Tailoring Solvation Structures via Precise Diluent Engineering for High-Rate 500 Wh kg Lithium-Metal Batteries.

Lithium metal batteries (LMBs), featuring lithium metal anodes (LMAs) paired with high-voltage cathodes, are promising candidates for achieving energy densities exceeding 500 Wh kg. However, their commercialization is hindered by unstable interphases and insufficient Li transport kinetics, especially under high-rate conditions. Here, a hybrid diluent strategy is reported for diluted high-concentration electrolytes (DHCEs) that decouples Li solvation from interfacial stabilization by combining fluorinated aromatics with fluorinated ethers. Fluorinated aromatics promote efficient Li desolvation and fast transport, while fluorinated ethers provide high oxidative stability and robust interphase formation. Their combination produces a synergistic solvation environment, simultaneously enhancing ion transport, extending voltage tolerance, and stabilizing electrode-electrolyte interfaces. The tailored electrolyte enables 0.78 Ah Li-NCM622 pouch cells to achieve over 300 cycles at 0.33C charge/0.66C discharge under practical conditions (Li: 50 µm; NCM622: 20 mg cm; electrolyte: 3 g Ah). Furthermore, a 2.95 Ah Li-NCM811 pouch cell demonstrates an energy density of 518 Wh kg/985 Wh L and retains over 92% of its initial capacity after 107 cycles at 0.2C charge/1C discharge. This work establishes a scalable and cost-effective electrolyte design strategy that directly addresses the key failure mechanisms of LMBs, offering a viable pathway toward practical high-energy and high-rate applications.