Modified Li1.5Al0.5Ge1.5(PO4)3 Nanoparticles Improve Dispersibility and Interfacial Compatibility of PVDF-Based Composite Electrolytes

Ceramic-in-polymer composite electrolytes have shown great potential in solid-state lithium metal batteries due to their high safety, outstanding flexibility, and scalable preparation. However, the dispersion and interfacial compatibility of ceramic fillers in the polymer still face challenges, especially for nanoparticles, which hinder the continuous Li⁺ migration of composite electrolytes. Herein, Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) nanoparticles (∼125 nm) modified by 3-aminopropyl-triethoxysilane (APS) are introduced into poly(vinylidene fluoride) (PVDF) composite electrolytes to enable uniform dispersion and great interfacial compatibility. The influence of APS@LAGP nanoparticles on the electrochemical performance of APS@LAGP-PVDF composite electrolytes is studied. The results show that the 15 wt % APS@LAGP-PVDF composite electrolytes integrate the features of high ionic conductivity (2.36 × 10^–4 S cm^–1 at 30 °C), high lithium-ion transference number (0.60), and high oxidation stability (>5.06 V). Meanwhile, these composite electrolytes exhibit outstanding Li stripping/plating reversibility in lithium symmetric cells (over 3000 h) and demonstrate remarkable cycling performance for solid-state LiFePO₄|Li (86.3% after 200 cycles) and LiNi_0.6Co_0.2Mn_0.2O₂|Li (83.8% after 200 cycles) batteries. This work provides a valuable strategy to achieve continuous and rapid Li⁺ migration in ceramic-in-polymer composite electrolytes.