Yolk-shell spheres constructed of ultrathin MoSe2 nanosheets as a high-performance anode for sodium dual ion batteries

As a promising candidate for large-scale electrical energy storage, sodium dual-ion battery (S-DIB) is attracting more and more interest owing to its merits of high voltage as well as the low cost and high abundance of sodium resources. It is highly crucial to develop suitable anode materials for large-scale practical applications of the S-DIBs. In this work, novel hierarchical MoSe2 yolk-shell spheres constructed of ultrathin nanosheets (designated as MoSe2 YSs) as anode materials for the S-DIBs are synthesized via the selenization of Mo-glycerate solid spheres and subsequent thermal annealing. The ultrathin feature of nanosheet subunits with expanded (002) interlayer spacing and whole yolk-shell structure not only endow the MoSe(2)YSs with superior reaction kinetics and high capacitive-controlled Na storage, but also provide effective buffer alleviating volume change during Na+ intercalation/deintercalation. The assembled S-DIB with the MoSe2 YSs as the anode and expanded graphite as the cathode delivers impressive discharge capacity of 70.1mAhg(-1) at a current density of 0.2Ag(-1) after 120 cycles. In addition, the assembled S-DIB exhibits good rate capability with a discharge capacity of 42.9mAhg(-1) and high coulombic efficiency beyond 93.5% at a current density of 2.0 Ag-1. Our results suggest that the hierarchical micro/nano-structured MoSe2 has promising potential as anode materials for high performance S-DIBs.