Enhanced interfacial stability with a novel boron-centered crosslinked hybrid polymer gel electrolytes for lithium metal batteries

Low coulombic efficiency and serious safety issues due to uncontrollable lithium dendrite growth has severely impeded the practical application of lithium-ion batteries (LIBs) with lithium metal as the anode. In this work, we design and fabricate a novel single ion conducting crosslinked polymer gel electrolytes containing negatively charged delocalized state borate structures and rich EO units via one-step photoinitiated in-situ radical polymerization in presence of PVDF-HFP as reinforcing materials. Herein, we synthesize a novel lithium bis(macid acid) borate to give anion covalently bonded to the polymer main chain and vinyl monomers containing rich EO units are chosen to build polymer framework to ensure fast ion transport. As expected, the tailored boron-centered single-ion-conducting polymer gel electrolytes exhibit high ionic conductivity up to 1.03×10−3 S cm−1 at 32 °C, excellent oxidation potential up to 5.05 V vs Li+/Li at 1 mV/s, and a near-single ion conducting behavior (lithium ion transference number of 0.65). The Lithium (Li) metal symmetric cells assembled with the novel boron-centered single-ion-conducting polymer gel electrolytes show long-term stable cycling over >700 h at room temperature without short circuit, which implies the excellent stability of blend membranes during lithium metal deposition and stripping processes. Moreover, the Li/LiFePO4 cells assembled with the boron-centered single-ion-conducting polymer gel electrolytes exhibit excellent rate performance and cycling performance. The initial discharge capacity is 161.3 mAh g−1 at 0.1 C and a capacity of 127.7 mAh g−1 maintains with nearly 100% coulombic efficiency after 100 cycles. Moreover, the Li/LiFePO4 cells deliver stable coulombic efficiency close to 100% at 0.5 C after 300 cycles.