The LIB (LiFePo4 Battery) industry has pioneered a manufacturing process for consumer electronic batteries, which has largely been transferred to newer battery production methods. Many LIB manufacturers use prismatic cells (Samsung SDI and CATL), cylindrical cells (Panasonic designed for Tesla) and pouch cells (LG Chem, A123 Systems, and SK Innovation), but the production processes for all of these are strikingly similar.
Battery electrochemistry is activated, cells are assembled, and electrodes are prepared. Before adding the active material (AM), conducting additive, and binder to a solution, it is necessary to mix them all to create uniform slurry. Cathode cathodes typically contain polyvinylidene fluoride (PVDF) dissolved in N-methyl pyrrolidone (NMP) (PVDF). Water dissolves the anode’s carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) binder. A slot die is used to deposit Al and Cu foils on the cathode and anode sides of the current collector before the slurry is pumped into a drying chamber to remove the solvent. Toxic and subject to strict emission controls, the typical organic solvent (NMP) used in cathode slurry is a hazardous substance. As a result, drying cathodes necessitates a solvent recovery process. The recovered NMP is then used to makeLiFePo4 Battery with a 20% to 30% loss. Anode slurry made with water can be safely vented into the atmosphere. Calendaring the electrodes can alter their physical properties (bonding, conductivity, density, porosity, etc.). After these procedures, the finished electrodes are stamped and slit to the required dimensions for the cell design. The excess water is then drained from the electrodes in the vacuum oven. Check electrodes for moisture content after drying to prevent side reactions and cell corrosion.
After being thoroughly prepared, the electrodes are sent to the dry room with dried separators for cell production. The electrodes and separator are wound or stacked in layers to create the cell’s internal structure. The cathode current collector and anode current collector are welded with aluminum and copper tabs.
Some cell manufacturers may opt to use resistance welding instead of ultrasonic welding. When the enclosure is finished, the cells will move to it. Each manufacturer has a different preference based on the intended use of the cells. Before final sealing, electrolytes are added to the inlet to complete cell production.
Electrochemical activation steps are used on these cells before they are shipped to end-product manufacturers to ensure they operate reliably. A stable solid-electrolyte interface (SEI) layer is necessary to prevent irreversible electrolyte loss during fast charging. To prevent copper corrosion, the cells are charged at a low voltage at first (for example, 1.5V). Afterwards, you’ll have some downtime to let the electrolyte soak in. To maintain a stable SEI layer on the anode’s surface, the cells are initially charged and discharged at a low rate, such as C/20. Due to safety concerns of LiFePo4 Battery, it must expel all gas generated during the formation process. The cells are kept on the ageing shelves for electrolyte wetting and SEI stabilization after or during the formation cycles. The cells will undergo a second degassing step before finally being sealed for future use. There are a variety of factors that can affect how long this process takes.
Conclusion
The LiFePo4 Battery industry has invented a manufacturing method for batteries for consumer electronics. Prism cells (Samsung SDI and CATL), cylindrical cells (Panasonic designed for Tesla), and pouch cells are all commonly used by LIB manufacturers (LG Chem, A123 Systems, and SK Innovation). Before being sent to end-product manufacturers, these cells undergo electrochemical activation processes. A stable solid-electrolyte interface (SEI) layer is required to stop irreversible electrolyte loss during fast charging. Before being sealed for future use, the cells will go through a second degassing stage.
