Fluorine-free Polysiloxane-based Single-Ion Conducting Polymer Electrolyte for Lithium-Metal Batteries

Herein, the synthesis and comprehensive characterization of a new, completely fluorine-free single-ion conducting polymer electrolyte (SIPE) for lithium-metal batteries is reported. For this new SIPE, lithium(4-styrenesulfonyl)(dicyanomethide) has been grafted onto a polysiloxane backbone. Self-standing membranes containing additionally non-toxic polyacrylonitrile and propylene carbonate reveal suitable mechanical properties, high ionic conductivity of more than 10-4 S cm-1, and a good anodic stability exceeding 4.1 V vs. Li+/Li at 40 °C. Symmetric Li║Li cells show an excellent cycle life with more than 1,000 h of lithium stripping and plating, thanks to the formation of a stable and low resistive interphase. As a result, also completely fluorine-free Li║LiFePO4 cells provide stable cycling for more than 500 cycles, rendering this new electrolyte system very promising for the realization of more sustainable and safer lithium batteries.