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

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.