Elucidating the conductivity enhancement effect of nano-sized SnO2 fillers in the hybrid polymer electrolyte PEO–SnO2–LiClO4

Uniform SnO2 nanoparticles were synthesized hydrothermally and calcined at elevated temperatures to obtain samples of different sizes, shapes and surface states. XPS and near-IR spectroscopy data prove that there exist a large amount of oxygen vacancies or interstitial Sn atoms on the SnO2 nanoparticle surface. The incorporation of these SnO2 particles into polyethylene oxide (PEO)–LiClO4 composite through sonicating dispersion and annealing in vacuum renders the latter amorphous and more conductive. The calcined SnO2 samples, which have higher oxygen vacancy concentrations, exhibit stronger conductivity enhancement effect in the hybrid polymer electrolyte (HPE). Therefore, the oxygen vacancies on SnO2 surface were regarded as the active Lewis acidic sites that interact with both PEO segments and ClO4− ions leading to conductivity improvement.