Novel Ladder-like Polysilsesquioxane Hybrid Polymer Electrolytes for Lithium Ion Batteries

A novel inorganic-organic hybrid crosslinker was prepared through synthesis of a fully condensed, high molecular weight, ladder-like structured poly(methacryloxypropyl)silsesquioxane (LPMASQ) in one-pot with a facile, base-catalysed system. The fully condensed LPMASQ revealed good thermal (~380 °C), and electrochemical stability (~5.0 V), and good solubility in various organic solvents due to the absence of uncondensed silanol groups as well as the presence of hundreds of methacryl pendant groups in each macromolecule. LPMASQ fully gelated a 1 M LiPF₆ (EC/DEC, 3/7, v/v) electrolyte solution through fast thermal and photo curing even at very low concentration of 2 wt %. This observation was attributed to the polymeric nature of LPMASQ containing over one hundred methacryl moieties on the rigid double-stranded siloxane backbone. To the best of our knowledge, formation of gel polymer electrolyte with 2 wt % gelator is the smallest gelation concentration that ever reported. This leads to the high ionic conductivity (~6.0 mS cm^–1), excellent Coulombic efficiency and battery cell performance, comparable with those of neat liquid electrolyte. The small crosslinker content, thermal and electrochemical stability, fast thermal and photo curing and facile processing of the LPMASQ based GPEs, as well as excellent Li battery cell performances strongly hold great promise for future industrial battery applications.