Coral-like CoSe2@N-doped carbon with a high initial coulombic efficiency as advanced anode materials for Na-ion batteries

Na-ion batteries (NIBs) have attracted great interest as a possible technology for grid-scale energy storage for the past few years owing to the wide distribution, low cost and environmental friendliness of sodium resources and similar chemical mechanisms to those of established Li-ion batteries (LIBs). Nonetheless, the implementation of NIBs is seriously hindered because of their low rate capability and cycling stability. This is mainly because the large ionic size of Na+ can reduce the structural stability and cause sluggish reaction kinetics of electrode materials. Herein, three-dimensional nanoarchitectured coral-like CoSe2@N-doped carbon (CL-CoSe2@NC) was synthesized through solvothermal and selenizing techniques. As a result, CL-CoSe2@NC for NIBs at 2 A g(-1) exhibits an ultrahigh specific capacity of 345.4 mA h g(-1) after 2800 cycles and a superhigh initial coulombic efficiency (ICE) of 93.1%. Ex situ XRD, HRTEM, SAED and XPS were executed to study the crystal structure evolution between Na and CoSe2 during sodiation/de-sodiation processes. The aforementioned results indicate that the improved sodium storage property of CL-CoSe2@NC could be attributed to better electrode kinetics and a stable SEI film because of the 3D nanoarchitecture and the existence of the NC layer.

Automated summary

Na-ion batteries (NIBs) have attracted great interest as a potential technology for grid-scale energy storage due to the wide distribution, low cost, and environmental friendliness of sodium resources. However, their implementation is hindered by low rate capability and cycling stability caused by the large ionic size of Na+. In this study, a three-dimensional nanoarchitectured coral-like CoSe2@N-doped carbon (CL-CoSe2@NC) was synthesized, and it exhibited improved sodium storage properties with better electrode kinetics and a stable SEI film.