From micro to macro: Freestanding electrode based on low crystalline Cu2−xSe for sodium storage

Abstract

The development of electrode materials is a crucial parameter in improving sodium storage’s electrochemical performance. In this study, Cu2−xSe obtained from Cu-based metal–organic frameworks embedded in nanofibers (Cu2−xSe@C@NCNFs) shows excellent electrochemical performance as a freestanding anode for sodium storage. The “macro” aspects of 1D nanofibers as the skeleton not only inhibit Cu2−xSe agglomeration and structural collapse during the charge–discharge process, but also enhance the electrical conductivity. In this “from micro to macro” unique structure, on the “micro” aspect, Cu2−xSe nanoparticles with low crystallinity enhance the specific capacity and electrochemical reaction kinetics further. Moreover, the initial Coulombic efficiency can be as high as 66.3%. Furthermore, after 1000 cycles at 2 A g−1, Cu2−xSe@C@NCNFs demonstrated a specific capacity of 74 mAh g−1. The outstanding electrochemical performance shows that “from micro to macro” Cu2−xSe@C@NCNFs is a potential electrode material for effective sodium storage.