Highly Adaptable Electrode–Electrolyte Interphases Constructed by Dual‐Additive‐Optimized Electrolyte for 4.5 V Lithium Metal Batteries

Abstract Lithium metal batteries (LMBs) with Li metal anodes and high‐voltage LiCoO 2 (LCO) cathodes offer high energy density but face challenges such as Li dendrite growth and LCO structure degradation, which primarily arises from the electrolyte's inability to form a stable interphase. Herein, a dual‐additive optimized carbonate‐based electrolyte is developed, incorporating tetraethylammonium nitrate (TEANO 3 ) and lithium difluorobis(oxalato) phosphate (LiDFBOP) as regulators. LiDFBOP enhances interfacial stability and compactness, while TEANO 3 facilitates Li + transport and suppresses excessive decomposition of LiDFBOP. The synergistic effect of TEANO 3 and LiDFBOP establishes robust, high ion‐conductive solid electrolyte interphase (SEI) and cathode–electrolyte interphase (CEI) enriched with P‐ and N‐containing inorganic compounds (including LiN x O y and P‐O/P‐F species), enabling dense Li deposition and stable cycling of LCO under a high cut‐off voltage of 4.5 V. The optimized electrolyte enables Li||LCO full cells with a high capacity retention of 84% even with high‐mass‐loading LCO cathode (3.5 mAh cm −2 ) and limited Li (N/P = 2). This work demonstrates a straightforward electrolyte design strategy for optimizing SEI and CEI, advancing the practical deployment of LMBs.