Preparation of a NbN/graphene nanocomposite by solution impregnation and its application in highperformance Li-ion hybrid capacitors

Lithium-ion hybrid capacitors (LIHCs) have received a mushrooming amount of attention due to their high power density and energy density. However, the imbalanced dynamics between positive and negative electrodes limit their practical applications. Thus, in order to develop a kind of anode material with high power, we report a simple synthesis technology of a NbN nanoparticles/graphene nanosheets (NbN/GNSs) nanocomposite with fast Li insertion/extraction properties. Through a facile solution impregnation followed by annealing treatment, we get a freestanding layer-stacked structure combining 2D graphene nanosheets and 0D NbN nanoparticles. It shows a high reversible capacity of z 450 mA h g(-1) at 0.1 A g(-1), moreover, as a result of the fast pseudocapacitive performance, it also shows a remarkable rate capability and cycle stability (90% capacity retention at 5 A g(-1)after 10 000 cycles). Meanwhile, the LIHC with a NbN/GNSs anode and activated polyaniline derived carbon (APDC) cathode delivers the maximum energy density of 136 W h kg(-1), and the highest power density of 25 kW kg(-1) as well as a stable cycle life in the potential range of 1.0-4.0 V.