Refined film-forming additive overcomes polytetrafluoroethylene challenges in dry-processed high-loading lithium-ion batteries

Abstract

The demand for high-energy-density lithium-ion batteries (LIBs) has led to progress in producing high-loading electrodes using dry-process, reducing costs and energy consumption related to toxic solvents used in wet-process. Polytetrafluoroethylene (PTFE), commonly used as a binder in dry electrodes, offers excellent adhesion and thermal stability but poses difficulties for graphite anodes due to substantial initial irreversible capacity loss caused by reductive decomposition (∼1.2 V vs. Li/Li⁺). This study introduces a novel approach showing the problem of PTFE reduction can be mitigated by incorporating N-phenyl-bis(trifluoromethanesulfonimide) (PTFSI), an electrolyte additive with strong reducibility and superior film-forming properties. PTFSI creates a protective solid-electrolyte interphase (SEI) layer on both graphite and PTFE surfaces, successfully inhibiting PTFE decomposition without introducing inert substances. The innovative method allowed high-loading pouch cells (LiNi_0.75Mn_0.25O₂/graphite) to achieve an initial discharge capacity of 227.7 mAh and a Coulombic efficiency of 78.2 %, with an energy density of 258.7 Wh/kg. After 400 cycles, the cells maintained a capacity of 183.4 mAh, retaining 80.5 % of their original capacity. The findings highlight the potential impact of PTFSI in significantly improving next-generation high-loading LIBs, addressing challenges with high-loading electrodes and advancing efficient and durable energy storage systems critical for electric vehicles and large-scale energy storage applications.