Optimising dry electrode processing formulation with improved rate capability and volumetric capacity for batteries

Dry electrode processing to eliminate conventionally used toxic, combustible organic solvent n-methyl-2-pyrrolidone (NMP) or any other solvent has gained interest due to its advantages of sustainability, cost reduction, and increasing electrode coating speed. However, there remains a need for understanding the dry electrode processing for relatively thick electrodes (≥70 µm), high mass loading (≥20 mg cm -2 ), and high active material proportion (≥94 wt%). Herein we study one of the key factors of materials composition for LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathodes and scaling up the dry powder rheology from the lab to the pilot scale. We compare the morphology and electrochemical performance of the electrodes made by conventional slurry coating and by dry processing. The optimised dry-processed cathode (NMC811:C65: PTFE = 94:3:3) exhibited the most homogeneous microstructure, lower porosity, and the lowest impedance among the other formulations. The optimised dry-processed electrode exhibited higher volumetric capacity at 0.05 – 3 C, e.g. 640 and 521 mAh cm -3 at 0.05 and 1 C respectively, compared with the wet-processed electrode. The results demonstrate that balancing conductive additive and PTFE binder content to form a uniform carbon-binder network reduces polarisation and enables improved high-rate performance in dry-processed NMC811 cathodes. • Dry processed electrode with the composition of NMC811:C65:PTFE=94:3:3 (wt%) exhibited the most particle distribution uniformity in the mixed powders. • Electrodes with 3 wt% PTFE had fibrillation network and better adhesion with current collector, 4 wt% PTFE led to particle agglomeration and poor electrode compaction. • Electrodes with NMC811:C65:PTFE=94:3:3 (wt%) exhibited the highest gravimetric and volumetric capacities, rate capability, and lowest impedance. • The improved performance is due to low porosity, increased electronic and ionic percolation, increased active material utilisation, and reduced overpotential.