Titanium dioxide nano-ceramic filler in solid polymer electrolytes: Strategy towards suppressed dendrite formation and enhanced electrochemical performance for safe lithium ion batteries

Solid polymer electrolytes (SPEs) in lithium-ion batteries (LIBs) are emerging as promising alternative for liquid electrolytes. However, one of the drawbacks of SPEs is incompatibility between lithium metal anode/electrolyte that leads to the low ionic conductivity and lower cycling performance of LIBs. The present study show that fabrication of free-standing flexible hybrid solid polymer electrolyte (HSPE) based on poly(vinylidene fluoride-co-hexafluoro propylene)/poly(vinyl acetate) polymer blend electrolyte with TiO2 nano-ceramic filler (NCF). The incorporation of TiO2-NCF aids in simultaneous improvements of the ionic conductivity and mechanical properties of host matrix. HSPE with 7.5 wt% TiO2 exhibits highest ionic conductivity of 2.69 × 10−3 S cm−1 at 30 °C, which is ~2.5 time higher than ceramic free HSPE. In addition, the incorporation of TiO2 enhances the high thermal stability (thermal degradation at 350 °C) and mechanical strength (stress 8.4 MPa) of the HSPE. Remarkably, HSPE with 7.5 wt% TiO2-NCF possess large Li+ transference number (0.53) with extended electrochemical stability window (5.4 V) and superior compatibility with lithium metal which is highly desirable for high voltage LIBs. The Li/HSPE/LiFePO4 cell showed superior charge discharge properties, cycling stability and rate capability. Suppression of growth and proliferation of Li dendrites was demonstrated by time dependent impendence analysis. Furthermore, density functional theory (DFT) calculations confirm the mutual interactions between TFSI− and ions in electrolytes and that between TiO2 segments and polymer segments. This work exemplifies the significant role of TiO2-NCF in enhanced electrochemical performance of polymer based free standing flexible HSPE.