Preparation Of Carbon Aerogel Derived From Cellulose And Its Performance Of Asymmetric Supercapacitors

Asymmetric supercapacitors?ASCs?are a new type of energy storage devices.Compared with traditional capacitors,ASCs exhibit higher energy density.They also have the advantages of high power density and rapid rate of charging and discharging to achieve the attention of the scholars.The performance of ASC is mainly affected by two factors,namely voltage range and specific capacitance.Therefore,the preparation of appropriate positive and negative electrode materials and reasonable assembling can contribute to the construction of high-performance asymmetric supercapacitors.In this paper,we studied carbon aerogels,which is commonly used as negative electrode material for ASC.The B/N co-doped carbon aerogel?BN-MC?material was synthesized by using the unique water solubility and cementitious property of methyl cellulose.The electrochemical performance tests showed that the capacitance of the prepared material was about 178.0 F g^-1 at current density of 1 A g^-1 and showed excellent conductivity and stability.Based on that,BN-MC was used as the coating layer to fabricate MnO₂ nanowire composite,which can effectively improve the conductivity of MnO₂ and reduce agglomeration phenomenon in the cycling process.The specific capacitance of the composite was 319.4 F g^-1,higher than that of pure MnO₂.In order to further enhance the behavior of MnO₂,MnO₂/PANI coaxial nanotube gel was prepared in this paper.This coaxial composite can provide abundant surface active sites and electron transport channels for electrolyte ions and the specific capacity reaches 575 F g^-1,which approves great conductivity and cycling stability.Finally,we assembled two kinds of asymmetric supercapacitors using BN-MC as negative,MnO₂/BN-MC and MnO₂/PANI hybrid as positive,respectively.The electrochemical performance test showed that the energy density of ASC with MnO₂/PANI positive reaching 52.7 Wh kg^-1,which is higher than that of MnO₂/BN-MC(31.7 Wh kg^-1).In addition,the capacity loss is only 9.8%after 2000 charge-discharge cycling.It is conductive to promoting the development and application of new ASCs.