Polyrotaxane-based electrolyte with excellent thermal stability for quasi-solid lithium metal batteries

Despite the high-energy densities, the safety problem of thermal runaway in lithium-ion batteries (LIBs) severely hinders their further application. Therefore, as an essential part of LIBs, the separator should ideally have good thermal stability at high temperatures. Here, a novel polyrotaxane (PR)-based gel polymer electrolyte (GPE) with good thermal stability is made by a simple solution casting method. The thermal shrinkage of the PR is less than 20% even heated at 200 °C; in contrast, the commercial Celgard 2400 separator undergoes dramatic deformation above 140 °C. The gel polymer electrolyte presents excellent compatibility in the cells of LiFePO4 and LiNi0.5Co0.2Mn0.3O2 cathode. The cell composed of Li/GPE/LiFePO4 presents good discharge performance and excellent stored performance. The cell composed of Li/GPE/LiNi0.5Mn0.3Co0.2O2 presents excellent capacity retention of 85.9% in 300 cycles while discharging at the 0.5 C rate. This GPE is promising to be applied to Li metal batteries with high safety and good cycle life.