I. Analysis of Dry Electrode Preparation Technology
1. Introduction to Dry vs. Wet Processes and Material Comparison
The traditional wet process involves mixing active material, conductive agent, and binder in a solvent at specific ratios, then coating the mixture onto the current collector surface via a slot-die coater by calendering.
The dry process involves dry-mixing active particles and conductive agents uniformly, adding a binder, forming a self-supporting film through binder fibrillation, and finally calendering it onto the current collector surface.
2. Dry Film Manufacturing Process
2.1 Self-Supporting Film Dry Preparation Process
Dry film methods include binder fibrillation and electrostatic spraying, with binder fibrillation being the mainstream technique. Electrostatic spraying underperforms binder fibrillation in subsequent processability, adhesion stability, electrode flexibility, and durability.
Binder fibrillation: Active material powder and conductive agent are mixed, PTFE binder is added, and external high shear force is applied to fibrillate PTFE, bonding electrode film powder. The mixture is then extruded into a self-supporting film.
Electrostatic spraying: Active material, conductive agent, and binder particles are pre-mixed with high-pressure gas. Powder is negatively charged via an electrostatic spray gun and deposited onto a positively charged metal foil current collector. The binder-coated collector is then hot-pressed; the melted binder adheres to other powders and is compressed into a self-supporting film.
2.2 Principle of Fibrillation Dry Process Technology
Fibrillation transforms PTFE into fibrils under external shear force. Due to PTFE’s low van der Waals forces and loose stacking, shear forces convert agglomerates into fibrils that form a network bonding electrode powder.
Temperature and shear are critical factors affecting PTFE fibrillation. Above 19°C, PTFE transitions from a triclinic to hexagonal crystal system, softening molecular chains and enabling fibrillation.
Fibrillation film-making precedes electrode calendering. Mainstream fibrillation equipment includes jet mills, screw extruders, and open mills.
After thorough mixing of PTFE and active material, the mixture is fed into a fibrillation machine. Under roller pressure, it forms a self-supporting film. Experimental data show lower feed speeds increase electrode film impedance, while greater calendering force reduces impedance.
II. Dry vs. Wet Electrode: Advantages and Disadvantages
1. Lower Cost: 18% Reduction in Manufacturing Costs
The dry process has fewer steps. Mass production reduces cell manufacturing costs by 18% (0.056 RMB/Wh). In wet processing, coating/drying and solvent recovery account for 22.76% and 53.99% of equipment, labor, facility, and energy costs, respectively. The dry process replaces slurry coating with self-supporting film formation, eliminating NMP solvent, electrode drying, and solvent recovery—significantly cutting costs.
The dry process is more eco-friendly and scalable. Toxic NMP (N-methylpyrrolidone) requires energy-intensive recycling in wet processes. Solvent-free dry processing simplifies workflows, reduces equipment footprint, and enables large-scale electrode production.
2. Higher Active Material Density: 20% Energy Density Increase
PTFE fibrillation enables smoother dry electrode morphology versus wet electrodes. Solvent evaporation in wet processing creates voids between active material and conductive agents, lowering compaction density. Without drying, dry electrodes eliminate voids, ensuring tighter particle contact.
Dry electrodes achieve higher compaction density with fewer cracks/micro-pores:
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LFP: 2.30 g/cm³ → 3.05 g/cm³ (+32.61%)
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NMC: 3.34 g/cm³ → 3.62 g/cm³ (+8.38%)
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Graphite anode: 1.63 g/cm³ → 1.81 g/cm³ (+11.04%)
Higher active material content per volume enables greater energy density.
Dry batteries achieve 20% higher energy density under identical conditions. Maxwell data show dry electrodes exceed 300 Wh/kg, with potential for 500 Wh/kg.
Dry electrodes support greater thickness limits (30 µm–5 mm vs. wet’s 160 µm), enhancing areal capacity and compatibility with diverse active materials.
3. Superior Electrical Performance
Lab tests confirm dry-process batteries excel in cycle life, durability, and impedance. The fibril network enhances material stability and electrical performance.
In wet processing, 500 cycles accumulate internal stress in active particles, causing cross-sectional cracks that degrade battery performance. In dry processing, the fibril network coats active materials, maintaining structural integrity after 500 cycles with minimal surface cracks. The mesh structure also suppresses active material expansion, prevents particle detachment from current collectors, and improves stability and electrical performance.
Contact us for more information about our dry electrode solutions.
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