Combustion Synthesis And Pseudo-capacitance Properties Of Metallic Oxide And Their Composites

With the development and progress of society,exploiting new energy storage devices is an efficient path to relieve even solve the confronting problems.Supercapacitors?SCs?,as new energy storage devices,have become a hot spot of current research,which is expected to use in vehicle,military,new energy,and consumer electronics etc.field.As the research about SCs materials continues,various electrode materials are emerging in an endless stream.Among them,metallic oxide become to one of the most promising SCs electrode material owing to its higher specific capacitance and better electrochemical stability.Now,the metallic oxide can be prepared by various methods,however,most of the methods are complex process or low yield,which limits its development.In this paper,we have successful synthesized MnCo₂O₄,MnO2/MnCo₂O₄,and NiO/C/CNTs composite in large-scale by combustion synthesis method,and their pseudocapacitor properties have been investigated.The main experimentation and conclusions are as follow:?1?MnCo₂O₄ was prepared by solution combustion method using Mn?NO₃?₂,Co?NO₃?₂·6H2O and urea as raw materials.The morphology features and pseudocapacitor properties influenced by the molar ratio between metal ions?Mn2+: Co2+ was set as 1:2 in the precursor mixed solution?PMS??and glycine were investigated.The results of XRD,SEM,and electrochemical measurements indicate that the molar ratio of metal ions and glycine in the PMS have the great influences on the particle size and electrochemical properties of the composites.The composite with Mn2+: Co2+: glycine molar ratio of 1: 2: 14/9 in the PMS exhibits the smallest particle size and the best electrochemical properties.The specific capacitances reach 458 and 300 F/g at the current density of 0.5 and10 A/g,respectively.?2?Large-scale porous MnO2/MnCo₂O₄ composites were prepared by solution combustion method.On the basis of the aforementioned optimal metal ion/glycine molar ratio,the effect of the molar ratio of Mn2+: Co2+ on the morphology and electrochemical properties of composites was investigated.The results show that the molar ratio of Mn2+/Co2+ in the PMS has a great influence on the particle size,roughness,pore size distribution and pore density of the composites.The electrochemical measurements indicate that MnO2/Mn Co₂O₄ composite with the Mn2+:Co2+ molar ratio of 3:4 has the best capacitance performance.The specific capacitances reach 497 F/g and 312 F/g at the current density of 0.5 A/g and 10 A/g,respectively.After 5000 cycling,the specific capacity of the composite still maintain 60 % at 5 A/g.?3?Large-scale porous Ni O/C composites were prepared by combustion method using Ni?NO₃?₂·6H2O and urea as raw material.The effects of different thermal treatment methods on the electrochemical properties of the composites were studied.The molar ratio of Ni2+: urea is 1: 6 in the PMS.The results showed that the optimum electrochemical performance of the composite could be obtained by the following thermal treatment process: the PMS was first heated up to 240 °C for 0.5 h,and then further heated up to 350 °C for 1 h.In order to further improve the electrochemical performance,a certain amount of CNTs were introduced into PMS to prepare NiO/C/CNTs composite.The specific capacitance of the NiO/C/CNTs composite reaches 1618 F/g at the current density of 1 A/g.An asymmetric supercapacitor?ASC?combined NiO/C/CNTs as anode and activated carbon as cathode was assembled.The specific capacitance of the ASC is 83 F/g at 0.2 A/g,and the corresponding energy density and power density were 93.4 Wh/kg and 0.6 kW/kg,respectively.After 1500 cycling,the specific capacity of the ASC remains 40 % at 3 A/g.