Direct synthesis of metal selenide hybrids as superior sodium storage anodes

Transition metal selenides (TMSs) are widely used as anodes in sodium-ion batteries (SIBs) due to their good electrical conductivity and high energy density. Herein, we reported and prepared a class of hybrids (FeSe2/CoSe2 and FeSe2/NiSe2) composed of two metal selenides by a controlled two-step solvothermal method, and assessed their sodium storage characteristics for the first time. The results show that such hybrids exhibit excellent electrochemical properties in terms of capacity (380 mA h g(-1) after 9000 cycles at a current density of 2 A g(-1)), rate capability (average specific capacities are 462, 441, 440, 424, 393 and 363 mA h g(-1) at 0.05, 0.1, 0.2, 0.5, 1 and 2 A g(-1)) and cycle stability (a capacity ratio rate of 82% after 9000 cycles), which are superior to those of single phase (FeSe2 and CoSe2) or a mechanical mixture (FeSe2 : CoSe2 = 1 : 1). What is more significant is that the sodium-ion full cell constructed with FeSe2/CoSe2 as the anode and Na-3(VPO4)(2)F-3 as the cathode exhibits excellent long cycle durability. This work provides a way for the study of transition metal hybrids or composite anodes used in SIBs.

Automated summary

Transition metal selenides, such as FeSe2/CoSe2 and FeSe2/NiSe2 hybrids, prepared by a controlled two-step solvothermal method, exhibit excellent electrochemical properties in sodium-ion batteries. These hybrids show higher capacity, rate capability, and cycle stability compared to single phase or mechanical mixtures, with the FeSe2/CoSe2 anode demonstrating exceptional long cycle durability in a full cell configuration. This work provides insights into the development of transition metal hybrids or composite anodes for SIBs.