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

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 parallel to Li symmetric cells and ultralong lifespans with capacity retention of 66% after 2000 cycles in Li parallel to LiFePO4. Targeted electrolyte engineering is presented as a promising approach for practical high-performance Li-metal batteries.