In Situ Formed Composite Polymer Electrolytes Based on Anion-Trapping Boron Moiety and Polyhedral Oligomeric Silsesquioxane for High Performance Lithium Metal Batteries

Quasi-solid and composite polymer electrolytes (QSPEs and CPEs) used in lithium-ion battery (LIB) have recently been a novel strategy owing to their high-safety comparing to traditional liquid counterparts. This study reported the preparation of CPEs based on boron moiety, poly(ethylene glycol) (PEG), and octahedral polyhedral oligomeric silsesquioxane (POSS) via in situ thermal polymerization method directly onto the lithium anode to improve the interfacial contact and electrochemical performance. The synergistic effect between the incorporation of anion-trapping boron moiety and in situ polymerization rendered the QSPEs exhibiting higher electrochemical voltage window, ionic conductivity, and transference number as well as better electrochemical performance than the PEG-based counterpart. Due to the Lewis acid effect, anion-trapping boron moiety could promote the dissociation of lithium salts, allowing more lithium ions to be in the free state, thereby enhancing the lithium-ion conductivity. With an optimal addition of POSS, the as-prepared CPEs exhibited lower overpotential during the lithium plating-stripping test and better electrochemical performance than the QSPE counterparts. The optimal POSS addition could facilitate the lithium-ion conduction and establishment of continuous ion pathways, further improving their electrochemical performance. This study pointed a promising approach for developing high performance lithium-ion batteries.