Improving Ionic Conductivity and Interface Stability in All-Solid-State Batteries Using Nanocomposite Solid Electrolytes

All-solid-state batteries (ASSBs) have emerged as promising candidates for next-generation energy storage due to their intrinsic safety and compatibility with high-energy-density lithium metal anodes. However, their commercialization is hindered by two persistent bottlenecks: the relatively low ionic conductivity of solid electrolytes compared to liquids and the instability of electrode-electrolyte interfaces. Existing approaches often improve one aspect in isolation but fail to simultaneously optimize both properties under practical cycling conditions. In this study, we propose an in situ-assembled nanocomposite solid electrolyte, where oxide nanoparticles are homogeneously dispersed within a sulfide-based host matrix through a sol-gel assisted synthesis. This design integrates percolation pathways that reduce activation energy for Li + transport and introduces a nanoscale passivation layer that suppresses interfacial side reactions. Electrochemical tests demonstrate a room-temperature ionic conductivity of 1.7 × 10 - 3 S·cm - 1 , a 2.3-fold improvement over pure sulfide and a 6.1-fold improvement over oxide baselines. Interfacial resistance was reduced to 18 Ω·cm 2 , and full-cell cycling retained 91% capacity after 300 cycles. Ablation and robustness studies further confirm the critical role of filler concentration, particle size, and interfacial engineering. These results establish a reproducible framework for enhancing both conductivity and interfacial stability in ASSBs. The proposed nanocomposite design provides a scalable pathway toward safer, high-performance solid-state batteries, directly supporting future applications in electric vehicles and grid-scale energy storage.