Electrochemical Properties Of Porous Bimetallic Oxide Nanospheres As Electrode Materials For Supercapacitors

Supercapacitors have attracted more and more attention in the application of energy storage systems because of their high specific power,fast charging/discharge speed and long cyclic stability.Because the pseudocapacitor shows a better than the double-layer capacitor,the transition metal oxide has become one of research focuses of the electrode materials that can be developed by supercapacitors as a result of the pseudocapacitor electrode material.However,the transition metal oxide is easy to reunite at high current density,which leads to poor cyclic stability.In addition,the conductivity of transition metal oxidation itself is poor,so it is of great significance to prepare bimetallic oxides or composite materials to achieve synergy,improve conductivity,and regulate the structure of electrode materials with good reversibility and long circulation life.In this paper,porous Fe-Co bimetallic oxide nanospheres(Fe_xCo_yO₄)were synthesized by simple and time-saving solvothermal method combined with calcination.The Fe ExCoYo4 electrode material showed excellent specific capacity and high cycling stability.The details are as follows:Porous Fe_xCo_yO₄ nanoparticles was successfully prepared from iron and cobalt nitrate by using solvothermal-calcination method.According to the structural results of SEM,XRD and BET,different calcination temperatures will affect the morphology and structure of the material,when the calcination temperature is 400?,porous Fe_xCo_yO₄ nanoparticles has the optimal specific surface area(63.51 m²g^-1)and pore structure(0.176 cm³ g^-1).In order to further improve the electrochemical properties of porous Fe_xCo_yO₄ nanoparticles,the effects of iron salts and cobalt salts with different molar ratios in the synthesis of materials on the morphology,structure and electrochemical properties of porous Fe_xCo_yO₄ nanoparticles were explored.The experimental results show that the prepared FeCoO₄ has the best electrochemical performance when the molar ratio of Fe-Co is 1:1.The FeCoO₄ can reach 584 F g^-1 at an current density of 0.5A g^-1.Assembled into a symmetric supercapacitor with a voltage window of 1.8V,and the capacity retention rate increases to 120%after20,000 cycles at the current density of 3A g^-1.Porous Fe₂O₃ nanoparticles were prepared by the same preparation method.Through ultrasonic method,it is compounded with the graphene oxide sheet layer,the sandwich thousand-layer Fe₂O₃-PNs/GO composite material is obtained,and the influence of adding different proportions of graphene oxide on the electrochemical properties of the composite is investigated.When Fe₂O₃-PNs is combined with graphene oxide in a ratio of 1:2,Fe₂O₃-PNs/GO has the highest specific capacitance(554 F g^-1).Assembled into an asymmetric supercapacitor with Fe₂O₃-PNs/GO as the negative electrode and FeCoO₄ as the positive electrode to test its cyclic performance.It also shows excellent energy density and power density,the energy density from29.4 Wh kg^-1to 7.5 Wh kg^-1with the power density from 450 W kg^-1 to 9000 W kg^-1.