Enhancing rate performance of dry-processed thick LiFePO4 cathodes for lithium-ion batteries

Solvent-free electrode manufacturing not only reduces energy consumption and cost, but also enables thick electrodes for high energy cells. However, thick electrodes often suffer from sluggish Li-ion diffusion, leading to low-capacity retention at fast charging. In this work, LiFePO 4 -based cathodes were dry-processed by binder fibrillation, and benchmarked with slurry-casted cathodes using a green solvent. By balancing thickness and porosity of dry-processed thick electrodes, we achieved similar C-rate performance as ∼50% thinner electrodes, such as 212 μm thick and 54.3% porosity vs. 99 μm thick and 34.5% porosity, leading to a significant enhancement of areal capacity by 47% at 0.1C and 72% at 1C. Moreover, a fair comparison of dry-processed cathodes against slurry-casted ones showed similar C-rate performance which was consistent with the ion diffusivities measured by GITT; however, dry-processed cathodes degraded faster during cycling at 0.5C. Consistently, XPS characterization revealed that dry-processed cathode formed larger amount of electrolyte decomposition products in cycling, such as carbonate compounds and Li x PO y F z . We believe it is due to higher exposure opportunities for cathode active particles to electrolyte within dry-processed electrodes, originated from the distinctive binder distribution versus slurry-casted ones. This study offers a new perspective on the adoption of dry electrode technology.