| With the continuous emergentdemand for renewable energy storage in various wearable electronic equipment,new energy storage devices with highly flexibility have attracted extensive attention in recent years.It appears to be particularly important for these flexible energy storage devices to maintain electrochemical stability under different deformations including stretching,bending,rolling and folding.Supercapacitors,as a type of new energy storage device between traditional capacitors and secondary batteries,which has great application promising in the field of wearable electronic products.Flexible active electrodes are the key components of supercapacitors,which decides the electrochemical properties and the deformation degree of the devices.Currently,the rapid development of carbon nanomaterials has created substantial opportunities for the fabrication of high-performance flexible electrodes.Among them,graphene-based flexible electrode have attracted great attention due to its excellent properties.Thus far,graphene-based flexible electrodes,such as freestanding graphene-based films have been showed great potential application in the flexible supercapacitors.The article mainly studies graphene-based film of fabrication and regulation of microstructure,which obtained high performance graphene based electrodes with various morphology.The flexible all-solid-state supercapacitors was assembled by employing graphene based film with different morphology as electrode materials,which exhibits excellent flexibility.The research content of this thesis is as follows:?1?The preparation of free-standing graphene/carbon nanotube composite film by vacuum filtration,carbon nanotubes as spacer to mitigate the stacking of graphene nanosheets during reduction or drying.The film reveal that excellent flexibility,even if the bent and folded without structural damage,the assembled supercapacitors show an ultra-high areal capacitance(1340 mF cm-2,26.5 mF cm-2),the volumetric capacitance(6.6 F cm-3 and 60 F cm-3).In addition,the device bending does not cause any obvious effect on the capacitive performance.?2?The preparation of microcorrugated freestanding graphene/carbon nanotube composite film by ion cross-linking and vacuum filtration,a free-standing graphene-based film with micro-corrugated graphene sheets was prepared by taking advantage of water molecule as lubricant layers during the reduction of a GO-based gel film.The water lubricant layers lower the interlayer attractive force and the interlayer frictional force.Accordingly,the graphene sheets are relatively easy to shrink and form micro-corrugation under the in-plane contraction force due to the removal of oxygen functional groups on the GO sheets during reduction.Such micro-corrugated mophology prevents the graphene-based film from compact stacking,and thus more graphene surface area is accessible by electrolyte ions.Electrochemical measurement results reveal that an all-solid flexible film supercapacitor based on such a micro-corrugated graphene-based film as both the active and current electrodes shows large areal and volumetric capacitances(127 mF cm-2,107 F cm-3),high volumetric energy density of 14.8 Wh L-1 at a power density of 53.6 W L-1,excellent capacitance retention of 97%over 3000 cycles at 1 mA cm-2,far exceeding that of the densely-stacked graphene-based film supercapacitor. |
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