Construction And Electrochemical Properties Of High-Performance Carbon-Based Electrochemical Energy Storage Devices

With the rapid development of portable electronics,electric vehicles and smart grids,improving the electrochemical performance of existing electrochemical energy storage devices and designing new energy storage devices have become two research hotspots.The development of electrode materials and the construction of devices are two important research designs to achieve the above goals.In this dissertation,we construct electrochemical energy storage devices based on carbon-based materials with high energy density,high power density and long cycling life from three perspectives of electrode materials,basic theoretical research and new device design.The main results achieved include:（1）Using the hard-template method and rational control of the preparation process,homogenous ordered microporous carbon materials suitable for the cathode and anode of sodium ion capacitors are obtained to construct high-performance energy storage devices.The research shows that the ordered microporous carbon has a relatively high degree of graphitization and expanded interlayer spacing,which is conducive to the intercalation/deintercalation process of sodium ions in the bulk phase of carbon materials to accelerate the reaction rate,thereby alleviating the issue of sluggish Faradaic reaction of the anode.During the preparation process,nitrogen-doped ordered microporous carbon is prepared by ingeniously introducing nitrogen source,which changes the surface charge density of the carbon material,improving the charge storage capacity.Combined with the electric double layer capacitance due to the high specific surface area and ordered microporous structure of carbon materials,the issue of low capacity of cathode is alleviated.In this paper,the sodium-ion capacitor with high energy density(119 Wh kg^-1),high power density(5807 W kg^-1)and long cycling life（1800 cycles）is constructed,which provides a design idea for the development of low-cost,high-energy,and high-power electrochemical energy storage devices.（2）From the perspective of view of energy storage devices design,the influences of charge storage mechanism,operating voltage window of electrode materials as well as kinetic matching of cathode and anode on the electrochemical performance of hybrid capacitors are studied.Due to the difference in energy storage mechanisms between capacitor-type cathode and battery-type anode,hybrid capacitors suffer from the kinetic mismatch of cathode and anode.The research shows that kinetic mismatch of cathode and anode will lead to lithium deposition of the device at high rates,which may cause security incident.Moreover,it is also revealed that the performance of the device is closely related to the energy storage mechanism and the working voltage window of the electrode materials.The electrode potential should be adjusted reasonably based on the type of electrode materials to fully exert the electrochemical performance of the materials,so as to construct high-performance electrochemical energy storage devices.This study provides a new way for optimizing the electrochemical performance of hybrid capacitors.（3）The idea of using the redox reaction of chloride ions to construct high-performance electrochemical energy storage devices is proposed.The redox reaction potential of chloride ions（1.358 V vs.standard hydrogen electrode）is very high,which can maximize the operating voltage window of the device,thereby improving the energy density.Using activated carbon as electrode material and chloride ions as electrochemically active component,a novel chlorine-based redox capacitor in an ionic liquid is constructed.The research shows that during the charging process,the chloride ions in the electrolyte migrate to the cathode driven by an external electric field,and are oxidized to generate neutral chlorine confined in the micropores of the material,which inhibit the escape of neutral chlorine effectively.During the discharging process,neutral chlorine is reduced to chloride ions and returns to the electrolyte.In addition to Faraday capacitance,carbon materials with high specific surface area(1744.3 m² g^-1)can also increase adsorption active sites,which can provide electric double layer capacitance,thus constructing high-performance chlorine-based redox capacitor with operating voltages of 3.5 V.