Uncovering the Redox Shuttle Degradation Mechanism of Ether Electrolytes in Sodium-Ion Batteries and its Inhibition Strategy.

Ether-based electrolytes exhibit excellent performance when applied in different anode materials of sodium ion batteries (SIBs), but their exploration on cathode material is deficient and the degradation mechanism is still undiscovered. Herein, various battery systems with different operation voltage ranges are designed to explore the electrochemical performance of ether electrolyte. It is found for the first time that the deterioration mechanism of ether electrolyte is closely related to the "redox shuttle" between cathode and low-potential anode. The "shuttle" is discovered to occur when the potential of anodes is below 0.57 V, and the gas products coming from "shuttle" intermediates are revealed by differential electrochemical mass spectrometry (DEMS). Moreover, effective inhibition strategies by protecting low-potential anodes are proposed and verified; ethylene carbonate (EC) is found to be very effective as an additive by forming an inorganics-rich solid electrolyte interphase (SEI) on low-potential anodes, thereby suppressing the deterioration of ether electrolytes. This work reveals the failure mechanism of ether-based electrolytes applied in SIBs and proposes effective strategies to suppress the "shuttle," which provides a valuable guidance for advancing the application of ether-based electrolytes in SIBs.