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.