Abstract
Commercial polyolefin separators used in lithium metal batteries (LMBs) have the disadvantages of insufficient thermal stability and poor wettability with electrolytes, which causes bad safety and battery performance. Poly(ε-caprolactone) (PCL)-based electrolytes have drawn widespread attention in the field of polymer electrolytes owing to their electrochemical stability and high lithium-ion transference number. This work proposes a strategy of functionalizing commercial polypropylene (PP) separator coated by blending PCL (M w ~ 50,000) and poly(ethylene oxide) (PEO, M V ~ 600,000). Compared to commercial PP separators, PP-blended PEO60w/PCL5w separators possess better wettability with electrolytes and electrochemical performances. The initial discharge specific capacity of LiFePO4-based LMBs assembled with PP-blended PEO60w/PCL5w separators reaches 144 mAh g-1 (1C) and 103 mAh g-1 (5C) at room temperature, respectively. Notably, Li/PP-blended PEO60w/PCL5w/LiFePO4 shows an improved capacity retention rate of 77% after 800 cycles, confirming that the functionalized separator with coated PEO/PCL blend has great potential for application in the field of LMBs.