Ligand Electronics and Metal‐Site Acidity Enable High‐Voltage MOF Electrolytes for Quasi‐Solid‐State Lithium‐Metal Batteries

Abstract

Lithium‐metal batteries (LMBs) coupled with Ni‐rich cathodes offer high energy density for next‐generation energy storage. Their practical implementation, however, is limited by electrolyte oxidation and interfacial degradation under high voltage. Metal‐organic frameworks (MOFs) would regulate ion solvation and stabilize electrode‐electrolyte interfaces in quasi‐solid‐state electrolytes, yet the molecular origins of their oxidation stability remain unclear. Here, we identify ligand electronics and metal‐site acidity as key descriptors for high‐voltage‐stable MOF electrolytes. Electron‐withdrawing ligands lower the HOMO energy levels of MOFs, while hard Lewis‐acidic Al sites further enhance oxidation resistance. Guided by this principle, we design a perfluorinated Al‐based MOF, Al‐FBDC, featuring a high oxidation onset potential of 4.82 V (vs. Li + /Li). Incorporating Al‐FBDC into a composite cathode reconstructs the local electrolyte environment at particle‐level interfaces, thereby suppressing parasitic reactions and cathode degradation under high‐voltage operation. As a result, Li||Al‐FBDC@NCM quasi‐solid‐state cells deliver excellent long‐term cycling stability and rate performance, retaining 82% of the capacity after 200 cycles at 1 C over 3.0‐4.5 V, while maintaining robust performance even at 4.6 and 4.8 V cut‐off voltages and with controlled electrolyte loading. This work identifies a general design principle for high‐voltage‐stable MOF electrolytes and offers a practical route toward high‐energy‐density LMBs.