A "tug-of-war" effect tunes Li-ion transport and enhances the rate capability of lithium metal batteries.

"Solvent-in-salt" electrolytes (high-concentration electrolytes (HCEs)) and diluted high-concentration electrolytes (DHCEs) show great promise for reviving secondary lithium metal batteries (LMBs). However, the inherently sluggish Li transport of such electrolytes limits the high-rate capability of LMBs for practical conditions. Here, we discovered a "tug-of-war" effect in a multilayer solvation sheath that promoted the rate capability of LMBs; the pulling force of solvent-nonsolvent interactions competed with the compressive force of Li-nonsolvent interactions. By elaborately manipulating the pulling and compressive effects, the interaction between Li and the solvent was weakened, leading to a loosened solvation sheath. Thereby, the developed electrolytes enabled a high Li transference number (0.65) and a Li (50 μm)‖NCM712 (4 mA h cm) full cell exhibited long-term cycling stability (160 cycles; 80% capacity retention) at a high rate of 0.33C (1.32 mA cm). Notably, Li (50 μm)‖LiFePO (LFP; 17.4 mg cm) cells with a designed electrolyte reached a capacity retention of 80% after 1450 cycles at a rate of 0.66C. An 6 Ah Li‖LFP pouch cell (over 250 W h kg) showed excellent cycling stability (130 cycles, 96% capacity retention) under practical conditions. This design concept for an electrolyte provides a promising path to build high-energy-density and high-rate LMBs.