Ternary Anion‐Engineered Solvation Sheaths in Lightweight Electrolyte Enable Dual‐Interface Stability for Lithium Metal Batteries

A lightweight electrolyte based on ternary anion chemistry –comprising TFSI⁻, DFOB⁻, and NO₃ ⁻ is proposed. The hierarchical linkages within the solvation sheaths, induced by hydrogen bond-like and ion–dipole interactions, facilitated the formation of an anion-enriched solvation structure and provided an anchoring effect for tetrahydrofuran. This rationally designed electrolyte enabled the formation of robust electrode–electrolyte interfaces at both the lithium metal anode and the Ni-rich cathode, thereby enhancing overall electrochemical performance.

Abstract

Ether-based electrolytes promise superior interfacial stability with lithium metal under high salt concentration, while poor oxidative stability limits the high-voltage operation. Extending the intrinsic electrochemical window and reducing the salt concentration to design high-voltage lithium metal batteries is challenging and urgent. Herein, lightweight electrolytes based on intermolecular interactions regulated by ternary anion chemistry are proposed. An anion-enriched solvation structure is achieved at a standard salt concentration (1 m) via enhanced ion-dipole interactions, generating an inorganic-rich electrode-electrolyte interphase and enabling facile lithium plating/stripping kinetics. This results in lithium metal exhibiting an average Coulombic efficiency of 97.9% and a prolonged cycling lifespan (1000 h) at 2 mA cm⁻². The hydrogen bond-like interactions between NO₃ ⁻/TFSI⁻ and tetrahydrofuran, coupled with the preferential decomposition of DFOB⁻ on the Ni-rich cathode, boosts the electrolyte oxidative stability and mitigates the structural degradation of the cathode. Consequently, the Li||LiNi_0.8Co_0.1Mn_0.1O₂ cells demonstrate improved cycling stability (retaining 75% capacity after 300 cycles) and superior rate capability (153.6 mAh g⁻¹ at 5C) at high cathode loading. This work supplies a molecular-level design strategy for low-concentration electrolytes tailored for high-voltage lithium metal batteries, offering a promising pathway toward practical high-energy-density storage systems.