Beyond concentrated electrolyte: further depleting solvent molecules within Li+ solvation sheath to stabilize high-energy-density lithium metal batteries

Detrimental decompositions of electrolytes, especially the dehydrogenation of solvents, would accelerate the batteries’ degradations and hinder the development of high-energy-density lithium-metal batteries (LMBs). The nature of building classic concentrated electrolytes is to decrease the proportion of solvents, so that the solvents-related parasitic reactions can be suppressed. However, accompanied with the reduction of solvents, electrolytes’ concentrating processes would reach their limits when saturated states are achieved. Herein, beyond concentrated electrolytes (solvent-definite state), electrolyte with a more aggregative configuration was obtained after we further depleting solvent molecules within Li+ solvation sheath. The prepared electrolyte demonstrated largely expanded electrochemical stability windows (enlarged from 4.5 V to 5.4 V vs. Li/Li+), enhanced stability towards high-Ni NCM-811 cathode and thin cathode electrolyte interlayer (CEI) film. Assembled with high-voltage cathodes (NCM-811 and 5.0 V-class LiCoMnO4 (LCMO)) and limited excess lithium-metal, high-energy-density LMBs full-cells (above 630 Wh kg−1) with ultra-stable cycling performance were achieved. We think this electrolyte design strategy will expand the family of electrolytes and remedy the inherent defects of conventional electrolytes for high-energy-density LMBs.