Entropy-Driven Electrolyte Design for Lithium Metal Batteries: Achieving Interfacial Stability With Fluorinated Fullerene Nanoparticle Additives.

Abstract

Lithium metal batteries are highly attractive for next-generation high-energy-density storage, and ether-based electrolytes such as LiFSI/DME are particularly promising for high-rate operation because of their low viscosity, high ionic conductivity, and favorable compatibility with Li metal. However, current electrolyte optimization strategies still rely mainly on small-molecule additives that regulate bulk solvation or the primary Li⁺ solvation sheath, whereas entropy-driven modulation of the interfacial solvation environment by large molecular additives remains largely unexplored. Herein, fluorinated fullerene C₆₀F₃₀ (FF) is introduced as a nanoparticle additive to create a dynamically disordered interface that enhances configurational entropy without sacrificing Li⁺ diffusivity, while accelerating Li⁺ desolvation and transport. Meanwhile, FF cooperates with FSI^--derived species to build a robust fluorine-rich SEI, suppressing dendrite growth and parasitic reactions. As a result, Li||Li symmetric cells cycle stably for 1500 h, while high-loading Li||LiFePO₄ cells retain 96.0% capacity after 500 cycles at 2C and 95.9% after 1000 cycles at 10C. Moreover, pouch cells and high-loading Li||NCM811 cells further verify the practical promise of the FF-enabled electrolyte for high-rate, long-cycling LMBs.