Removing electrochemical constraints on polytetrafluoroethylene as dry-process binder for high-loading graphite anodes

The environmentally friendly polytetrafluoroethylene (PTFE) binder, known for its strong bonding, is ideal for high-loading electrode preparation in solvent-free dry processes. However, its use in graphite anodes is hindered by a tendency to undergo reduction at low potentials, causing substantial capacity loss. Herein, we identified an irreversible reductive of PTFE at ∼1.2 V vs. Li/Li⁺, involving partial substitution of F atoms with H in its carbon chain and subsequent LiF formation. Using this insight, we developed a polyethylene oxide coating to prevent electrical contact between graphite and PTFE binder, successfully inhibiting PTFE reduction. This coating facilitated the effective use of PTFE in high-loading lithium-ion battery (LIB) pouch cells (4.8 mAh/cm² LiNi_0.75Mn_0.25O₂ and 5.2 mAh/cm² graphite) via dry-process fabrication, achieving an energy density of 258.7 Wh/kg and reducing initial irreversible decompositions from 52.91% to 16.34%. The cost-effective PTFE, coupled with solvent-free, high-loading electrode fabrication, offers an economical and green approach to large-scale electrification. © 2024 Elsevier Inc.