A double-redox aqueous capacitor with high energy output (original) (raw)
Related papers
Solvent-controlled morphology of bismuth sulfide for supercapacitor applications
Journal of Materials Science, 2018
In our study, we report a facile solvothermal method for the synthesis of Bi 2 S 3 nanoparticles with unique morphologies using water and mixed solvent systems, such as ethylene glycol/water (1:1, v/v) and butyldiglycol/water (1:1, v/v). Altering the solution mixtures used in the solvothermal synthesis allowed the shape of the Bi 2 S 3 nanoparticles to be controlled. The synthesis of Bi 2 S 3 in water at 150°C for 24 h led to the formation of sphere-like particles 100-300 nm in size. Very uniform spherical nanospheres with diameters from 50 to 90 nm formed when ethylene glycol/water mixture (1:1, v/v) was used as the solvent under the same solvothermal conditions. The butyldiglycol/water mixture promoted the formation of plate-shaped Bi 2 S 3 nanoparticles composed of nanorods. The electrochemical properties of the Bi 2 S 3 samples were determined in a three-electrode cell in 6 mol L-1 KOH using cyclic voltammetry, galvanostatic charging/discharging and impedance spectroscopy. Among the synthesized materials, the Bi 2 S 3 sample obtained in the butyldiglycol/water mixture exhibited a superior capacitive behavior with an outstanding capacitance of 550 F g-1 (at 0.5 A g-1), and great cycle stability, which was reflected by a capacitance retention of 87% after 500 charge/discharge cycles. These results demonstrate the high potential of Bi 2 S 3 as an active electrode material for supercapacitors.
Electrochimica Acta, 2019
Two asymmetric aqueous electrochemical capacitors operated in 5M LiNO 3 are reported: C/Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δδ (BSCF) a BSCF) and FeWO 4 /BSCF, with activated carbon and FeWO 4 (BSCF) a synthesized by a precipitation method) as negative electrodes, respectively, and BSCF (BSCF) a synthesized by a modified glycine-δnitrate process) as positive electrodes. These two devices were operated between 0 and 1.6 V and between 0 and 1.4 V, respectively. They demonstrated a remarkable cycling ability with a high capacitance retention over 10,000 and 45,000 cycles, respectively. Thanks to the high density of BSCF, the C/BSCF device exhibits a volumetric energy density up to 2.7 Wh.L-δ1 at low current densities. This study demonstrates the advantages and limits of the use of high density multicationic oxides with pseudocapacitive behavior to improve the volumetric energy density of aqueous electrochemical capacitors.
Chemically deposited Bi2S3:PbS solid solution thin film as supercapacitive electrode
g r a p h i c a l a b s t r a c t SILAR deposited Bi 2 S 3 :PbS solid solution thin film towards stable and energy efficient supercapacitive electrode. a b s t r a c t Low-cost, easily synthesized, and high energy/power density embedded stable supercapacitive electrodes are the demands for today's renewable and green energy dependent generation. In search of that, Bi 2 S 3 : PbS solid solution in thin film form has been synthesized by modest successive ionic layer adsorption and reaction (SILAR) method and characterized by XRD, FESEM, and HRTEM. Formation of solid solution in the form of nanoparticles gilded thin film exposes sufficient electroactive cavities for electroactive ions to incorporate. The composite exhibited excellent specific capacitance of 402.4 F/g at current density of 1 mA/cm 2 with modest charge-discharge cycles. In terms of energy storage, it exhibited maximum specific power of 20.1 Wh/kg with accepting specific power of 1.2 kW/kg. The combination of two nanoparticles in nanocomposites thin film supplies new tactic for energy storage applications.
ABSTRACT: We report a new electrochemical capacitor with an aqueous KIKOH electrolyte that exhibits a higher specific energy and power than the stateof- the-art nonaqueous electrochemical capacitors. In addition to electrical double layer capacitance, redox reactions in this device contribute to charge storage at both positive and negative electrodes via a catholyte of IOx −/I− couple and a redox couple of H2O/Had, respectively. Here, we, for the first time, report utilizing IOx −/I− redox couple for the positive electrode, which pins the positive electrode potential to be 0.4−0.5 V vs Ag/AgCl. With the positive electrode potential pinned, we can polarize the cell to 1.6 V without breaking down the aqueous electrolyte so that the negative electrode potential could reach −1.1 V vs Ag/AgCl in the basic electrolyte, greatly enhancing energy storage. Both mass spectroscopy and Raman spectrometry confirm the formation of IO3 − ions (+5) from I− (−1) after charging. Based on the total mass of electrodes and electrolyte in a practically relevant cell configuration, the device exhibits a maximum specific energy of 7.1 Wh/kg, operates between −20 and 50 °C, provides a maximum specific power of 6222 W/kg, and has a stable cycling life with 93% retention of the peak specific energy after 14 000 cycles.
Supercapacitor modified with methylene blue as redox active electrolyte
Electrochimica Acta, 2012
MWCNT-based supercapactors (SC) containing methylene blue (MB) as redox active electrolyte were studied. MWCNTs were employed as model of electrode active material due to their ideal doublelayer behavior facilitates the investigation of the energy storage mechanisms involved. MB led to a cell capacitance enhancement equal to 4.5 times the original cell capacitance of MWCNTs in sulphuric acid with a capacitance reduction of only 12 % after 6000 charge-discharge cycles. The potential evolution of each electrode during galvanostatic cycling revealed that MB redox reaction develops in both electrodes simultaneously in the voltage range of 0-0.104 V and that this is the main cause of cell capacitance enhancement. Beyond this voltage range, the faradaic contribution from the MB redox reaction decreases because the anode behaves as a capacitative electrode with a rather reduced chargecapacity due to the small surface area of MWCNTs. By means of a modified assembly composed of a Nafion membrane and MB and sulfuric acid solutions located in the cathode and anode compartments, respectively, it was demonstrated the limiting role of the capacitative electrode in the cell chargecapacity in this type of hybrid devices. 2 KEYWORDS. Methylene blue, multiwalled carbon nanotubes, faradaic reactions, redox electrolyte, supercapacitor. 1.-INTRODUCTION Supercapacitors (SCs) are energy storage devices that have attracted great attention because they can store higher energy than dielectric capacitors and, simultaneously, deliver higher power in a shorter time than batteries. SCs based on carbon materials (CBSCs) have been the most developed and employed in commercial applications to date due to their excellent properties, such as low cost, good electronic conductivity, large capacitance and long cycling life 1,2. Thanks to these characteristics, CBSCs are used in a great number of electronic devices. However, for their use in certain potential applications, such as hybrid electric vehicles, it is first necessary to increase their energy density 3. In this context, a great deal of effort has been made in order to increase the energy stored by CBSCs, these being for the most part centred on capacitance enhancement through the use of pseucapacitive contributions provided by functional groups from physical /chemical activations 4,5 , oxidation with strong acid, bases or air 6 , or polymers deposition 7,8. However, as it is well known, the enhancement of capacitance by pseudocapacitive contributions is significantly sensitive to long-term cycling because functional groups generated during the above treatments are usually unstable and disappear with cycling 5,9,10 or, in the case of conducting polymers, suffer shrinkage and swelling which lead to the gradual degradation of the electrodes 8,11,12. Our research group has recently proposed a highly efficient and low cost alternative route to enhance cell capacitance, based on the incorporation of an electrochemically active molecule (such as hydroquinone or indigo carmine) into the SC electrolyte 11-15. Capacitance increases up to 4.5 times the original capacitance value with no significant modification of the equivalent series resistance (ESR) of the device can be achieved with this simple method, which have led to a carbon-based device 12 with a maximum energy density of 31 Wh Kg-1 , 14 close to that of some batteries 16 .
Strategies to Improve the Performance of Carbon/Carbon Capacitors in Salt Aqueous Electrolytes
Journal of the Electrochemical Society, 2015
Strategies are presented to enhance operating potential and cycle life of AC/AC capacitors using salt aqueous electrolytes. Li 2 SO 4 (pH = 6.5) allows 99% efficiency to be exhibited at 1.6 V cell potential with low self-discharge, while in BeSO 4 (pH = 2.1) efficiency is low (81%). Li 2 SO 4 performs better due to high di-hydrogen over-potential at the negative electrode and related pH increase in AC porosity. When stainless steel current collectors are used in Li 2 SO 4 , the cell resistance suddenly increases after 12 hours floating at 1.6 V, due to corrosion of the positive collector. With nickel negative and stainless steel positive collectors, the electrode potentials are shifted by −105 mV at cell potential of 1.6 V, allowing stable cell parameters (capacitance, resistance) and reduction of corrosion products formation on positive steel collector after 120 hours floating. Phenanthrenequinone was grafted on activated carbon to get an additional faradaic contribution in buffer solutions (pH = 4.0 or 7.2). The three-electrode cell CVs show that the redox peaks of the phenanthrenequinone graft shift toward negative values when pH increases from 4 to 7.2. The grafted carbon displays a capacitance value of 194 F g −1 at pH = 4.0 as compared to 82 F g −1 for the as-received carbon.
Electrosynthesis of Bi2O3 thin films and their use in electrochemical supercapacitors
Journal of Power Sources, 2006
Bismuth oxide (Bi 2 O 3) thin films are grown on copper substrates at room temperature by electrodeposition from an aqueous alkaline nitrate bath. The usefulness of electrochemically deposited Bi 2 O 3 for electrochemical supercapacitors is proposed for the first time. The supercapacitor properties of Bi 2 O 3 electrode are studied in aqueous NaOH solution. The Bi 2 O 3 electrode exhibits very good electrochemical supercapacitive characteristics as well as stability in aqueous NaOH electrolyte. The effect of electrolyte concentration, scan rate, and number of cycles on the specific capacitance of Bi 2 O 3 electrodes has been studied. The highest specific capacitance achieved with the electrodeposited Bi 2 O 3 films is 98 F g −1 .
Principles and applications of electrochemical capacitors
Electrochimica Acta, 2000
Electrochemical capacitors (EC) also called 'supercapacitors' or 'ultracapacitors' store the energy in the electric field of the electrochemical double-layer. Use of high surface-area electrodes result in extremely large capacitance. Single cell voltage of ECs is typically limited to 1-3 V depending on the electrolyte used. Small electrochemical capacitors for low-voltage electronic applications have been commercially available for many years. Different applications demanding large ECs with high voltage and improved energy and power density are under discussion. Fundamental principles, performance, characteristics, present and future applications of electrochemical capacitors are presented in this communication.
Solid state electrolytes for electrochemical energy devices
Journal of Materials Science: Materials in Electronics, 2019
The modern technology needs the electrochemical energy devices with increased safety, larger power and energy densities in addition to long cycle lifetime. The solid state electrolytes (SSE) have been developed due to the dramatic development of portable consumer electronics and the increasing concerns on flexibility of energy-storage devices as well as the elimination of some drawbacks of the liquid electrolytes. This review introduces all types of the SSEs for various electrochemical devices including batteries, fuel cells, solar cells and supercapacitors (SCs) with an emphasis on the SCs. The review is followed by the presentation of new SSEs containing redox agents, nano metal oxides and carbon materials along with the other nano fillers. Herein, we show that the use of novel SSEs could contribute greatly to enhance the electrochemical performance of the energy related devices with improved specific capacitances, energy and power densities.
ACS Applied Materials & Interfaces, 2020
Electrolyte solutions and electrode active materials, as core components of energy storage devices, have a great impact on the overall performance. Currently, supercapacitors suffer from the drawbacks of low energy density and poor cyclic stability in typical alkaline aqueous electrolytes. Herein, the ultrathin Co 3 O 4 anode material is synthesized by a facile electrodeposition, followed by post-heat treatment process. It is found that the decomposition of active materials induces reduction of energy density and specific capacitance during electrochemical testing. Therefore, a new strategy of pre-adding Co 2+ cations to achieve the dissolution equilibrium of cobalt in active materials is proposed, which can improve the cyclic lifetime of electrode materials and broaden the operation window of electrochemical devices. Co 2+ and Li + embedded in carbon electrode during charging can enhance H + desorption energy barrier, further hampering the critical step of bulk water electrolysis. More importantly, the highly reversible chemical conversion mechanism between Co 3 O 4 and protons is demonstrated to be the fact that a large amount of quantum dots and second-order flaky CoO layers were in-situ formed in the electrochemical reaction process, which is firstly discovered and reported in neutral solutions. The as-assembled device achieves a high operation voltage (2.2 V), excellent cycling stability (capacitance retention of 168 % after 10000 cycles) and ultrahigh energy density (99 W h kg-1 at a power density of 1100 W kg-1). The as-prepared electrolytes and highly active electrode materials will open up new opportunities for aqueous supercapacitors with high safety, high voltage, high energy density and long-lifespan.