Electrochemical and Nanomechanical Properties of TiO₂ Ceramic Filler Li-Ion Composite Gel Polymer Electrolytes for Li Metal Batteries

Ionically conductive polymers are a promising family of electrolytes for electrochemical devices, including batteries, and flexible electronics. The polymer electrolytes with an excellent mechanical property probably can inhibit the dendrites growth during charging/discharging. Herein, the mechanical properties of an N−methyl−N−propyl piperidinium bis(trifluoromethanesulfonyl)imide/poly(vinylidene fluoride-hexafluoropropylene) gel polymer electrolyte is improved through compositing with %TiO₂ nanoparticles. The gel polymer electrolyte shows increased loss modulus after compositing with 5 wt% TiO₂, indicating that the inorganic nanoparticles can increase the viscous response of polymer electrolytes. The Li-ion conductivity shows a noticeable dependence on %TiO₂ and the highest ionic conductivity is obtained at 5 wt% TiO₂. The presence of TiO₂ in the gel polymer electrolyte also allows for smaller interfacial resistance and a more stable Li−electrolyte interface upon long-term storage and battery cycling. As a result, when assembled with the LiFePO₄ and LiNi_0.6Mn_0.2Co_0.2O₂ cathodes, the composite gel polymer electrolyte improves the full-cell performance, such as higher Coulombic efficiency, improved cycling stability, and more stable electrode–electrolyte interface.