Advanced sodium storage of carbon coated Co-MoSe2 nanosheets assembled spheres

Transition metal selenides with high theoretical capacity have been deemed as promising anode candidates for sodium storage, however, the terrible capacity decay and unsatisfied high-rate property impede their applications. Herein, N-doped carbon coated Co-doped MoSe2 nanosheets assembled spheres are synthesized via a carbonization-selenization process on polydopamine coated CoMo metal-organic frameworks. The microspheres assembled by Co-MoSe2 nanosheets with expanded interlayer provide short diffusion path for fast ion transport, which also supply voids for buffering the volume change. The carbon coating layer benefits the electric conductivity and alleviates the structure deterioration. Importantly, cobalt dopants contribute to surface pseudocapacitance and boost reaction kinetics. As expected, Co-MoSe2@NC exhibits high sodium storage performances of large specific capacity of 477.6 mAh g−1 at 0.1 A g−1 after 100 cycles, durable stability of 362.5 mAh g−1 after 1000 cycles at 2 A g−1, and excellent rate capability (331.5 mAh g−1 at 5 A g−1). •N-doped carbon coated Co-doped MoSe2 nanosheets assembled spheres are prepared.•Nanosheets with expanded interlayer benefit ion diffuision.•Carbon coating improves conductivity and maintains electrode integrity.•Cobalt dopants induce enhanced pseudocapacitive behavior and reaction kinetics.•Large reversible capacity, stable cycling, and high rate performance are obtained.