Negative pole piece containing porous copper foil, preparation method of negative pole piece and method for preparing lithium ion battery by negative pole piece

Abstract

The invention belongs to the technical field of lithium ion battery preparation, and discloses a negative pole piece containing a porous copper foil, a preparation method and a method for preparing a lithium ion battery by using the negative pole piece. The porous copper foil is prepared by adopting a composite etching-electrochemical deposition method, then the porous copper foil is subjected to surface modification, the surface and pores of the porous copper foil are uniformly coated with the electrode slurry, the prepared negative electrode containing the porous copper foil is applied to the lithium ion battery, the injection process of the electrolyte is optimized, and a gradient pressure regulation mode is adopted, so that the lithium ion battery is prepared. The electrolyte can rapidly and fully infiltrate the porous copper foil and the electrode material, and the ion conduction rate of the battery is improved, so that the rate capability and the cycle life of the battery are improved. The initial capacity of the obtained battery is higher than 170mAh / g, the cycle life can reach more than 1000 times, the capacity retention ratio is more than 80%, and the capacity retention ratio of rate capability (under 5C charge and discharge conditions) is more than 70%.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, and in particular to a negative electrode sheet containing porous copper foil, its preparation method, and a method for preparing lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, with their high energy density and long cycle life, are widely used in portable electronic devices, electric vehicles, and energy storage systems. In lithium-ion batteries, the electrode current collector plays a crucial role in collecting and conducting current, and copper foil is a commonly used negative electrode current collector. However, traditional copper foil has a dense structure, resulting in a small specific surface area and weak adhesion to the electrode active material, which limits the performance of lithium-ion batteries to some extent. Specifically, the smaller specific surface area restricts the loading of active material, affecting the battery's energy density; secondly, weak adhesion leads to the active material easily detaching during charge-discharge cycles, shortening the battery's cycle life.

[0003] To address these issues, porous copper foil has gradually come into the research spotlight. By removing some unnecessary copper material, porous copper foil reduces its weight while maintaining the conductive framework. It also boasts a large specific surface area and good permeability, which can improve the loading capacity and bonding strength with active materials. However, the application of porous copper foil in lithium-ion batteries currently faces numerous challenges. These include complex manufacturing processes, high costs, and difficulties in ensuring the stability and consistency of battery performance when applied to lithium-ion battery production, thus hindering its large-scale application. Summary of the Invention

[0004] The purpose of this invention is to provide a negative electrode sheet containing porous copper foil, a method for preparing it, and a method for preparing lithium-ion batteries, thereby solving the problems that existing methods for preparing porous copper foil negative electrode sheets are complex, costly, and have poor initial capacity, cycle life, and rate performance.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a negative electrode sheet containing porous copper foil, comprising the following steps:

[0007] (1) Immerse the copper foil in the etching solution to perform preliminary etching and obtain the initial etched copper foil;

[0008] (2) In a dual-electrode system, the initially etched copper foil is electrodeposited in an electrodeposition solution to obtain a porous copper foil;

[0009] (3) A mixture of oxygen and argon is introduced into a plasma processing device to perform surface modification treatment on the porous copper foil to obtain a modified porous copper foil.

[0010] (4) The electrode paste is coated on the modified porous copper foil, and then dried and rolled in sequence to obtain a negative electrode sheet containing porous copper foil.

[0011] Furthermore, in the method for preparing a negative electrode sheet containing porous copper foil, in step (1), the etching solution is a mixture of ferric chloride, hydrochloric acid and water; the concentration of ferric chloride in the etching solution is 0.3-0.8 mol / L; the concentration of hydrochloric acid in the etching solution is 0.1-0.3 mol / L.

[0012] In step (1), the initial etching temperature is 30-40°C and the initial etching time is 10-20 min.

[0013] Furthermore, in the method for preparing a negative electrode sheet containing porous copper foil, in step (2), the dual electrode system is as follows: the initial etched copper foil serves as the cathode, and the copper sheet serves as the anode;

[0014] In step (2), the electrodeposition solution is a mixture of copper sulfate, sulfuric acid, additives, and water; the concentration of copper sulfate in the electrodeposition solution is 0.8–1.2 mol / L; the concentration of sulfuric acid in the electrodeposition solution is 0.5–1 mol / L; the additives include one or more of polyvinylpyrrolidone, sodium dipropane sulfonate, and polyethylene glycol; the concentration of the additives in the electrodeposition solution is 0.05–0.2 g / L.

[0015] In step (2), the electrodeposition conditions include: a temperature of 40–50°C and a current density of 10–20 mA / cm². 2 The time is 5 to 10 minutes.

[0016] Furthermore, in the method for preparing a negative electrode sheet containing porous copper foil, in step (3), the volume ratio of oxygen to argon is 1:1 to 3;

[0017] In step (3), the surface modification treatment conditions include: power of 100-200W, vacuum degree of 10-30Pa, and time of 3-5min.

[0018] Furthermore, in the method for preparing a negative electrode sheet containing porous copper foil, in step (4), the electrode paste is a mixture of active material, conductive agent, binder and solvent; the solid content of the electrode paste is 40-50%.

[0019] The mass ratio of the active material, the conductive agent, and the binder is 85-90:5-8:5-8;

[0020] The active material includes graphite; the conductive agent includes one or more of acetylene black, carbon nanotubes, and Ketjen black; the binder includes polyvinylidene fluoride.

[0021] In step (4), the wet film thickness of the electrode paste coated on the modified porous copper foil is 50-80 μm.

[0022] Furthermore, in the method for preparing a negative electrode sheet containing porous copper foil, in step (4), the drying temperature is 80-100°C and the drying time is 1-2 hours;

[0023] In step (4), the rolling conditions include: a pressure of 5–10 MPa, a linear pressure of 20–50 kN / m, and a compaction density of the active material of 1.5–1.7 g / cm³. 3 .

[0024] The present invention also provides a method for preparing a negative electrode sheet containing porous copper foil, which yields a negative electrode sheet containing porous copper foil.

[0025] The present invention also provides a method for preparing a lithium-ion battery using the aforementioned porous copper foil negative electrode sheet, comprising the following steps:

[0026] (1) The negative electrode sheet containing porous copper foil, the polyethylene diaphragm, and the positive electrode sheet are stacked alternately and packaged; pre-treatment is carried out under vacuum conditions to obtain an unfilled battery cell;

[0027] (2) Electrolyte is injected into the unfilled cell under gradient pressure, and ultrasonic-assisted wetting, negative pressure standing, formation and capacity testing are performed in sequence to obtain a lithium-ion battery.

[0028] Furthermore, in the method for preparing a lithium-ion battery, step (2), the method of injecting electrolyte into the unfilled cell under gradient pressure specifically includes:

[0029] Electrolyte is introduced at an initial pressure of 0.02–0.05 MPa and maintained for 5–10 minutes.

[0030] Each stage increases the pressure by 0.03–0.05 MPa, gradually increasing the pressure to 0.1–0.3 MPa, and maintaining each stage for 2–5 minutes.

[0031] Furthermore, in the method for preparing lithium-ion batteries, in step (2), the conditions for ultrasonic-assisted impregnation include: pressure of 0.1 to 0.3 MPa, ultrasonic frequency of 20 to 50 kHz, and time of 10 to 20 min.

[0032] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention uses a composite etching-electrochemical deposition method to prepare porous copper foil, which makes the porous copper foil have the characteristics of uniform pore size distribution (average pore size in the range of 1 to 5 μm) and high porosity (30 to 50%). The preparation process is simple, low cost, and can be mass-produced.

[0034] (2) The present invention performs surface modification treatment on the prepared porous copper foil and adopts plasma treatment process to introduce active groups such as hydroxyl groups on the surface of the copper foil to improve its wettability and bonding force with the electrode active material; then, the electrode slurry is uniformly coated on the surface and pores of the porous copper foil. By controlling the coating speed and thickness, it is ensured that the active material can fully fill the pores and improve the volumetric energy density of the electrode.

[0035] (3) This invention alternately stacks the negative electrode, separator, and positive electrode containing porous copper foil to ensure precise alignment between layers and reduce the risk of short circuits inside the battery. Simultaneously, the electrolyte injection process is optimized by employing gradient pressure control, enabling the electrolyte to quickly and fully wet the porous copper foil and electrode materials, improving the battery's ion conduction rate and thus enhancing its rate performance and cycle life. The lithium-ion batteries prepared using the above method all have an initial capacity higher than 170 mAh / g, a cycle life (under 1C charge / discharge conditions) exceeding 1000 cycles, a capacity retention rate exceeding 80%, and a rate performance (under 5C charge / discharge conditions) capacity retention rate exceeding 70%. Detailed Implementation

[0036] This invention provides a method for preparing a negative electrode sheet containing porous copper foil, comprising the following steps:

[0037] (1) Immerse the copper foil in the etching solution to perform preliminary etching and obtain the initial etched copper foil;

[0038] (2) In a dual-electrode system, the initially etched copper foil is electrodeposited in an electrodeposition solution to obtain a porous copper foil;

[0039] (3) A mixture of oxygen and argon is introduced into a plasma processing device to perform surface modification treatment on the porous copper foil to obtain a modified porous copper foil.

[0040] (4) The electrode paste is coated on the modified porous copper foil, and then dried and rolled in sequence to obtain a negative electrode sheet containing porous copper foil.

[0041] In this invention, in step (1), the copper foil is preferably pretreated before initial etching. The pretreatment includes the following steps: immersing the copper foil in sulfuric acid solution, cleaning, and drying.

[0042] In this invention, during the pretreatment, the volume fraction of the sulfuric acid solution is preferably 5-10%, more preferably 6-8%, and even more preferably 7%.

[0043] In this invention, during the pretreatment, the temperature of the immersion in the sulfuric acid solution is preferably room temperature; the immersion time in the sulfuric acid solution is preferably 5 to 10 minutes, more preferably 6 to 9 minutes, and even more preferably 8 minutes.

[0044] In this invention, the cleaning reagent used in the pretreatment is preferably water.

[0045] In this invention, the drying temperature during the pretreatment is preferably 60-80°C, more preferably 65-75°C, and even more preferably 70°C.

[0046] In this invention, the purpose of the pretreatment is to remove the oxide layer on the surface of the copper foil.

[0047] In this invention, in step (1), the thickness of the copper foil is preferably 8 to 12 μm, more preferably 8 to 10 μm, and even more preferably 8 μm.

[0048] In this invention, in step (1), the etching solution is preferably a mixture of ferric chloride, hydrochloric acid and water.

[0049] In this invention, the concentration of ferric chloride in the etching solution is preferably 0.3 to 0.8 mol / L, more preferably 0.5 to 0.8 mol / L, and even more preferably 0.6 mol / L.

[0050] In this invention, the concentration of hydrochloric acid in the etching solution is preferably 0.1 to 0.3 mol / L, more preferably 0.15 to 0.25 mol / L, and even more preferably 0.2 mol / L.

[0051] In this invention, in step (1), the temperature of the initial etching is preferably 30-40°C, more preferably 32-37°C, and even more preferably 35°C; the time of the initial etching is preferably 10-20 min, more preferably 12-18 min, and even more preferably 15 min.

[0052] In this invention, in step (2), the dual-electrode system is preferably: the initial etched copper foil serves as the cathode, and the copper sheet serves as the anode.

[0053] In this invention, in step (2), the electrodeposition solution is preferably a mixture of copper sulfate, sulfuric acid, additives and water.

[0054] In this invention, the concentration of copper sulfate in the electrodeposition solution is preferably 0.8 to 1.2 mol / L, more preferably 0.9 to 1.1 mol / L, and even more preferably 1 mol / L.

[0055] In this invention, the concentration of sulfuric acid in the electrodeposition solution is preferably 0.5 to 1 mol / L, more preferably 0.5 to 0.7 mol / L, and even more preferably 0.6 mol / L.

[0056] In this invention, the additive preferably includes one or more of polyvinylpyrrolidone, sodium didithiopropane sulfonate, and polyethylene glycol, more preferably includes multiple of polyvinylpyrrolidone, sodium didithiopropane sulfonate, and polyethylene glycol, and more preferably includes three of polyvinylpyrrolidone, sodium didithiopropane sulfonate, and polyethylene glycol.

[0057] In this invention, the molecular weight of the polyvinylpyrrolidone is preferably 40,000 to 50,000 Da, more preferably 40,000 to 45,000 Da, and even more preferably 40,000 Da.

[0058] In this invention, the molecular weight of the sodium polydisulfide dipropane sulfonate is preferably 250-300 Da, more preferably 270-290 Da, and even more preferably 280 Da.

[0059] In this invention, the molecular weight of the polyethylene glycol is preferably 5500-6500 Da, more preferably 5800-6200 Da, and even more preferably 6000 Da.

[0060] In this invention, the concentration of the additive in the electrodeposition solution is preferably 0.05 to 0.2 g / L, more preferably 0.05 to 0.15 g / L, and even more preferably 0.105 g / L.

[0061] In this invention, the electrodeposition conditions in step (2) include: a temperature preferably of 40–50°C, more preferably 42–47°C, and even more preferably 45°C; and a current density preferably of 10–20 mA / cm². 2 More preferably 12–18 mA / cm 2 More preferably 15 mA / cm 2 The preferred time is 5 to 10 minutes, more preferably 6 to 8 minutes, and even more preferably 7 minutes.

[0062] In this invention, in step (3), argon gas is preferably introduced before surface modification treatment; the time for introducing argon gas is preferably 5 to 10 minutes, more preferably 5 to 7 minutes, and even more preferably 5 minutes.

[0063] In this invention, in step (3), the volume ratio of oxygen to argon is preferably 1:1 to 3, more preferably 1:1.5 to 2.5, and even more preferably 1:2.

[0064] In this invention, the surface modification treatment conditions in step (3) include: power preferably 100-200W, more preferably 120-180W, and more preferably 150W; vacuum preferably 10-30Pa, more preferably 15-25Pa, and more preferably 20Pa; and time preferably 3-5min, more preferably 3.5-4.5min, and more preferably 4min.

[0065] In this invention, in step (4), the electrode paste is preferably a mixture of active material, conductive agent, binder and solvent.

[0066] In this invention, in step (4), the solid content of the electrode slurry is 40-50%, more preferably 42-48%, and even more preferably 45%.

[0067] In this invention, the active material preferably includes graphite.

[0068] In this invention, the conductive agent preferably includes one or more of acetylene black, carbon nanotubes, and Ketjen black, more preferably acetylene black and / or carbon nanotubes, and even more preferably acetylene black.

[0069] In this invention, the adhesive preferably comprises polyvinylidene fluoride.

[0070] In this invention, the molecular weight of the polyvinylidene fluoride is preferably 500,000 to 800,000 g / mol, more preferably 550,000 to 700,000 g / mol, and even more preferably 600,000 g / mol.

[0071] In this invention, the mass ratio of the active material, the conductive agent, and the binder is preferably 85-90:5-8:5-8, more preferably 88-90:5-6:5-6, and even more preferably 90:5:5.

[0072] In this invention, the solvent is preferably N-methylpyrrolidone.

[0073] In this invention, in step (4), the coating method is preferably blade coating.

[0074] In this invention, in step (4), the coating speed is preferably 1 to 2 m / min, more preferably 1.2 to 1.7 m / min, and even more preferably 1.5 m / min.

[0075] In this invention, in step (4), the wet film thickness of the electrode paste coated on the modified porous copper foil is preferably 50-80 μm, more preferably 60-70 μm, and even more preferably 65 μm.

[0076] In this invention, in step (4), the drying temperature is preferably 80-100°C, more preferably 85-95°C, and even more preferably 90°C; the drying time is preferably 1-2 hours, more preferably 1.2-1.6 hours, and even more preferably 1.5 hours.

[0077] In this invention, the conditions for roller pressing in step (4) include: a pressure preferably of 5-10 MPa, more preferably 6-8 MPa, and even more preferably 7 MPa; a linear pressure preferably of 20-50 kN / m, more preferably 30-45 kN / m, and even more preferably 35 kN / m; and a compaction density of the active material preferably of 1.5-1.7 g / cm³. 3 More preferably, it is 1.55–1.65 g / cm³. 3 More preferably 1.6 g / cm³ 3 .

[0078] The present invention also provides a method for preparing a negative electrode sheet containing porous copper foil, which yields a negative electrode sheet containing porous copper foil.

[0079] The present invention also provides a method for preparing a lithium-ion battery using the aforementioned porous copper foil negative electrode sheet, comprising the following steps:

[0080] (1) The negative electrode sheet containing porous copper foil, the polyethylene diaphragm, and the positive electrode sheet are stacked alternately and packaged; pre-treatment is carried out under vacuum conditions to obtain an unfilled battery cell;

[0081] (2) Electrolyte is injected into the unfilled cell under gradient pressure, and ultrasonic-assisted wetting, negative pressure standing, formation and capacity testing are performed in sequence to obtain a lithium-ion battery.

[0082] In this invention, in step (1), the polyethylene diaphragm is preferably a commercially available product.

[0083] In this invention, in step (1), the positive electrode sheet is preferably a commercially available product or preparation method known in the art.

[0084] In this invention, in step (1), a liquid injection port is reserved during the encapsulation process.

[0085] In this invention, in step (1), the vacuum degree of the pretreatment is preferably -0.09 to -0.095 MPa, more preferably -0.091 to -0.093 MPa, and even more preferably -0.092 MPa; the pretreatment time is preferably 10 to 30 min, more preferably 15 to 25 min, and even more preferably 20 min.

[0086] In this invention, the purpose of the pretreatment is to remove air from inside the battery cell and gas from the pores of the electrode plates.

[0087] In this invention, in step (2), the electrolyte is preferably a solution well known in the art. Specifically, in the embodiments, the electrolyte is preferably a 1 mol / L LiPF6 solution in a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, wherein the volume ratio of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate is 1:1:1.

[0088] In this invention, in step (2), the amount of electrolyte injected is preferably 1.1 to 1.3 times the volume of the battery cell, more preferably 1.15 to 1.25 times, and even more preferably 1.2 times.

[0089] In this invention, step (2), specifically the method of injecting electrolyte into the unfilled cell under gradient pressure, includes:

[0090] Electrolyte is introduced at an initial pressure of 0.02–0.05 MPa (more preferably 0.02–0.04 MPa, more preferably 0.03 MPa) and maintained for 5–10 min (more preferably 7–9 min, more preferably 8 min).

[0091] Each stage increases the pressure by 0.03–0.05 MPa (more preferably 0.03–0.04 MPa, more preferably 0.03 MPa), gradually increasing the pressure to 0.1–0.3 MPa (more preferably 0.15–0.25 MPa, more preferably 0.2 MPa), and maintaining each stage for 2–5 minutes (more preferably 3–4 minutes, more preferably 3 minutes).

[0092] In this invention, the purpose of injecting electrolyte in the above manner is to use the pressure difference to drive the electrolyte to permeate into the pores inside the electrode.

[0093] In this invention, the conditions for ultrasonic-assisted immersion in step (2) include: pressure preferably 0.1-0.3 MPa, more preferably 0.15-0.25 MPa, and more preferably 0.2 MPa; ultrasonic frequency preferably 20-50 kHz, more preferably 30-40 kHz, and more preferably 35 kHz; and time preferably 10-20 min, more preferably 12-18 min, and more preferably 15 min.

[0094] In this invention, the purpose of using ultrasonic-assisted wetting is to break the gas film in the pores of the electrode through the ultrasonic cavitation effect, thereby promoting the electrolyte to enter the micropores.

[0095] In this invention, in step (2), the pressure of the negative pressure settling is preferably -0.05 to -0.07 MPa, more preferably -0.055 to -0.065 MPa, and even more preferably -0.06 MPa; the time of the negative pressure settling is preferably 5 to 10 min, more preferably 7 to 9 min, and even more preferably 8 min.

[0096] In this invention, the purpose of using negative pressure for static setting is to expel air bubbles generated by pressure changes, allowing the electrolyte to diffuse fully within the electrode.

[0097] In this invention, in step (2), the formation and the capacity separation can be carried out using solutions well known in the art.

[0098] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0099] Example 1

[0100] This embodiment provides a method for preparing a negative electrode sheet containing porous copper foil, including the following steps:

[0101] (1) Place the original copper foil with a thickness of 8μm into a 7vt% dilute sulfuric acid solution and soak it at 28℃ for 8min; rinse it with deionized water and dry it at 70℃; place the treated copper foil into an etching solution (ferric chloride concentration 0.7mol / L, hydrochloric acid concentration 0.2mol / L, deionized water) and etch it at 35℃ for 15min to obtain the initial etched copper foil;

[0102] (2) Using the initially etched copper foil as the cathode and the pure copper sheet as the anode, the electrodeposition solution (copper sulfate concentration 1.0 mol / L, sulfuric acid concentration 0.6 mol / L, polyvinylpyrrolidone 40,000 Da concentration 0.05 g / L, sodium dithiopropane sulfonate 280 Da concentration 5 mg / L, polyethylene glycol 6000 Da concentration 0.05 g / L) was applied at 45℃ and a current density of 15 mA / cm². 2 Under the given conditions, porous copper foil was obtained by electrodeposition for 7 minutes;

[0103] (3) The porous copper foil was placed in a plasma treatment device. Argon gas was first introduced for 5 minutes to remove the air. Then a mixture of oxygen and argon gas (volume ratio 1:2) was introduced and treated for 4 minutes under the conditions of 150W power and 20Pa vacuum to obtain the modified porous copper foil.

[0104] (4) Graphite (90 parts), acetylene black (5 parts, Tianjin Yiborui Chemical Co., Ltd.), and polyvinylidene fluoride 600,000 g / mol (5 parts) were mixed, and N-methylpyrrolidone was added. The mixture was stirred to prepare an electrode slurry with a solid content of 45%. The slurry was coated using a doctor blade at a speed of 1.5 m / min, resulting in a wet film thickness of 65 μm. The coated electrode was dried in a 90℃ oven for 1.5 h, and then rolled using a roller press under a pressure of 7 MPa and a linear pressure of 35 kN / m until the graphite compaction density reached 1.6 g / cm³. 3 This yields a negative electrode sheet containing porous copper foil.

[0105] This embodiment also provides a method for preparing a lithium-ion battery using a negative electrode sheet containing porous copper foil, comprising the following steps:

[0106] (1) By mass fraction, 90% lithium iron phosphate active material, 5% acetylene black conductive agent, and 5% polyvinylidene fluoride binder (600,000 g / mol) are mixed, and N-methylpyrrolidone is added and stirred at high speed to prepare a slurry with a solid content of 50%; this slurry is coated onto aluminum foil (wet film thickness 65 μm), dried (90℃, 4 min), and then rolled (compacted density 2.8 g / cm³). 3 The cutting and inspection dimensions are accurate (±0.2mm), the electrode tabs are firmly welded, and they are coated with adhesive for protection, resulting in a positive electrode sheet.

[0107] A negative electrode sheet containing porous copper foil, a 16μm thick polyethylene separator (Foshan Jinhui High-Tech Optoelectronic Materials Co., Ltd.), and the above-mentioned positive electrode sheet are stacked alternately, with the stacking accuracy controlled within ±0.1mm. After stacking, they are placed in an aluminum-plastic film for sealing, and a liquid injection port is reserved. The unfilled cell is placed in a vacuum chamber and left to stand for 20 minutes under a vacuum of -0.092MPa to obtain an unfilled cell.

[0108] (2) Electrolyte (1 mol / L LiPF6, ethylene carbonate: dimethyl carbonate: methyl ethyl carbonate vt = 1:1:1) was introduced into the vacuum chamber, and the amount of electrolyte injected was 1.1 times the volume of the un-injected cell; the initial pressure was 0.03 MPa and held for 8 min; the pressure was gradually increased to 0.2 MPa (0.03 MPa per stage, held for 3 min per stage); at a pressure of 0.2 MPa, ultrasonic vibration at 35 kHz was applied for 15 min; the chamber pressure was reduced to -0.06 MPa and held for 8 min; during the formation stage, the battery was charged to 3.0 V at 0.1 C (and left to stand for 1 h), charged to 4.2 V at 0.2 C, and discharged to 2.75 V at 0.5 C; during the capacity testing stage, the battery was charged and discharged 4 times at 0.5 C to obtain a lithium-ion battery.

[0109] Constant current charge-discharge tests were conducted using the LAND CT2001A. Under 1C charge-discharge conditions, the initial battery capacity was 183mAh / g; under 1C charge-discharge conditions, the cycle life reached 1200 cycles with a capacity retention rate of 83%; under 5C charge-discharge conditions, the capacity retention rate of the rate performance was 75%.

[0110] Example 2

[0111] This embodiment provides a method for preparing a negative electrode sheet containing porous copper foil, including the following steps:

[0112] (1) Place the original copper foil with a thickness of 10 μm into a 5 wt% dilute sulfuric acid solution and soak it at 25 °C for 5 min; rinse it with deionized water and dry it at 60 °C; place the treated copper foil into an etching solution (ferric chloride concentration 0.5 mol / L, hydrochloric acid concentration 0.1 mol / L, deionized water) and etch it at 30 °C for 10 min to obtain the initial etched copper foil;

[0113] (2) Using the initially etched copper foil as the cathode and the pure copper sheet as the anode, the electrodeposition solution (copper sulfate concentration 0.8 mol / L, sulfuric acid concentration 0.5 mol / L, polyvinylpyrrolidone 40,000 Da concentration 0.1 g / L) was applied at 40℃ and a current density of 10 mA / cm². 2 Under the given conditions, porous copper foil was obtained by electrodeposition for 5 minutes.

[0114] (3) The porous copper foil is placed in a plasma treatment device. Argon gas is first introduced for 5 minutes, the air in the foil is then discharged, and a mixture of oxygen and argon gas (volume ratio 1:3) is introduced. The foil is then treated for 3 minutes under the conditions of 100W power and 10Pa vacuum to obtain the modified porous copper foil.

[0115] (4) Graphite (90 parts), Ketjen Black EC600JD (5 parts, Lion Corporation of Japan), and polyvinylidene fluoride 600,000 g / mol (5 parts) were mixed, and N-methylpyrrolidone was added. The mixture was stirred to prepare an electrode slurry with a solid content of 40%. The slurry was coated using a doctor blade at a speed of 1 m / min, resulting in a wet film thickness of 50 μm. The coated electrode was dried in an oven at 80℃ for 1 h, and then rolled using a roller press under a pressure of 5 MPa and a linear pressure of 30 kN / m until the graphite compaction density reached 1.5 g / cm³. 3 This yields a negative electrode sheet containing porous copper foil.

[0116] This embodiment also provides a method for preparing a lithium-ion battery using a negative electrode sheet containing porous copper foil, comprising the following steps:

[0117] (1) By mass fraction, 90% lithium iron phosphate active material, 5% acetylene black conductive agent, and 5% polyvinylidene fluoride binder (600,000 g / mol) are mixed, and N-methylpyrrolidone is added and stirred at high speed to prepare a slurry with a solid content of 50%; this slurry is coated onto aluminum foil (wet film thickness 65 μm), dried (90℃, 4 min), and then rolled (compacted density 2.8 g / cm³). 3 The cutting and inspection dimensions are accurate (±0.2mm), the electrode tabs are firmly welded, and they are coated with adhesive for protection, resulting in a positive electrode sheet.

[0118] A negative electrode sheet containing porous copper foil, a 12μm thick polyethylene separator (Foshan Jinhui High-Tech Optoelectronic Materials Co., Ltd.), and the above-mentioned positive electrode sheet are stacked alternately, with the stacking accuracy controlled within ±0.1mm. After stacking, they are placed in an aluminum-plastic film for sealing, and a liquid injection port is reserved. The unfilled cell is placed in a vacuum chamber and left to stand for 10 minutes under a vacuum of -0.09MPa to obtain an unfilled cell.

[0119] (2) Electrolyte (1 mol / L LiPF6, ethylene carbonate: dimethyl carbonate: methyl ethyl carbonate vt = 1:1:1) was introduced into the vacuum chamber, and the amount of electrolyte injected was 1.3 times the volume of the un-injected cell; the initial pressure was 0.02 MPa and held for 5 min; the pressure was gradually increased to 0.1 MPa (0.05 MPa per stage, held for 2 min per stage); at a pressure of 0.1 MPa, 20 kHz ultrasonic vibration was applied for 10 min; the chamber pressure was reduced to -0.05 MPa and held for 5 min; during the formation stage, the battery was charged to 3.0 V at 0.1 C (and left to stand for 1 h), charged to 4.2 V at 0.2 C, and discharged to 2.75 V at 0.5 C; during the capacity testing stage, the battery was charged and discharged 3 times at 0.5 C to obtain a lithium-ion battery.

[0120] Constant current charge-discharge tests were conducted using the LAND CT2001A. Under 1C charge-discharge conditions, the initial battery capacity was 170mAh / g; under 1C charge-discharge conditions, the cycle life reached 1000 cycles with a capacity retention rate of 80%; under 5C charge-discharge conditions, the capacity retention rate of the rate performance was 70%.

[0121] Example 3

[0122] This embodiment provides a method for preparing a negative electrode sheet containing porous copper foil, including the following steps:

[0123] (1) Place the original copper foil with a thickness of 12μm into a 10vt% dilute sulfuric acid solution and soak it at 30℃ for 10min; rinse it with deionized water and dry it at 80℃; place the treated copper foil into an etching solution (ferric chloride concentration 0.3mol / L, hydrochloric acid concentration 0.3mol / L, deionized water) and etch it at 40℃ for 18min to obtain the initial etched copper foil;

[0124] (2) Using the initially etched copper foil as the cathode and the pure copper sheet as the anode, the electrodeposition solution (copper sulfate concentration 1.2 mol / L, sulfuric acid concentration 1.0 mol / L, polyvinylpyrrolidone 40,000 Da concentration 0.05 g / L, polyethylene glycol 6000 Da concentration 0.05 g / L) was applied at 50℃ and a current density of 20 mA / cm². 2 Under the given conditions, porous copper foil was obtained by electrodeposition for 10 minutes;

[0125] (3) The porous copper foil is placed in a plasma treatment device. Argon gas is first introduced for 10 minutes to remove the air. Then a mixture of oxygen and argon gas (volume ratio 1:1.5) is introduced and treated for 5 minutes under the conditions of 200W power and 30Pa vacuum to obtain the modified porous copper foil.

[0126] (4) Graphite (90 parts), carbon nanotubes (5 parts, TF410 series carbon nanotubes, Shandong Carbon Peak New Material Technology Co., Ltd.), and polyvinylidene fluoride (600,000 g / mol, 5 parts) were mixed, and N-methylpyrrolidone was added. The mixture was stirred to prepare an electrode slurry with a solid content of 50%. The slurry was coated using a doctor blade at a speed of 2 m / min, resulting in a wet film thickness of 80 μm. The coated electrode was dried in an oven at 100℃ for 2 h, and then rolled using a roller press under a pressure of 10 MPa and a linear pressure of 40 kN / m until the graphite compaction density reached 1.6 g / cm³. 3 This yields a negative electrode sheet containing porous copper foil.

[0127] This embodiment also provides a method for preparing a lithium-ion battery using a negative electrode sheet containing porous copper foil, comprising the following steps:

[0128] (1) By mass fraction, 90% lithium iron phosphate active material, 5% acetylene black conductive agent, and 5% polyvinylidene fluoride binder (600,000 g / mol) are mixed, and N-methylpyrrolidone is added and stirred at high speed to prepare a slurry with a solid content of 50%; this slurry is coated onto aluminum foil (wet film thickness 65 μm), dried (90℃, 4 min), and then rolled (compacted density 2.8 g / cm³). 3 The cutting and inspection dimensions are accurate (±0.2mm), the electrode tabs are firmly welded, and they are coated with adhesive for protection, resulting in a positive electrode sheet.

[0129] A negative electrode sheet containing porous copper foil, a 20μm thick polyethylene separator (Foshan Jinhui High-Tech Optoelectronic Materials Co., Ltd.), and the above-mentioned positive electrode sheet are stacked alternately, with the stacking accuracy controlled within ±0.1mm. After stacking, they are placed in an aluminum-plastic film for sealing, and a liquid injection port is reserved. The unfilled battery cell is placed in a vacuum chamber and left to stand for 30 minutes under a vacuum of -0.095MPa to obtain an unfilled battery cell.

[0130] (2) Electrolyte (1 mol / L LiPF6, ethylene carbonate: dimethyl carbonate: methyl ethyl carbonate vt = 1:1:1) was introduced into the vacuum chamber, and the amount of electrolyte injected was 1.2 times the volume of the un-injected cell; the initial pressure was 0.05 MPa and held for 10 min; the pressure was gradually increased to 0.3 MPa (0.04 MPa per stage, held for 5 min per stage); at a pressure of 0.3 MPa, 50 kHz ultrasonic vibration was applied for 20 min; the chamber pressure was reduced to -0.07 MPa and held for 10 min; during the formation stage, the battery was charged to 3.0 V at 0.1 C (and left to stand for 1 h), charged to 4.2 V at 0.2 C, and discharged to 2.75 V at 0.5 C; during the capacity testing stage, the battery was charged and discharged 5 times at 0.5 C to obtain a lithium-ion battery.

[0131] Constant current charge-discharge tests were conducted using the LAND CT2001A. Under 1C charge-discharge conditions, the initial battery capacity was 175mAh / g; under 1C charge-discharge conditions, the cycle life reached 1100 cycles with a capacity retention rate of 82%; under 5C charge-discharge conditions, the capacity retention rate for rate performance was 73%.

[0132] Comparative Example 1

[0133] This comparative example provides a method for preparing a lithium-ion battery using a negative electrode sheet containing porous copper foil as described in Example 1. The difference from Example 1 is that when introducing electrolyte into the vacuum chamber in step (2), a constant pressure of 0.1 MPa is used for injection, while other parameters and conditions are the same as in Example 1.

[0134] Constant current charge-discharge tests were conducted using the LAND CT2001A. Under 1C charge-discharge conditions, the initial battery capacity was 155mAh / g. Under 1C charge-discharge conditions, the cycle life reached 820 cycles, with a capacity retention rate of only 61%. Under 5C charge-discharge conditions, the capacity retention rate of the rate performance was 57%.

[0135] Comparative Example 2

[0136] This comparative example provides a method for preparing a negative electrode sheet containing porous copper foil. The difference from Example 1 is that step (3) is deleted, while other parameters and conditions are the same as in Example 1. The lithium-ion battery is prepared using the scheme of Example 1.

[0137] Constant current charge-discharge tests were conducted using the LAND CT2001A. Under 1C charge-discharge conditions, the initial battery capacity was 162 mAh / g. Under 1C charge-discharge conditions, the cycle life reached 900 cycles, with a capacity retention rate of only 67%. Under 5C charge-discharge conditions, the capacity retention rate of the rate performance was 63%.

[0138] The comparative experimental results above show that, under different parameter conditions, the batteries prepared using the method of the present invention (Examples 1-3) all have an initial capacity higher than 170 mAh / g, a cycle life exceeding 1000 cycles, a capacity retention rate greater than 80%, and a 5C rate discharge capacity retention rate greater than 70%. These results demonstrate the consistency and feasibility of the preparation method of the present invention.

[0139] In contrast, when the electrolyte injection pressure method was changed (Comparative Example 1) or the plasma treatment step in the electrode preparation process was omitted (Comparative Example 2), the aforementioned performance indicators (initial capacity, cycle life, capacity retention, and 5C rate capacity retention) of the resulting batteries did not reach the levels of Examples 1-3. This further demonstrates that the battery performance obtained by the preparation method of the present invention has significant advantages, and that the electrolyte injection pressure control and electrode plasma treatment process steps included therein are crucial and indispensable for achieving the aforementioned superior performance.

[0140] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a negative electrode sheet containing porous copper foil, characterized in that, Includes the following steps: (1) Immerse the copper foil in the etching solution to perform preliminary etching and obtain the initial etched copper foil; (2) In a dual-electrode system, the initially etched copper foil is electrodeposited in an electrodeposition solution to obtain a porous copper foil; (3) A mixture of oxygen and argon is introduced into a plasma processing device to perform surface modification treatment on the porous copper foil to obtain a modified porous copper foil. (4) The electrode paste is coated on the modified porous copper foil, and then dried and rolled in sequence to obtain a negative electrode sheet containing porous copper foil.

2. The method for preparing a negative electrode sheet containing porous copper foil according to claim 1, characterized in that, In step (1), the etching solution is a mixture of ferric chloride, hydrochloric acid and water; the concentration of ferric chloride in the etching solution is 0.3-0.8 mol / L; the concentration of hydrochloric acid in the etching solution is 0.1-0.3 mol / L. In step (1), the initial etching temperature is 30-40°C and the initial etching time is 10-20 min.

3. A method for preparing a negative electrode sheet containing porous copper foil according to claim 1 or 2, characterized in that, In step (2), the dual-electrode system is as follows: the initial etched copper foil serves as the cathode, and the copper sheet serves as the anode; In step (2), the electrodeposition solution is a mixture of copper sulfate, sulfuric acid, additives, and water; the concentration of copper sulfate in the electrodeposition solution is 0.8–1.2 mol / L; the concentration of sulfuric acid in the electrodeposition solution is 0.5–1 mol / L; the additives include one or more of polyvinylpyrrolidone, sodium dipropane sulfonate, and polyethylene glycol; the concentration of the additives in the electrodeposition solution is 0.05–0.2 g / L. In step (2), the electrodeposition conditions include: a temperature of 40–50°C and a current density of 10–20 mA / cm². 2 The time is 5 to 10 minutes.

4. The method for preparing a negative electrode sheet containing porous copper foil according to claim 3, characterized in that, In step (3), the volume ratio of oxygen to argon is 1:1 to 3; In step (3), the surface modification treatment conditions include: power of 100-200W, vacuum degree of 10-30Pa, and time of 3-5min.

5. A method for preparing a negative electrode sheet containing porous copper foil according to claim 1 or 4, characterized in that, In step (4), the electrode paste is a mixture of active material, conductive agent, binder and solvent; the solid content of the electrode paste is 40-50%; The mass ratio of the active material, the conductive agent, and the binder is 85-90:5-8:5-8; The active material includes graphite; the conductive agent includes one or more of acetylene black, carbon nanotubes, and Ketjen black; the binder includes polyvinylidene fluoride. In step (4), the wet film thickness of the electrode paste coated on the modified porous copper foil is 50-80 μm.

6. The method for preparing a negative electrode sheet containing porous copper foil according to claim 5, characterized in that, In step (4), the drying temperature is 80-100℃, and the drying time is 1-2 hours; In step (4), the rolling conditions include: a pressure of 5–10 MPa, a linear pressure of 20–50 kN / m, and a compaction density of the active material of 1.5–1.7 g / cm³. 3 .

7. A negative electrode sheet containing porous copper foil prepared by the method for preparing a negative electrode sheet containing porous copper foil according to any one of claims 1 to 6.

8. A method for preparing a lithium-ion battery using the negative electrode sheet containing porous copper foil as described in claim 7, characterized in that, Includes the following steps: (1) The negative electrode sheet containing porous copper foil, the polyethylene diaphragm, and the positive electrode sheet are stacked alternately and packaged; pre-treatment is carried out under vacuum conditions to obtain an unfilled battery cell; (2) Electrolyte is injected into the unfilled cell under gradient pressure, and ultrasonic-assisted wetting, negative pressure standing, formation and capacity testing are performed in sequence to obtain a lithium-ion battery.

9. The method for preparing a lithium-ion battery according to claim 8, characterized in that, In step (2), the method of injecting electrolyte into the unfilled cell under gradient pressure specifically includes: Electrolyte is introduced at an initial pressure of 0.02–0.05 MPa and maintained for 5–10 minutes. Each stage increases the pressure by 0.03–0.05 MPa, gradually increasing the pressure to 0.1–0.3 MPa, and maintaining each stage for 2–5 minutes.

10. The method for preparing a lithium-ion battery according to claim 8 or 9, characterized in that, In step (2), the conditions for ultrasonic-assisted infiltration include: pressure of 0.1 to 0.3 MPa, ultrasonic frequency of 20 to 50 kHz, and time of 10 to 20 min.