Multifunctional “Solvent‐in‐Diluent” High Voltage Electrolyte for Lithium Metal Batteries

Sulfone liquids can be used as solvents for high‐voltage electrolytes and have been extensively studied for their strong oxidation resistance. However, the problem of high viscosity and susceptibility to side reactions with metallic lithium has been the subject of criticism. To solve the issue of incompatibility with lithium, researchers adopted a high‐concentration electrolyte, namely solvent‐in‐salt, which allows the anions in the lithium salt to preferentially contact the surface of the lithium metal and react to form an SEI film to block the reaction between sulfone solvents and lithium. However, the issue of high viscosity is particularly severe. This work proposes a new solvent model called “solvent‐in‐diluent” electrolyte to address both of these issues simultaneously, different from previous models of salt‐in‐solvent, the model not only effectively prevents sulfone contact with lithium metal surfaces, but also maintains a capacity retention rate of 82% after 500 cycles in the voltage range of 2.8–4.6 V, additionally, the temperature range in which the battery can operate using this electrolyte model has been extended (−20–60°C). This work proposes a new solvent model and challenges the minimum concentration of high‐voltage electrolytes (0.04 m), providing a new approach and possibility for studying high‐voltage electrolytes. The novel solvent model “solvent‐in‐diluent” has a wide range of potential applications. Inert diluents encapsulate the reactive components of the electrolyte without impeding the transport of lithium ions. The capacity retention rate of NCM811/Li battery with SDSE‐4 electrolyte reaches up to 80% after 500 cycles in the voltage range of 2.8–4.6V.