Preparation method of negative electrode plate and button cell

Abstract

The invention discloses a preparation method of a negative electrode plate and a button cell, and the preparation method of the negative electrode plate comprises the following steps: S1, carrying out micron-scale grinding on an oxide solid electrolyte material, and after grinding, mixing with NMP to obtain first slurry; s2, mixing and stirring a polymer solid electrolyte and the first slurry to obtain a second slurry; s3, adding a single-walled carbon nanotube material into the second slurry, and stirring to obtain third slurry; s4, introducing nitrogen into the third slurry to enable the third slurry to be filled with fine bubbles, coating the surface of the copper foil with the third slurry, and drying to form a negative electrode plate; and a porous structure coating is formed on the surface of the negative electrode plate. The porous structure coating can provide more diffusion channels for lithium ions, promote ion transmission, relieve the problem of volume expansion in the lithium deposition process, and improve the cycle life, safety and energy density of the battery and the overall cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of battery materials, and particularly relates to a method for preparing a negative electrode sheet and a button cell. Background Technology

[0002] With the development of lithium-ion batteries, traditional lithium batteries using intercalated materials can no longer meet the energy density requirements of various emerging fields. Therefore, lithium metal batteries, with their high energy density, have once again attracted the attention of researchers. Among them, anode-free lithium metal batteries, which remove the negative electrode active material through anode-free technology, can maximize battery energy density while significantly reducing battery production costs, and are considered one of the development directions for next-generation high-energy-density lithium battery systems. However, existing anode-free technologies still have the following drawbacks: 1. In lithium metal batteries without a negative electrode, there is no stable lithium intercalation material on the negative electrode side. During charging and discharging, the continuously deposited metallic lithium is prone to the formation of lithium dendrites. These dendrites can not only pierce the separator, but also cause short circuits, leading to safety hazards. 2. Without excessive active lithium ion compensation, the dead lithium generated during battery cycling and the side reactions between the electrolyte and metallic lithium will lead to irreversible loss of lithium ions. These factors hinder the formation of a stable interface layer on the negative electrode side and accelerate the loss of active lithium ions, which will directly lead to the loss of battery capacity. 3. Due to the low density of lithium metal materials and the formation of a highly porous lithium metal layer when lithium ions are deposited on the negative electrode side, the battery experiences significant volume expansion, affecting the safety performance of negative electrode-free lithium metal batteries. This may even lead to deformation or cracking of the battery casing, further increasing the risk of use.

[0003] Therefore, it is urgent to design a method for preparing negative electrode sheets to solve the problems mentioned above. Summary of the Invention

[0004] To address the technical problems mentioned in the background art, such as the safety hazards and capacity loss that can easily arise from existing negative electrode-less technologies, a method for preparing a negative electrode sheet and a button cell are provided.

[0005] To achieve the above objectives, the present invention provides a method for preparing a negative electrode sheet and a specific technical solution for a button cell as follows: A method for preparing a negative electrode sheet includes the following steps: S1. The oxide solid electrolyte material is ground at the micron level, and then mixed with NMP to obtain the first slurry. S2. The polymer solid electrolyte is mixed with the first slurry and stirred to obtain the second slurry; S3. Add single-walled carbon nanotube material to the second slurry and stir to obtain the third slurry; S4. Nitrogen gas is introduced into the third slurry to fill the interior of the third slurry with microbubbles and to coat the surface of the copper foil with the third slurry. After drying, it forms a negative electrode sheet. A porous coating is formed on the surface of the negative electrode sheet.

[0006] Furthermore, Oxide solid electrolyte materials include one or more of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphate, and lithium titanium aluminum phosphate. Polymer solid electrolyte materials include one or more of polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, and polyvinylidene fluoride; Single-walled carbon nanotube materials include one or more of conductive carbon black, multi-walled carbon nanotubes, single-layer / multi-layer graphene, and conductive carbon cloth.

[0007] Furthermore, in step S1, the oxide solid electrolyte material is subjected to micron-level grinding by mechanical ball milling so that the particle size of the oxide solid electrolyte particles is 1-2 μm.

[0008] Furthermore, the single-walled carbon nanotube material has a diameter of 1-2 nm and a length of 1-5 μm.

[0009] Furthermore, the mass component ratio in the third slurry is as follows: Polymer solid electrolyte: oxide solid electrolyte: single-walled carbon nanotube material = (82-100): (0-8): (0-15).

[0010] Furthermore, the stirring speed in steps S1, S2, S3 and S4 is set to 600-2000 rpm / min, and the stirring time is 1-4 h.

[0011] Furthermore, the thickness of the porous coating is 20-150 μm, and the thickness of the copper foil is 4.5-10 μm.

[0012] A button cell battery includes a positive electrode and a negative electrode. The negative electrode is manufactured using the aforementioned method for preparing negative electrode sheets. The button cell battery is manufactured using the following method: Lithium nickel cobalt manganese oxide ternary material, conductive carbon black and polyvinylidene fluoride are dissolved in NMP solvent, stirred and coated on the surface of aluminum foil, and after drying, a positive electrode sheet is formed. The positive electrode sheet and the negative electrode sheet are die-cut; Assemble the positive and negative electrode plates to make a button cell.

[0013] Furthermore, the temperature of the die-cutting environment for the positive electrode sheet and the negative electrode sheet, and the assembly environment for the positive electrode sheet and the negative electrode sheet, are both 20 degrees Celsius, and the dew point condition is -60°C.

[0014] Furthermore, the mass ratio of 9-series lithium nickel cobalt manganese oxide ternary material, conductive carbon black, and polyvinylidene fluoride is 8:1:1; During stirring, the viscosity of the mixture should be between 7000-10000 mPa·s, and the fineness should be below 30. After stirring, the mixture is sieved through a double-layer filter screen to obtain the electrode slurry; The positive electrode slurry is coated onto aluminum foil and dried. Then, it is rolled to obtain the positive electrode sheet.

[0015] The method for preparing the negative electrode sheet of the present invention has the following advantages: 1. The polymer solid electrolyte material used has good flexibility and plasticity. After constructing a porous structure inside, it can serve as a substrate for porous coatings, and the large number of porous structures inside significantly increases the deposition space for lithium ions. Moreover, as the interface layer of the negative electrode sheet in a negative electrodeless battery, the polymer solid electrolyte material not only isolates the metallic lithium negative electrode from side reactions with the electrolyte, but also has good ionic conductivity that can induce rapid lithium ion transport. 2. The oxide solid electrolyte material used has high mechanical strength and excellent ionic conductivity. While suppressing the formation of lithium dendrites, it works synergistically with the polymer solid electrolyte material to further accelerate the deposition / dissolution rate of lithium ions in the porous coating, so that the battery has better rate performance and safety performance. 3. The single-walled carbon nanotube material used has a large specific surface area and excellent conductivity. Its surface and internal pore edges have high curvature, resulting in higher current density in this region. This can induce lithium deposition on the surface of the single-walled carbon nanotubes in the porous structure, effectively inhibiting the growth of lithium dendrites on the surface of the porous coating. Furthermore, the lithiophilic properties of the single-walled carbon nanotube material can reduce the nucleation overpotential of lithium ions on the copper foil current collector, which can effectively improve the deposition / dissolution behavior of lithium ions, thereby improving the rate performance and cycle stability of the electrodeless battery.

[0016] The button battery of the present invention has the following advantages: The button cell battery made using this negative electrode preparation method, combined with a specific positive electrode preparation process, can fully leverage the advantages of the porous structure and material combination of the negative electrode, effectively suppress lithium dendrite growth, reduce dead lithium generation, and improve the battery's cycle life, safety, and energy density. By grinding an oxide solid electrolyte and mixing it with NMP, then adding a polymer solid electrolyte and single-walled carbon nanotubes, and introducing nitrogen gas to form microbubbles inside the slurry, the slurry is coated onto a copper foil surface and dried, resulting in a negative electrode sheet with a porous coating. This porous structure provides more diffusion channels for lithium ions, promotes ion transport, alleviates the volume expansion problem during lithium deposition, and improves the cycle stability of the coin cell battery. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the overall process for preparing the negative electrode sheet of the present invention. Figure 2 This is a schematic diagram of the structure of the negative electrode sheet of the present invention; Figure 3 This is a flowchart of the method for preparing the negative electrode sheet in Embodiment 1 of the present invention; Figure 4 This is a comparison chart of the gram capacity of batteries from different embodiments of the present invention after 50 cycles of discharge; Figure 5 This is a comparison chart of the battery discharge capacity performance at different rates according to different embodiments of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0020] The following is a reference to the appendix. Figure 1 To be continued Figure 5 This invention describes a method for preparing a negative electrode sheet and a button cell.

[0021] This embodiment provides a method for preparing a negative electrode sheet. Figure 1 This is a flowchart illustrating the overall process for preparing the negative electrode sheet of the present invention. Figure 2 This is a schematic diagram of the structure of the negative electrode sheet of the present invention; as shown. Figure 1 and Figure 2 As shown, it includes the following steps: S1. The oxide solid electrolyte material is ground at the micron level, and then mixed with NMP to obtain the first slurry. S2. The polymer solid electrolyte is mixed with the first slurry and stirred to obtain the second slurry; S3. Add single-walled carbon nanotube material to the second slurry and stir to obtain the third slurry; S4. Nitrogen gas is introduced into the third slurry to fill the interior of the third slurry with microbubbles and to coat the surface of the copper foil with the third slurry. After drying, it forms a negative electrode sheet. A porous coating is formed on the surface of the negative electrode sheet.

[0022] The method for preparing the negative electrode sheet of the present invention has the following advantages: 1. The polymer solid electrolyte material used has good flexibility and plasticity. After constructing a porous structure inside, it can serve as a substrate for porous coatings, and the large number of porous structures inside significantly increases the deposition space for lithium ions. Moreover, as the interface layer of the negative electrode sheet in a negative electrodeless battery, the polymer solid electrolyte material not only isolates the metallic lithium negative electrode from side reactions with the electrolyte, but also has good ionic conductivity that can induce rapid lithium ion transport. 2. The oxide solid electrolyte material used has high mechanical strength and excellent ionic conductivity. While suppressing the formation of lithium dendrites, it works synergistically with the polymer solid electrolyte material to further accelerate the deposition / dissolution rate of lithium ions in the porous coating, so that the battery has better rate performance and safety performance. 3. The single-walled carbon nanotube material used has a large specific surface area and excellent conductivity. Its surface and internal pore edges have high curvature, resulting in higher current density in this region. This can induce lithium deposition on the surface of the single-walled carbon nanotubes in the porous structure, effectively inhibiting the growth of lithium dendrites on the surface of the porous coating. Furthermore, the lithiophilic properties of the single-walled carbon nanotube material can reduce the nucleation overpotential of lithium ions on the copper foil current collector, which can effectively improve the deposition / dissolution behavior of lithium ions, thereby improving the rate performance and cycle stability of the electrodeless battery.

[0023] Preferably, as a preferred embodiment, step S1 is as follows: AR-grade LATP powder is added to AR-grade NMP, wherein the mass ratio of LATP powder to NMP is 5:1250, and micron-level grinding is performed by mechanical ball milling under controlled ambient temperature of 20 degrees Celsius and dew point of -60 degrees Celsius to finally obtain the first slurry.

[0024] Preferably, as a preferred embodiment, step S2 is as follows: PVDF material is added to the first slurry, and under controlled ambient temperature of 20 degrees Celsius and a dew point of -60 degrees Celsius, the mixture is stirred in a glass container to obtain a uniformly mixed second slurry. The optimal mass ratio of PVDF material to LATP material is 85:5.

[0025] Preferably, as a preferred embodiment, step S3 is as follows: Single-walled carbon nanotube material is added to the second slurry, and under controlled ambient temperature of 20 degrees Celsius and a dew point of -60 degrees Celsius, the mixture is stirred in a glass container to obtain a uniformly mixed third slurry. The optimal mass ratio of PVDF, LATP, and single-walled carbon nanotube material is 85:5:10.

[0026] Preferably, as a preferred embodiment, step S4 is as follows: High-purity nitrogen gas is continuously introduced into the third slurry, with the nitrogen gas flow rate controlled at 1-2 L / min. The mixture is stirred to fill the third slurry with a large number of microbubbles, wherein the microbubble size is 1-2 μm. The third slurry is then coated onto the surface of a copper foil and dried overnight at 60 degrees Celsius, ultimately forming a negative electrode sheet with a porous coating. The purity (volume fraction) of the high-purity nitrogen gas is ≥99.999%.

[0027] Oxide solid electrolyte materials include one or more of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), lithium aluminum germanium phosphate (LAGP), and lithium titanium aluminum phosphate (LATP); Polymer solid electrolyte materials include one or more of polyethylene oxide (PEO), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF); Single-walled carbon nanotube materials include one or more of conductive carbon black, multi-walled carbon nanotubes, single-layer / multi-layer graphene, and conductive carbon cloth.

[0028] Oxide solid electrolytes, polymer solid electrolytes, and single-walled carbon nanotube materials each contain a variety of optional components, which can be combined and matched according to different performance requirements. The conductivity, mechanical strength, and other characteristics of the electrode sheets can be flexibly adjusted to adapt to different battery application scenarios.

[0029] Preferably, the oxide solid electrolyte material is lithium titanium aluminum phosphate (LATP) material; the polymer solid electrolyte material is polyvinylidene fluoride (PVDF) material.

[0030] Furthermore, in step S1, the oxide solid electrolyte material is subjected to micron-level grinding by mechanical ball milling so that the particle size of the oxide solid electrolyte particles is 1-2 μm.

[0031] Using mechanical ball milling to grind oxide solid electrolyte particles to a particle size of 1-2 μm helps to reduce the contact resistance between particles, improve the ionic conductivity of the electrolyte, and make the particles more uniformly dispersed in the slurry, which is beneficial to the formation and performance stability of subsequent coatings.

[0032] Furthermore, the single-walled carbon nanotube material has a diameter of 1-2 nm and a length of 1-5 μm.

[0033] The dimensional parameters of single-walled carbon nanotubes, with a diameter of 1-2 nm and a length of 1-5 μm, give them a large specific surface area and excellent electrical conductivity. This enables them to effectively construct conductive networks, improve the electronic conduction efficiency of electrode sheets, and thus improve the rate performance of batteries.

[0034] Furthermore, the mass component ratio in the third slurry is as follows: Polymer solid electrolyte: oxide solid electrolyte: single-walled carbon nanotube material = (82-100): (0-8): (0-15).

[0035] The mass ratio of polymer solid electrolyte, oxide solid electrolyte and single-walled carbon nanotube material in the third slurry is set to (82-100):(0-8):(0-15). This range ensures that the electrode sheet has good mechanical properties and ionic conductivity while taking into account conductivity and cost control. The synergistic effect of the performance of each component is achieved through reasonable proportioning.

[0036] Furthermore, the stirring speed in steps S1, S2, S3 and S4 is set to 600-2000 rpm / min, and the stirring time is 1-4 h.

[0037] Specifically, in step S2, the stirring speed is 600 rpm / min and the stirring time is 4 hours; in step S2, the stirring speed is 600 rpm / min and the stirring time is 4 hours; in step S2, the stirring speed is 600 rpm / min and the stirring time is 1 hour; in step S2, the stirring speed is 2000 rpm / min and the stirring time is 1 hour.

[0038] The parameters set in steps S1 to S4, namely a stirring speed of 600-2000 rpm / min and a stirring time of 1-4 h, can ensure that all materials are fully and evenly mixed, avoid agglomeration in the slurry, ensure the uniformity of the coating composition, and thus improve the consistency and reliability of the electrode sheet performance.

[0039] Furthermore, the thickness of the porous coating is 20-150 μm, and the thickness of the copper foil is 4.5-10 μm.

[0040] The combination of a porous coating thickness of 20-150μm and a copper foil thickness of 4.5-10μm provides sufficient ion transport pathways and space for lithium deposition while controlling the overall thickness and weight of the electrode sheet, which helps to improve the energy density of the battery. At the same time, the thinner copper foil can also reduce the internal resistance of the battery.

[0041] In this embodiment, a porous coating with a thickness of 50 μm is preferred, and the copper foil with a thickness of 6 μm is preferred.

[0042] This embodiment also provides a button cell battery, including a positive electrode and a negative electrode. The negative electrode is made using the above-described method for preparing negative electrode sheets. The button cell battery is made using the following method: Lithium nickel cobalt manganese oxide ternary material, conductive carbon black and polyvinylidene fluoride are dissolved in NMP solvent, stirred and coated on the surface of aluminum foil, and after drying, a positive electrode sheet is formed. Preferably, a certain proportion of positive electrode active material NCM, conductive agent (SP), binder (PVDF), and solvent (NMP) are mixed to prepare a positive electrode slurry. After stirring evenly, the slurry is coated onto the surface of aluminum foil and dried overnight at 60 degrees Celsius. The electrode sheet is then rolled and baked to obtain the positive electrode sheet. The preferred mass ratio of the total positive electrode active material NCM, binder, and conductive agent in the above steps is 8:1:1.

[0043] It is understandable that the NCM of the aforementioned positive electrode active materials is as follows: 9-series single-crystal ternary LiNi0.9Co0.05Mn0.05, 9-series polycrystalline ternary LiNi0.9Co0.05Mn0.05, 8-series single-crystal ternary LiNi0.8Co0.1Mn0.1, 8-series polycrystalline ternary LiNi0.8Co0.1Mn0.1, 5-series single-crystal ternary LiNi0.5Co0.2Mn0.3, and 5-series polycrystalline ternary LiNi0.5Co0.2Mn0.3. The cathode material is selected from at least one of 0.5Co0.2Mn0.3, single-crystal NCM111, and polycrystalline NCM111, or other commonly used cathode materials such as lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and lithium-rich manganese-based materials. In this embodiment, a 9-series single-crystal ternary material is preferred. The conductive agent is preferably at least one of conductive carbon black (SP), acetylene black, carbon nanotubes, and Ketjen black. In this embodiment, SP material is preferred. The solvent is N-methyl-2-pyrrolidone (NMP). Other substances known in the art can also be used for the cathode active material, conductive agent, and solvent.

[0044] It is understood that the adhesive used in the above steps is one or a mixture of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and poly(m-phenylene isophthalamide) (PMIA). PVDF is the preferred adhesive, but other adhesives known in the art may also be used.

[0045] Preferably, as a preferred embodiment, the preparation method of the above-mentioned positive electrode slurry is as follows: Controlling the ambient temperature at 20 degrees Celsius and the dew point at -60 degrees Celsius, an appropriate amount of PVDF binder is first added to NMP solvent, and stirred in a glass container at a stirring speed of 600 rpm / min for 4 hours to obtain a uniformly mixed slurry. Then, a certain proportion of conductive agent and positive electrode active material are added sequentially and mixed evenly to obtain the positive electrode slurry. The preferred mass ratio of positive electrode active material NCM, binder PVDF, conductive agent SP, and solvent NMP is 8:1:1:10. The prepared slurry is uniformly coated onto an aluminum foil current collector at an appropriate coating density, dried in an oven at 40-80 degrees Celsius, and then rolled to obtain a positive electrode sheet.

[0046] It is understood that the aforementioned current collector can be an aluminum foil or a carbon-coated aluminum foil with a thickness of 8-20 μm, preferably an aluminum foil with a thickness of 12 μm; the aforementioned positive electrode sheet coating surface density can be 200-550 g / m². 2 The preferred size is 450g / m 2 .

[0047] The positive electrode sheet and the negative electrode sheet are die-cut; Preferably, under controlled ambient temperature conditions of 20 degrees Celsius and a dew point of -60 degrees Celsius, the negative electrode sheet and the positive electrode sheet with a porous coating are die-cut. The electrode sheets are then placed in a die-cutting machine for die-cutting, wherein the negative electrode sheet is die-cut into a negative electrode sheet with a diameter of 16 mm, and the positive electrode sheet is die-cut into a positive electrode sheet with a diameter of 12 mm.

[0048] Assemble the positive and negative electrode plates to make a button cell.

[0049] Preferably, the specific assembly method of the positive and negative electrode sheets follows the button cell manufacturing process from bottom to top: battery positive electrode shell / the positive electrode sheet prepared above / separator / the negative electrode sheet prepared above / pad / battery negative electrode shell, ultimately producing a negative electrode-free lithium metal battery with a porous coating on the negative electrode sheet. The prepared battery is then used for corresponding performance tests and evaluations.

[0050] Furthermore, the temperature of the die-cutting environment for the positive electrode sheet and the negative electrode sheet, and the assembly environment for the positive electrode sheet and the negative electrode sheet, are both 20 degrees Celsius, and the dew point condition is -60°C.

[0051] Strict control of the ambient temperature (20 degrees Celsius) and dew point (-60°C) during the die-cutting and assembly of the positive and negative electrode sheets prevents moisture and impurities in the air from adversely affecting the performance of the electrode sheets, ensuring that the battery is processed and assembled in a low-humidity environment, thereby improving the battery's storage performance and cycle stability.

[0052] Furthermore, the mass ratio of 9-series lithium nickel cobalt manganese oxide ternary material, conductive carbon black, and polyvinylidene fluoride is 8:1:1; During stirring, the viscosity of the mixture should be between 7000-10000 mPa·s, and the fineness should be below 30. After stirring, the mixture is sieved through a double-layer filter screen to obtain the electrode slurry; The positive electrode slurry is coated onto aluminum foil and dried. Then, it is rolled to obtain the positive electrode sheet.

[0053] The ternary material of 9-series nickel-cobalt-manganese oxide, conductive carbon black and polyvinylidene fluoride in a mass ratio of 8:1:1, and parameters such as viscosity of 7000-10000 mpa·s and fineness below 30 after stirring, enable the positive electrode slurry to have good coating performance and conductivity. The double-layer filter screen further removes impurities and large particles, ensuring the quality of the positive electrode sheet, thereby synergistically improving the overall performance of the button battery with the negative electrode sheet.

[0054] Specifically, the electrolyte used in the above-mentioned button battery is an organic solvent containing lithium hexafluorophosphate (LiPF6) or lithium bis(trifluoromethanesulfonyl)imide (LTFSI), or other electrolytes known in the art. The present invention preferably uses a commonly used 1 mol / L LiPF6 / EC-DMC electrolyte, and the button battery includes pouch, cylindrical or prismatic models, etc., which are not specifically limited here.

[0055] Furthermore, to demonstrate the superiority of the negative electrode sheet with a porous coating, several embodiments are provided below for further verification: Example

[0056] Figure 3 This is a flowchart of the preparation method of the negative electrode sheet in Embodiment 1 of the present invention, as shown below. Figure 3 As shown, the method is as follows: S11. 5g of LATP powder was ground to micron level by mechanical ball milling. After grinding, it was mixed with 1250g of NMP to obtain the first slurry, wherein the particle size of LATP particles was 1-2μm. S12. Add 85g of PVDF material to the first slurry and stir in a glass container at a stirring speed of 600rpm / min for 4h to obtain a uniformly mixed second slurry. S13. Take 10g of single-walled carbon nanotube material and add it to the second slurry above. Stir in a glass container at a stirring speed of 600rpm / min for 1h to obtain a uniformly mixed third slurry. The single-walled carbon nanotube material has a tube diameter of 1-2nm and a tube length of 1-5μm. S14. High-purity nitrogen gas is continuously introduced into the third slurry, and the nitrogen gas flow rate is controlled at 1-2 L / min. The mixture is stirred at 2000 rpm / min for 1 hour to fill the third slurry with a large number of microbubbles with a size of 1-2 μm. The third slurry is then coated onto the surface of the copper foil and dried at 60 degrees Celsius overnight to form a negative electrode sheet with a porous structure coating. The purity (volume fraction) of the high-purity nitrogen gas is ≥99.999%, the copper foil thickness is 6 μm, and the thickness of the porous structure coating is 50 μm. S15. Weigh 25g of PVDF and add it to 1L of NMP. Stir at 600rpm / min for 4 hours in a glass container to obtain a uniformly mixed slurry. Then, add 200g of 9-series high-nickel ternary NCM cathode material and 25g of conductive carbon black SP sequentially. Stir at 600rpm / min for 4 hours to obtain a uniformly mixed slurry. Measure the viscosity with a viscometer to ensure it is around 7000-10000mPa·s and the fineness is below 30. Sieve through a 160-mesh double-layer filter. The resulting electrode slurry is coated with a surface density of 450g / m². 2 The coating is uniformly applied to a 12μm thick aluminum foil, dried in an oven at 60℃, and then rolled to obtain a positive electrode sheet. It is then placed in a vacuum oven at 60℃ for 48 hours to remove moisture and solvent, and then vacuum-stored for later use. S16. Place the above electrode sheet in a stamping machine for stamping, wherein the negative electrode sheet is die-cut into a negative electrode sheet with a diameter of 16mm, and the positive electrode sheet is die-cut into a positive electrode sheet with a diameter of 12mm. S17. Assemble the positive electrode and negative electrode of this embodiment into a 2032 button cell.

[0057] Example 2: The basic conditions are the same as in Example 1, except that the mass ratio of polymer solid electrolyte PVDF: oxide solid electrolyte LATP: single-walled carbon nanotubes is 88:2:10.

[0058] Example 3: The basic conditions are the same as in Example 1, except that the mass ratio of polymer solid electrolyte PVDF: oxide solid electrolyte LATP: single-walled carbon nanotubes is 82:8:10.

[0059] Example 4: The basic conditions are the same as in Example 1, except that the mass ratio of polymer solid electrolyte PVDF: oxide solid electrolyte LATP: single-walled carbon nanotubes is 90:5:5.

[0060] Example 5: The basic conditions are the same as in Example 1, except that the mass ratio of polymer solid electrolyte PVDF: oxide solid electrolyte LATP: single-walled carbon nanotubes is 80:5:15.

[0061] Comparative Example 1: The basic conditions were the same as in Example 1, except that the mass ratio of polymer solid electrolyte PVDF: oxide solid electrolyte LATP: single-walled carbon nanotubes was 100:0:0. Comparative Example 2: Comparative Example 2: The basic conditions are the same as in Example 1, except that the mass ratio of polymer solid electrolyte PVDF: oxide solid electrolyte LATP: single-walled carbon nanotubes is 95:5:0.

[0062] Comparative Example 3: The basic conditions are the same as in Example 1, except that the mass ratio of polymer solid electrolyte PVDF: oxide solid electrolyte LATP: single-walled carbon nanotubes is 90:0:10.

[0063] Based on the above embodiments and comparative examples, a comparative experiment was conducted, wherein... Figure 4 This is a comparison chart of the gram capacity of batteries from different embodiments of the present invention after 50 cycles of discharge; Figure 5 The table shows a comparison of the specific capacity performance of batteries at different discharge rates according to different embodiments of the present invention; Table 1 shows the conditions and the first discharge capacity obtained from the experiments for the above embodiments 1-5 and comparative examples 1-3, combined with... Figure 4 , Figure 5 Based on Table 1, the following conclusions can be drawn: the optimal formulation of the modified example can maximize the initial discharge and produce the best quality button cell.

[0064] Table 1

[0065] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a negative electrode sheet, characterized in that, Includes the following steps: S1. The oxide solid electrolyte material is ground at the micron level, and then mixed with NMP to obtain the first slurry. S2. The polymer solid electrolyte is mixed with the first slurry and stirred to obtain the second slurry; S3. Add single-walled carbon nanotube material to the second slurry and stir to obtain the third slurry; S4. Nitrogen gas is introduced into the third slurry to fill the interior of the third slurry with microbubbles and to coat the surface of the copper foil with the third slurry. After drying, it forms a negative electrode sheet. A porous coating is formed on the surface of the negative electrode sheet.

2. The method for preparing the negative electrode sheet according to claim 1, characterized in that, Oxide solid electrolyte materials include one or more of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphate, and lithium titanium aluminum phosphate. Polymer solid electrolyte materials include one or more of polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, and polyvinylidene fluoride; Single-walled carbon nanotube materials include one or more of conductive carbon black, multi-walled carbon nanotubes, single-layer / multi-layer graphene, and conductive carbon cloth.

3. The method for preparing the negative electrode sheet according to claim 1, characterized in that, In step S1, the oxide solid electrolyte material is ground to the micron level by mechanical ball milling so that the particle size of the oxide solid electrolyte particles is 1-2 μm.

4. The method for preparing the negative electrode sheet according to claim 1, characterized in that, Single-walled carbon nanotube materials have a diameter of 1-2 nm and a length of 1-5 μm.

5. The method for preparing the negative electrode sheet according to claim 1, characterized in that, The mass component ratio of the third slurry is: Polymer solid electrolyte: oxide solid electrolyte: single-walled carbon nanotube material = (82-100): (0-8): (0-15).

6. The method for preparing the negative electrode sheet according to claim 1, characterized in that, The stirring speed in steps S1, S2, S3 and S4 is set to 600-2000 rpm / min, and the stirring time is 1-4h.

7. The method for preparing the negative electrode sheet according to claim 1, characterized in that, The thickness of the porous coating is 20-150μm, and the thickness of the copper foil is 4.5-10μm.

8. A button cell battery, comprising a positive electrode and a negative electrode, characterized in that, The negative electrode sheet is manufactured using the method for preparing a negative electrode sheet as described in any one of claims 1-7, and the button cell is manufactured using the following method: Lithium nickel cobalt manganese oxide ternary material, conductive carbon black and polyvinylidene fluoride are dissolved in NMP solvent, stirred and coated on the surface of aluminum foil, and after drying, a positive electrode sheet is formed. The positive electrode sheet and the negative electrode sheet are die-cut; Assemble the positive and negative electrode plates to make a button cell.

9. The button battery according to claim 8, characterized in that, The temperature of the die-cutting environment for the positive and negative electrode sheets, and the assembly environment for the positive and negative electrode sheets, are both 20 degrees Celsius, and the dew point condition is -60°C.

10. The method for preparing the negative electrode sheet according to claim 8, characterized in that, The mass ratio of 9-series lithium nickel cobalt manganese oxide ternary material, conductive carbon black and polyvinylidene fluoride is 8:1:1; During stirring, the viscosity of the mixture should be between 7000-10000 mPa·s, and the fineness should be below 30. After stirring, the mixture is sieved through a double-layer filter screen to obtain the electrode slurry; The positive electrode slurry is coated onto aluminum foil and dried. Then, it is rolled to obtain the positive electrode sheet.

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