Modulating Solvation Structure and Electrical Double Layer via Anion-Additive Weak Interactions for High-Voltage Lithium Metal Batteries

High-voltage lithium metal batteries have attracted attention due to their exceptional energy density. However, their practical deployment is impeded by the instability of the electrode-electrolyte interface (EEI). Here, we report a strategy to construct a mechanically robust yet flexible EEI by synergistically regulating the solvation structure and electrical double layer (EDL) via weak interactions between DFOB⁻ and the 2-thiophenecarbonitrile (2-TC) additive in weakly solvating electrolytes. Specifically, the ion-dipole interactions between strongly solvating 2-TC and DFOB⁻ facilitate DFOB⁻-rich contact ion pairs and aggregate structures. Concurrently, preferential co-adsorption of 2-TC/DFOB⁻ at the cathode surface synergizes with intermolecular weak interactions to reconfigure the EDL into a DFOB⁻-enriched and solvent-deficient architecture. This synergistic modulation of the solvation sheath and interfacial EDL facilitates the formation of LiF/LiB_xO_y-rich EEI. Furthermore, electric field-induced in situ polymerization of 2-TC generates a flexible polythiophene network, endowing the EEI with exceptional volume strain tolerance. This electrolyte enables Li||NCM811 battery to deliver stable cycling over a wide temperature range (−20°C to 60°C) and at a high voltage of 4.7 V. Furthermore, practical 4.8 Ah Li||NCM90 and 4.4 Ah Li||LiCoO₂ pouch cells with this electrolyte achieve energy densities of 472 Wh kg⁻¹ and 429 Wh kg⁻¹, respectively, while maintaining stable cycling performance.