Designing robust electrolytes for extreme environments: Overcoming voltage and thermal constraints in sodium-ion batteries

Sodium-ion batteries (SIBs) have emerged as promising candidates for large-scale energy storage due to their cost-effectiveness and abundant sodium resources. However, operation under extreme conditions characterized by high-voltage polarization and sustained thermal stress poses significant safety challenges, primarily driven by interfacial degradation, electrolyte decomposition, lattice oxygen release, irreversible phase transitions, and cascading failure mechanisms. In this review, we systematically examine the progress in developing robust non-aqueous liquid electrolytes (NLEs) for SIBs capable of operating under extreme temperatures and high-voltage conditions, and provide a comprehensive analysis of the challenges imposed by thermal stress and high energy density. Subsequently, we focus on the fundamental failure mechanisms arising from harsh operational environments, proposing a comprehensive framework of feasible stabilization strategies encompassing sodium salt optimization, solvent/additive selection, modulation of concentration effects, and hydrogen-bonding network engineering. Furthermore, transitioning from electrolyte engineering to electrode-interface interactions, we critically evaluate the thermal and high-voltage compatibility of diverse electrode-electrolyte systems. Building upon this comprehensive assessment, we present valuable insights into electrolyte engineering from the perspectives of artificial intelligence, novel electrolytes design, intrinsic mechanisms, and degradation models, thereby guiding the future evolution of practical battery technologies employing advanced NLEs with enhanced thermal and electrochemical stability.