Dynamics-enhanced sandwich solid-state electrolyte separator for wide-temperature operation of lithium metal batteries

The separator is an essential component of the battery, and its performance can be significantly enhanced through modifications. Some studies have attempted to use solid-state electrolytes as coating materials to replace inert materials that do not participate in ion transport. However, the mechanism of the solid-state electrolyte coatings remains elusive and lacks in-depth investigation. Herein, a dynamics-enhanced separator (SWS@PE) is designed by using LLZTO and LATP as asymmetric coating materials. The solid-state electrolyte coatings not only participate in Li⁺ transport, but the LLZTO layer also absorbs FSI⁻ to help Li⁺ desolvation, which enhances Li⁺ transport dynamics and enables excellent capacity release at low temperatures. Additionally, the LATP layer can absorb dissolved transition metal ions and inhibit the formation of the rock salt phase, further extending the stable cycling of the high-nickel cathode at elevated temperatures. Ultimately, Li||NCM811 cell using SWS@PE with excellent physical and electrochemical properties achieves better capacity release and retention across a wider temperature range. Notably, the 355 mAh Li||NCM83 pouch cell achieves excellent capacity retention of 95.89 % after 150 cycles. This work provides insight into the interfacial mechanism of solid-state electrolyte coatings and offers a new perspective on separator modification.