High-Performance Composite Solid Electrolyte Containing PVDF/PEO and Surface-Functionalized Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ for Solid-State Li Batteries

The compatibility among the components in composite solid electrolytes (CSEs) plays a crucial role in determining the overall performance of solid-state lithium-ion batteries. To address this deficiency, a series of CSEs were prepared by incorporating Li1.3Al0.3Ti1.7(PO4)3 (LATP) powders into the PVDF/PEO polymer matrix via a solution casting method, with LATP functionalized with vinyltriethoxysilane (VTES) to enhance its interfacial compatibility and dispersion uniformity with the PVDF/PEO matrix. The effect of the VTES content on the physical integrity and electrochemical properties of CSEs was systematically investigated. The results demonstrate that the incorporation of an appropriate amount of VTES significantly enhances the dispersion of LATP within the PVDF/PEO polymer matrix and improves the ionic conductivity, Li+ transfer number, rate capability, cycling stability, and thermal stability of CSEs. Among them, 2VS-CSE with a VTES-to-LATP mass ratio of 2:1 exhibits the optimal overall performance, with a high ionic conductivity of 0.542 mS·cm–1, Li+ transfer number of 0.617, a wider electrochemical stability window to 5.39 V (vs. Li/Li+), and better compatibility with the lithium metal anode (over 1000 h). Li|LiFePO4 battery assembled with 2VS-CSE shows excellent cycling stability of 86.6% after 300 cycles at 0.5 and 25 °C. The addition of VTES-modified LATP provides a strategy for promoting the application of CSEs in solid-state lithium-ion batteries.