Functional carbon-based covalent bridging bonds unlocking superior sodium-ion storage

Abstract

The development of sodium-ion batteries has gained significant momentum as a promising alternative to lithium-ion batteries, particularly for large-scale energy storage. However, the advancement of sodium-ion batteries is impeded by challenges associated with the performance of electrode materials, especially conversion-type materials such as transition metal oxides and dichalcogenides. These materials often suffer from severe volume expansion during cycling, poor electronic conductivity, and instability at the electrode/electrolyte interface. Surface modification with carbonous materials has been demonstrated to be an effective strategy to solve these challenges. This review explores the transformative role of interfacial chemical bridge bonds, particularly C–X–M bonds (where C represents carbon; X represents elements like S, O, N, P and Se; and M represents transition metals) for performance enhancement. By forming strong covalent connections between carbon materials and transition metal compounds, the carbon-coated conversion-type anode materials show enhanced structural stability, improved electronic conductivity and reduced charge transfer resistance. This review also covers advanced characterisation techniques applied to characterise and analyse these bonds, offering a detailed understanding of their contributions to sodium-ion storage. Additionally, challenges and prospects in this field are discussed for optimising electrode materials through the strategic implementation of chemical bridge bonds, providing valuable insights for advancing the next-generation high-performance sodium-ion batteries.