The Research On Iron-based Supercapacitor Electrode Materials

The supercapacitor,as a promising energy storage device,has been widely used in many fields.It has the advantages of a high power density,long cycle life,wide working temperature range and environmental benign.However,due to the low energy density,although the supercapacitor has broad application prospects,it has to make a further research.The electrochemical performance of the supercapacitor is dominated by many factors,and the electrode material undoubtedly is a very important one.Within a variety of electrode materials,because iron element is rich in the earth's crust and non-toxic,iron-based material is considered as a promising electrode material.In order to improve the electrochemical performance of electrode materials,we did a prelimary investigation on iron salts,and then carried out further studies.Due to the close relations between the structure and performance,our schemes mainly include:1)the synthesis of one-dimensional or quasi one-dimensional structure materials,to create efficient charge transfer electronic channels;2)preparing nano-structure or hollow structure materials,to improve the specific surface areas of the electrode materials.Firstly,we prepare FeOOH products via the hydrothermal method by using different single iron salts,including FeSO4,FeCl2,Fe2(SO4)3,FeCl3 and Fe(NO3)3.We will have a overall understanding on hydrolysis products of the five kinds ferric salts.In this experiment,except for Fe2(SO4)3,we have successfully synthesized highly electroactive FeOOH products wuth different morphologies,in which the rod product by Fe(NO3)3 has a high specific capacitance of 619.6F/g under the current density of 1 A/g.This simple synthetic method and high specific capacitance indicated that iron-based electrode materials will have a great potential in the practical application of high performance supercapacitor electrode materials.In the solvothermal reactions,we use ethylenediamine-assisted Fe2(SO4)3 to prepare Fe2O3 products,which are of microspindle like structure and have a quasi one-dimensional structure.The more amount of the added EN,the spindle Fe2O3 particle's size is bigger.Microspindle Fe2O3 samples with different sizes show higher specific capacitances under the current density of 1A/g,and the highest value reaches 558.7F/g.This experiment shows that quasi one-dimensional structure has a good electrochemical performance,and proves that the smaller of the spindle Fe2O3 size,the specific surface area is larger,then the specific capacitance will be higher.In order to prepare the hollow iron-based materials,we use the self-sacrificial template of microscale Cu2O octahedron and FeCl3 at room temperature to synthesize Fe(OH)x colloid aggregations.The electrochemical properties of Fe(OH)x samples were tested,and the product prepared by Cu2O and FeCl3 molar ratio of 1:1 shows the highest specific capacitance of 242.7F/g under the current density of 1A/g,which may be contributed by the high activity of Fe(OH)x samples prepared at the room temperature.The whole work shows that the iron-based electrode materials have a high application value in the development of the supercapacitor.