Fabrication,Structure And Energy Storage Mechanism Of High-performance Micro-supercapacitors

In this dissertation,micro-supercapacitors work as the starting point of research.A range of high-performance microscale devices are designed and fabricated based on the synthesis of nanomaterial electrodes.Meanwile,related energy storage mechanism of devices is investigated.Some meaningful research results are obtained and the detailed are summarized briefly as follows:?1?In order to study the graphene and holey graphene enhancement mechanism for energy storage of micro-supercapacitors,lithography,physical vapor deposition and electrochemicaldeposition were employed to design and fabricate micro-supercacitors with bare polyaniline film,unmodified graphene-polyaniline heterostructuresandholeygraphene-polyanilineheterostructures.The electrochemical measurement shows that,after holey graphene intermediate layers introduction,the volumetrical capacitance of micro-supercapacitors is 271.1 F cm^-3which is much higher than those of micro-supercapacitors with bare polyaniline film,unmodified graphene-polyaniline heterostructures.The electrical transport between polyaniline film and current collectors is enhanced with graphene intermediate layers introduction.The holey graphene intermediate layers introduction further leads the improvments in electrolyte ions adsorption amount in electrodes.Thus,more electrons transfer occurs,which results in the higher capacitance of micro-supercapacitors.?2?To address the low energy density and poor application flexibility of micro-supercapacitors,three-simensional spiral-shaped micro-supercapacitors were first put forward.To address the low energy density and poor application flexibility of micro-supercapacitors,three-dimensionalspiral-shapedsymmetricalmicro-supercapacitors were first put forward.Using e-beam lithography,physical vapor deposition,sputtering and electrochemical deposition techniques,we designed and fabricated three-simensional spiral-shaped micro-supercapacitors,where Co?OH?₂ or MnO₂ served as active materials and conductive metal coated micro-pillar array was introduced.The electrochemical measurement shows that the specific capacitance,energydensityandpowedensityofthree-simensionalspiral-shaped micro-supercapacitors reach at the high levels.Moreover,as-prepared devices exhibit good cycling performance during charge-discharge processes.For muti-electrodes structure,the energy density and power density could be tuned using different combination ways.From the view of engineering,this spiral-shaped design could realize integration of arbitrary micro-szied geometry,which shows the great application flexibility.?3?To realize the flexibility and transparency for micro-supercapacitors at the same time.We fabricated flexible and semi-transparent three-dimensional micro-supercapacitors through electrospining and atomic layer deposition approachs with MEMS technology assistance.The mass production of microscale energy storage devices is also realized.Compared with devices without vanadium oxide coating,three-dimensional nanowire network based micro-supercapacitors exhibits19.3 F cm^-3at the scan rate of 100 mV s^-1.Moreover,it shows stable charge-discharge characteristic under different bending status.?4?In order to overcome the poor matching of miro-electrodes in micro-supercapacitors.NiO symmetrical micro-supercapacitors,MnO₂ symmetrical micro-supercapacitors and NiO//MnO₂ asymmetrical micro-supercapacitors were fabricated on SiO₂/Si substrate using lithography and physical vapor deposition techniques.The electrochemical measurement shows that the specific capacitance of NiO//MnO₂ asymmetrical micro-supercapacitors reaches 37.7 F cm^-3.,which is much higher than those of symmetrical devices.Moreover,NiO//MnO₂ asymmetrical energy storage devices show the god cycling stability.