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

Dry electrodes are being actively developed for sustainable and efficient battery manufacturing. Currently, polytetrafluoroethylene (PTFE) binders dominate dry processes, yet their production contributes to significant CO2 emissions, and concerns persist regarding their high fluorine content, especially considering evolving per- and polyfluoroalkyl substances (PFAS) restrictions. Moreover, the poor adhesion of bare current collectors necessitates a wet coating-based primer layer, which dilutes its main objectives. This study introduces an alternative dry processing concept based on a thermoplastic fluorine-free binder with low environmental impact and high productivity. Parafilm® M (hereafter Parafilm), a well-known laboratory sealing film formulated with low-cost paraffin and polyethylene (PE), is a mixture of primarily saturated linear hydrocarbons, which are the most stable chemical species owing to its C-H covalent bonds and the wide gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies. It also has a low glass transition temperature (Tg), allowing facile cohesion of the active materials to be interconnected by mild pressing activation without wet-coated primer layers. This dry electrode binder provides substantial electrochemical properties based on both NCM811 cathodes over 5 mAh cm−2 for 700 cycles. Furthermore, the binder mechanics were maintained at the elevated temperature over Tg with its cheesy nature rather than liquefied melting. This integrated approach bridges the gap between materials and processes, paving the way for sustainable advancements in battery electrode manufacturing.