Study Of Manganese Dioxide And Iron Oxide Based Micro-supercapacitors

With the development in miniaturized electronic devices and systems,which play a great role in promoting social development and our daily life,the demand for micro-power sources is increasing.Supercapacitors fabricated by micromachining technology,also named as micro-supercapacitors or on-chip supercapacitors,are used as energy supply units complementing with micro-batteries and electrolytic capacitors in miniaturized electronic devices.To meet the compatible demand on micro-chips,it is important to develop the microsized current collectors with ideal electrodes construction.However,micro-supercapacitors suffer from their narrow voltage window and low energy density.Significantly,it becomes exceedingly necessary and urgent to develop micro-supercapacitors with high energy density and wide operating voltage window in limited space,while maintaining high power density,fast charging/discharging rate and long cycling life.Thus,the asymmetric structure has been widely investigated in micro-supercapacitors.To integrate different metal oxides into micro-supercapacitors,the critical challenge is how to match up different faradic metal oxides.Herein,we proposed a strategy of matching the voltage and capacitance of two faradic materials that are fully integrated into one high-performance asymmetric micro-supercapacitor by a facile and controllable fabrication process.In this work,MnO₂ cathode and Fe₂O₃ anode based asymmetric micro-supercapacitor were successfully fabricated.For comparison,MnO₂ based micro-supercapacitors and Fe₂O₃ based micro-supercapacitors were also fabricated.The main research contents and results obtained are as follows:?1?MnO₂ and Fe₂O₃ have been synthesized via an electrochemical deposition method.Field emission scanning electron microscopy is employed to characterize the as-prepared materials.The results show these materials have uniform morphology.When used as micro-supercapacitors,they have the complete structures.A new strategy to fabricate metal oxide based asymmetric micro-supercapacitors by microfabrication,physical vapor deposition and electrochemical deposition was proposed.?2?The asymmetric micro-supercapacitors of MnO₂ cathode and Fe₂O₃ anode ware fabricated for the first time.The asymmetric micro-supercapacitors show higher capacitance(60 F cm^-3),higher energy density(12 mWh cm^-3),wider operation voltage window?up to 1.2 V?and better cycle performance?up to 80%after 2500 cycles?than those of other reported micro-supercapacitors with alkaline aqueous electrolyte.?3?The mechanisms of their high-performance are discussed and it is proposed that the synergistic effect between MnO₂ and Fe₂O₃ is responsible for the enhanced performance of the asymmetric micro-supercapacitors.