A Low-Cost, Fluorine-Free Localized Highly Concentrated Electrolyte Toward Ultra-High Loading Lithium Metal Batteries

Localized highly concentrated electrolytes have revitalized the advancement of secondary batteries. However, fluorinated diluents typically have the drawbacks of high toxicity, serious environmental pollution, challenging synthesis, and high cost. This work develops a low-cost, eco-friendly localized highly concentrated electrolyte by utilizing benzene as a diluent, simultaneously achieving highly reversible lithium-metal anodes and long-term stable cycling of single crystal LiNi_0.8Co_0.1Mn_0.1O₂ (SC811) cathode. The unique conjugated structure and absence of electron-withdrawing groups provide benzene the decent redox stability and inertness, which enables it to modulate the highly concentrated solvation structure. The PhH-LHCE supports SC811-Li cells with a cathode loading of 9 mg cm⁻² achieving 87.3% capacity retention after 450 cycles. Cells consisting of ultra-high loading Ni83 cathode (≈31 mg cm⁻²) and ultra-thin Li (50 µm) anode achieve stable 70 cycles with a lean electrolyte condition. This work can be generalized to promising electrochemical energy storage systems such as sodium and potassium metal batteries to solve the cost and environmental pollution problems in the large-scale production process.