Star-shaped polyethylene glycol methyl ether methacrylate-co-polyhedral oligomeric silsesquioxane modified poly(ethylene oxide)-based solid polymer electrolyte for lithium secondary battery

Poly(ethylene oxide) (PEO)-based solid polymer electrolyte (SPE), as a key component connecting the internal channels, can improve the safety performance for lithium secondary battery , but it is still challenged by limited ionic conductance due to high polymer crystallinity at room temperature . Here, we develop a SPE by blending PEO with star -shaped polymer of polyethylene glycol methyl ether methacrylate- co -polyhedral oligomeric silsesquioxane (POSS-(PPEGMEM) 8 ), which is synthesized by atom transfer radical polymerization (ATRP) under octa (2-bromoisobutyryloxyethyl sulfide) octasilsesquioxane (POSS-Br 8 ) as initiator and poly(ethylene glycol) methyl ether methacrylate (PEGMEM) as polymerization monomer . The unique star -shaped structure of POSS-(PPEGMEM) 8 is helpful to increasing the segmental motion by reducing the crystallinity of PEO polymer and supporting more ion transport channels to obtain higher ion conductivity. The mixed electrolyte containing 40% POSS-(PPEGMEM) 8 exhibits the highest ionic conductivity (1.4 × 10 −4  S cm −1 , 50 °C) with a Li + transference number of 0.51 and a wide electrochemical window (5.0 V vs. Li/Li + ) and a high mechanical strength . The LiFePO 4 ||Li battery , assembled with PEO/POSS-(PPEGMEM) 8 –40%, carries out 100 cycles at a current density of 0.1C, provides a stable reversible capacity of 129.4 mAh g −1 and a high capacity retention rate due to the high ratio of free volume of polymer electrolyte formed by the star-shaped POSS-(PPEGMEM) 8 , which indicates that PEO/POSS-(PPEGMEM) 8 has good application prospects in high-performance all-solid-state lithium secondary battery.