Effects of addition of TiO 2 nanoparticles on mechanical properties and ionic conductivity of solvent-free polymer electrolytes based on porous P(VdF-HFP)/P(EO-EC) membranes

To enhance the performance (i.e., mechanical properties and ionic conductivity) of pore-filling polymer electrolytes, titanium dioxide (TiO ₂) nanoparticles are added to both a porous membrane and its included viscous electrolyte, poly(ethylene oxide- co-ethylene carbonate) copolymer (P(EO-EC)). A porous membrane with 10 wt.% TiO ₂ shows better performance (e.g., homogeneous distribution, high uptake, and good mechanical properties) than the others studied and is therefore chosen as the matrix to prepare polymer electrolytes. A maximum conductivity of 5.1 × 10 ^-5 S cm ^-1 at 25 °C is obtained for a polymer electrolyte containing 1.5 wt.% TiO ₂ in a viscous electrolyte, compared with 3.2 × 10 ^-5 S cm ^-1 for a polymer electrolyte without TiO ₂. The glass transition temperature, T _g is lowered by the addition of TiO ₂ (up to 1.5 wt.% in a viscous electrolyte) due to interaction between P(EO-EC) and TiO ₂, which weakens the interaction between oxide groups of the P(EO-EC) and lithium cations. The overall results indicate that the sample prepared with 10 wt.% TiO ₂ for a porous membrane and 1.5 wt.% TiO ₂ for a viscous electrolyte is a promising polymer electrolyte for rechargeable lithium batteries.