Te-Doped Nickel Cobalt Selenide (NiCoSe) Nanostructures for Enhanced Sodium Storage

Transition metal selenides (TMSs) have been widely believed as promising anode materials for sodium-ion batteries (SIBs). Element doping is a promising but ambiguous strategy to further enhance sodium storage performance due to the complexity of doping conditions and the sensitivity of the selenization process. Herein, tellurium (Te) is selected to fabricate Te-doped nickel cobalt selenide (Te-NiCoSe) using a melting method. Besides the common merit of expanding the interplanar space of NiCoSe, the melted Te can also result in a "size splitting effect" to decrease the particle size of bulk NiCoSe, exposing more surface active sites and accelerating the intercalation/deintercalation reaction kinetics. In addition, the introduction of Te can also inhibit the "reduction effect" of the selenization process induced by high temperature, which results in the charge redistribution of NiCoSe, stabilizing the electronic structure. As a result, the fabricated Te-NiCoSe exhibits a high reversible capacity of 448.7 mA h g–1 at 1 A g–1, a superior rate capacity of 324.9 mA h g–1 at 30 A g–1, and an outstanding capacity retention rate of 88.5% after 1000 cycles at 20 A g–1.