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

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.