Additive‐Driven Regulating Solvation Structure Toward Stable High‐Voltage Lithium Metal Batteries

ABSTRACT Raising the upper cutoff voltage is an effective route to high‐energy lithium‐metal batteries (LMBs), but severe interfacial instability at Ni‐rich cathodes and lithium‐metal anodes limits their operation. Conventional additives such as vinylene carbonate (VC), fluoroethylene carbonate (FEC), and lithium bis(oxalato)borate (LiBOB) are usually regarded as sacrificial film‐forming agents, while their role in regulating bulk Li ⁺ solvation remains underexplored. Herein, we develop a ternary‐additive carbonate electrolyte and reveal a “solvation reconstruction‐interphase coupling” mechanism, supported by spectroscopy, simulations, and interphase analyses. VC/FEC/LiBOB synergistically reshapes the Li ⁺ primary solvation sheath and tunes the SSIP/CIP/AGG distribution, shifting the electrolyte from a solvent‐dominated structure toward an anion‐/additive‐involved coordination environment without compromising bulk ion transport. Meanwhile, their preferential decomposition constructs inorganic‐rich CEI/SEI layers with enhanced mechanical robustness and reduced interfacial resistance, thereby suppressing electrolyte oxidation, cathode degradation, and Li dendrite growth. As a result, Li||NCM92 cells deliver >185 mAh g ⁻¹ after 50 cycles at 3.0−4.7 V and 150 mAh g ⁻¹ at 10 C, Li||Li cells operate stably for >1300 h, and Gr||NCM811 pouch cells retain 90% capacity after 100 cycles. This work redefines conventional film‐forming additives as dual‐function solvation/interphase regulators for high‐voltage LMBs.