A novel room temperature POSS ionic liquid-based solid polymer electrolyte

Ionic liquids-based solid polymer electrolytes enhance the battery's overall performance without drawbacks in safety compared with conventional electrolyte. In order to develop a novel solid electrolyte, we synthesized a series of novel room temperature imidazolium-based polyhedral oligomeric silsesquioxane ionic liquids (POSS-ILs) consisting of POSS-COO⁻ anions and a variety of imidazolium cations, which will be used as plasticizers of solid polymer electrolyte in this work. The thermal stabilities of POSS-ILs have been dramatically enhanced by the introduction of POSS moiety, and the initial decomposition temperatures of POSS-ILs have increased by at least 94 °C compared to their corresponded succinamic acid ionic liquids. The glass transition temperatures of POSS-ILs also have increased to − 15.9 to − 25.4 °C. Then the POSS-ILs are employed to obtain a novel solid polymer electrolyte based on blend of polyethylene oxide, poly(vinylidene fluoride-hexafluoropropylene), propylene carbonate and lithium bis(trifluoromethanesulfonyl) imide with high ionic conductivity and electrochemical windows. The ionic conductivities of POSS-ILs-based solid polymer electrolytes are up to 8.0 × 10⁻⁴ S cm⁻¹ at 22 °C and 2.0 × 10⁻³ S cm⁻¹ at 62 °C, and the electrochemical windows of POSS-ILs-based solid polymer electrolytes are stable up to 5.0 V. Moreover, the Li/LiFePO₄ cell containing POSS-ILs-based solid polymer electrolytes exhibits good cycling performance and high rate stability. These results suggest that the POSS-ILs-based solid polymer electrolytes could be a suitable prospective electrolyte material for lithium-ion battery applications.