Production process of lithium iron phosphate square aluminum shell battery cell

Abstract

The invention relates to the technical field of battery cell production, in particular to a production process of a lithium iron phosphate square aluminum shell battery cell, which comprises the following steps: S1, drying a positive electrode raw material, and feeding a positive electrode and a negative electrode; s2, mixing the positive electrode and the negative electrode to prepare slurry; s3, sieving the positive electrode slurry and the negative electrode slurry; s4, coating and drying the positive electrode and the negative electrode; s5, rolling the positive and negative pole pieces, slitting the pole pieces, and performing die cutting and baking on the pole pieces; s6, positive and negative electrode winding and lamination; s7, assembling is carried out; s8, liquid injection; s9, performing negative pressure formation; s10, carrying out capacity grading; s11, detection is carried out; internal resistance, voltage, size and weight of the batteries are detected, and the batteries are sorted according to test results; and picking out short-circuit and low-voltage battery cells with micro-short-circuit defects in the battery cells. The battery product produced by the invention has higher capacity, higher energy density, longer cycle life and reliable safety attribute.

Description

Technical Field

[0001] This invention relates to the field of battery cell manufacturing technology, specifically a manufacturing process for a square aluminum-cased lithium iron phosphate battery cell. Background Technology

[0002] Energy storage batteries can be widely used in power systems, including power generation, transmission and distribution, and power consumption. The rapid growth of renewable energy power system construction has laid the foundation for the deployment of large-scale energy storage systems. Simultaneously, technological advancements and increased production scale have driven down the cost of energy storage batteries. Furthermore, the rapid development of the energy storage battery industry has also spurred the application of related technologies in energy storage batteries, further reducing their cost. As the cost of energy storage batteries continues to decline, the energy storage battery market will enter a phase of rapid and large-scale development, achieving a low-carbon energy transformation.

[0003] Safety incidents involving energy storage systems worldwide have drawn widespread attention from the industry. Therefore, improving the safety performance of energy storage batteries is the most effective measure to address system safety issues. It is anticipated that continuous upgrades in energy storage battery performance will further improve their safety and lifespan, achieving green and low-carbon goals and contributing to the realization of dual-carbon objectives. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention proposes a manufacturing process for lithium iron phosphate square aluminum-cased cells, which produces battery products with higher capacity, higher energy density, longer cycle life, and reliable safety attributes.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] The manufacturing process of a lithium iron phosphate square aluminum shell battery cell according to the present invention includes the following steps;

[0007] S1. Drying of positive electrode raw materials and feeding of positive and negative electrodes: Feeding is carried out in a closed batching room using an automatic feeding system. When feeding, first close the silo valve, turn on the vacuum pump to create a vacuum in the silo and conveying pipeline, and then the operator weighs and unpacks the powder raw materials, inserts the vacuum suction gun into the raw material barrel, seals it, and the material is sucked into the conveying pipeline and enters the silo.

[0008] S2. Positive and negative electrode mixing and slurry preparation: After the positive electrode powder raw material, active material, binder, and conductive agent are added, N-methylpyrrolidone (NMP) solvent is added, and the mixture is stirred evenly in a vacuum mixer to form a slurry-like positive electrode coating material; The negative electrode powder raw material, active material, binder, thickener, conductive agent, etc. are added to a vacuum mixer, deionized water is added, and the mixture is stirred evenly in a vacuum mixer to form a slurry-like negative electrode material;

[0009] S3. The positive and negative electrode slurries are sieved. After the positive and negative electrode slurries are mixed, they will be conveyed to the diaphragm pump for filtration under pressure to remove small particulate impurities in the slurry and ensure high-quality coating operation.

[0010] S4. Positive and negative electrode coating and drying: The sieved positive and negative electrode slurries will be transported to a transfer tank and stored by low-speed vacuum stirring to prevent slurry separation or sedimentation; when in use, they will be transported to the coating machine nozzle through a closed pipeline to spray the foil surface.

[0011] S5. Positive and negative electrode sheet rolling, electrode sheet slitting, electrode sheet die cutting and baking: After coating and drying, the positive and negative current collectors are coated with a mixture of positive and negative electrode materials, and need to be compacted into thin sheets by rolling equipment.

[0012] S6. Positive and negative electrode winding and stacking: The positive and negative electrode sheets and the separator are installed on the automatic winding machine for automatic winding as required; then the positive and negative electrode sheets and the separator are installed on the automatic stacking machine for automatic stacking as required, and the battery cell is made by alternating layers of positive and negative electrode sheets.

[0013] S7. Assembly: The winding and stacked core is subjected to hot pressing, X-ray inspection, ultrasonic welding of electrode adapter, laser welding of clamp cover plate, hot melting of coating, cell insertion into the shell, top cover sealing welding, helium inspection, vacuum drying, and laser welding of sealing nails in sequence.

[0014] S8. Electrolyte injection: The workshop is equipped with a drying room for electrolyte injection. The temperature in the injection room is within the range of 25±5℃ and the humidity is <1%. The dried battery cells are placed in the sealed drying room for electrolyte injection. After injection, they are left to stand in the designated area.

[0015] S9, Negative Voltage Formation: The battery is charged with a small current in an automated forming cabinet to activate the electrode materials, allowing the polymer on the positive and negative electrodes to permeate with the electrolyte.

[0016] S10, Capacity Assessment: The selected qualified batteries are charged and discharged in the capacity assessor for approximately 6 hours. The first charge is to fully charge any batteries that were not fully charged during formation; the discharge refers to the automatic discharging of fully charged batteries. The capacity assessor automatically records the capacity of each battery based on the amount of discharge, and then separates the batteries according to their different capacities, thus achieving the purpose of capacity assessment; the final charge is to recharge each battery to 70% SOC.

[0017] S11. Testing; Testing the battery's internal resistance, voltage, size, and weight, and sorting the batteries according to the test results; Picking out short-circuited and low-voltage cells with micro-short-circuit defects inside the cells to ensure battery performance.

[0018] The beneficial effects of this invention are as follows: This invention innovatively develops lithium iron phosphate battery cells, improving lifespan and increasing energy conversion efficiency throughout the entire life cycle: in-situ doping of X / Y elements in the positive electrode and the development of a radial spherical precursor improve cycle life, reduce DCR growth, and maintain high energy conversion efficiency throughout the entire life cycle; the application of a new current collector coating material achieves a cycle performance of up to 15,000 cycles; the independently developed electrolyte formula improves high-temperature cycle performance by 30%; the innovative assembly method increases energy density and improves assembly efficiency, resulting in increased energy density, improved assembly efficiency, and reduced costs. Battery products produced using this invention have higher capacity, higher energy density, longer cycle life, and reliable safety attributes (the battery does not catch fire or explode after extreme safety tests such as needle penetration, 200°C hot box, 50V overcharge, and thermal runaway triggered by heating). Detailed Implementation

[0019] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0020] The manufacturing process of a lithium iron phosphate square aluminum shell battery cell according to the present invention includes the following steps;

[0021] S1. Drying of positive electrode raw materials and feeding of positive and negative electrodes;

[0022] The positive electrode material may contain small amounts of moisture and oily substances, requiring baking in an oven, usually electrically heated, at around 80℃ for about 2 hours. This allows the moisture and oily substances to evaporate fully, improving the material's performance. The positive electrode active material, binder, and conductive agent, as well as the negative electrode active material, binder, solubilizer, and conductive agent, are all powder raw materials. Feeding is done in a sealed batching room using an automatic feeding system. During feeding, the silo valve is first closed, and the vacuum pump is turned on to create a vacuum in the silo and conveying pipeline. Then, operators weigh and unpack the powder raw materials, insert the vacuum suction gun into the raw material container, seal it, and the material is sucked into the conveying pipeline and into the silo. Once a sufficient amount of material has been added to the silo, the vacuum pump stops, and the air valve at the top of the silo and the bottom valve are opened, allowing the powder raw material to fall from the silo into a vacuum mixer with a vacuum degree ≤-0.080MPa. This completes one feeding process.

[0023] S2, positive and negative electrode mixing and pulping;

[0024] Positive electrode mixing and slurry preparation: Positive electrode powder raw materials, active materials, binders, and conductive agents are added. After the materials are fed, N-methylpyrrolidone (NMP) solvent is added. The mixture is then stirred evenly in a vacuum mixer to form a slurry-like positive electrode coating material.

[0025] Negative electrode mixing and slurry preparation: The active material, binder, thickener, conductive agent, etc. of the negative electrode powder raw material are added into a vacuum mixer, deionized water is added, and the mixture is stirred evenly in a vacuum mixer to form a slurry-like negative electrode material.

[0026] S3. The positive and negative electrode slurries are sieved;

[0027] After the positive and negative electrode slurries are mixed, they will be pressure-transmitted to a diaphragm pump for filtration to remove any small particulate impurities that may be present in the slurry, ensuring high-quality coating operations.

[0028] S4. Positive and negative electrode coating and drying;

[0029] The sieved positive and negative electrode slurries will be transported to a transfer tank and stored using low-speed vacuum stirring to effectively prevent slurry stratification or sedimentation. During use, the slurries are conveyed through a closed pipeline to the nozzle of a coating machine for spraying onto the foil surface.

[0030] S5. Positive and negative electrode sheet rolling, electrode sheet slitting, electrode sheet die cutting and baking;

[0031] After coating and drying, the positive and negative current collectors are coated with a mixture of positive and negative electrode materials. They need to be compacted into thin sheets using a roller press to achieve the designed density and thickness. The thickness is controlled at approximately 0.100–0.170 mm.

[0032] S6, Positive and negative electrode winding & stacking;

[0033] Winding: The positive and negative electrode sheets and the separator are installed on the automatic winding machine according to the requirements for automatic winding. The main functions include electrode unwinding, separator unwinding, electrode dust removal, separator static electricity removal, automatic deviation correction, alignment detection, automatic tension detection, winding, cold pressing & i-pot testing, material feeding, and tail adhesive application.

[0034] Stacking: The positive and negative electrode plates and the separator are installed on the automatic stacking machine according to the requirements for automatic stacking, and the battery cell is made by alternating multiple layers of positive and negative electrode plates.

[0035] S7. Assembly;

[0036] The assembly process involves sequentially performing the following steps on the wound and stacked core: hot pressing, X-ray inspection, ultrasonic welding of the tab adapter, laser welding of the gripper cover plate, hot melting of the coating, cell insertion into the casing, sealing welding of the top cover, helium inspection, vacuum drying, and laser welding of the sealing nails.

[0037] S8, Injection;

[0038] The workshop is equipped with a drying room and a liquid injection room. The temperature in the liquid injection room is within the range of 25±5℃ and the humidity is <1%. The dried battery cells are placed in the sealed drying room and the electrolyte (propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, lithium hexafluorophosphate) is injected. After the electrolyte is injected, the cells are left to stand in the designated area.

[0039] S9, negative pressure formation;

[0040] The battery is charged with a small current in an automated assembly cabinet, activating the electrode materials and allowing the polymer on the positive and negative electrodes to interpenetrate with the electrolyte. Charging process: An external power source charges the battery. During this process, electrons from the positive electrode reach the negative electrode through the external circuit. Li+ ions enter the electrolyte from the positive electrode, pass through the composite separator, and reach the negative electrode, where they combine with electrons. Discharging process: An external resistor is applied. During discharge, electrons travel from the negative electrode through the external circuit to the positive electrode. Li+ ions enter the electrolyte from the negative electrode, pass through the composite separator, and reach the positive electrode, where they combine with electrons from the external circuit.

[0041] After formation, the battery cell needs to undergo a high-temperature resting period of 24 to 48 hours, typically at 45 to 60°C. This high-temperature resting period results in a more uniform film formation inside the battery cell, reduces polarization on the electrode surfaces, and optimizes the cell's performance.

[0042] S10, capacity testing;

[0043] The qualified batteries are placed in an aging chamber for a certain period of time. Based on the voltage distribution after this period, they are screened, and short-circuited or low-voltage batteries with micro-short-circuit defects are removed. The selected qualified batteries are then charged and discharged for approximately 6 hours in a capacity grading cabinet. The first charge is to fully charge any batteries that were not fully charged during formation; the discharge refers to the automatic discharge of fully charged batteries. The capacity grading cabinet automatically records the capacity of each battery based on the amount of discharge and then separates the batteries according to their different capacities, thus achieving the purpose of capacity grading; the final charge is to recharge each battery to 70% SOC.

[0044] Inspection involves testing the battery's internal resistance, voltage, size, and weight. Based on the test results, the batteries are sorted, and short-circuited or low-voltage cells with micro-short-circuit defects are removed to ensure battery performance.

[0045] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A manufacturing process for a lithium iron phosphate square aluminum-cased battery cell, characterized in that, Includes the following steps; S1. Drying of positive electrode raw materials and feeding of positive and negative electrodes: Feeding is carried out in a closed batching room using an automatic feeding system. When feeding, first close the silo valve, turn on the vacuum pump to create a vacuum in the silo and conveying pipeline, and then the operator weighs and unpacks the powder raw materials, inserts the vacuum suction gun into the raw material barrel, seals it, and the material is sucked into the conveying pipeline and enters the silo. S2. Positive and negative electrode mixing and slurry preparation: After the positive electrode powder raw material, active material, binder, and conductive agent are added, N-methylpyrrolidone solvent is added, and the mixture is stirred evenly in a vacuum mixer to form a slurry-like positive electrode coating material; The negative electrode powder raw material, active material, binder, thickener, conductive agent, etc. are added to a vacuum mixer, deionized water is added, and the mixture is stirred evenly in a vacuum mixer to form a slurry-like negative electrode material; S3. The positive and negative electrode slurries are sieved. After the positive and negative electrode slurries are mixed, they will be conveyed to the diaphragm pump for filtration under pressure to remove small particulate impurities in the slurry and ensure high-quality coating operation. S4. Positive and negative electrode coating and drying: The sieved positive and negative electrode slurries will be transported to a transfer tank and stored by low-speed vacuum stirring to prevent slurry separation or sedimentation; when in use, they will be transported to the coating machine nozzle through a closed pipeline to spray the foil surface. S5. Positive and negative electrode sheet rolling, electrode sheet slitting, electrode sheet die cutting and baking: After coating and drying, the positive and negative current collectors are coated with a mixture of positive and negative electrode materials, and need to be compacted into thin sheets by rolling equipment. S6. Positive and negative electrode winding and stacking: The positive and negative electrode sheets and the separator are installed on the automatic winding machine for automatic winding as required; then the positive and negative electrode sheets and the separator are installed on the automatic stacking machine for automatic stacking as required, and the battery cell is made by alternating layers of positive and negative electrode sheets. S7. Assembly: The winding and stacked core is subjected to hot pressing, X-ray inspection, ultrasonic welding of electrode adapter, laser welding of clamp cover plate, hot melting of coating, cell insertion into the shell, top cover sealing welding, helium inspection, vacuum drying, and laser welding of sealing nails in sequence. S8. Electrolyte injection: The workshop is equipped with a drying room for electrolyte injection. The temperature in the injection room is within the range of 25±5℃ and the humidity is <1%. The dried battery cells are placed in the sealed drying room for electrolyte injection. After injection, they are left to stand in the designated area. S9, Negative Voltage Formation: The battery is charged with a small current in an automated forming cabinet to activate the electrode materials, allowing the polymer and electrolyte on the positive and negative electrodes to permeate each other. S10, Capacity Sorting: Select qualified batteries and charge and discharge them in the capacity sorting cabinet for about 6 hours. The first charge is to fully charge the batteries that were not fully charged during formation. Discharging means that the fully charged batteries are automatically discharged. The capacity sorting cabinet automatically records the capacity of each battery according to the amount of discharge, and then separates the batteries according to their different capacities, thereby achieving the purpose of capacity sorting. The last charge is to recharge each battery to 70% SOC. S11. Testing; Testing the battery's internal resistance, voltage, size, and weight, and sorting the batteries according to the test results; Picking out short-circuited and low-voltage cells with micro-short-circuit defects inside the cells to ensure battery performance.