Anionic solvation reconstruction stabilizes interfacial chemistry for high-temperature and high-voltage Li metal...

The development of high-voltage Li metal batteries is crucial to meeting increasing demand for high specific energy. However, their high-temperature operation remains a huge challenge due to reduced electrolyte oxidation stability and aggravated interfacial side reactions. Herein, a multimodal ¹⁹F nuclear magnetic resonance technique is developed to reveal temperature-mediated evolution of electrolyte anion solvation chemistry, thus identifying its vital roles in stabilizing high-voltage positive electrodes. A universal solvent screening strategy is proposed to customize an anion-anchored compact solvation structure electrolyte with large-size and anion-compressed solvation structure. This strategy simultaneously elevates anti-oxidation ability, stabilizes electrode-electrolyte interphase, and maintains structural integrity of the positive electrodes. Consequently, a 317 Wh kg^-1 Li metal pouch cell based on the total cell mass achieves high thermal safety and cycling stability at 55 °C. Our work elucidates the reaction mechanisms of solvation structure and interfacial chemistry in high-temperature and high-voltage Li metal batteries, which offers insightful guidance for designing wide-temperature battery electrolytes.