Effects of siloxane nanoparticles on glass transition temperature and crystallization in PEO-LiPF6 polymer electrolytes

• 3 nm siloxane nanoparticles were used as an additive in polymer electrolytes.
• We observed enhancement of the conductivity with siloxane nanoparticles.
• Siloxane nanoparticles affect to reduce the crystallization in polymer electrolytes.
• Glass transition temperature reduction was observed with siloxane nanoparticles.
• High enhancement in conductivity is originated from the enlarged amorphous area in electrolytes.

We study the glass transition temperature and the crystallization in PEO-based polymer electrolytes with addition of siloxane nanoparticles of <3 nm. The PEO nanocomposite electrolytes with 39 wt% of siloxane nanoparticles show maximum conductivity enhanced by 400 times to that of pure PEO when siloxane nanoparticles were added to pure PEO with 22 wt% of LiPF6, the molar ratio for maximum conductivity. Differential scanning calorimetry and wide angle X-ray scattering results show that siloxane nanoparticles reduce the crystallization of PEO by increasing the amount of complexes of ethylene oxide (EO) and Li ions in PEO-LiPF6. In contrast to other additives, the glass transition temperature of the electrolyte is lowered with increasing concentration of siloxane nanoparticles. Enhancement of the conductivity with siloxane nanoparticles is due to the increased ion mobility and amorphous area in electrolytes.