Effects of Fe Impurities on Self-Discharge Performance of Carbon-Based Supercapacitors

Abstract

Activated carbon is widely used as an electrode material in supercapacitors due to its superior electrochemical stability, excellent electrical conductivity, and environmental friendliness. In this study, the self-discharge mechanisms of activated carbon electrodes loaded with different contents of Fe impurities (Fe and Fe3O4) were analyzed by multi-stage fitting to explore the tunability of self-discharge. It is was found that a small quantity of Fe impurities on carbon materials improves the self-discharge performance dominated by redox reaction, by adjusting the surface state and pore structure of carbon materials. As the content of Fe impurities increases, the voltage loss of activated carbon with the Fe impurity concentrations of 1.12 wt.% (AF-1.12) decreases by 37.9% of the original, which is attributable to the reduce of ohmic leakage and diffusion, and the increase in Faradic redox at the electrode/electrolyte interface. In summary, self-discharge performance of carbon-based supercapacitors can be adjusted via the surface state and pour structure, which provides insights for the future design of energy storage.

Carbon nanomaterials and their composites for supercapacitors

“…The experimental results show that the reduction of functional groups on the surface of SWCNT by heat treatment can indeed inhibit self‐discharge. Du et al 156 introduced different contents of Fe/Fe 3 O 4 into AC by vacuum impregnation and annealing, and systematically studied the effect of Fe doping on the self‐discharge of carbon supercapacitor. The experimental results show that the self‐discharge of supercapacitor decreases significantly by more than 39.7% after introducing a low content of Fe/Fe 3 O 4 into AC.…”

Application of Ionic Liquids for Batteries and Supercapacitors

“…Supercapacitors (SCs) can store energy via redox reaction or the formation of electric double layers (EDLs) of ionic species over the surface of electrodes at the electrode/electrolytes interface. They can reach the global requirements for ESS due to rapid power output, fast charge–discharge ability and longer lifetime than batteries [ 4 , 120 , 121 , 122 , 123 ]. SCs can be independently used as an alternative renewable energy source in the place of batteries in many fields such as wearable electronics, electric buses, laptops, mobiles, aerospace and various diagnostic instruments in medical systems, which boosts the growing interests in the field of advanced SCs research.…”

“…The low energy density of SCs obstructs its large-scale industrialization. The energy density of SCs is related to voltage window (V), and specific capacitance (C) of the device (E a = ½ CV 2 ) [ 4 , 6 ]. As energy density is directly proportional to the square of potential window (V 2 ), then significant improvement can be accomplished by developing new high-capacity electrode materials and/or widening the electrochemical potential window of the SC device.…”

“…With the remarkable development of low-cost, lightweight, portable electronic devices, electrical vehicles, aerospace and medical systems in our daily lives, the demand for a sustainable energy supply is becoming one of the greatest challenges for the whole world [ 1 , 2 , 3 , 4 ]. In the search for advanced sustainable energy sources, the urgent development of long-term high-efficient high energy-power resources is required.…”

Review—Influencing Factors and Suppressing Strategies of the Self-Discharge for Carbon Electrode Materials in Supercapacitors

“…4. 64,65 Briefly, the electrochemical process consists of multiple steps such as redox species transfer to the electrode surface (diffusioncontrolled process), electrochemical reaction (activation-controlled process), generation and diffusion of products. The electrochemical reaction rate depends on the slowest step.…”