Bimetallic MOF-derived CoSe2 embedded within N-doped carbon with enhanced lithium storage properties

Abstract

Transition metal selenides are considered to be a potential anode material for lithium-ion batteries (LIBs) owing to their excellent electronic conductivity and high theoretical capacity. However, the application of transition metal selenides electrodes is still limited by their large volume expansion and sluggish kinetics during cycling. Herein, CoSe2 nanoparticles embedded in N-doped carbon nanotubes (CNTs) and carbon layer (CoSe2@NC) were constructed by pyrolysis of CoZn-based zeolitic imidazolate framework (CoZn-ZIFs) and melamine mixtures followed by selenization. During the pyrolytic process, the volatilization of zinc derived from CoZn-ZIFs, the retardation of the complete decomposition of g-C3N4 derived from melamine by Zn species played important roles in the formation of enriched N-doped carbon nanotubes (CNTs) and amorphous carbon layer. As a result, CoSe2@NC could show a large reversible lithium-ion storage capacity of 395 mAh g−1 at 0.5 A g−1 over 200 cycles, good rate capabilities of 367 mAh g−1 even at 2 A g−1, which outperformed CoSe2@NC-1 and CoSe2@NC-2 derived from carbonization of Co-Zn-ZIFs and Co-ZIF/melamine precursors followed by selenization, respectively. The enhanced lithium storage performance of CoSe2@NC could owe to the unique structure, where the N-doped CNTs and amorphous carbon layer can provide a rapid electron transfer channel and enable surface-dominated pseudocapacitive lithium storage, and the robust interface between CoSe2 and carbon can also effectively alleviate the volume expansion and enhance the integrity during the charge-discharge process.