Host–Guest\nInteractions for Electrochemically\nStable and Thermally Safe Lithium Metal Batteries

Safety concerns have been a long-standing barrier hindering\nwidespread\napplications of lithium metal batteries. Herein, we introduce host–guest\ninteractions to regulate the working models of electrolytes with a\nbuilt-in safety switch. At ambient temperature, the host–guest\nliquid electrolyte with high-concentration-electrolyte host and polymer\nmonomer 1,1′-(methylenedi-4,1- phenylene)bismaleimide guest\nrenders Li||LiNi<sub>0.5</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub>O<sub>2</sub> (3 mAh cm<sup>–2</sup>) coin battery 87% capacity\nretention after 210 cycles due to the regulations in the solvation\nstructure and anode interface. When facing thermal safety hazards,\npolymer monomers undergo molecular conformation change. It rapidly\nconstructs a thermally stable polymer matrix with various binding\nsites of lithium ions to host the high-concentration electrolyte,\nenabling batteries to work when they cool to room temperature. Under\nextreme abuse conditions, thermal runaway triggering temperatures\nof 2.0 Ah cycled pouch batteries are increased from 150 to 194 °C.\nThe host–guest interactions are highly effective in constructing\nelectrochemically stable and thermally safe lithium metal batteries.