Silica nanofiber-reinforced carbonate-based composite polymer electrolytes: interfacial effects on Li-ion transport

Abstract

Polymer electrolytes have been actively investigated as safer alternatives to liquid electrolytes; however, their electrochemical performance often remains limited. In this study, carbonate-based composite polymer electrolytes (CPEs) were prepared using a PEC-LiFSI matrix with two types of silica fillers: SiO2 nanoparticles and electrospun silica nanofibers (SNFs). Filler contents of 1, 5, and 10 wt% were used to examine the morphology and interface-related effects. Compared with the filler-free PEC-LiFSI electrolyte (SPE), both fillers increased thermal stability. FT-IR analysis of the carbonyl stretching region revealed changes with filler addition, indicating changes in the Li+ coordination environment. The ionic conductivity exhibited an optimum at 5 wt% loading for both fillers, followed by a decrease at 10 wt%. Linear sweep voltammetry further indicated improved oxidation stability with the addition of silica, with the highest oxidation onset potential observed at 5 wt% SNFs. The mechanical properties were enhanced much more strongly by SNFs than by SiO2, especially at high loadings. The capacity of the battery increased during the initial cycles and approached approximately 140 mAh g−1. Overall, these results highlight that the surface/interface effects and loading of silica fillers together influence key thermal, mechanical, and electrochemical properties of carbonate-based CPEs and that SNFs are an effective filler for mechanically robust PEC-LiFSI-based CPEs. PEC-based composite polymer electrolytes (CPEs) reinforced by electrospun silica nanofibers (SNFs), prepared without calcination. SNF incorporation enhances both ionic conductivity and mechanical strength, with an optimal conductivity observed at 5 wt% loading. The high-aspect-ratio fibrous morphology and polar surface groups (Si-OH and aminopropyl) promote effective filler–electrolyte interactions, resulting in improved overall performance of carbonate-based CPEs.