Integrated Solvation Chemistry Enables High Energy Li Metal Batteries

Rational electrolyte design for high-energy Li metal batteries (LMBs) demands the simultaneous suppression of solvent reactivity and the promotion of anion reduction. However, existing approaches often fall short due to inadequate control over the solvation structure, leading to excessive free solvent and anion species and continual side reactions. Here, we propose a solvation integration strategy that confines both solvent molecules and anions within the first solvation sheath, thereby minimizing their reactivity. As a proof of concept, we employ lithiophilic (trifluoromethoxy)fluorobenzene (TFMFB) to tune Li⁺ solvation by enhancing the affinity of solvents toward Li⁺, ensuring favorable Li⁺ kinetics. Simultaneously, lipophilic (trifluoromethyl)cyclohexane (FMCH) forms an outer-layer kinetic barrier that inhibits solvent/anion desolvation. This inner-lithiophilic and outer-lipophilic configuration creates synergistic confinement, significantly enhancing oxidation stability and enabling robust interfacial chemistry. As a result, an anode-free Cu∥LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) pouch cell utilizing the tailored solvation-integrated electrolyte (SIE) achieves 80% capacity retention after 120 cycles. Furthermore, the aggressive 10 Ah Li∥LiNi_0.9Co_0.05Mn_0.05O₂ (NCM955) pouch cell with an ultralean electrolyte (1.1 g Ah^-1) delivers an ultrahigh energy density of 568 Wh kg^-1. This solvation integration concept provides a promising guideline for the electrolyte design toward practical high-energy LMBs.