The Research And Application Of Metal Nitrides In Supercapacitor

Recently,wearable electronic devices including electronic sensors,flexible display screen and health monitor,have received wide attention.Wearable devices put forward high requirement for suitable flexible,wearproof devices with small volume,light weight,and excellent performance in electrochemical.Besides,high safety,stretchable and high energy density were the key to fabricated wearable energy storage devices.Wearable supercapacitor attends important application value in developing all flexible devices,due to the advantages with high stability,low cost,fast charging/discharging,and high efficiency.Though the commercial supercapacitors can provide more higher energy(～5 Wh kg^-1)contrast to traditional solid electrolyte supercapacitor,still lower than battery(200 Wh kg^-1)and full cell(350 Wh kg^-1).Therefore,the application of supercapacitor has been widely limited.According to the problem above,there are two ways to solve it.Firstly,to solve the challenge of supercapacitor with relative low energy density,developing asymmetric supercapacitor is a feasible approach.This type supercapacitor can realize the energy storage of battery,without sacrificing of power density and cycle stability.Using two different electrode materials,asymmetric supercapacitor can extend the working voltage window to the electrolyte thermodynamic decomposition voltage,at the same time solve the limitation of energy storage.Secondly,the energy-harvesting energy of solar cell,nanogenerators and energy storage devices of supercapacitor can be combined to form self-powered systems.This device can realize the long operation and shorten the charging/discharging number.Flexible supercapacitor attracted great attention in wearable electronic devices because of fast charging/discharging,ultralong span life.Flexible/wearable supercapacitor as the new wearable electronic storage devices,have widespread developing prospects.As for the materials of supercapacitor,metal nitrides with the advantages for high conductivity,excellent cycle stability,and better capacitance,have attracted great interest and widespread research,and becoming the potential electrode materials.What is more,metal nitrides generally have larger volume energy density for larger tap density.This thesis uses sample method to fabricated helical structure of molybdenum nitride and nanosheet morphology of cobalt nitride.This unique morphology is benefit to relive the expansion and shrinkage of the structure at the process of charging/discharging,preventing collapse and aggregation,thus obtaining excellent electrochemical cycle stability.