Multiclaw-shaped octasilsesquioxanes functionalized ionic liquids toward organic-inorganic composite electrolytes for lithium-ion batteries

Abstract In this work, we have successfully synthesized a series of multiclaw-shaped octasilsesquioxanes functionalized ionic liquids and then used it developing novel hybrid solid polymer electrolytes (SPEs) with high room temperature ionic conductivity. The effect of POSS ionic liquids with varying chain in imidazole on the microstructures, thermal stabilities and electrochemical properties of the obtained SPEs were studied. The scanning electron microscope images of SPEs membranes confirm that the POSS ionic liquids were uniformly distributed in the polymer matrix. The solid polymer electrolytes exhibit high electrochemical stabilities with a wide electrochemical window up to 5.0 V, a lithium-ion transference number (tLi+) of 0.32 and high ionic conductivity of 3.06 × 10−4 S cm−1 at 22 °C. Moreover, the Li/LiFePO4 cells containing POSS-ILs-SPEs exhibit excellent cycling performance and rate capability, the initial discharge capacity is 150.7 mAh g−1 and initial coulombic efficiency is 100% at a rate of 0.1C. The capacity of the cells can reach to 130 mAh g−1 and the coulombic efficiency is 99.9% after 90 cycles.