Realizing highly stable selenium vacancy construction in transition-metal selenides through carbon matrix structure engineering enables fast-charging and durable sodium-storage performance

Vacancy engineering is highly effective in optimizing the electrochemical performance of transition-metal selenide anodes for sodium-ion batteries. However, traditional construction strategies face the problems of low vacancy stability, additional internal structure destruction for the host material, limited vacancy content and a complicated preparation process with high energy consumption. Here we for the first time demonstrated that an aligned carbon matrix with the abundant low-tortuosity channels is capable of effectively inducing the formation of abundant selenium vacancies in the transition-metal selenide anode, meanwhile existing stably throughout its long-term cycle process. Benefiting from the advantage that abundant selenium vacancies with high stability can continuously restrain the polyselenides dissolution in the electrolyte, the prepared anode exhibits significantly improved cycling stability. Meanwhile, the fast mass and charge transport allowed by both the abundant aligned straight channels and selenium vacancies also promise it an exceptionally excellent rate capability with an ultrahigh capacity retention of 95.1% when increasing the current density from 8 to 16 A g−1. Impressively, it also accomplishes a remarkable fast-charging performance with about 90 s for continuous 500 cycles at up to 16 A g−1, accompanied with the high-rate capacity of 417.7 mAh g−1 and capacity retention above 92%. This work may bring a paradigm shift in the traditional selenium-deficient modulation strategy to carbon matrix structure engineering for functionalizing transition-metal selenides.