S-Doped 2H-MoSe 2 (i.e., 2H-MoS 2x Se 2-2x ) mesoporous nanospheres assembled from several-layered nanosheets are synthesized by sulfurizing freshly-prepared 1T-MoSe 2 nanospheres, and they serve as a robust host material for sodium storage. The sulfuration treatment is found to be beneficial for…