Optimization of NixCo1-x-yMnySe2 composition for efficient sodium storage

Due to the low cost and the abundance of Na resources, sodium-ion batteries (SIBs) have emerged as leading candidates for next-generation energy storage devices. For Se-based anodes, large volume expansion during cycling leads to poor structural reversibility and fast capacity fade. To overcome it, the heterostructured Ni1/3-xCo1/3-yMn1/3-zSe2/MnSe2 is constructed via tuning metal ratio with good controllability, in which the functionalities of heterostructure in realizing high-performance SIBs is comprehensively studied. Benefiting from the synergistic effect of element ratio optimization and heterostructure construction, Ni1/3-xCo1/3-yMn1/3-zSe2/MnSe2 simultaneously realizes high capacity, fast Na+ storage performance, and long-cycling durability. Remarkably, it exhibits a specific capacity of around 400 mAh g−1 at 2 A g−1, and achieves a capacity retention as high as ∼ 99.9 % after 2000 cycles, outperforming most Se-based anodes. Therefore, this work not only demonstrates the significance of heterostructure engineering in a cubic NixCo1-x-yMnySe2 anode, but also opens a new avenue for achieving high-performance electrode materials based on heterostructure construction.