Preparation And Electrochemical Properties Of Flexible Nickel-Cobalt-Based And Iron-Based Electrode Materials

As a new generation of energy storage devices,supercapacitors have high power density and fast charge and discharge capability.However,the low energy density seriously restricts its application in practice.The primary method of increasing the energy density of a supercapacitor is to prepare an electrode material having a high specific capacity and to increase the potential window of the electrode material.Nickel-cobalt-based metal oxides generally have a high specific capacity,but have poor conductivity and insufficient stability,therefore need to be combined with a highly conductive carbon material to prepare an electrode material having both high stability and high capacity.The ionic liquid electrolyte has a wide electrochemical window,and the iron-based metal oxide/hydroxide has the ability to work in an ionic liquid electrolyte,thereby preparing an iron-based metal oxide/hydrogen hydroxide capable of stable operation in an ionic liquid are important.The main research contents and results of this paper are as follows:?1?Carbon nanofibers were used as flexible substrates and surface modification treatment was carried out by different activating reagents.The results showed that the carbon nanofibers modified by potassium permanganate had the best hydrophilic effect.After hydrothermal treatment and subsequent annealing treatment,the nano-sheet-like nickel cobaltate material is uniformly supported on the carbon nanofibers,and good mechanical properties are maintained.Electrochemical tests show that the nickel cobaltate/carbon nanofiber composite electrode material has a maximum specific capacitance of 1077.9 F/g at a current density of 1 A/g,and after 3000 cycles of charge and discharge tests at a current density of 5 A/g can maintain an initial specific capacity of95.6%.?2?Urea and glucose were used as raw materials,the high-nitrogen-doped porous carbon nanosheet material was prepared by two-step calcination,and the iron oxyhydroxide quantum dot material was loaded on the carbon nanosheet after a simple room temperature solution stirring method.The morphological characterization results show that the nitrogen-doped carbon nanosheets effectively improve the dispersion of quantum dots.By adjusting the ratio of nitrogen-doped carbon and iron oxyhydroxide,the prepared iron oxyhydroxide/nitrogen-doped carbon nanosheet composite electrode exhibited a maximum specific capacity of 419.8 F/g at 0.5 A/g.After 3000 cycles of charge and discharge at a current density of 5 A/g,the capacity was only attenuated by 3.9%,showing excellent cycle stability and electrochemical reversibility.?3?The iron oxyhydroxide/nitrogen doped carbon nanosheet composite was mixed with the oxidized carbon nanotubes,and vacuum-filtered to obtain a flexible film electrode,and the electrochemical performance of the electrode material was tested in an ionic liquid.The volume specific capacitance of the FeOOH/NC-CNT flexible film electrode at a current density of 1 A/cm³ was 130.9 F/cm³.The energy storage mechanism of FeOOH/NC-CNT flexible film electrode in EMIMBF₄ ionic liquid electrolyte was preliminarily analyzed by capacitive contribution quantitative calculation.In order to test the practical application performance of the material,a FeOOH/NC-CNT//CNT-G flexible asymmetric supercapacitor based on ion gel electrolyte was assembled.The test results show that the potential window of the device can reach 3V and the maximum energy density is up to 9.42mW h/cm³ shows its good application prospect and practical value.