode sheet according to claim 1, characterized in that: In step 4, the contents of the components of the mixture are: by mass fraction, 90-93% of the modified nickel-cobalt-manganese active material, 3-5% of the composite conductive material, and the remainder is the polytetrafluoroethylene binder.

8. The method for preparing a dry electrode sheet according to claim 1, characterized in that: In step 4, the low temperature ball milling parameters are: temperature of 2-5°C, rotation speed of 300-500rpm, ball milling time of 1-2h; the thickness of the self-supporting film is 100-3000μm.

9. A dry electrode plate, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the dry electrode sheet according to claim 9 in a battery.