Dual-carbon coupled Co_5.47N composites for capacitive lithium-ion storage

Transition metal nitrides are of great interest as potential anodes for lithium-ion batteries (LIBs) owing to their high theoretical capacity. However, poor cycling stability and rate performance greatly hinder their practical applications. To better alleviate these problems, a unique 3D hierarchical nanocomposite constructed by dual carbon-coated Co_5.47N nano-grains wrapped with carbon and reduced graphene oxide (Co_5.47N@C@rGO) was synthesized through one-step simultaneous nitridation and carbonization of zeolitic imidazolate frameworks@GO precursor. The 3D hierarchical Co_5.47N@C@rGO composite can combine the good conductivity and mechanical strength of rGO and a high theoretical capacity of Co_5.47N. When explored as anode material for LIBs, Co_5.47N@C@rGO exhibits a high reversible capacity of ~860 mAh g^-1 at a current density of 1.0 A g^-1 after 500 cycles and excellent high-rate capability (665 and 573 mAh g^-1 at current densities of 3.2 and 6.4 A g^-1, respectively). The excellent electrochemical performance of Co_5.47N@C@rGO can be ascribed to its hierarchically porous structure and the synergistic effect between Co_5.47N nano-grains and rGO.