Lithium metal batteries (LMBs) with high energy density show substantial promise as advanced electrochemical energy storage solutions, although they encounter persistent challenges pertaining to cycling stability and safety performance. Conventional homogeneous electrolytes widely employed in LMBs are inherently flammable, possessing a limited electrochemical window, thereby presenting obstacles to meeting the stringent safety and cycling criteria. In this investigation, we devised an asymmetric fire-retardant quasi-solid polymer electrolyte to mitigate thermal runaway risks and chemical/electrochemical instability at the electrolyte–electrode interface in LMBs. Specifically, on the cathode side, a poly(vinylidene fluoride-co-hexafluoropropylene gel electrolyte incorporating flame-retarded organophosphates exhibited remarkable compatibility and heightened thermal stability when paired with high-voltage Ni-rich layered materials. Simultaneously, a thin yet resilient polyether gel electrolyte was in-situ synthesized on lithium metal anodes, expanding the applicability of fire-retardant electrolytes to lithium metal anodes while suppressing the formation of lithium dendrites. Consequently, high-voltage LMBs utilizing asymmetric fire-retardant electrolytes demonstrated a substantial enhancement in safety performance and cycling stability. This research delineates a viable pathway toward realizing secure and consistent cycling in high-energy-density energy storage systems.

With a high cell-level specific energy and a low cost, lithium-sulfur (Li-S) battery has been intensively studied as one of the most promising candidates for competing the next-generation energy storage campaign. Currently, the practical use of Li-S battery is hindered by the rapidly declined storage performance during battery operation, as caused by irreversible loss of electroactive sulfide species at the cathode, dendrite formation at the anode and parasitic reactions at the electrode-electrolyte interface due to unfavorable cathode-anode crosstalk. In this perspective, we propose to stabilize the Li-S electrochemistry, and improve the storage performance of battery by designing asymmetric electrode-electrolyte interfaces that helps to simultaneously address the differentiated issues at both electrodes and facilitate charge transfer in the electrode/electrolyte and across the interfaces. The strategies that etare discussed would shed lights on reasonable design of battery interfaces towards realization of high-performance Li-S batteries.