Robust thiol-branched all-solid-state polymer electrolyte featuring high ionic conductivity for lithium-metal batteries

The high energy density of lithium metal batteries (LMBs) causes great attention of researchers. However, side effects of liquid electrolytes and dendrite growth problem limit the development of LMBs. Solid electrolytes with high ionic conductivity, good film-forming ability, and compatible interface with electrodes are highly desired yet remain to be explored. Herein, we design and fabricate a thiol-branched all-solid-state polymer electrolyte (SPE) with high ionic conductivity (1.09 × 10 −4  S cm −1 , 40 °C) and good film-forming ability for the first time. The SPE is prepared via covalently cross-linking hyperbranched poly(glycidol) (chemical decorated by –SH, named as HPG-SH) and trimethylolpropane propoxylate triacrylate through multiple –C–S–C bonds. Specifically, the HPG is synthesized by anionic polymerization, followed by esterification reaction of HPG with mercaptoacetic acid to obtain HPG-SH. The SPE also exhibits an impressive lithium-ion transference number (0.31). Such design and prepare strategy makes the Li/SPE/LiFePO 4 cell successfully cycle and the capacity reaches 145 mAh g −1 with average coulombic efficiency close to 100% over 70 cycles at low temperature. This work offers a new perspective to design high-performance SPEs at the molecular level.