Synergistic enhancement of the 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 an in situ process. The addition of PAN effectively disrupts the crystalline structure of PEO and increases the amorphous phase and polymer chain flexibility, which facilitates improved lithium ion mobility. The in situ formation of SiO₂ via tetraethyl orthosilicate (TEOS) hydrolysis ensures the uniform dispersion of ceramic fillers, which enhances the mechanical properties, thermal stability, and ion-transport pathways. The optimized CSE-15 sample demonstrates a notable ionic conductivity of 3.81 × 10⁻⁴ S cm⁻¹ at an elevated temperature and a lithium-ion transference number of 0.36, indicative of efficient lithium transport. Electrochemical testing reveals a wide electrochemical stability window, extending to 4.5 V (vs. Li/Li⁺), while the lithium symmetric cells exhibit prolonged cycling stability and the effective suppression of dendritic growth. Furthermore, full cell tests using LiFePO₄ as the cathode show a high specific capacity of 151.4 mA h g⁻¹, with a Coulombic efficiency of 99.8% over 150 cycles at 0.5C and 60 °C. The synergistic effect of polymer blending and in situ filler incorporation is found to optimize the balance between ionic conductivity, mechanical integrity, and interfacial compatibility, which are critical parameters for advancing solid-state lithium batteries. 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.