The manufacturing of lithium-ion batteries hinges on precise engineering techniques to optimize performance and durability. Among these, thermal and cold pressing stand out as critical processes that shape the structural and electrochemical properties of battery cells. Below, we dissect these methods, their scientific underpinnings, and their real-world implications.
1. Thermal Pressing: Precision Through Heat and Pressure
Thermal pressing operates at elevated temperatures (80–120°C) and moderate pressure (5–15 MPa), leveraging dual forces to enhance battery functionality. The heat acts as a catalyst, increasing ionic mobility within the electrolyte—akin to “lubricating” lithium-ion pathways between electrodes. For example, trials at MIT’s Energy Lab demonstrated that thermal-treated batteries achieve 15% higher discharge rates under high-current conditions compared to non-treated counterparts.
Structural Enhancements
Pressure application during heating compacts electrode materials, reducing voids between particles. This densification improves electrical contact, slashing internal resistance by up to 20%. Microscopically, heat induces crystalline lattice rearrangement in cathode materials like NMC (LiNiMnCoO₂), boosting energy density by 8–12%. Advanced thermal presses now integrate infrared monitoring systems to maintain ±1°C uniformity across electrodes, preventing separator pore collapse—a common failure mode in early-generation equipment.
Industrial Case Study
Tesla’s Nevada Gigafactory employs multi-zone thermal presses for its 4680 cells. By maintaining 110°C with 12 MPa pressure, they achieve electrode porosity of 29%, a 10% improvement over standard methods. This translates to a 6% increase in vehicle range for their Model Y batteries.
2. Cold Pressing: Room-Temperature Compaction
Conducted at ambient temperatures (≤23°C) with higher pressures (10–25 MPa), cold pressing relies on mechanical force alone to densify electrodes. The process eliminates 15–20% of interparticle gaps but faces material rebound challenges—post-pressing thickness recovery averages 6 μm due to residual elastic energy in graphite anodes.
Operational Nuances
Roller speed optimization is critical. Samsung SDI’s latest cold presses operate at 12 m/s, balancing throughput with uniformity. Their proprietary “wave-dampening” rollers reduce edge deformation by 40%, addressing historical issues with pressure distribution. However, cold-pressed NCA cathodes exhibit 35% porosity, slightly higher than thermal-pressed variants, increasing electrolyte consumption by 8% per cell.
Performance Trade-offs
A 2023 study by CATL revealed cold-pressed cells retain 85% capacity after 500 cycles in smartphone batteries, versus 92% for thermal-pressed equivalents. This gap stems from microcracks forming during room-temperature compression, accelerating capacity fade.
3. Performance Comparison: Key Metrics
| Parameter | Thermal Pressing | Cold Pressing | Industry Benchmark |
| Thickness Tolerance | ±0.03 mm | ±0.05 mm | ±0.07 mm |
| Porosity Range | 28–32% | 30–35% | 35–40% |
| Cycle Life (3C Battery) | 92% @ 500 cycles | 85% @ 500 cycles | 80% @ 500 cycles |
| Energy Density | 720 Wh/L | 680 Wh/L | 650 Wh/L |
Electrochemical Insights
- Low-Temperature Operation: Thermal-pressed cells deliver 12% higher discharge capacity at -20°C due to optimized ion diffusion paths.
- Production Costs: Cold pressing reduces energy consumption by 30% per cell but requires 15% more raw material to compensate for rebound losses.
- Scalability: Hyundai’s new ASEAN plant uses thermal pressing for EV batteries but adopts cold pressing for consumer electronics, citing 18% faster production speeds.
Conclusion
As the core link of battery manufacturing, the technological progress of cold pressing process directly affects the improvement of energy density. Through the refined control of process parameters and innovation of material system, the comprehensive performance of batteries can be broken through. It is recommended to pay attention to the intelligent upgrading of equipment and the coordinated optimization of process and materials to continuously improve production yield and product competitiveness.
