Solid electrolyte based on waterborne polyurethane and poly(ethylene oxide) blend polymer for all-solid-state lithium ion batteries

A series of solid polymer electrolytes (SPEs) based on waterborne polyurethane (WPU), poly(ethylene oxide) (PEO) and lithium bis(trifluoromethane sulfonimide) (LiTFSI) are fabricated via a solvent free process. Field emission-scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry techniques are used to characterize the morphological features of the SPEs. The self supported blend SPEs have sufficient mechanical strength and electrochemical stability compared to the pristine PEO electrolyte. The SPE2 (30 wt% LiTFSI in PEO:WPU = 3:1) electrolyte presents the superior comprehensive performance with a stress of 1.3 MPa and electrochemical window exceeding 4.8 V. All-solid-state LiFePO4/SPE2/Li cell using this blend solid polymer electrolyte exhibits both superior discharge capability and cycle performance (high initial discharge capacity of 160 mAh g(-1) at 0.2 C, 122 mAh g(-1) discharge capacity and 96% capacity retention after 100 cycles at 1 C) at 80 degrees C. All of these results demonstrate that this new WPU/PEO blend solid polymer electrolyte is a promising candidate for all-solid-state lithium ion batteries.