Succinonitrile‐Rich Electrolyte Solvation Structure Enables Wide‐Temperature‐Range Operation of Lithium‐Metal Batteries

Stable lithium-metal batteries (LMBs) with wide-temperature-range operability can be achieved through the rational design of electrolytes based on their physicochemical and electrochemical characteristics, such as their freezing behavior and functional integrity at battery heterointerfaces. This study demonstrates that succinonitrile (SN)-dominated solvation chemistry and fluoroethylene carbonate (FEC)-derived interface engineering can enable the wide-temperature-range operation of LMBs while optimally tuning the microstructures of the electrolyte for facile Li-ion conduction. A mechanically and chemically stable LiF-rich primary solid-electrolyte interphase (SEI) is constructed using FEC and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE). Subsequently, lithium bis(trifluoromethanesulfonyl) imide and SN are utilized to produce ion-conductive Li₃N in the SEI. SN promoted the build-up of an electron- and N-rich C≡N based cathode-electrolyte interface that could mitigate transition metal-ion dissolution, microcrack formation, and structural degradation in a LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode. TTE, which exhibits low solvation power, enabled the formation of desirable Li-ion conduction pathways, including a deep depression of the melting point of the electrolyte and low-viscosity Li-ion channels, for low-temperature operation. The integration of interface engineering and electrolyte chemistry provides an efficient strategy for preparing Li|NCM811 full cells demonstrating stable operation under various temperature conditions.