Simultaneously formed and embedding-type ternary MoSe 2 /MoO 2 /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 2 /MoO 2 /carbon are rationally designed and synthesized through a supermolecule-assisted strategy. Through using supermolecules that are constructed from MoO 4 2- and polydopamine as the precursor and sulfonated polystyrene microspheres as the sacrificial template, the in situ formed ternary phases MoSe 2 /MoO 2 /carbon are fabricated into a hollow microspherical structure, which is assembled from ultrathin nanosheets with MoSe 2 and MoO 2 nanocrystallites strongly embedded in a nitrogen-doped carbon matrix. In the ternary phases, the MoSe 2 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 2 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 2 during repeated sodiation/desodiation reaction. The as-prepared MoSe 2 /MoO 2 /carbon manifests excellent rate behaviour (a Na-ion storage capacity of 461 mA h g -1 at an extremely high current density of 70 A g -1 ) and outstanding cycle performance (610 mA h g -1 after 1000 cycles).