Safe electrolyte design with isolated solvation nanoclusters for high-energy lithium metal batteries

The pursuit of high-energy-density lithium metal batteries is often hampered by severe safety hazards and limited cycle life, leading to increased environmental impact and higher costs. Here, we demonstrate that tuning the underappreciated miscibility between electrolyte components could provide an effective approach. By introducing a non-coordinating, non-flammable cyclic fluorinated diluent, we minimize diluent-ion pair intermolecular forces, thereby enabling the formation of isolated solvation nanoclusters. The designed microstructure could facilitate enhanced Li⁺ transport to suppress dendrite growth and foster an inorganic-rich interphase to enhance interfacial electrochemical and thermal stability. This electrolyte design enables 50 μm Li | |2.5 mAh cm^-2 LiNi_0.8Mn_0.1Co_0.1O₂ cells to retain 80% capacity after 800 cycles and over 95% capacity following an 8-month calendar aging test. Moreover, the Ah-level pouch cells could achieve a specific energy exceeding 500 Wh kg^-1 based on the total mass of the pouch cell, while withstanding fully charged nail penetration and 200% overcharge without fire or swelling. Therefore, the nanocluster electrolyte reduces lifetime safety costs and material consumption per unit energy delivered, collectively enhancing practical sustainability for high-energy-density, safe, and long-lasting lithium metal batteries.