Synergistic Enhancement in Properties of Composite Solid Electrolytes via PAN and in-situ SiO2 for All-Solid-State Lithium Batteries

Abstract

This work presents the fabrication of a composite solid polymer electrolyte (CSE) by blending poly(ethylene oxide) (PEO) with polyacrylonitrile (PAN) and incorporating SiO₂ nanoparticles generated via in-situ process. The addition of PAN effectively disrupted the crystalline structure of PEO and increased the amorphous phase and polymer chain flexibility, which facilitated improved lithium ion mobility. The in-situ formation of SiO₂ via TEOS (tetraethyl orthosilicate) hydrolysis ensured uniform dispersion of ceramic fillers, which enhanced mechanical property, thermal stability, and ion transport pathways. The optimized CSE-15 sample demonstrated notable ionic conductivity of 3.81 × 10⁻⁴ S·cm⁻¹ at elevated temperature and a lithium-ion transference number of 0.36, indicative of efficient lithium transport. Electrochemical testing revealed a wide electrochemical stability window extending to 4.5 V (vs. Li/Li⁺), while lithium symmetric cells exhibited prolonged cycling stability and effective suppression of dendritic growth. Furthermore, full cell tests using LiFePO₄ as the cathode revealed a high specific capacity of 151.4 mAh·g⁻¹ with a Coulombic efficiency of 99.8% over 150 cycles at 0.5 C and 60°C. The synergistic effect of polymer blending and in-situ filler incorporation was found to optimize the balance between ionic conductivity, mechanical integrity, and interfacial compatibility, which are critical parameters for advancing solid-state lithium battery. These findings provide valuable insights into the rational design of composite electrolytes. Therefore, the obtained CSE is a promising candidate for developing safe and high performance lithium metal batteries.