A Solvent-Free Process Enabled by Polytetrafluoroethlyene/Carbon Black Composites for Fabricating Electrodes for Lithium-Ion Batteries with a High Volumetric Energy

Abstract

Manufacturing electrodes for lithium-ion batteries (LIBs) consists of making a slurry, coating the slurry onto a current collector, drying the slurry to remove the solvent, and calendaring the electrode. Cathodes for LIBs are fabricated by a wet process using a toxic chemical, N-methyl-2-pyrrolidone (NMP). However, it is preferable to use a dry process without toxic chemicals, and with fewer manufacturing operations, which saves money. However, the powder-mixing step of the dry process makes it difficult to ensure a uniform distribution of the carbonaceous conducting agents and binder used, which agglomerate in the dry mixed product. To solve this problem, we fabricate a composite of polytetrafluoroethylene (PTFE) and carbon black (CB) nanoparticles. The electrode fabricated using the PTFE/CB composite has a 98 wt% active material content and 3.8 g cc−1 of electrode density. An electrode produced by the conventional wet process using a polyvinylidene fluoride (PVDF) binder and NMP solvent has a 96 wt% active material content and an electrode density of 3.4 g cc−1. The dry-processed electrode has a higher volumetric capacity (760 mAh cc−1) as well as a higher discharge rate capability and cycle life than a conventional wet-processed electrode.