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

ABSTRACT 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 x O 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||LiCoO 2 pouch cells with this electrolyte achieve energy densities of 472 Wh kg −1 and 429 Wh kg −1 , respectively, while maintaining stable cycling performance.