Tailoring Solvation Structures via Precise Diluent Engineering for High-Rate 500 Wh kg^-1 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^-1. 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^-2; electrolyte: 3 g Ah^-1). Furthermore, a 2.95 Ah Li-NCM811 pouch cell demonstrates an energy density of 518 Wh kg^-1/985 Wh L^-1 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.