High-stability cathode materials for sodium-ion batteries: optimization strategies and promising future applications

Abstract

Sodium-ion batteries (SIBs) are considered potential alternatives to lithium-ion batteries (LIBs) due to their similar working principles, cost-effectiveness, and abundant and sustainable availability of sodium resources. However, SIB cathodes face several challenges including low air stability, unstable cathode–electrolyte interface, and irreversible phase transitions, all of which contribute to subpar battery performance. This review aims to examine these critical issues, explore their important causes and degradation mechanisms, and deliver a comprehensive overview of conventional modification approaches. Strategies such as chemical substitution, surface modification, and structural engineering focus on improving air stability, minimizing interfacial side reactions, and suppressing phase transitions. The ultimate objective is to enhance structural stability, facilitate fast Na⁺ kinetics, and achieve greater electrochemical performance. The review also discusses traditional and multifunctional binders in terms of their bonding strength, wettability, thermal stability, conductivity, cost, and environmental impact. Furthermore, the roles of various electrolytes including liquid, solid-state, and ionic liquids are evaluated for their effectiveness in promoting ion transport and maintaining battery stability. Overall, literature findings highlight significant advancements in SIB performance, driven by innovations in material design and synthesis, which led to notable improvements in capacity and long-term stability. This understanding of modification strategies is crucial for the development of practical SIBs for commercial scale applications.