Sulfone-Based Cosolvents Stabilize PF₆^– to Enable High-Voltage Lithium Metal Batteries

Pairing high-voltage cathode materials with a lithium metal anode is recognized as a promising strategy for advancing the development of high-specific-energy batteries. Sulfone-based solvents were generally considered to have high oxidation stability due to the electron-withdrawing nature of their sulfonyl groups. Herein, an interesting phenomenon was observed in the LiPF6/sulfolane electrolyte, sulfolane induces the decomposition of LiPF6 at high potentials, ultimately affecting battery performance. Herein, a sulfone-based binary electrolyte system that weakens the sulfone-PF6– interaction and enhances the Li+-PF6– interaction was proposed. High-voltage lithium metal batteries with an LNMO cathode were achieved in a sulfone electrolyte with low-concentration LiPF6. The binary electrolyte not only effectively suppresses the decomposition of LiPF6 in the battery but also promotes the formation of a fluorine-rich cathode-electrolyte interface (CEI) and an organic/nonpolar mixed solid electrolyte interface (SEI) on the anode. The battery exhibits a capacity retention rate of 81% after 300 cycles at 0.5C/1C within the voltage range of 3.5–4.85 V.