A promising TPU/PEO blend polymer electrolyte for all-solid-state lithium ion batteries

Solid polymer electrolyte (SPE) membranes composed of thermoplastic polyurethane (TPU), poly(ethylene oxide) (PEO) and lithium bis(trifluoromethane sulfonimide) (LiTFSI) are prepared and investigated in this work. The results show that addition of TPU to the blend polymer results in loss of the crystallinity of PEO and improve the dissolution of lithium salts into the SPE matrix. TPU can also improve the mechanical stability and the electrochemical properties. Among the TPU/PEO blend electrolytes, the TPU/PEO = 1:3 based electrolyte presents an ionic conductivity of 5.3 × 10−4 S cm−1 with electrochemical stability above 5 V (vs. Li+/Li) at 60 °C. The LiFePO4/SPE/Li coin cell based on SPE (TPU/PEO = 1:3) is assembled and shows the attractive discharge capacity (140 and 154 mAh g−1 at 0.2C under 60 and 80 °C, 112 and 127 mAh g−1 at 1C under 60 and 80 °C) and outstanding cycling stability (close to 96% and 94% after 100th cycles at 1C under 60 and 80 °C), respectively. These results demonstrated that the TPU/PEO blend polymer electrolyte should be a promising electrolyte for all-solid-state lithium ion batteries.