One-dimensional Nanomaterials Network For Transparent Supercapacitors

The development of transparent batteries and supercapacitors is of great interest in the rapidly evolving field of transparent electronics.However,fabricating transparent energy storage devices presents significant challenges.All the components involved,including current collectors,electrodes,separators and electrolytes in the devices should be prepared into transparent configuration to allow visual light transmission.Although some transparent full devices were successfully constructed using H3PO4(or H2SO4)/PVA(poly(vinyl alcohol))gel as electrolyte and separator,the thickness of these gel electrolyte films sandwiched in between two electrodes are difficult to control because of the easy deformation characteristic and viscous flow behavior owned by the gels.The uncontrollable electrode spacing will lead to much difficulty to repeatedly fabricate a stable-performance supercapacitor device.To overcome this shortage,some cases even used opaque commercial separators(e.g.,Celgard micro-porous films)in full devices,neglecting the original intention of the preparation of transparent supercapacitors.Hence developing a separators with stable structure and wide compatibility to other components is important and necessary for transparent energy storage devices.In this thesis,polystyrene(PS)microspheres were proposed as electrode spacing materials and mixed with gel electrolyte to replace traditional membranes such as polypropylene and cellulose separator paper.Based on this novel strategy,transparent supercapacitors are fabricated using carbon nanotubes(CNTs)and indium tin oxide(ITO)glass as the active materials and current collectors.The main progress is as follows:1.Transparent supercapacitors were fabricated using SWCNT-spray-coated ITO/glass as transparent electrodes,Li Cl/PVA gel as electrolyte and PS spheres as spacers,respectively.The electrode spacing distance was tuned by varying the size of PS spheres from 10,20 to 40 ?m.The transparency of electrodes was changed by altering the coverage amount of SWCNTs.The experimental results indicate that the transparent supercapacitors fabricated on 20 ?m PS spheres demonstrated the best performance.The areal specific capacitance of the full devices could reach 70 m F/cm2 at transparency of 80%,and maintained a coulomb efficiency over 92%.2.In order to improve the specific capacitance of the supercapacitors,we have prepared transparent devices using Mn O2 modified MWCNTs(Mn O2/MWCNTs)as composite electrode materials Compared with the devices on pure MWCNT electrodes,the Mn O2/MWCNTs transparent supercapacitors increased the specific capacitance by an order of magnitude.Similarly,the transparency of the capacitors is affected by loading of Mn O2/MWCNTs.The specific capacitance of the transparent devices reached 678 ?F/cm2 at transparency of 78.9%.In addition,the capacitance retention was 88.6% after 1000 charging and discharging cycling.3.All-solid flexible transparent supercapacitors were constructed by replacing rigid ITO/glass by flexible gold nanomesh/PET or ITO/PET.The fabricated transparent supercapacitors shown outstanding electrochemical properties,whose specific capacitance was 952.5 m F/cm2 at transparency of 48%.The capacitance retention was 87.4% after 1000 charging and discharging cycling.The devices maintained acceptable performance at bending angle of 45°,90°,135° and 180°,whose capacitance was about 80% of the original value after bending to 180°.