Graphene / NiOOH / Ni (OH) ₂ - Activated Carbon System Electrochemical Hybrid Capacitor

Electrochemical hybrid capacitors, as a new type of supercapacitor, with high working voltage own not only the advantages of electric double layer capacitors but also that of the pseudocapacitance. Therefore, it provides the best way to meet the discharging in a very short time for hybrid electric vehicle power supply on the condition of appropriate energy density. The reaserch on the electrode materials and the match between negative and anode eletrode materials is the focus of hybrid capacitors owing to the two different materials as electerode in hybrid capacitor.In this paper, hierarchicaliy porous Ni00H/Ni(OH)2was prepared by simple chemical bath on the basis of the summary of the supercapacitor electrode materials and its physical structure was characterized by means of XRD, SEM, TEM et al. The electrochemical performance was analyzed by galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectra in detail. In addition, the aqueous coin hybrid capacitors consisting of a GP/Ni-30cathode and an activated carbon anode were fabricated and its performance was studied. The main conclusions are given as follows.1. Hierarchically porous graphene/NiOOH/Ni(OH)2composite were developed via a facile chemical bath deposition. The materials with different proportion were obtained by changing the amount of reaction liquid. SEM images show that the obtained porous composite are formed by the stack of single-layered or few-layered graphene covered by porous Ni00H/Ni(OH)2composite. The pseudocapacitive behaviors of the porous composite were obviously observed by cyclic voltammetry(CV) tests in1M KOH. The composite prepared in30ml NiSO4exhibits the highest specific capacitance of2178Fg"1at a current density of2Ag-1during the galvanostatic charge-discharge measurements and it still retain a capacity of1444Fg-1at10Ag-1. It is obviously that the material owns the high power density.2. The hybrid capacitor based on GP/Ni-30cathode and AC anode was assembled. The mass ratio of anode to cathode was optimized and the working voltage range was determined. The experimental results revealed that the capacitance of the hybrid capacitor reached101Fg-1at the current density of0.2Ag-1when mass ratio mAC/mGP/Ni-30was4.6±0.1and the voltage range was0-1.6V and it delivers an energy density of35.76Whkg-1in1M KOH at a power of162Wkg-1, which is much higher than that of symmetric capacitor of8.8Whkg-1. It also shows an energy density of11.92Whkg-1at a power density of662Wkg-1at800mAg-1.3. GP/NiOOH/Ni(OH)2with different proportion were synthesized by changing the amount of reaction liquid, and it was used as the anode material for lithium-ion battery. SEM images show that the proportion of material has no influnce on the morphology of materials. Among the composition, GP/Ni-5exhibits the best performance, which deliver an initial reversible capacity of1287.4mAhg-1at a constant current density of100mAg-1and it retains830mAhg-1after80cycles.