The production process of lithium batteries involves multiple precision steps, which require strict quality control and environmental management. The following are the main production processes of typical lithium-ion batteries (such as ternary lithium or lithium iron phosphate batteries or 18650 lithium battery or lithium ion solar battery):
1. Electrode Preparation (Core Process)
Cathode Material Preparation
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Raw Material Mixing: Cathode active material (e.g., ternary material LiNiCoMnO₂ or LiFePO₄), conductive agent (carbon black), binder (PVDF), and solvent (NMP) are blended into a slurry.
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Coating: The slurry is uniformly coated onto an aluminum foil current collector to form cathode sheets.
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Drying: Solvent is removed in a high-temperature oven to solidify the sheets.
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Calendering: Sheets are compressed by high-pressure rollers to enhance energy density and uniformity.
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Slitting: Wide sheets are cut into designed dimensions.
Anode Material Preparation
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Similar to the cathode process, using graphite/silicon-carbon materials and binders (CMC/SBR) coated onto copper foil, followed by drying, calendering, and slitting.
2. Cell Assembly
Stacking/Winding
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Stacking: Alternately layering cathode/anode sheets with separators (common for prismatic/pouch cells).
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Winding: Rolling cathode/anode sheets and separators into cylindrical shapes (e.g., 18650 cells, 18650 lithium battery).
Welding & Encapsulation
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Tab Welding: Cathode/anode tabs are welded to current collectors for external circuit connections.
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Housing Sealing: Encapsulation using aluminum laminate (pouch cells) or steel/aluminum casing (cylindrical/prismatic cells), with electrolyte injection ports retained.
3. Electrolyte Injection & Sealing
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Electrolyte Filling: Liquid electrolyte (LiPF₆ + organic solvents) is injected in a dry environment (dew point ≤ -40°C).
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Pre-sealing: Temporary sealing followed by resting to ensure electrolyte saturation of electrodes.
4. Formation & Aging
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Formation: Initial charging activates the battery, forming the SEI (Solid Electrolyte Interphase) layer on the anode surface, critical for cycle life.
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Aging: Cells are rested and monitored for voltage stability; defective cells with excessive self-discharge are rejected.
5. Grading & Testing
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Capacity Grading: Charge/discharge testing to sort cells by capacity for consistency.
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Safety Testing: Extreme-condition tests (overcharge, nail penetration, high temperature) to ensure safety compliance.
6. Module & PACK Integration
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Module Assembly: Series/parallel connections of multiple cells, integrated with BMS, thermal management, etc.
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PACK Packaging: Structural design tailored to applications (e.g., EVs, energy storage systems).
Key Technologies & Challenges
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Environmental Control: Humidity/dust management (Class 1,000 cleanrooms) to prevent moisture contamination.
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Process Optimization: Coating uniformity and electrode porosity directly impact performance.
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Emerging Tech: Dry electrode processes (Tesla), solid-state battery production variations.
Industry Chain Collaboration
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Upstream: Lithium/cobalt/nickel mining, separator/electrolyte suppliers.
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Equipment: Heavy reliance on imported machinery (Japan/Korea/Germany) for coaters, winders, formation systems.
Lithium battery production is capital- and technology-intensive, where yield rate and cost control are critical. Ongoing innovations (e.g., CTP, Blade Battery) continue to optimize processes for higher energy density and safety.