Does filler surface chemistry impact filler dispersion, polymer dynamics and conductivity in nanofilled solid polymer electrolytes?

We study the impact of nanofiller surface chemistry on filler dispersion, polymer dynamics and ionic conductivity in acidic $\alpha $-Al$_{2}$O$_{3}$ filled PEO+LiClO$_{4}$ solid polymer electrolytes (SPEs).SPEs are the key to light-weight and high energy density rechargeable Li ion batteries but suffer from low room temperature ionic conductivity. Addition of ceramic nanofillers improves conductivity of SPEs and their surface chemistry influences extent of conductivity enhancement. The ionic conductivity of acidic $\alpha $-Al$_{2}$O$_{3}$ filled SPE is enhanced for salt concentrations at and below eutectic, while neutral $\gamma $-Al$_{2}$O$_{3}$ filler enhances conductivity only at eutectic composition. Li ion motion is coupled to segmental mobility of polymer and we study how this is affected by addition of $\alpha $-Al$_{2}$O$_{3}$ using quasi-elastic neutron scattering. Aggregation extent of nanoparticles in SPE matrix, a less explored factor in filled SPEs, can affect segmental mobility of polymer. This can vary with surface chemistry of particles and we quantify this using small angle neutron scattering. All measurements are performed as a function of Li concentration, nanoparticle loading and temperature.