Highly Stable Electrolyte Design Enables Improved Electrode/Electrolyte Interface Stability for Lithium-Metal Batteries

Abstract

In lithium (Li)-metal batteries (LMBs), the functional electrolytes need to be compatible with both a high-voltage cathode and a highly reactive anode. However, the carbonate-based electrolytes in commercial lithium-ion batteries (LIBs) exhibit insufficient reductive stability due to severe side reactions and the formation of lithium dendrites on the Li anode. In this study, the use of LiPF₆ and lithium difluorobis(oxalato) phosphate (LiDFBOP) dual-salt electrolyte composed of ester and ether cosolvents (FEC/DME) enables the stabilization of the high-voltage LMBs through modulating the interfacial electrochemistry. Such an electrolyte design strategy is demonstrated to regulate the Li plating/stripping behavior by forming a robust anion-derived solid electrolyte interphase (SEI) film on the anode and to improve the cathode/electrolyte interfacial stability under high-voltage conditions. As a result, the as-developed electrolyte exhibits stable cycling over 800 h in Li∥Li symmetric cells and ultralong lifespans with capacity retention of 66% after 2000 cycles in Li∥LiFePO₄. Targeted electrolyte engineering is presented as a promising approach for practical high-performance Li-metal batteries.