Insights into the Chemistry of the Cathodic Electrolyte Interphase for PTFE-Based Dry-Processed Cathodes

Dry processing is a promising method for high-performance and low-cost lithium-ion battery manufacturing which uses polytetrafluoroethylene (PTFE) as a binder. However, the electrochemical stability of the PTFE binder in the cathodes and the generated chemistry of the cathode electrolyte interphase (CEI) layers are rarely reported. Herein, the CEI properties and PTFE electrochemical stability are studied via cycling the high-loading dry-processed electrodes in electrolytes with LiPF₆ or LiClO₄ salt. Using LiClO₄ salt can eliminate other possible F sources, allowing the decomposition of PTFE to be studied. The detection of LiF in cells with the LiClO₄ salt confirms that PTFE undergoes side reaction(s) in the cathodes. When compared with LiClO₄, the CEI layer is much thicker when LiPF₆ is used as the electrolyte salt. These results provide insights into the CEI layer and may potentially enlighten the development of binders and electrolytes for the high efficiency and long durability of DP-based LIBs.