A carbon-encapsulated ZnSe/NiSe2 nanotube for efficient electrochemical Na+ storage

Abstract

Transition metal selenides are promising anode materials for sodium-ion batteries, but it remains a challenge to deal with the big volume strain during the electrochemical reaction. Here in this study, plum pudding-like ZnSe/NiSe₂@carbon composite nanotubes are synthesized by a metal–organic framework-templated strategy, in which a great deal of dual-metallic selenide nanoparticles are evenly encapsulated within nitrogen-doped porous carbon nanotube matrix. The electrochemical results show that such metal–organic framework-derived ZnSe/NiSe₂@carbon composite nanotubes with ultrasmall selenide nanoparticles could be a promising anode material for electrochemical Na⁺ storage, and they exhibit good cycling stability (380mAh g⁻¹ after 1500 cycles at 2 A g⁻¹) and high-rate capability (400mAh g⁻¹ at 10 A g⁻¹). The superior electrochemical performance of such composite nanotubes is attributed to the hollow nanotube structure and plum pudding-like structure, which facilitates the Na⁺ ion diffusion and improves the structural integrity. In addition, in situ X-ray diffraction indicates a lattice distortion behavior of the bimetallic ZnSe/NiSe₂ system, in which the lattice constant of ZnSe becomes larger while the lattice constant of NiSe₂ gets smaller in the sodiation process, leading to the mitigation of volume strain. This work offers a viable alternative to design robust electrode materials for advanced energy storage.