A preparation method of a novel high-magnification high-energy-density battery

Abstract

This invention discloses a novel method for preparing a high-rate, high-energy-density battery. Using nickel foam as a three-dimensional current collector, the current collector is pre-pressed, and then coated with slurry twice, with an annealing treatment added between the two coating processes to obtain positive and negative electrode strips. These strips are then cut into sheets, have tabs welded, adhesive applied to the tabs, and stacked to form a battery cell. The cell is then installed in a casing, injected with electrolyte, and encapsulated. After formation, capacity testing, and aging, a high-rate, high-energy-density lithium-ion battery is obtained. This invention achieves a three-dimensional network bond between a multi-porous framework and the electrode material. Combined with pre-pressing and two-step rolling, it effectively improves the utilization rate and processing performance of the electrode material, increases the content of active material per unit area, thereby obtaining a high electrode areal density and corresponding high energy density, and ensuring the battery's stable performance, exhibiting excellent cycle performance and rate performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a novel method for preparing a high-rate, high-energy-density battery. Background Technology

[0002] The increasing scarcity of petroleum energy and the environmental pollution caused by fuel combustion have made the search for a clean and recyclable new energy technology imperative, especially in emerging fields such as electric vehicles, electric aircraft, and robotics, which require power sources that can stably provide power and have high energy density (mass energy density and volumetric energy density). Currently, power batteries mainly include lead-acid batteries, nickel-cadmium batteries, and lithium-ion batteries. Among them, lithium-ion batteries, as energy storage units, have advantages such as high specific energy, no memory effect, light weight, small size, low self-discharge, and high voltage, and are therefore widely used.

[0003] The charging and discharging process of a lithium-ion battery is... + The electrode material is inserted and extracted back and forth between the two electrodes. To meet the ever-increasing energy density requirements, lithium-ion battery anode materials have evolved from conductive graphite-based anode materials to nano-silicon-carbon anodes. Cathode materials mainly consist of existing lithium cobalt oxide (LiCoO2), ternary layered (NCM / NCA), lithium-rich manganese (Li-rich or OLO), lithium manganese oxide (LiMn2O4), and lithium nickel manganese oxide (LiNi). 0.5 Mn 1.5 Further optimization of the O4 cathode material is needed. Simultaneously, the selection of electrolyte (non-aqueous liquid organic electrolyte), separator (polymer film), and conductive additive materials must be based on considerations of interfacial compatibility with the cathode and anode materials, as well as the inherent performance of the materials themselves.

[0004] Based on the embedded reaction mechanism, the intrinsic carrier conduction and transport behavior of lithium-ion batteries depends on the conductivity and lithium-ion diffusion coefficient of the positive and negative electrode materials, as well as the conductivity of the organic electrolyte. However, the lithium-ion diffusion coefficient in both positive and negative electrode materials is generally several orders of magnitude lower than the rate constant of heterogeneous redox reactions in aqueous secondary batteries, and the ionic conductivity of organic electrolytes is two orders of magnitude lower than that of electrolytes in aqueous secondary batteries. Furthermore, under high-rate conditions, the polarization of the powder electrode in the organic electrolyte makes lithium deposition on the negative electrode surface easy, and changes occur in the lattice of the positive electrode material. These factors will accelerate capacity decay and seriously affect the lifespan of the power battery. Therefore, due to the limitations of the intrinsic transport characteristics of the positive / electrolyte / negative electrode material combination system, it is difficult for lithium-ion batteries to achieve high-rate charge-discharge performance, or the cycle life of a single cell will decrease significantly under high-rate charge-discharge modes, and the battery performance will significantly degrade in the later stages of use.

[0005] Patent application CN202111123271.2 discloses an ultra-low temperature high-rate lithium-ion battery and its preparation method. This method increases the content of carbon black and magnetic carbon nanotubes in the positive / negative electrode slurry and reduces internal resistance by controlling the coating density and compaction density through electrode processing, thereby improving high-rate charge-discharge performance. Patent application CN202110886214.3 discloses a thick electrode structure for lithium-ion batteries. Through multi-level voids and surface trench structures, it facilitates electrolyte wetting, improves the rate and cycle performance of thick electrode batteries, and reduces the risk of lithium plating under high-rate charge-discharge. Although increasing conductive additive materials, controlling coating and compaction processes, and optimizing battery electrode structures can all achieve higher charge-discharge rates, these current techniques all sacrifice battery energy density. It remains difficult for a single lithium-ion battery cell to simultaneously achieve both high energy density and high rate. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a novel method for preparing high-rate, high-energy-density batteries. The method uses nickel foam as a three-dimensional current collector to achieve high loading of electrode materials, and improves the cycle stability, capacity utilization and rate performance of lithium-ion batteries through material compounding and process parameter control.

[0007] Meanwhile, the study found that the internal structure of nickel foam is brittle, and cracking and breakage can occur during rolling, leading to uneven charge distribution on the current collector. Furthermore, the three-dimensional network of nickel foam is compressed during processing, and the change in tortuosity affects internal lithium-ion conduction, increasing concentration polarization of the electrode and impacting battery performance. Therefore, this application also addresses electrode processability by improving the structural stability of the current collector and the bonding force between the active material and the current collector, thereby further improving battery performance.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A novel method for preparing a high-rate, high-energy-density battery includes the following steps:

[0010] S1. Material Preparation: Using nickel foam as the current collector, a ceramic composite membrane as the separator, and a mixed solution containing lithium salt, organic solvent, film-forming agent, and surfactant as the electrolyte; using LiNi... 0.5 Mn 1.5 O4 or LiMn2O4 is used as the positive electrode active material, and a mixture of conductive carbon black, conductive graphite and carbon nanotubes is used as the positive electrode conductive agent; graphite and silicon monoxide are used as the negative electrode active material, and a mixture of conductive carbon black and carbon nanotubes is used as the negative electrode conductive agent.

[0011] S2. Preparation of positive electrode strip: The current collector is pre-pressed according to the slurry-coated area and the unslurry-free area. Positive electrode slurry is first coated on both sides of the slurry-coated area. After drying and rolling, it is heated to 400~450℃ in an inert atmosphere (i.e., annealing treatment), held at that temperature for 30~40 min, and then cooled to room temperature in the furnace. Then, positive electrode slurry is coated on both sides of the slurry-coated area again. After drying and rolling, the positive electrode strip is obtained.

[0012] The positive electrode slurry is formed by dispersing positive electrode powder in N-methylpyrrolidone. The positive electrode powder includes positive electrode active material, positive electrode conductive agent, positive electrode additive, and positive electrode binder. In the first coating of the positive electrode slurry, the positive electrode additive is tin metal powder and the positive electrode binder is hydroxypropyl methylcellulose. In the second coating of the positive electrode slurry, the positive electrode additive is graphene and the positive electrode binder is polyvinylidene fluoride.

[0013] S3. Preparation of negative electrode strip: The current collector is pre-pressed according to the slurry-coated area and the unslurry-free area. The negative electrode slurry is first coated on both sides of the slurry-coated area. After drying and rolling, the temperature is raised to 400~450℃ in an inert atmosphere and held for 20~40 min. Then, it is cooled to room temperature in the furnace. Then, the negative electrode slurry is coated on both sides of the slurry-coated area again. After drying and rolling, the negative electrode strip is obtained.

[0014] The negative electrode slurry is formed by dispersing negative electrode powder in a negative electrode solvent. The negative electrode powder includes negative electrode active material, negative electrode conductive agent, negative electrode additive, and negative electrode binder. In the first coating of the negative electrode slurry, the negative electrode additive is tin metal powder and the negative electrode binder is hydroxypropyl methylcellulose. In the second coating of the negative electrode slurry, the negative electrode additive is graphene and the negative electrode binder is hydroxypropyl methylcellulose and polyacrylic acid.

[0015] S4. Cell preparation: Cut the positive and negative electrode strips into sheets, weld tabs in the slurry-free area of ​​the current collector, and apply adhesive to the tabs to obtain the positive and negative electrode sheets; stack the positive electrode sheets, separator, and negative electrode sheets in a Z-shape to form the cell.

[0016] S5. Electrolyte injection and encapsulation: The cell is installed in the casing and vacuum baked at 80~85℃ for 1~2 hours; electrolyte is injected, and after standing, it is encapsulated under vacuum conditions to form a battery cell;

[0017] S6. The battery cells are formed, capacity tested, and aged to obtain high-rate, high-energy-density lithium-ion batteries.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) This application selects nickel foam as the current collector. It achieves a three-dimensional network combination with the electrode material through a multi-porous skeleton. Combined with pre-pressing and two-step rolling, it can effectively improve the utilization rate of the electrode material, increase the content of active material per unit area, obtain a higher electrode surface density and a corresponding high energy density, thereby reducing the number of electrode sheets and the amount of separator used in the battery, and reducing the overall manufacturing cost of the battery.

[0020] (2) In this application, a two-step sizing process is adopted when preparing positive electrode strip and negative electrode strip. The two-step sizing can reduce the thickness of each sizing, effectively alleviate the internal stress caused by the uneven distribution of internal components and temperature of the material during the drying process of the sizing, and avoid cracking or separation of active material from current collector. An annealing treatment is added between the two sizing processes to reduce the hardness and increase the toughness of the foamed nickel, thereby solving the problem of cracking and breakage when further rolled to reduce thickness.

[0021] (3) In the electrode slurry that is coated twice, a small amount of metallic tin powder or graphene is added as an additive. After annealing, tin can form a relatively stable covalent bond with the aggregated nickel to suppress the volume expansion of the material. The two-dimensional sheet structure of graphene can greatly increase the contact between active material particles and buffer the volume expansion generated during the lithium intercalation process. A small amount of additive helps to increase the conductivity of the electrode material and the bonding force between particles, improve the electrochemical lithium storage performance of the electrode material, and show excellent cycle performance and rate performance.

[0022] (4) In the first coating of electrode slurry, both the positive and negative electrode binders are hydroxypropyl methylcellulose, which can ensure the adhesion between the active material and the current collector after coating. After annealing, the binder is carbonized, which can increase the electrochemical active area of ​​the material and also help the adhesion of the second coating slurry to it, thereby improving the overall bonding strength between the electrode materials. In the second coating of electrode slurry, the positive electrode binder is polyvinylidene fluoride, and the negative electrode binder is hydroxypropyl methylcellulose and polyacrylic acid, both of which have excellent flexibility. This further improves the adhesion of the second coating slurry, prevents the deformation and warping of the electrode material, and provides resistance to the volume expansion / contraction of the electrode material.

[0023] (5) This application achieves defoaming by adding surfactants to the electrolyte, thereby avoiding residual gas on the electrode surface from affecting the electrolyte penetration process and improving the uniformity of the SEI film on the electrode surface.

[0024] To provide a larger contact area and reaction surface for the three-dimensional structure of the current collector, the nickel foam described in step S1 has a thickness of 0.6~1.2 mm and a bulk density of 0.20~0.45 g / cm³. 3To prevent powder shedding, the current collector needs to be pre-pressed before being sizing. After pre-pressing, the current collector in step S2 has a thickness reduction rate of 15-30% in the sizing area and a thickness reduction rate of 75-90% in the sizing-free area.

[0025] To formulate a suitable and high-performance positive electrode slurry, the positive electrode powder in step S2 includes the following raw materials by mass percentage: 2-4% positive electrode conductive agent, 1.5-2.5% positive electrode additive, 3-4% positive electrode binder, with the balance being positive electrode active material. To ensure wetting efficiency, the amount of N-methylpyrrolidone in the positive electrode slurry is 60-120% of the mass of the positive electrode powder. The positive electrode conductive agent is composed of conductive carbon black, conductive graphite, and carbon nanotubes mixed in a mass ratio of 10:2-3:0.2-0.5. The conductive carbon black has an aggregate structure, allowing it to be uniformly dispersed among the positive electrode active materials, maintaining the conductive network. Carbon nanotubes have a large specific surface area and numerous active sites, allowing them to be smoothly distributed and positioned on the surface of the positive electrode active material particles, improving conductivity. Conductive graphite has high stability and lubricity, improving the machinability of the electrode sheet.

[0026] To further ensure the mechanical properties and energy density of the positive electrode, the first coating of positive electrode slurry in step S2, after drying and rolling, is recorded as the first positive electrode powder coating. The second coating of positive electrode slurry, after drying and rolling, is recorded as the second positive electrode powder coating. The powder coating amount for the first positive electrode coating is 330~380 g / m³. 2 The total powder coating amount from primary and secondary positive electrode powdering is 1510~1650 g / m³. 2 Compared with the thickness of the current collector sizing area after pre-compression, the thickness reduction rate of the positive electrode material after the first positive electrode powder coating is 31~45%; compared with the thickness of the current collector sizing area after pre-compression, the thickness reduction rate of the positive electrode material after the second positive electrode powder coating is 45~58%.

[0027] To formulate a suitable and high-performance negative electrode slurry, the negative electrode powder in step S3 includes the following raw materials by mass percentage: 2-3% negative electrode conductive agent, 2-3% negative electrode additive, 1.5-3% negative electrode binder, and the balance being negative electrode active material; wherein, the negative electrode active material is a mixture of negative electrode graphite and silicon monoxide in a mass ratio of 10-20:1; the negative electrode conductive agent is a mixture of conductive carbon black and carbon nanotubes in a mass ratio of 30-40:1; in the first coating negative electrode slurry, the negative electrode solvent is N-methylpyrrolidone; in the second coating negative electrode slurry, the negative electrode solvent is a mixture of N-methylpyrrolidone and water in a mass ratio of 1-5:100, and the negative electrode binder is a mixture of hydroxypropyl methylcellulose and polyacrylic acid in a mass ratio of 1:4-10.

[0028] Furthermore, to ensure the mechanical properties and energy density of the negative electrode sheet, the initial coating of the negative electrode slurry in step S3, after drying and rolling, is recorded as the first negative electrode powder coating. The second coating of the negative electrode slurry, after drying and rolling, is recorded as the second negative electrode powder coating. Therefore, the powder coating amount for the first negative electrode powder coating is 340~430 g / m³. 2 The total powder coating amount from primary and secondary negative electrode powder coating is 1720~1850 g / m³. 2 Compared with the thickness of the current collector sizing area after pre-compression, the thickness reduction rate of the negative electrode material after the first negative electrode powder coating is 36~45%; compared with the thickness of the current collector sizing area after pre-compression, the thickness reduction rate of the negative electrode material after the second negative electrode powder coating is 46~58%.

[0029] To facilitate the formation of the SEI film, in the electrolyte of step S1, the mass percentage of lithium salt is 11-15%, the mass percentage of film-forming agent is 5-7%, and the mass percentage of surfactant is 1-3%. Specifically, the lithium salt is lithium hexafluorophosphate; the organic solvent is selected from two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; the film-forming agent is selected from one of fluoroethylene carbonate, propylene sulfite, and vinylene carbonate; and the surfactant is selected from glycerol fatty acid esters or fatty acid polyethylene glycol esters.

[0030] In order to control production efficiency and energy consumption, the drying temperature in steps S2 and S3 is 85~105℃ to ensure the drying efficiency of the positive electrode slurry and the negative electrode slurry and to prevent cracking; when heating in an inert atmosphere in steps S2 and S3, the heating time is no more than 5 minutes.

[0031] In summary, the preparation method described in this invention is easy to control, low in cost, and highly reproducible. By combining electrode materials and electrolyte, it significantly improves the energy density of the battery by increasing the loading of active material on the current collector. On the other hand, it ensures the power density of the battery by promoting the transport and storage of ions at the electrode-electrolyte interface. Furthermore, combined with process control, it improves the structural stability of the electrode materials and the effective adhesion of active materials, suppresses material volume expansion, or buffers the resulting volume shrinkage / expansion. This results in excellent cycle performance and rate performance, and has promising application prospects in the new energy field. Detailed Implementation

[0032] To make the technical objectives, technical solutions, and beneficial effects of the present invention clearer, the technical solutions of the present invention will be further described below in conjunction with specific embodiments. However, the embodiments are intended to explain the present invention and should not be construed as limiting the present invention. Where no specific technology or conditions are specified in the embodiments, they shall be carried out in accordance with the technology or conditions described in the literature in the field or in accordance with the product instructions. The raw materials used in the following embodiments are all common commercially available products.

[0033] A novel method for preparing a high-rate, high-energy-density battery includes the following steps:

[0034] S1. Material preparation: Materials with a thickness of 1.0 mm and a bulk density of 0.29 g / cm³. 3 Nickel foam was used as the current collector, and a ceramic composite membrane (purchased from Tianjin Kaipurite New Energy Technology Co., Ltd.) was used as the separator. LiNi was used as the separator. 0.5 Mn 1.5 O4 (purchased from Chengdu Xingneng New Materials Co., Ltd., model XNN5) or LiMn2O4 (purchased from Xinxiang Zhongtian New Energy Technology Co., Ltd., model ZTM-06) are used as positive electrode active materials, and a mixture of conductive carbon black (superconducting carbon black SP, particle size 20 nm), conductive graphite (flake graphite, 15 μm) and carbon nanotubes (single-walled carbon nanotubes, diameter 2 nm, length 5~20 μm) is used as positive electrode conductive agent; graphite (spherical graphite, 6.5 μm) and silicon monoxide are used as negative electrode active materials, and a mixture of conductive carbon black and carbon nanotubes is used as negative electrode conductive agent;

[0035] The electrolyte is a mixed solution containing lithium salt, organic solvent, film-forming agent, and surfactant. In the electrolyte, the mass percentage of lithium salt is 11-15%, the mass percentage of film-forming agent is 5-7%, and the mass percentage of surfactant is 1-3%. The organic solvent is selected from two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. The lithium salt is lithium hexafluorophosphate, the film-forming agent is fluoroethylene carbonate, and the surfactant is a glycerol fatty acid ester.

[0036] S2. Preparation of positive electrode strip: The current collector is pre-pressed according to the slurry-coated area and the unslurry-free area. After pre-pressing, the thickness of the slurry-coated area, which serves as the positive electrode current collector, is 0.8 mm and the thickness of the unslurry-free area is 0.2 mm. Positive electrode slurry is first coated on both sides of the slurry-coated area. After drying and rolling, the temperature is raised to 400~450℃ in an inert atmosphere and held for 30~40 min. Then, it is cooled to room temperature in the furnace. Positive electrode slurry is then coated on both sides of the slurry-coated area again. After drying and rolling, the positive electrode strip is obtained.

[0037] The positive electrode slurry is formed by dispersing positive electrode powder in N-methylpyrrolidone. The positive electrode powder is composed of the following raw materials in the indicated mass percentages: 2-4% positive electrode conductive agent, 1.5-2.5% positive electrode additive, 3-4% positive electrode binder, with the remainder being positive electrode active material. The amount of N-methylpyrrolidone in the positive electrode slurry is 60-120% of the mass of the positive electrode powder. Furthermore, in the first coating of the positive electrode slurry, the positive electrode additive is tin metal powder (purchased from Xuzhou Jiechuang New Material Technology Co., Ltd., with an average particle size of 100 nm), and the positive electrode binder is hydroxypropyl methylcellulose. In the second coating of the positive electrode slurry, the positive electrode additive is graphene (purchased from Xuzhou Jiechuang New Material Technology Co., Ltd., with a single-layer size of 0.6-1.2 nm and a length of 0.8-2 nm). μm), the positive electrode binder is polyvinylidene fluoride; the positive electrode conductive agent is a mixture of conductive carbon black, conductive graphite and carbon nanotubes in a mass ratio of 10:2~3:0.2~0.5;

[0038] The process of first coating the positive electrode slurry in step S2, drying it at 95°C, and then rolling it is recorded as the first positive electrode powder coating. The process of second coating the positive electrode slurry, drying it at 95°C, and then rolling it is recorded as the second positive electrode powder coating. The powder coating amount of the first positive electrode powder coating is 330~380 g / m. 2 The total powder coating amount from primary and secondary positive electrode powdering is 1510~1650 g / m³. 2 After the first positive electrode powder coating, the thickness of the positive electrode material (referring to the overall material after the current collector is rolled and powdered) is 0.45~0.55 mm. After the second positive electrode powder coating, the thickness of the positive electrode material is 0.34~0.44 mm.

[0039] S3. Preparation of negative electrode strip: The current collector is pre-pressed according to the slurry-coated area and the unslurry-free area. The thickness of the slurry-coated area as the negative electrode current collector is 0.75 mm and the thickness of the unslurry-free area is 0.15 mm. The negative electrode slurry is first coated on both sides of the slurry-coated area. After drying at 95℃ and rolling, the temperature is raised to 400~450℃ in an inert atmosphere and held for 20~40 min. Then, it is cooled to room temperature in the furnace. Then, the negative electrode slurry is coated on both sides of the slurry-coated area again. After drying at 95℃ and rolling, the negative electrode strip is obtained.

[0040] The negative electrode slurry is formed by dispersing negative electrode powder in a negative electrode solvent. The negative electrode powder is composed of the following raw materials in the indicated mass percentages: 2-3% negative electrode conductive agent, 2-3% negative electrode additive, 1.5-3% negative electrode binder, with the remainder being negative electrode active material. The negative electrode active material is composed of negative electrode graphite and silicon monoxide mixed in a mass ratio of 10-20:1. The negative electrode conductive agent is composed of conductive carbon black and carbon nanotubes mixed in a mass ratio of 30-40:1. In the first coating of the negative electrode slurry, the negative electrode additive is tin metal powder, and the negative electrode solvent is N-methylpyrrolidone. In the second coating of the negative electrode slurry, the negative electrode solvent is composed of N-methylpyrrolidone and water mixed in a mass ratio of 1-5:100, the negative electrode additive is graphene, and the negative electrode binder is composed of hydroxypropyl methylcellulose and polyacrylic acid mixed in a mass ratio of 1:4-10.

[0041] The initial coating of negative electrode slurry in step S3, followed by drying and rolling, is recorded as the first negative electrode powder coating. The subsequent coating of negative electrode slurry, followed by drying and rolling, is recorded as the second negative electrode powder coating. The powder coating amount for the first negative electrode coating is 340~430 g / m³. 2 The total powder coating amount from primary and secondary negative electrode powder coating is 1720~1850 g / m³. 2 After the first negative electrode powder coating, the thickness of the negative electrode material (referring to the overall material after roller pressing of the current collector plus the powder) is 0.42~0.48 mm; after the second negative electrode powder coating, the thickness of the negative electrode material is 0.32~0.4 mm.

[0042] S4. Cell preparation: Cut the positive and negative electrode strips into sheets, weld tabs in the slurry-free area of ​​the current collector, and apply adhesive to the tabs to obtain the positive and negative electrode sheets; stack the positive electrode sheets, separator, and negative electrode sheets in a Z-shape to form the cell.

[0043] S5. Electrolyte injection and encapsulation: The cell is installed in the casing and vacuum baked at 80~85℃ for 1~2 hours; electrolyte is injected, and after standing, it is encapsulated under vacuum conditions to form a battery cell;

[0044] S6. The battery cells are formed, capacity tested, and aged to obtain high-rate, high-energy-density lithium-ion batteries.

[0045] Example 1

[0046] A novel method for preparing a high-rate, high-energy-density battery includes the following steps:

[0047] S1. Material Preparation: 1.0 mm thick nickel foam is used as the current collector, a ceramic composite membrane is used as the diaphragm, and LiNi... 0.5 Mn 1.5O4 is used as the positive electrode active material, and a mixture of conductive carbon black, conductive graphite and carbon nanotubes is used as the positive electrode conductive agent; graphite and silicon monoxide are used as the negative electrode active materials, and a mixture of conductive carbon black and carbon nanotubes is used as the negative electrode conductive agent.

[0048] Propylene carbonate and dimethyl carbonate were mixed evenly at a mass ratio of 1:1, and then lithium hexafluorophosphate, fluoroethylene carbonate, and glycerol fatty acid esters were added and dispersed thoroughly to obtain an electrolyte. In the electrolyte, the mass percentage of lithium hexafluorophosphate was 12%, the mass percentage of fluoroethylene carbonate was 6%, and the mass percentage of glycerol fatty acid esters was 2%.

[0049] S2. Preparation of positive electrode strip: The current collector is pre-pressed according to the sizing region and the unsizing region. After pre-pressing, the thickness of the sizing region as the positive electrode current collector is 0.8 mm and the thickness of the unsizing region is 0.2 mm.

[0050] Conductive carbon black, conductive graphite, and carbon nanotubes were mixed uniformly at a mass ratio of 10:2.5:0.5 to obtain a positive electrode conductive agent; the following materials were prepared at a mass ratio of 92:3:2:3:80: LiNi 0.5 Mn 1.5 O4, positive electrode conductive agent, tin metal powder, hydroxypropyl methylcellulose, N-methylpyrrolidone. Hydroxypropyl methylcellulose is fully dispersed in N-methylpyrrolidone, and then LiNi, which has been thoroughly mixed, is added. 0.5 Mn 1.5 O4, positive electrode conductive agent, and tin metal powder are thoroughly mixed to obtain the first positive electrode slurry; the following materials are prepared according to a mass ratio of 92:3:2:3:80: LiNi 0.5 Mn 1.5 O4, positive electrode conductive agent, graphene, polyvinylidene fluoride, N-methylpyrrolidone. Polyvinylidene fluoride is fully dispersed in N-methylpyrrolidone, and then LiNi, after being thoroughly mixed, is added. 0.5 Mn 1.5 O4, positive electrode conductive agent and graphene are thoroughly mixed to obtain the second positive electrode slurry;

[0051] The first positive electrode slurry is applied to both sides of the sizing area. After drying at 95℃ and rolling, this is recorded as the first positive electrode powder coating. Then, the temperature is raised to 420℃ in an inert atmosphere and held for 30 minutes (the holding time is selected according to the material thickness). After cooling to room temperature in the furnace, the second positive electrode slurry is applied to both sides of the sizing area. After drying at 95℃ and rolling, this is recorded as the second positive electrode powder coating, resulting in the positive electrode strip. The powder coating amount of the first positive electrode coating is 350 g / m. 2 The total powder coating amount from primary and secondary positive electrode powdering is 1610 g / m³. 2After the first coating of the positive electrode, the thickness of the positive electrode material is 0.50 mm; after the second coating of the positive electrode, the thickness of the positive electrode material is 0.4 mm.

[0052] S3. Preparation of negative electrode strip: The current collector is pre-pressed according to the sizing region and the unsizing region. The thickness of the sizing region of the negative electrode current collector is 0.75 mm and the thickness of the unsizing region is 0.15 mm.

[0053] A negative electrode active material is obtained by uniformly mixing graphite and silicon monoxide at a mass ratio of 15:1; a negative electrode conductive agent is obtained by uniformly mixing conductive carbon black and carbon nanotubes at a mass ratio of 35:1; a negative electrode solvent is obtained by mixing N-methylpyrrolidone and water at a mass ratio of 1:25; a negative electrode binder is obtained by mixing hydroxypropyl methylcellulose and polyacrylic acid at a mass ratio of 1:9; and the following materials are prepared in a mass ratio of 93:2.5:2.5:2:100: negative electrode active material, negative electrode conductive agent, tin metal powder, hydroxypropyl methylcellulose, etc. N-Methylpyrrolidone: Hydroxypropyl methylcellulose is fully dispersed in N-methylpyrrolidone, and then a well-mixed negative electrode active material, negative electrode conductive agent, and tin metal powder are added. After thorough mixing, the first negative electrode slurry is obtained. The following materials are prepared according to a mass ratio of 93:3:2:3:100: negative electrode active material, negative electrode conductive agent, graphene, negative electrode binder, and negative electrode solvent. The negative electrode binder is fully dispersed in the negative electrode solvent, and then a well-mixed negative electrode active material, negative electrode conductive agent, and graphene are added. After thorough mixing, the second negative electrode slurry is obtained.

[0054] The first negative electrode slurry is applied to both sides of the sizing area. After drying at 95℃ and rolling, this is recorded as the first negative electrode powder coating. The area is then heated to 400℃ in an inert atmosphere, held for 30 minutes, and then cooled to room temperature in the furnace. A second negative electrode slurry is then applied to both sides of the sizing area, dried at 95℃, and rolled, which is recorded as the second negative electrode powder coating, resulting in the negative electrode strip. The powder coating amount in the first negative electrode powder coating is 390 g / m². 2 The total powder coating amount from primary and secondary negative electrode powder coating is 1795 g / m³. 2 After the first negative electrode powder coating, the thickness of the negative electrode material is 0.45 mm; after the second negative electrode powder coating, the thickness of the negative electrode material is 0.35 mm.

[0055] S4. Cell preparation: Cut the positive and negative electrode strips into sheets, weld tabs in the slurry-free area of ​​the current collector, and apply adhesive to the tabs to obtain the positive and negative electrode sheets; stack the positive electrode sheet, separator, and negative electrode sheet in a Z-shape (the negative electrode has one more sheet than the positive electrode) to make the cell.

[0056] S5. Electrolyte injection and encapsulation: The cell is installed in the casing and vacuum baked at 80°C for 1.5 h; electrolyte is injected, and after standing, it is encapsulated under vacuum conditions to form a battery cell;

[0057] S6. Formation, Capacity Differentiation, and Aging: Charge to 15% of the nominal capacity using a constant current of 0.02 C, vacuum age at 55°C for 20 hours, then charge to 100% of the nominal capacity using a constant current of 0.02 C, complete the degassing and shaping packaging, and discharge to a constant current of 0.5 C until the cutoff voltage is 3.0 V; perform capacity differentiation using alternating constant current charging and discharging (the specific steps of capacity differentiation can be performed using conventional techniques in this field, and are not the innovation of this invention, so they will not be described in detail), then perform constant voltage and constant current charging again, age at 40°C for 36 hours, and cool to room temperature to obtain the final product.

[0058] Example 2

[0059] A novel method for preparing a high-rate, high-energy-density battery, which differs from the method in Example 1, is as follows:

[0060] (1) Electrolyte in step S1: Propylene carbonate and dimethyl carbonate are mixed evenly at a mass ratio of 1:1, and then lithium hexafluorophosphate, fluoroethylene carbonate and glycerol fatty acid ester are added and fully dispersed to obtain the electrolyte; in the electrolyte, the mass percentage of lithium hexafluorophosphate is 13%, the mass percentage of fluoroethylene carbonate is 5%, and the mass percentage of glycerol fatty acid ester is 2%;

[0061] (2) The first positive electrode slurry in step S2: LiNi 0.5 Mn 1.5 O4, positive electrode conductive agent, tin metal powder, hydroxypropyl methylcellulose, N-methylpyrrolidone (mass ratio 92:3.5:1.5:3:80); second positive electrode slurry: LiNi 0.5 Mn 1.5 O4, positive electrode conductive agent, graphene, polyvinylidene fluoride, N-methylpyrrolidone in a mass ratio of 92:3.5:1.5:3:80;

[0062] (3) In step S3, the first negative electrode slurry consists of negative electrode active material, negative electrode conductive agent, tin metal powder, hydroxypropyl methylcellulose, and N-methylpyrrolidone in a mass ratio of 93:2:3:2:100; the second negative electrode slurry consists of negative electrode active material, negative electrode conductive agent, graphene, negative electrode binder, and negative electrode solvent in a mass ratio of 93:2:3:3:100.

[0063] Example 3

[0064] A novel method for preparing a high-rate, high-energy-density battery, which differs from the method in Example 1, is as follows:

[0065] (1) Electrolyte in step S1: Propylene carbonate and dimethyl carbonate are mixed evenly at a mass ratio of 1:1, and then lithium hexafluorophosphate, fluoroethylene carbonate and glycerol fatty acid ester are added and fully dispersed to obtain the electrolyte; in the electrolyte, the mass percentage of lithium hexafluorophosphate is 14%, the mass percentage of fluoroethylene carbonate is 5%, and the mass percentage of glycerol fatty acid ester is 1%;

[0066] (2) The first positive electrode slurry in step S2: LiNi 0.5 Mn 1.5 O4, positive electrode conductive agent, tin metal powder, hydroxypropyl methylcellulose, N-methylpyrrolidone (mass ratio 90:4:2:4:80); second positive electrode slurry: LiNi 0.5 Mn 1.5 O4, positive electrode conductive agent, graphene, polyvinylidene fluoride, N-methylpyrrolidone in a mass ratio of 90:4:2:4:80;

[0067] (3) In step S3, the first negative electrode slurry consists of negative electrode active material, negative electrode conductive agent, tin metal powder, hydroxypropyl methylcellulose, and N-methylpyrrolidone in a mass ratio of 92:3:2:3:100; the second negative electrode slurry consists of negative electrode active material, negative electrode conductive agent, graphene, negative electrode binder, and negative electrode solvent in a mass ratio of 92:3:2:3:100.

[0068] Comparative Example 1

[0069] A method for preparing a lithium-ion battery, following the method of Example 1, except that no annealing treatment is performed between the two coating processes in steps S2 and S3.

[0070] Comparative Example 2

[0071] A method for preparing a lithium-ion battery, which differs from the method in Example 1, in that:

[0072] (1) In step S2, a one-step coating of the positive electrode slurry is used. The positive electrode slurry is made of LiNi 0.5 Mn 1.5 O4, positive electrode conductive agent, polyvinylidene fluoride, and N-methylpyrrolidone are mixed in a mass ratio of 92:4.5:3.5:80.

[0073] (2) In step S3, a one-step coating of negative electrode slurry is used. The negative electrode slurry is made by mixing negative electrode active material, negative electrode conductive agent, negative electrode binder and negative electrode solvent in a mass ratio of 93:3:2:3:100.

[0074] The batteries obtained in Examples 1-3 and Comparative Examples 1 and 2 were subjected to rate discharge tests and cycle performance tests (room temperature, charge / discharge current 3 C, voltage 3.0-4.2 V), and the results are shown in Tables 1 and 2.

[0075] Table 1. Rate discharge performance of batteries obtained in the examples and comparative examples (unit: %)

[0076]

[0077] Table 2 Cycle performance of batteries obtained in the examples and comparative examples (unit: %)

[0078]

[0079] As can be seen from Tables 1 and 2, the rate performance and cycle performance of the batteries obtained in the examples are significantly better than those of the comparative examples. This application uses nickel foam as the current collector, achieving a three-dimensional network bond with the electrode material through a multi-porous framework, increasing the content of active material per unit area. Combined with adjustments to other raw materials and optimization of the process, the electrode further improves cycle performance and rate performance while maintaining high energy density.

[0080] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

[0081] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. 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 present invention.

Claims

1. A method for preparing a novel high-rate, high-energy-density battery, characterized in that, Includes the following steps: S1. Material Preparation: Using nickel foam as the current collector, a ceramic composite membrane as the separator, and a mixed solution containing lithium salt, organic solvent, film-forming agent, and surfactant as the electrolyte; using LiNi... 0.5 Mn 1.5 O4 or LiMn2O4 is used as the positive electrode active material, and a mixture of conductive carbon black, conductive graphite and carbon nanotubes is used as the positive electrode conductive agent; graphite and silicon monoxide are used as the negative electrode active material, and a mixture of conductive carbon black and carbon nanotubes is used as the negative electrode conductive agent. S2. Preparation of positive electrode strip: The current collector is pre-pressed according to the slurry-coated area and the unslurry-free area. Positive electrode slurry is first coated on both sides of the slurry-coated area. After drying and rolling, the temperature is raised to 400~450℃ in an inert atmosphere and held for 30~40 min. Then, it is cooled to room temperature in the furnace. Then, positive electrode slurry is coated on both sides of the slurry-coated area again. After drying and rolling, the positive electrode strip is obtained. The positive electrode slurry is formed by dispersing positive electrode powder in N-methylpyrrolidone. The positive electrode powder includes positive electrode active material, positive electrode conductive agent, positive electrode additive, and positive electrode binder. In the first coating of the positive electrode slurry, the positive electrode additive is tin metal powder and the positive electrode binder is hydroxypropyl methylcellulose. In the second coating of the positive electrode slurry, the positive electrode additive is graphene and the positive electrode binder is polyvinylidene fluoride. S3. Preparation of negative electrode strip: The current collector is pre-pressed according to the slurry-coated area and the unslurry-free area. The negative electrode slurry is first coated on both sides of the slurry-coated area. After drying and rolling, the temperature is raised to 400~450℃ in an inert atmosphere and held for 20~40 min. Then, it is cooled to room temperature in the furnace. Then, the negative electrode slurry is coated on both sides of the slurry-coated area again. After drying and rolling, the negative electrode strip is obtained. The negative electrode slurry is formed by dispersing negative electrode powder in a negative electrode solvent. The negative electrode powder includes negative electrode active material, negative electrode conductive agent, negative electrode additive, and negative electrode binder. In the first coating of the negative electrode slurry, the negative electrode additive is tin metal powder and the negative electrode binder is hydroxypropyl methylcellulose. In the second coating of the negative electrode slurry, the negative electrode additive is graphene and the negative electrode binder is hydroxypropyl methylcellulose and polyacrylic acid. S4. Cell preparation: Cut the positive and negative electrode strips into sheets, weld tabs in the slurry-free area of ​​the current collector, and apply adhesive to the tabs to obtain the positive and negative electrode sheets; stack the positive electrode sheets, separator, and negative electrode sheets in a Z-shape to form the cell. S5. Electrolyte injection and encapsulation: The cell is installed in the casing and vacuum baked at 80~85℃ for 1~2 hours; electrolyte is injected, and after standing, it is encapsulated under vacuum conditions to form a battery cell; S6. The battery cells are formed, capacity tested, and aged to obtain high-rate, high-energy-density lithium-ion batteries.

2. The method for preparing the novel high-rate, high-energy-density battery according to claim 1, characterized in that: The nickel foam described in step S1 has a thickness of 0.6~1.2 mm and a bulk density of 0.20~0.45 g / cm³. 3 After the current collector is pre-pressed in step S2, the thickness reduction rate of the current collector slurry area is 15-30%, and the thickness reduction rate of the current collector non-slurry area is 75-90%.

3. The method for preparing the novel high-rate, high-energy-density battery according to claim 2, characterized in that: The positive electrode powder in step S2 includes the following raw materials by mass percentage: 2-4% positive electrode conductive agent, 1.5-2.5% positive electrode additive, 3-4% positive electrode binder, and the balance being positive electrode active material; wherein, the positive electrode conductive agent is a mixture of conductive carbon black, conductive graphite and carbon nanotubes in a mass ratio of 10:2-3:0.2-0.

5.

4. The method of claim 3, wherein the method further comprises: The first coating of positive electrode slurry in step S2, followed by drying and rolling, is recorded as the first positive electrode powder coating. The second coating of positive electrode slurry, followed by drying and rolling, is recorded as the second positive electrode powder coating. The powder coating amount of the first positive electrode coating is 330~380 g / m. 2 The total powder coating amount from primary and secondary positive electrode powdering is 1510~1650 g / m³. 2 Compared with the thickness of the current collector sizing area after pre-compression, the thickness reduction rate of the positive electrode material after the first positive electrode powder coating is 31~45%; compared with the thickness of the current collector sizing area after pre-compression, the thickness reduction rate of the positive electrode material after the second positive electrode powder coating is 45~58%. ​ 5. The method of claim 3, wherein the method further comprises: In the positive electrode slurry, the amount of N-methylpyrrolidone is 60-120% of the mass of the positive electrode powder. ​ 6. The method of claim 2, wherein the method further comprises: In step S3, the negative electrode powder comprises the following raw materials by mass percentage: 2-3% negative electrode conductive agent, 2-3% negative electrode additive, 1.5-3% negative electrode binder, and the remainder being negative electrode active material; wherein, the negative electrode active material is a mixture of negative electrode graphite and silicon monoxide in a mass ratio of 10-20:1; the negative electrode conductive agent is a mixture of conductive carbon black and carbon nanotubes in a mass ratio of 30-40:1; in the first coating of the negative electrode slurry, the negative electrode solvent is N-methylpyrrolidone; in the second coating of the negative electrode slurry, the negative electrode solvent is a mixture of N-methylpyrrolidone and water in a mass ratio of 1-5:100, and the negative electrode binder is a mixture of hydroxypropyl methylcellulose and polyacrylic acid in a mass ratio of 1:4-10. ​ 7. The method of claim 6, wherein the method further comprises: The initial coating of negative electrode slurry in step S3, followed by drying and rolling, is recorded as the first negative electrode powder coating. The subsequent coating of negative electrode slurry, followed by drying and rolling, is recorded as the second negative electrode powder coating. The powder coating amount for the first negative electrode coating is 340~430 g / m³. 2 The total powder coating amount from primary and secondary negative electrode powder coating is 1720~1850 g / m³. 2 Compared with the thickness of the current collector sizing area after pre-compression, the thickness reduction rate of the negative electrode material after the first negative electrode powder coating is 36~45%; compared with the thickness of the current collector sizing area after pre-compression, the thickness reduction rate of the negative electrode material after the second negative electrode powder coating is 46~58%. ​ 8. The method for preparing the novel high-rate, high-energy-density battery according to claim 1, characterized in that: In the electrolyte of step S1, the mass percentage of lithium salt is 11-15%, the mass percentage of film-forming agent is 5-7%, and the mass percentage of surfactant is 1-3%.

9. The method of claim 8, wherein the method further comprises: The lithium salt is lithium hexafluorophosphate, the organic solvent is two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, the film-forming agent is one of fluoroethylene carbonate, propylene sulfite, and vinylene carbonate, and the surfactant is a glycerol fatty acid ester or a fatty acid polyethylene glycol ester. ​ 10. The method for preparing the novel high-rate, high-energy-density battery according to claim 1, characterized in that: The drying temperature in steps S2 and S3 is 85~105℃; when heating in an inert atmosphere in steps S2 and S3, the heating time is no more than 5 min.

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