Engineering 3D electron and ion transport channels by constructing sandwiched holey quaternary metal oxide nanosheets for high-performance flexible energy storage

Due to the enhanced electrochemical activities,mixed metal oxides offer new and fascinating opportunities for high-performance supercapacitor electrodes.However,sluggish ionic and electronic kinetics within the electrode fundamentally limit further improvement of their electrochemical performance.To compensate for the deficiency,a flexible electrode(CNTF/Ni-Co-Mn-Mo NS/CNTN)composed of vertically-aligned areolate quaternary metal oxide nanosheets sandwiched between carbon nanotubes(CNTs)is constructed in this study,which demonstrates a unique hierarchical porous structure that can provide three-dimensional transport channels for both ions and electrons.The vertically aligned areolate quaternary metal oxide nanosheets enable increased exposed surface area and paths for ion transport,diffusion and redox reactions,resulting in an evident enhancement in electrochemical activities.Besides,the CNT networks provide improved conductivity,which can accelerate the electron transport.As a result,the flexible supercapacitor based on the CNTF/Ni-Co-Mn-Mo NS/CNTN electrode demonstrates a specific areal capacitance of 3738 m F cm^-2,corresponding to a high energy density of 1.17 m W h cm^-2,which outperforms most of the flexible devices reported recently.Additionally,excellent flexibility of up to 180°bend and superior performance stability of 87.87%capacitance retention after 10,000 charge-discharge cycles can be obtained.This unique design opens up a new way in the development of flexible energy storage devices with high performance.

High performance flexible energy storage device based on copper foam supported NiMoO4 nanosheets-CNTs-CuO nanowires composites with core–shell holey nanostructure

Because of the intensified electrochemical activities,mixed metal oxides as a representative for pseudocapacitive materials play a key role for high performance supercapacitor electrodes.Nevertheless,low ion and electron transfer rate and poor cycling performance in the electrode practically restrict further promotion of their electrochemical performance.In order to offset the defect,a novel copper(Cu)foamsupported nickel molybdate nanosheet decorated carbon nanotube wrapped copper oxide nanowire array(NiMoO4 NSs-CNTs-CuO NWAs/Cu foam)flexible electrode is constructed.The as-prepared electrode demonstrates a unique core-shell holey nanostructure with a large active surface area,which can provide a large number of active sites for redox reactions.Besides,the CNTs networks supply improved conductivity,which can hasten electron transport.Through this simple and efficient design method,the spatial distribution of each component in the flexible electrode is more orderly,short and fast electron transport path with low intrinsic resistance.As a result,the NiMoO4 NSs-CNTs-CuO NWAs/Cu foam as an adhesiveless supercapacitor electrode material exhibits excellent ene rgy storage perfo rmance with high specific areal capacitance of 23.40 F cm^(-2)at a current density of 2 mA cm^(-2),which outperforms most of the flexible electrodes re ported recently.The assembled asymmetric supercapacitor demonstrates an energy density up to 96.40 mW h cm^(-3)and a power density up to 0.4 W cm^(-3)under a working voltage window of 1.7 V.In addition,outstanding flexibility of up to 100°bend and good cycling stability with the capacitance retention of 82.53%after 10,000 cycles can be obtained.