Preparation And Properties Of Composite Electrode Material Based On Novel Graphene Nanosheets

A novel fluffy graphene nanosheets(FGNs)were prepared from coal-tar pitch with nano-Al2O3 as filler by high-temperature carbonization under vacuum conditions.Based on this new method,the Ni(OH)2/GNs and PANi/GNs composite materials were fabricated by hydrothermal reaction and oxidation polymerization,respectively.Such strategy could take the advantage of the 3D structure,conductive and mechanical property from novel fluffy GNs to optimize the system of composite electrode and improve its electrochemical properties.The main results are as follows:The GNs with fluffy structure were prepared directly by high-temperature carbonization and characterized by XRD,TEM,Raman and XPS.The results showed that few-layer fluffy FGNs with fine crystalline and uniform size can be prepared effectively by above method.The optimum conditions are as follows:mass ratio of coal-tar pitch and nano-Al2O3 is 1:1,carbonization temperature is among 1800? and holding one hour.Meanwhile,a Al2O3-C-Al4C3 carbonthermal reduction system was proposed to explain the growth and exfoliation mechanism of FGNs and the key role of carbon-aluminum intermediate compound(Al4C3)in the growth and exfoliation of GNs was studied by XRD and SEM.The Ni(OH)2/GNs composite electrode materials with a 3D graphene conductive network were synthesized by depositing the Ni(OH)2 on FGNs via hydrothermal reaction.The optimum conditions are as follows:the mass ration of Ni2+/C is 8.5:1.5,the mole ratio of co-precipitator NaOH/urea is 8:2,180? hydrothermal reaction for 4 h.This as-prepared composite electrode exhibits the good capacity and excellent cycle life.The specific capacitance of 2260 F·g-1 was obtained at a current density of 1 A·g-1,and maintained 115.6%of its initial capacitance after 4000 cycles,while only had 2.6%capacitance decay after 1000 cycles at large current density of 16 A·g-1.The PANi/GNs composite electrode materials were prepared by oxidation polymerization.In this part,the effect of different ratio of An and graphene for the morphology,structure and electrochemical performance of composite electrode materials were studied.The results showed that the addition of FGNs not only improved the conductivity and stability of polyaniline,but also was an importance role in generation of ordered polyaniline fiber arrays.The optimum conditions are as follows:the mass ratio of An/graphene is 8:2(PG20%),the mole ratio is 1:1 and doping acid is HCl.Such PG20%composite electrode exhibits good capacity and stable long-term life.The specific capacitance of 783 F g"1 was obtained at a current density of 0.5 A·g-1,and maintained 95.8%of its initial capacitance after1000 cycles,while only had 0.414‰ capacitance decay each cycle.