Weakly coordinated Li ion in single-ion-conductor-based composite enabling low electrolyte content Li-metal batteries

The pulverization of lithium metal electrodes during cycling recently has been suppressed through various techniques, but the issue of irreversible consumption of the electrolyte remains a critical challenge, hindering the progress of energy-dense lithium metal batteries. Here, we design a single-ion-conductor-based composite layer on the lithium metal electrode, which significantly reduces the liquid electrolyte loss via adjusting the solvation environment of moving Li⁺ in the layer. A Li||Ni_0.5Mn_0.3Co_0.2O₂ pouch cell with a thin lithium metal (N/P of 2.15), high loading cathode (21.5 mg cm^-2), and carbonate electrolyte achieves 400 cycles at the electrolyte to capacity ratio of 2.15 g Ah^-1 (2.44 g Ah^-1 including mass of composite layer) or 100 cycles at 1.28 g Ah^-1 (1.57 g Ah^-1 including mass of composite layer) under a stack pressure of 280 kPa (0.2 C charge with a constant voltage charge at 4.3 V to 0.05 C and 1.0 C discharge within a voltage window of 4.3 V to 3.0 V). The rational design of the single-ion-conductor-based composite layer demonstrated in this work provides a way forward for constructing energy-dense rechargeable lithium metal batteries with minimal electrolyte content.