Flexible and rigid polyurethane based polymer electrolyte for high-performance lithium battery

The development of new polymer electrolytes is greatly significant due to the improvement of the energy density and safety of lithium batteries. Comparing with a single polymer electrolyte, the composite polymer electrolyte has better performance, especially some based on the concept of rigid–flexible coupling polymer electrolytes. In this study, a series of polyurethane with various proportion of soft and rigid segments are synthesized and used as a composite polymer electrolyte (C-PU) together with cellulose membrane. The optimized polymer electrolyte C-PU20 (with 20 wt% of the hard segment) exhibits high ionic conductivity of 2.4 mS/cm at 25°C and wide electrochemical stability window up to 4.8 V. Moreover, the C-PU20 electrolyte for LiFePO 4 /Li cell shows more fantastic cycling performance with capacity retention of 96% after 300 cycles at 0.5 C and better C-rate capability compared with the pristine cellulose membrane. All the findings indicate that the C-PU20 electrolyte is a very prospective polymer electrolyte for high-performance lithium batteries.