Building a PEG-C@MoSe2@CNT heterostructure via in-situ selenidation as highly reversible anodes for Na+ batteries

Herein, we describe a simple and efficient method to build C@MoSe2@CNT composites that exhibit good electrochemical performance as anode materials for sodium-ion batteries. The protocol uses commercially available and cheap carbon nanotubes (CNT) as the conductive network. Molybdenum selenide (MoSe2), in-situ-synthesized from Mo-ethylene glycol (poly(ethylene glycol) (PEG, Mn ≈ 200)) complexes, grows along the CNT with a discontinuous morphology, which creates multiple channels for the insertion of Na+. Meanwhile, PEG-C provides a thin carbon coating layer to increase stability. For PEG-200-2-C/MoSe2/CNT at room temperature, the storage at 2 A g−1 is 426 mA h g−1 after 500 cycles and 212 mA h g−1 after 3,000 cycles. Compared with pure MoSe2, density functional theory calculations indicate that the Na+ diffusion barrier in the MoSe2 of C@MoSe2@CNT effectively decreases from 0.91 to 0.72 eV, hence promoting the reversibility of the Na+ storage.