Preparation And Capacitive Properties Of The Transition Metal Oxide Based Electrode Materials

Supercapacitor is an efficient and clean energy storage device,and its properties greatly depend on the inherent features of electrode materials.Transition metal oxides attract much attention to be used in supercapacitor electrode materials,owing to the good supercapacitive performances.Recently,some transition metal oxides have been reported to be used as electrode materials of supercapacitors,but they also have some defects.Therefore,it is very necessary to develop some other metal oxides to serve as electrode materials.In this paper,it is first time to investigate the supercapacitive behaviors of chromium oxides and MMoS₄（M represents the metal ions）,which will contribute to select the suitable electrode materials in supercapacitors.However,the poor conductivity of transition metal oxides and short diffusion distance between electrolyte and electrode lead to their low cycle stability and specific capacitance values（<<theoretical values）.In this paper,the supercapacitor properties of binary metal oxides,metal sulfides,metal oxides/substrate and metal oxides with special morphogy were investigated.（1）Compared with Cr₂O₃（130 F/g at 1 A/g）,90%),NiCr₂O₄（329 F/g at 1.2 A/g,90%）and CoCr₂O₄（233 F/g at 1 A/g,99%）exhibit the higher specific capacitances and capacitance retention at 100 mV/s after 1000-cycle.（2）The specific capacitance of the prepared CoMoS₄ by a simple chemical precipitation method can reach 661 F/g at 1 A/g,much higher than that of the reported CoMoO₄.（3）The specific capacitance and cycle stability of In₂O₃/RGO and MnMoO₄/RGO are superior to those of the single components.The CoWO₄/NiWO₄composite shows the high specific capacitance（668 F/g at 1.2 A/g）and good cycle stability.（4）The dandelion-like NiCo₂O₄/N-doped carbon/Ni foam and flower-like NiCoO₂/Ni foam can be dicrectly used as the electrodes of supercapcitors,and their specific capacitances are 864 F/g at 1 A/g and 756 F/g at 0.75 A/g respectively.In addition,the CoMoS₄///h-RGO and Ni CoO₂/Ni foam//h-RGO hybrid supercapacitors were assembled using CoMoS₄ and NiCoO₂/Ni foam as positive electrodes respectively,h-RGO as negative electrode,and their energy densities can reach 27.2 and 25.7 Wh/kg respectively.The walnut shell derived activated carbon all-solid-state supercapacitor own good electrochemical performances.