Advanced electrolytes for sodium metal batteries under extreme conditions

Sodium metal batteries (SMBs) are promising candidates for next-generation high-energy-density storage devices, given their high theoretical specific capacity and low cost. Despite their potential, the path to commercialization presents several critical challenges. To satisfy the requirements of modern energy storage, SMBs must achieve substantial advancements in application versatility, safety, energy density, and fast charging capabilities. The electrolyte, as the pivotal component of SMBs, plays a crucial role in achieving these performance metrics. This paper provides a detailed and comprehensive overview of the significant challenges that SMBs encounter, particularly in extreme conditions characterized by wide temperature ranges, flame retardancy, high voltage, and high rate capabilities, and how the synergistic effects of salts and solvents in the electrolyte can be leveraged to regulate the thermodynamic, kinetic, and electrochemical behaviors of SMBs under these conditions. Additionally, the paper also presents an informed outlook on future developments, highlighting the potential pathways for advanced electrolyte design to enhance the overall performance and commercial viability of SMBs.