Design Of Supercapacitor Based On Transition Metal Oxide/laser-induced Graphene Composite Electrode

Flexible planar micro supercapacitors（MSCs）have become one of the most important energy storage devices in wearable and portable electronic devices due to their small size,easy integration and expansion.However,most processes involve independent preparation of electrode materials,design of electrode shapes and subsequent modular integration,making the steps very complex,and the disadvantage of low specific capacitance of supercapacitors limits their application in practical environments.In this paper,a novel and simple laser direct writing technology is developed,and a laser-induced graphene supercapacitor with transition metal oxide nanoparticles with controllable plane shape is designed to be uniformly embedded on different flexible substrates.The specific research contents are as follows:Supercapacitors based on laser-induced manganese dioxide/graphene composite electrode（Mn O₂/LIG MSCs）and laser-induced ferric oxide/graphene composite electrode（Fe O_x/LIG MSCs）were designed and fabricated.The preparation process of transition metal oxide composite electrode was studied,and the process flow was optimized to obtain the composite electrode with transition metal oxide nanoparticles evenly embedded in laser-induced graphene（LIG）.The composite electrode can improve the specific capacitance of supercapacitor due to the synergistic effect of double electric layer and pseudocapacitance.The influences of electrode shape,laser power and laser scanning rate on supercapacitor were studied.The results show that Mn O₂/LIG MSCs have a high area specific capacity of 15.04 m F cm^-2 and a corresponding energy density of 1.34 m Wh cm^-2 at a scanning rate of 5 m V s^-1.The retention rate of capacitance is 86.4%after 10000 cycles.In addition,the Fe O_x/LIG MSCs had a high area specific capacity of 27.50 m F cm^-2 and a corresponding energy density of 2.44 m Wh cm^-2 at the scanning rate of 5 m V s^-1.The retention rate of capacitance is still82.5%after 10000 cycles.Several sets of ultracapacitors are integrated as power sources for LED lights and electronic watches,successfully lighting LED lights and driving electronic watches.The ultracapacitors have good adaptability to different substrates（PI-based,cloth-based and paper-based）.The uniform insertion of transition metal oxide nanoparticles into the 3D porous LIG electrode by laser direct writing technology can effectively improve the wettability of the electrode,thus significantly enhancing the electrochemical storage characteristics of water electrolyte MSCs.Meanwhile,the prepared MSCs also have good mechanical flexibility and significant module integration.Thus,the application field of flexible wearable electronic devices is expanded.