Hierarchical MoSe2 yolk-shell microspheres with superior Na-ion storage properties

Yolk-shell-structured MoSe2 microspheres were prepared via a simple selenization process of MoO3 microspheres. The yolk-shell-structured MoSe2 and MoO3 microspheres delivered initial discharge capacities of 527 and 465 mA h g(-1) in the voltage range of 0.001-3 V vs. Na/Na+ at a current density of 0.2 A g(-1), respectively, and their discharge capacities after 50 cycles were 433 and 141 m Ahg(-1) 1, respectively. The yolk-shell structured MoSe2 microspheres also exhibited outstanding high rate capabilities. The hierarchical yolk-shell structure comprised of wrinkled nanosheets facilitated fast Na-ion and electron kinetics, and buffered the large volume changes encountered during cycling.