Rational design of few-layer MoSe confined within ZnSe-C hollow porous spheres for high-performance lithium-ion and sodium-ion batteries.

Rechargeable battery systems, including Li-ion batteries and Na-ion batteries, have attracted great interest in energy storage because of their high energy density, low cost, efficient energy storage and suitable redox potential. Nevertheless, their rapid development is still greatly hampered by some typical constraints including low coulombic efficiency, large volume changes and severe particle agglomeration and pulverization during the charge-discharge process. Here, we fabricate a few-layer MoSe2 confined within a ZnSe-C hollow porous sphere nanocomposite through a simple self-assembly strategy followed by selenization, which efficiently circumvents these problems. The fabricated ZnSe/MoSe2@C electrode demonstrates diverse advantages, including the existence of a few-layer structure, an in situ porous carbon matrix, multicomponent coordination and excellent pseudocapacitive behavior. When used as an anode material, it displays extraordinarily attractive electrochemical performance for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The reversible capacity of ZnSe/MoSe2@C for LIBs reaches as high as 1051 mA h g-1 at 0.2 A g-1 (150 cycles). A long-term high-rate cycling test reveals an excellent stability of 524 mA h g-1 at 4 A g-1 after 600 cycles. In addition, for SIBs, ZnSe/MoSe2@C also manifests a high initial coulombic efficiency of 89% at 0.2 A g-1 and a remarkable reversible capacity of 381 mA h g-1 at a high current density of 4 A g-1 even after 250 cycles with negligible capacity loss. This is one of the best performances of ZnSe-based anode materials for SIBs reported so far. The regulation strategy reported in the present work is expected to offer new insights into the fabrication of high performance anode materials for SIBs.