Semiconductor TiO2 ceramic filler for safety-improved composite ionic liquid gel polymer electrolytes

Gel polymer electrolytes are one of the candidates for solid electrolytes to solve safety issues and improve the energy density of solid-state lithium batteries. Gel polymer electrolyte has high ionic conductivity at room temperature (~ 10−3 S cm−1), but its mechanical properties are poor. Herein, we prepared a series of composite gel polymer electrolytes by N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide, poly(vinylidene fluoride-hexafluoropropylene), LiTFSI, and various inorganic fillers. The addition of 5 wt% TiO2 can not only increase the ionic conductivity of gel polymer electrolytes but also improve the mechanical properties of gel polymer electrolytes. Besides, as a semiconductor, the TiO2 has safety risk when uses in composite gel polymer electrolyte. TiO2-ILGPE safety is investigated by cyclic voltammetry and battery performance. Additionally, TiO2-ILGPE displays a perfect flame-retarding ability, and TiO2 would not be reduced by the lithium metal anode.