Co@N-Doped Carbon Frameworks Anchored on Graphene as High-Rate and Long-Lifespan Anode Materials for Advanced Li-Ion Hybrid Capacitors

Li-ion hybrid capacitors (LIHC) are becoming a prospective candidate for energy storage and can achieve high energy density and power density at the same time. As it uses a battery-type anode, improving its sluggish charge-discharge mechanism becomes important in the LIHC study. Herein, we report a solvothermal method to fabricate Co@N-doped carbon frameworks anchored to graphene (Co-NCF/G) as an anode material for LIHC. Co nanoparticles are generated in the heterohedral carbon matrix with N-doping, and the heterohedral Co@N-doped carbon frameworks were uniformly decorated within three-dimensional (3D) graphene networks. The existence of Co ultrafine nanoparticles and N element can greatly increase the conductivity of Co-NCF/G, and thus strengthen its electrochemical properties. Moreover, the high surface area and effective pore structure formed by graphene networks can shorten the Li-ion transfer route, enhancing the reaction kinetics of the electrode. The device assembled using Co-NCF/G as the anode and active carbon as the cathode exhibits a high specific capacity of 579.5 mAh g-1 after 100 cycles at a current density of 0.5 A g-1, and also delivers a high energy density of 77.17 Wh kg-1 at a high power density of 6801 W kg-1 and long cycling stability with an energy retention of 78.7% after 2000 cycles at a high current density of 5.0 A g-1.