Study On All-solid-state Planar Supercapacitors Based On Graphene

With the development of miniaturized and wearable electronics,there is a growing need for micro-storage systems.Planar supercapacitors realize the practical purpose of integrating micro-storage device,due to their many advantages,including the highly compatible,highly energy-storage density and highly integrated.Graphene as a new member of condensed matter physics,which is a kind of monolayer film by the two-dimensional sp2 hybrid carbon atoms.Since the unique mechanical properties and electrical properties of graphene,it is basically satisfied with all the requirements of electrode material for the energy storage device.Based on the principle of chemical gas phase deposition,the optimum preparation parameters were obtained by exploring the influence of different growth conditions on the quality of graphene films.The experimental results show that under the condition of low pressure,the thickness of grapheme was increased with the increasing of the growth time,growth temperature and CH4 concentration.The best growth conditions of monolayer graphene is controlling the growth time in 30 min and keeping up CH4 flow rate 35 sccm at the constant temperature of 1000 ℃.Based on this,the transmittance and the square resistance of the film are 95.2% and 155.75?/sq,respectively.By contrast,the multilayer graphene films with excellent quality were obtained by controlling the growth time in 60 min when the flow rate of CH4 was 35 sccm at the constant temperature of 1000 ℃.In addition,we found that the multilayer graphene films possess a small square resistance of about 60.28?/sq when CH4 flow keeping up 65 sccm at the constant temperature of 1000 ℃,but the surface uniformity of the films is poor.Multilayer graphene films are obtained by repeated transfer of single layer grapheme,with a transmittance of 97.2% at visible wavelengths of 550 nm.And it shows the better light transmittance but higher resistance than that of the monolayer graphene films were obtained under the growth temperature 1000℃,CH4 flow keeping up 35 sccm,H2 flow keeping up 10 sccm and the growth time in 30 min.Homemade and purchased single layer and multilayer graphene films were used as planar super capacitor electrodes to prepare all-solid-state planar supercapacitors,and the supercapacitor characteristics are investigated by cyclic voltammograms test.The results show that with the lower scan rate,the circular voltammetry curve of planar supercapacitor is closer to the spindle shape,and with the better electrochemical performance.When scan rate was 20mVs-1,the area capacitance and the energy density of home-made monolayer graphene super capacitor were 62.924mFcm-2 and 320.117mWhcm-3,respectively,which are greater than that of the purchased monolayer graphene films.Similarly,when scan rate was 100mVs-1,the purchased multiple grapheme supercapacitors correspond to the area capacitance was 23.642mFcm-2 and the energy density was 47.511mWhcm-3,greatly higher than that of the purchased monolayer graphene films.When scan rate was 20mVs-1,the area capacitance of the multilayer graphene planar supercapacitors obtained by multilayer transfer was 20.464mFcm-2,the energy density was 1.312mWhcm-3.In conclusion,this paper achieved good results on the study of the preparation process of graphene film electrode by optimizing CVD method,and the multilayer graphene transfer film preparation process remains to be improved.Moreover,this paper provides an important reference for the study of the preparation of graphene electrode all-solid-state planar microsupercapacito based on CVD method.