Janus-structured composite nanofiber membranes with heterointerfacial engineering for high-performance all-solid-state lithium metal batteries

Abstract

Composite solid electrolytes (CSEs) are promising for solid-state lithium batteries (SSLMBs) due to their enhanced mechanical strength and safety. However, their low ionic conductivity and interfacial instability hinder practical applications. In this study, a Janus-structured composite fiber membrane is introduced to improve the performance of PEO-based electrolytes. The Janus structure creates a heterogeneous interface within the PEO matrix, providing multiple ion transport pathways. Density functional theory (DFT) calculations show that the Janus fiber membrane alters the lithium-ion solvation environment, enhancing lithium-ion migration. The C-F groups and Lewis acid-base sites on the fiber surface promote lithium salt dissociation and facilitate the formation of a stable Li₃N/LiF interfacial SEI. This design reduces the Li⁺ migration barrier, ensuring uniform lithium deposition and improving interface stability. The PHSL-CSE electrolyte achieves 7.60 × 10⁻⁴ S cm⁻¹ ionic conductivity at 50°C, with a lithium-ion transference number of 0.75 and excellent mechanical strength. Batteries with this electrolyte show high cycling stability, rate performance, and flexibility. Pouch cells power flexible devices such as ACEL light-emitting devices and EMG sensors, maintaining functionality under extreme conditions, including folding and puncturing. This work provides insights for high-performance, flexible all-solid-state lithium batteries for energy storage and wearable electronics.