Dual‐Salts Localized High‐Concentration Electrolyte for Li‐ and Mn‐Rich High‐Voltage Cathodes in Lithium Metal Batteries

Abstract Limited electrochemical stability windows of conventional carbonate‐based electrolytes pose a challenge to support the Lithium (Li)– and manganese (Mn)–rich (LMR) high‐voltage cathodes in rechargeable Li‐metal batteries (LMBs). To address this issue, a novel localized high‐concentration electrolyte (LHCE) composition incorporating LiPF 6 and LiTFSI as dual‐salts (D‐LHCE), tailored for high‐voltage (>4.6 V vs.Li ) operation of LMR cathodes in LMBs is introduced. 7 Li nuclear magnetic resonance and Raman spectroscopy revealed the characteristics of the solvation structure of D‐LHCE. The addition of LiPF 6 provides stable Al‐current‐collector passivation while the addition of LiTFSI improves the stability of D‐LHCE by producing a more robust cathode‐electrolyte interphase (CEI) on LMR cathode and solid‐electrolyte interphase (SEI) on Li‐metal anode. As a result, LMR/Li cell, using the D‐LHCE, achieved 72.5% capacity retention after 300 cycles, a significant improvement compared to the conventional electrolyte (21.9% after 100 cycles). The stabilities of LMR CEI and Li‐metal SEI are systematically analyzed through combined applications of electrochemical impedance spectroscopy and distribution of relaxation times techniques. The results present that D‐LHCE concept represents an effective strategy for designing next‐generation electrolytes for high‐energy and high‐voltage LMB cells.