In response to the change of energy landscape, sodium‐ion batteries (SIBs) are becoming one of the most promising power sources for the post‐lithium‐ion battery (LIB) era due to the cheap and abundant nature of sodium, and similar electrochemical properties to LIBs. The electrochemical performance of electrode materials for SIBs is closely bound up with their crystal structures and intrinsic electronic/ionic states. Apart from nanoscale design and conductive composite strategies, heteroatom doping is another effective way to enhance the intrinsic transfer characteristics of sodium ions and electrons in crystal structures to accelerate reaction kinetics and thereby achieve high performance. In this review, the recent advancements in heteroatom doping for sodium ion storage of electrode materials are reviewed. Specifically, different doping strategies including nonmetal element doping (e.g., nitrogen, sulfur, phosphorous, boron, fluorine), metal element doping (magnesium, titanium, iron, aluminum, nickel, copper, etc.), and dual/triple doping (such as N–S, N–P, N–S–P) are reviewed and summarized in detail. Furthermore, various doping methods are introduced and their advantages and disadvantages are discussed. The doping effect on crystal structure and intrinsic electronic/ionic state are illustrated and the relationship with capacity and energy/power density is interrogated. Finally, future development trends in doping strategies for advanced SIBs electrodes are analyzed.

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The mechanism of Ti3C2-MXene ambient oxidation has been revealed by electron microscopy, disclosing the effects of defects and Ti-ion diffusion.

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Transition-metal selenides have emerged as promising anode materials for sodium ion batteries (SIBs). Nevertheless, they suffer from volume expansion, polyselenide dissolution, and sluggish kinetics, which lead to inadequate conversion reaction toward sodium and poor reversibility during the desodiation process. Therefore, the transition-metal selenides are far from long cycling stability, outstanding rate performance, and high initial Coulombic efficiency, which are the major challenges for practical application in SIBs. Here, an efficient anode material including an FeSe 2 core and N-doped carbon shell with inner void space as well as high conductivity is developed for outstanding rate performance and long cycle life SIBs. In the ingeniously designed FeSe 2 @NC microrods, the N-doped carbon shell can facilitate mass transport/ electron transfer, protect the FeSe 2 core from the electrolyte, and accommodate volume variation of FeSe 2 with the help of the inner void of the core. Thus, the FeSe 2 @NC microrods can maintain strong structural integrity upon long cycling and ensure a good reversible conversion reaction of FeSe 2 during the discharge/charge process. As a result, the as-prepared FeSe 2 @NC microrods exhibit excellent sodium storage performance and ultrahigh stability, achieving an excellent rate capability (411 mAh g −1 at 10.0 A g −1 ) and a long-term cycle performance (401.3 mAh g −1 after 2000 cycles at 5.0 A g −1 ).