Preparations And Properties Of Novel Graphene Micro-supercapacitors

The rapid development of integrated electronics has increased the demand for miniaturization and on-chip energy storage units,and the electronics industry has evolved toward micro,portable,flexible and highly integrated electronics.At present,thin-film batteries or micro-batteries have been used in commercial micro devices with the characteristics of short life,complex structure,difficult to integrate and so on.Super capacitor can overcome these shortcomings,especially micro super capacitor(MSC)with the design of positive and negative electrodes in the same plane is prone to prepare and integrate into the on-chip electronics.Graphene with unique structure and excellent properties has higher theoretical capacitance and is very promising for the electrode material.By exploring various preparing methods of graphene MSC,it is one of the interests to find out a cheap,environmentally friendly and large-scale production method.The research contents of this paper are as follows:1.Preparation of graphene MSCs by laser scribe.Graphene oxide(GO)was prepared by the improved Hummers method and diluted to 3.7 mg/mL.A certain amount of GO was drop-casted on PET substrate and dry at room temperature to form GO film.Then the film was glued on the laser scribe disc and inserted into the driver and patterning according to the design.The effects of the amount of deposition and the number of laser scribe times on the morphology and structure of the samples were studied by means of corresponding tests.When the number of laser scribe was fixed and the deposition amount was 0.38 mg/cm~2,the specific capacitance of the device was the highest(0.885 mF/cm~2);When the deposition amount was 0.38 mg/cm~2,the number of laser scribe times was 20,the degree of reduction of GO was higher,and the specific capacitance can reach to 2.9 mF/cm~2.2.Preparation of graphene MSCs by screen printing.The multi-layer graphene and binder were mixed to prepare the slurry according to a certain proportion.Screen printed interdigital electrode.Through microscope and SEM,it can be observed that the property of printing was better.But the value of specific capacitor was poor.The characterization of the raw materials showed that the interlayer spacing of the multi-layer graphene was small,and the layer was gathered together,resulting in a lower specific surface area.Simultaneously,the slurry was prepared by GO-2 that we made,and then the electrode was reduced by hydrazine hydrate,hydrogen iodate and infrared lamp.Through series characterization,it was found that the capacitance of electrode reduced by hydrazine hydrate was the best,which was 4.9mF/cm~2.3.Preparation of graphene MSCs by inkjet printing.Through the preparation of different concentrations of GO-2 dispersion and the measurement of its viscosity and surface tension,it can be determined that the optimal concentration of GO-2 is 6 mg/mL.In order to reduce the surface tension of the ink,perfluorinated surfactant(FS-30)was used.6 mg/mL GO-2 and certain amount of surfactant were mixed by various concentrations of surfactant.The ink that can be printed by universal printer was 6 mg/mL GO-2 and 2.5 mg/mL FS-30.First the universal printer was used to print interdigital electrodes 20 times,and then reduced by hydrazine hydrate.The electrochemical performance was characterized by electrochemical workstation,and the specific capacitance was 1.9mF/cm~2.