From challenge to utilization: Exploiting the Jahn–Teller effect in manganese-based layer-structured oxides for sodium batteries

The rapid development of sodium ion batteries (SIBs) drives the in-depth research on the design, synthesis and mechanism of high-energy, long-life cathode materials. Layer-structured oxides, as cathode materials in SIBs, have garnered significant attention due to the advantages, including simple synthesis process, abundant raw materials and superior structure. Among them, manganese-based layered oxides (MLOs) have attracted wide attention owing to the cheap cost manganese resource, high theoretical specific capacity, broad adjustable voltage range and environmentally friendly characteristics. However, the presence of Mn 3+ ions in MLOs readily triggers the Jahn–Teller effect, causing significant lattice distortion and a consequent decline in capacity during cycling. Therefore, it is essential to comprehensively analyze the mechanisms of structural degradation, explore effective inhibition strategies and develop rational approaches to leverage the Jahn–Teller effect in MLO cathodes for SIBs. Herein, the recent research progresses and underlying mechanisms on the Jahn–Teller effect of MLOs were generalized. Subsequently, we offer a unique perspective on the effective utilization of the Jahn–Teller effect in MLOs. Finally, we propose future directions to guide the mitigation of adverse effects caused by Jahn–Teller distortions and to inspire innovative designs of manganese-based layered oxides as cathodes for SIBs and other energy storage systems.