Dual-carbon coupled CoN 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 CoN nano-grains wrapped with carbon and reduced graphene oxide (CoN@C@rGO) was synthesized through one-step simultaneous nitridation and carbonization of zeolitic imidazolate frameworks@GO precursor. The 3D hierarchical CoN@C@rGO composite can combine the good conductivity and mechanical strength of rGO and a high theoretical capacity of CoN. When explored as anode material for LIBs, CoN@C@rGO exhibits a high reversible capacity of ~860 mAh g at a current density of 1.0 A g after 500 cycles and excellent high-rate capability (665 and 573 mAh g at current densities of 3.2 and 6.4 A g, respectively). The excellent electrochemical performance of CoN@C@rGO can be ascribed to its hierarchically porous structure and the synergistic effect between CoN nano-grains and rGO.