Simultaneously formed and embedding-type ternary MoSe/MoO/nitrogen-doped carbon for fast and stable Na-ion storage.

To obtain an electrode material that is capable of manifesting high Na-ion storage capacity during long-term cycling at a rapid discharge/charge rate, ternary heterophases MoSe/MoO/carbon are rationally designed and synthesized through a supermolecule-assisted strategy. Through using supermolecules that are constructed from MoO and polydopamine as the precursor and sulfonated polystyrene microspheres as the sacrificial template, the formed ternary phases MoSe/MoO/carbon are fabricated into a hollow microspherical structure, which is assembled from ultrathin nanosheets with MoSe and MoO nanocrystallites strongly embedded in a nitrogen-doped carbon matrix. In the ternary phases, the MoSe phase contributes to a high Na-ion storage capacity by virtue of its layered crystalline structure with a wide interlayer space, while the surrounding MoO and porous nitrogen-doped carbon phases are conducive to rate behaviour and cycling stability of the ternary hybrids since both the two phases are beneficial for electronic transport and structural stability of MoSe during repeated sodiation/desodiation reaction. The as-prepared MoSe/MoO/carbon manifests excellent rate behaviour (a Na-ion storage capacity of 461 mA h g at an extremely high current density of 70 A g) and outstanding cycle performance (610 mA h g after 1000 cycles).