Improvement of cycle life for layered oxide cathodes in sodium-ion batteries

Abstract

Sodium-ion batteries (SIBs) possess enormous development potential and broad market prospects in the field of large-scale energy storage and low-speed electric vehicles with low cost and abundant resources. The current cycle life of SIBs is only 1000–2000 cycles, which can meet the basic needs of low-speed electric vehicles, but it is insufficient for large-scale energy storage applications. The energy density, rate capability, cycle life and cost of SIBs depend largely on the cathode material used. Among the cathode materials for SIBs, the development of a layered oxide route is the most mature and promising strategy to take the lead in industrialization. Thus, the cycle life of a layered oxide cathode will directly affect the economy and practicability of SIBs. According to previous studies, the cycle life of layered oxide cathodes is mainly limited by irreversible phase transformation, the Jahn–Teller effect and the interface deterioration of materials during charging and discharging. In this review, the latest progress on layered oxide cathode materials is summarized, with emphasis on the problems of poor cycle life caused by irreversible phase transition, the Jahn–Teller effect and interface deterioration, and several strategies are proposed to alleviate these problems (multi-phase combination, morphology and structure optimization, chemical element substitution and surface coating). Furthermore, opportunities and challenges in the practical application of electrode materials are elucidated, which will guide the development of layered oxide cathodes in the future.