High-energy LiFePO4 battery with methodically controlled dry electrode processing

Abstract

Batteries using the LiFePO4 (LFP) cathode have emerged as the most notable option for electric vehicle applications owing to their low cost and safety relative to other chemistries. However, the fabrication of a high-energy electrode through the conventional wet electrode processing with the LFP nanoparticles faces challenges because the polymer binders heterogeneously agglomerate with the nanoplate LFP cathode throughout the electrode owing to the capillary traction in the solvent drying process. Herein, a high-energy LFP electrode is innovatively fabricated through methodical control of dry electrode processing from the particle to electrode level. The high tap density micron-sized LFP particles coated with a small amount (0.3 wt%) of carbon nanotubes (CNTs) are used as cathode materials (LFP@CNTs). In the dry electrode processing, the continuous fibrillation between LFP@CNTs (99 wt%) and polytetrafluoroethylene (PTFE) binder (1 wt%) enabled by regulating the shear force can produce the robust and elastic network, ensuring high electrode density over 2.4 g cc−1 of the dry-processed LFP electrode (LFP-DE) without mechanical rupture of LFP@CNTs. The uniform pore distribution and robust electrical pathways in LFP-DE enhances the Li+ diffusion and electron transport kinetics during the charge[sbnd]discharge processes. Even under a high capacity loading of 5 mAh cm−2, the LFP-DE demonstrates a high reversible capacity of 148.4 mAh g−1, an excellent capacity retention of 99 % over 100 cycles at 5 mA cm−2, and outstanding power capability up to 15 mA cm−2. The LFP-DE demonstrates practical applicability with long-term cycling over 700 cycles in a pouch-type full-cell with a graphite anode.