Fluorine-free binder-based dry thick electrodes with Parafilm^® M toward sustainable and efficient battery manufacturing.

Abstract

Dry electrodes are being actively developed for sustainable and efficient battery manufacturing. Currently, polytetrafluoroethylene binders dominate dry processes, raising concerns about high fluorine content regarding restrictions on per- and polyfluoroalkyl substances. Moreover, the poor adhesion necessitates a wet coating-based primer layer, which dilutes its main objectives. Here, we show dry processing approach using a thermoplastic, fluorine-free binder with low environmental impact and high productivity. Parafilm^® M, a laboratory sealing film formulated with low-cost paraffin and polyethylene, consists of saturated linear hydrocarbons, offering high chemical stability from strong C-H covalent bonds and a large highest occupied molecular orbital - lowest unoccupied molecular orbital energy gap. It also has a low glass transition temperature, enabling mild-pressure activation to interconnect active materials while achieving true solvent-free adhesion without the wet-coating of primers on the current collector. This dry electrode binder provides substantial electrochemical properties based on LiNi_0.8Co_0.1Mn_0.1O₂ positive electrode over 5 mAh cm^-2 for 600 cycles. This integrated approach bridges the gap between materials and processes, paving the way for sustainable advancements in battery electrode manufacturing.