Nitrogen-doped carbon decorated 3D NiCoSe2 micro-flowers as high-performance anode materials for lithium-ion batteries

Abstract

Compared with monometallic selenides, bimetallic selenides have better synergistic effects and more abundant active sites for electrochemical reactions. As an important member of the transition metal oxide family, NiCoSe₂ has been widely used in energy storage devices and has shown excellent electrochemical performance. So in this paper, nitrogen-doped carbon decorated NiCoSe₂ composites (NiCoSe₂/NC-700, NiCoSe₂/NC-800, and NiCoSe₂/NC-900) with a microflower structure were synthesized by calcining nickel–cobalt bimetallic organic skeleton materials at different temperatures, and were used as anode materials for rechargeable lithium-ion batteries. Because the MOF precursor has many advantages such as structural controllability, and a bimetal synergistic effect, the test results showed that the prepared NiCoSe₂/NC composites have a special morphology, outstanding electrical conductivity, excellent lithium storage performance and electrochemical cycling performance in the process of being used as anode materials for lithium-ion batteries. The NiCoSe₂/NC-800 materials displayed a high initial capacity (2099.8/1084.3 mA h g⁻¹), and still maintained a high capacity (1041.2/989.9 mA h g⁻¹) after 100 cycles at a current density of 0.1 A g⁻¹ and in the voltage range of 0.01–3.0 V. In addition, at high current densities of 0.5 A g⁻¹ and 1.0 A g⁻¹, the increased capacity of NiCoSe₂/NC composites may be due to the activation of electrodes and the pseudocapacitance during cycling. Through ex situ XRD experiments, the lithium storage mechanism of the NiCoSe₂/NC-800 electrode material during cycling was further studied, and NiCoSe₂/NC-800 was continuously converted into Ni, Co, and Li₂Se during cycling.