Sodium-metal batteries are an appealing, sustainable, low-cost alternative to lithium metal batteries due to the high abundance and theoretical specific capacity (1,165 mA h g⁻¹) of sodium. However, the poor compatibility of the electrolyte with the cathode and anode leads to unstable electrode–electrolyte interphases. Here we introduce the concept of using a salt as a diluent, which enables the use of a single non-flammable solvent, such as trimethyl phosphate. By using sodium nitrate (NaNO₃) salt as a model diluent, we report a 1.1 M NaFSI–NaNO₃–trimethyl phosphate electrolyte that forms a stable interface with sodium-metal anode. In addition, the formation of robust cathode–electrolyte interphases on Na(Ni_0.3Fe_0.4Mn_0.3)O₂ cathode facilitates smooth phase transitions, thus leading to stable cycle life with a capacity retention of 80% over 500 cycles at C/5 rate in Na||Na(Ni_0.3Fe_0.4Mn_0.3)O₂ cells. The work demonstrates a promising approach towards the development of safe, low-cost, sustainable high-performance sodium-metal batteries.

由于钠的高丰度和理论比容量（1,165 mA h g ^-1），钠金属电池是锂金属电池的一种有吸引力的、可持续的、低成本的替代品。然而，电解质与正极和负极的相容性差导致电极-电解质界面不稳定。在这里，我们引入了使用盐作为稀释剂的概念，这使得可以使用单一的不易燃溶剂，例如磷酸三甲酯。通过使用硝酸钠 (NaNO ₃ ) 盐作为模型稀释剂，我们报道了一种 1.1 M NaFSI-NaNO ₃ -磷酸三甲酯电解质，它与钠金属阳极形成稳定的界面。此外，在Na(Ni _0.3 Fe _0.4 Mn _0.3 )O ₂正极上形成坚固的正极-电解质界面，有利于平稳的相变，从而实现稳定的循环寿命，在C/5倍率下500次循环后容量保持率为80%在Na||Na(Ni _0.3 Fe _0.4 Mn _0.3 )O ₂电池中。这项工作展示了一种开发安全、低成本、可持续的高性能钠金属电池的有前途的方法。