Electric Double Layer Capacitor Applications Research Articles

Enhancing EDLC applications with [BMIM]BF4-integrated cellulose gel electrolyte for sustainable energy storage

Researchers worldwide have extensively carried out the fabrication of supercapacitors using ionic liquid-based gel electrolytes. Gel polymer electrolytes (GPEs) are an excellent alternative electrolyte due to their high ionic conductivity and lack of safety issues associated with solid and liquid polymer electrolytes. This work highlights the performance of a GPE composed of 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM]BF4 mixed with ammonium nitrate (NH4NO3) as the charge carrier, entrapped in methylcellulose (MC) for its application as an electrolyte in supercapacitors. The results of the Fourier transform infrared spectroscopy (FTIR) study are in good agreement with the literature, confirming the interaction between the materials observed through the shifting of the hydroxyl band. Moreover, the addition of [BMIM]BF4 successfully reduced the degree of crystallinity and crystallite size, thus enhancing the amorphous region of the electrolytes, as observed in the X-ray diffraction (XRD) diffractogram. The sample with 10 wt% [BMIM]BF4 (IL10) exhibits the highest ambient conductivity of (2.44 ± 0.36) × 10−2 S cm−1. The obtained ionic transference number (tion) of 0.98 confirms that ions are the dominant charge carriers. Considering its electrochemically stability up to 2.6 V within a potential range of 3.0 V, the IL10 electrolyte was chosen as a separator for application in an electric double-layer capacitor (EDLC). The EDLC is characterized via cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) analysis.

Isinglass as an Alternative Biopolymer Membrane for Green Electrochemical Devices: Initial Studies of Application in Electric Double-Layer Capacitors and Future Perspectives.

The presented work discusses in detail the preparation of a cheap and environmentally friendly biopolymer membrane from isinglass and its physicochemical characterisation. One of the possible uses of the obtained membrane can be as a separator between electrodes in novel green electrochemical devices as in, for example, electric double-layer capacitors (EDLCs). The functionality of the mentioned membrane was investigated and demonstrated by classical electrochemical techniques such as cyclic voltammetry (CV), galvanostatic cycling with potential limitation (GCPL), and electrochemical impedance spectroscopy (EIS). The obtained values of capacitance (approximately 30 F g-1) and resistance (approximately. 3 Ohms), as well as the longevity of the EDLC during electrochemical floating at a voltage of 1.6 V (more than 200 h), show that the proposed biopolymer membrane could be an interesting alternative among the more environmentally friendly energy storage devices, while additionally it could be more economically justified.

Environmentally friendly plasticized electrolyte based on chitosan (CS): Potato starch (PS) polymers for EDLC application: Steps toward the greener energy storage devices derived from biopolymers

Biopolymer membranes derived from natural resources are environmentally friendly materials and their use for electrochemical energy storage devices has attracted a great deal of attention. Here, chitosan (CS) and potato starch (PS) doped with ammonium thiocyanate (NH4SCN) were used as host electrolyte. Various weight percent of glycerol (Gly) as a non-toxic plasticizer are used to prepare novel plasticized solid biopolymer electrolytes (PSBEs) through solution casting method, which is subsequently used as a mediator in electric double-layer capacitor (EDLC) application. Inclusion of Gly participated significantly in minimizing the crystallinity nature of the membranes as revealed by the X-ray diffraction (XRD) patterns. Fourier transform infrared (FTIR) spectroscopy revealed the complexation among the constituents of the electrolyte. Ion transport parameters determined by FTIR and electrochemical impedance spectroscopy (EIS) techniques have shown comparable results. The optimum composition of PSBE is achieved when 24 wt% of Gly is added (CPNHG3), which has shown the best ion conductivity (1.62×10−3Scm−1) from the EIS study. This film has exhibited also an excellent ion transference number (tion) of (0.989) and a large electrochemical potential stability (2.1 V) measured by transfer number measurement (TNM) and linear sweep voltammetry (LSV) methods. The restriction to ion movement was observed for the samples overloaded with Gly (32 and 40 wt%) due to the blockage effect, which reflected on ion conductivity and transport parameters. The assembled EDLC device provided a specific capacitance (Cspc) of 16.1 F/g at 10 mV/s scan rate with no sign of redox reaction, which was proven by either cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques. Further, the cyclic stability and high performance of the EDLC regarding energy density, power density, and coulombic efficiency were confirmed throughout the 2500 cycles.

Study on the reaction mechanism of the potassium bicarbonate alkali activation process in black liquor

The alkaline hydrothermal separation of cellulose is a crucial step in biofuel generation, wherein black liquor containing lignin and alkali is produced as a by-product. This study explored the reaction mechanism of the residual alkali during the activation process. In this reaction, the impregnated K reagent exhibited unusual behavior owing to its bonding with the lignin structure, which was confirmed by the K 2p peak shift in x-ray photoelectron spectra. This behavior resulted in the formation of a microporous and mesoporous substance with a high surface area of 2146 m2 g−1 without requiring additional chemical reagents. Furthermore, the activated carbon derived from black liquor possessed outstanding properties, allowing its use in supercapacitors. This study demonstrates that giant miscanthus-derived black liquor can be used as an activated carbon precursor for application in electric double-layer capacitors owing to its superior electrochemical capabilities.

Structural, thermal, and electrochemical studies on PVA-LiTf-TiO2 nanocomposite polymer electrolyte and the performance on electric double layer capacitor application

Structural, thermal, and electrochemical studies on PVA-LiTf-TiO2 nanocomposite polymer electrolyte and the performance on electric double layer capacitor application

All-solid-state electric double layer supercapacitors using Li1.3Al0.3Ti1.7(PO4)3 reinforced solid polymer electrolyte

In this work, we report the fabrication and characterization of all-solid-state supercapacitors based on a conductive filler dispersed solid polymer electrolyte. Fast ionic Li1.3Al0.3Ti1.7(PO4)3 (LATP) reinforced PEO-PEG-LITFSI composite solid polymer electrolyte (CSPE) membranes are prepared by milling assisted route. The electric double-layer capacitor (EDLC) cells, using a hot-roll lamination technique, are fabricated using a CSPE membrane as electrolyte and activated charcoal (surface area ∼ 817m2g−1) on graphite sheet as electrode. The EDLCs display appreciable areal capacitance of ∼ 12 Fcm−2 and ∼40 Fcm−2 at 40 °C and 80 °C, respectively at ∼0.65 mAcm2 and 2 V. These solid-state EDLCs at 40 °C exhibit stability up to ∼16,000 cycles. Further, the electrode-electrolyte (solid-solid) interface remains quite stable after the charge-discharge cycling. The electrical conductivity of the CSPE membranes correlates well with the EDLC performance. The LATP content in the CSPE membranes play important role in enhancing the capacitance. The present investigation suggests that CSPE membranes with conductivity between ∼10−4–10−5 Scm−1 are useful for low-power EDLC applications. The EDLCs cells with LATP dispersed CSPE exhibit better stability during thermal cycling between 40 °C-80 °C.

Sodium ion conducting flame-retardant gel polymer electrolyte for sodium batteries and electric double layer capacitors (EDLCs)

We report a trimethyl phosphate (TMP) based sodium ion conducting flame-retardant gel polymer electrolyte for safer electrochemical applications. The physical investigations reveal superior amorphicity and thermal stability of electrolyte utilizing TMP solvent as compared to the conventionally used binary mixture of ethylene carbonate (EC) and propylene carbonate (PC). The TMP based electrolyte membrane displays better ionic conductivity (∼ 1.40 mS cm−1) as compared to the membrane with EC:PC solvent mixture (∼ 0.72 mS cm−1) at 30°C with higher electrochemical stability window of ∼ 4.5 V and superior Na+ transport characteristics. The TMP based electrolyte has been utilized for proto-type sodium battery and EDLC application. The proto-type Na battery displays an open circuit potential of ∼ 2.3 V and specific discharge capacity of ∼ 225 mA h g−1. The electric double layer capacitor (EDLC) fabricated using the TMP based electrolyte and activated carbon electrodes shows specific capacitance of ∼100 F g−1 and is stable up to 4000 charge–discharge cycles.

Ion conducting methylcellulose‐polyvinyl alcohol blend based electrolytes incorporated with ammonium thiocyanate for electric double layer capacitor application

AbstractSolid polymer electrolytes (SPEs) have received numerous attention for application in energy storage devices due to their safety performance and mechanical flexibility. However, further improvement of amorphousness and electrochemical performance is needed to realize the commercial potential of SPEs. In this work, a series of methylcellulose (MC) – polyvinyl alcohol (PVA) blend‐based electrolyte doped with ammonium thiocyanate (NH4SCN) salt has been prepared using solvent casting technique. MC‐PVA‐NH4SCN electrolytes have been characterized and the most amorphous sample has been used as electrolyte in an electric double layer capacitor (EDLC). Thermogravimetric analysis is carried out to analyze the thermal stability of the electrolytes. From X‐ray diffraction analysis, the addition of salt up to 40 wt% decreases the percentage of crystallinity and crystallite size indicating the improvement in amorphousness of the polymer electrolytes. From transference number measurements analysis, it is revealed that ions are the dominant charge carriers. Linear sweep voltammetry shows that the most amorphous electrolyte is electrochemically stable in the potential range of −1.97 V to +1.90 V. Using the most amorphous MC‐PVA‐NH4SCN electrolyte, an EDLC has been fabricated and characterized using impedance technique, cyclic voltammetry and galvanostatic charge–discharge.

Design of plasticized proton conducting Chitosan:Dextran based biopolymer blend electrolytes for EDLC application: Structural, impedance and electrochemical studies

In this work, for the use of an electrical double-layer capacitor (EDLC) device applications, the fabrication and characterization of solid polymer electrolytes (SPEs) based on chitosan-dextran (CS-DN) blended polymer doped and plasticized with ammonium thiocyanate (NH 4 SCN) and glycerol are studied, respectively. The Fourier transform infrared (FTIR) spectroscopy method has been used to investigate the structural behavior of electrolytes. It was observed that the FTIR bands are shifted and decreased in their intensities with the increased glycerol plasticizer content and it results in the complex formation. According to the electrical impedance spectra (EIS), the electrolyte incorporated with high contents of plasticizer (42 wt%) revealed the highest ionic conductivity of (3.08 × 10 −4 S/cm). The electrical equivalent circuits (EEC) were used to investigate the circuit elements of the electrolytes further. Increasing glycerol plasticizers verified an improvement in ions density number (n), mobility (μ), and diffusion coefficient (D). The transference number measurements (TNM) indicated that the predominant charge carriers in the conduction process are ions where the ( t ion ) is 0.95. According to the linear sweep voltammetry (LSV) study, the uppermost conducting sample was found to have sufficient anode stability with a breakdown voltage of 1.9 V that can be used in electrochemical devices. The absence of peaks in the cyclic voltammetry (CV) demonstrated that the charge storage mechanism within the constructed EDLC is fully capacitive. Based on this finding, the starting specific capacitance ( C s ), energy density ( E d ), and power density ( P d ) have been identified to be 118F/g, 13.2 Wh/kg, and 1560 W/kg, respectively. Throughout its 100 cycles, the equivalence series resistance ESR value was between 53 and 117 Ω.

The effect of ionic liquid on the development of poly(vinyl alcohol) (PVA)-based ion conductors for electric double layer capacitors application

Poly(vinyl alcohol) (PVA)-lithium trifluoromethanesulfonate (also known as lithium triflate) (LiTf) polymer electrolytes incorporated with different weight ratios of ionic liquid, 1-butyl-3-methylimidazolium bromide (BmImBr), were prepared by solution casting method. Upon the addition of 50 wt% BmImBr, the ionic conductivity increases from (9.73 ± 0.04) × 10−6 S cm−1 to (1.96 ± 0.01) × 10−4 S cm−1 at room temperature. Besides, the ionic liquid free-polymer electrolyte obeys the Arrhenius theory which is related to thermally-activated principle. The glass transition temperature (Tg) of polymer electrolytes also demonstrate a decreasing trend in Differential Scanning Calorimetry (DSC) thermogram. This decrease in Tg is mainly due to the plasticising effect of BmImBr. The Fourier-Transform Infrared (FTIR) studies indicate complexation between the PVA, LiTf and BmImBr. The fabricated EDLC demonstrate its specific capacitance of 19.5 Fg−1, energy density of 1.4 W h kg−1 and power density of 15 kW kg−1.

Correction to: Ion transport, dielectric and electrochemical properties of sodium ion-conducting polymer nanocomposite: application in EDLC

The present paper reports the investigation of structural, electrical, dielectric, and transport properties of the polyethylene oxide (PEO)-based polymer nanocomposite (PNC), with sodium hexafluorophosphate (NaPF6) salt and barium titanate (BaTiO3) as nanofillers. The PNC has been prepared via standard solution casting technique. The structural investigation has been investigated by X-ray diffraction and evidence the enhancement in amorphous content. The presence of polymer–ion and ion–ion interaction has been confirmed by the Fourier transform infrared spectra (FTIR) and evidences the PNC formation. The impedance spectroscopy has been performed to evaluate the ionic conductivity in the temperature range 40–100 °C. The increase of conductivity is obtained with the addition of nanofiller and temperature-dependent conductivity follows Arrhenius behavior. The PNC film having the highest conductivity exhibits low activation energy and indicates the fast ion migration. The ion transference number is close to unity and the voltage stability window is within the desirable limit. The complex permittivity and complex conductivity have been obtained and the plot has been fitted in the whole frequency window. The fitted plot is in perfect agreement with experimental data. The PNC having the highest conductivity has high dielectric strength and low relaxation time. It confirms the nanofiller role in enhancing ion migration. The ion transport parameters (n, μ, D) are also in correlation with impedance and dielectric analysis. The optimized PNC films have been used to prepare the Electric double-layer capacitors (EDLC) and it demonstrates the improved performance which may be attributed to the effective role played by nanofiller in boosting ion dynamics.

Development of poly(vinyl alcohol) (PVA)-based sodium ion conductors for electric double-layer capacitors application

In this work, ionic liquid, poly(vinyl alcohol) (PVA)-based sodium ion conductors were prepared by solution casting technique. The additives-free ion conductors illustrated poor ionic conductivity which is not applicable in any electrochemical device. Therefore, ionic liquid was added to improve the ionic conductivity of polymer electrolytes. Ionic liquid, 1-butyl-3-methylimidazolium bromide (BmImBr)-added solid polymer electrolytes comprising poly(vinyl alcohol) (PVA) and sodium acetate trihydrate (CH3COONa·3H2O) was investigated. The ionic conductivity of BmImBr-added polymer electrolyte (PE) showed an increment about five orders of magnitude from (1.07 ± 0.03) × 10−8 S cm−1 to (1.95 ± 0.01) × 10−3 S cm−1 with doping of 20 wt% of BmImBr under ambient temperature. The BmImBr-added PEs obey the Vogel–Tamman–Fulcher (VTF) theory. The plasticizing effect of BmImBr reduces the glass transition temperature (Tg) of the PEs. Complexation between PVA, CH3COONa·3H2O, and BmImBr was proven in Fourier-transform Infrared (FTIR) spectroscopy studies. Quantitative analysis of the interaction between PVA, CH3COONa·3H2O, and BmImBr was also scrutinized in FTIR study. The electrochemical potential window of the electrolyte was wider upon the addition of ionic liquid. Electric double-layer capacitors (EDLCs) were assembled. The assembled EDLC illustrated a specific capacitance of 0.684F g−1 with excellent electrochemical stability.

Plasticized H+ ion-conducting PVA:CS-based polymer blend electrolytes for energy storage EDLC application

In this work, plasticized proton-conducting polymer blend electrolytes based on poly (vinyl alcohol): chitosan were synthesized, characterized, and utilized in an electric double-layer capacitor (EDLC). A structural study was performed using X-ray diffraction. The scarification and decrease of intensity of the crystalline peak were detected upon the addition of glycerol plasticizer (GP). The morphological appearance of the plasticized blend electrolyte films was examined through scanning electron microscopy, in which the role of GP on ion dissociation was indicated to be important. Electrochemical impedance spectroscopy was performed to estimate the conductivity of the films. Before the EDLC application, other electrochemical techniques, such as transference number measurement (TNM), linear sweep voltammetry (LSV), and cyclic voltammetry (CV), were carried out. To evaluate the performance of the EDLC, the charge–discharge profile was then examined. The EDLC has been cycled 250 times at a current density of 0.75 mA cm−2. The specific capacitance (Cspe) of the EDLC, which is known as an essential parameter, was found to be constant after the first cycle. The reduction in Cspe value was correlated with the increase of equivalent series resistance. Finally, the manners of energy (E) and power (P) densities as a function of the number of cycles were studied.

Metal framework as a novel approach for the fabrication of electric double layer capacitor device with high energy density using plasticized Poly(vinyl alcohol): Ammonium thiocyanate based polymer electrolyte

High performance electric double-layer capacitors (EDLCs) based on poly (vinyl alcohol) (PVA): ammonium thiocyanate (NH4SCN):Cu(II)-complex plasticized with glycerol (GLY) have been fabricated. The maximum DC ionic conductivity (σDC) of 2.25 × 10-3 S cm−1 is achieved at ambient temperature. The X-ray diffraction (XRD) patterns confirmed that the addition of both Cu(II)–complex and GLY enhanced the amorphous region within the samples. Through the Fourier transform infrared (FTIR) the interactions between the host polymer and other components of the prepared electrolyte are observed. The FESEM images reveal that the surface morphology of the samples showed a uniform smooth surface at high GLY concentration. This is in good agreement with the XRD and FTIR results. Transference numbers of ion (tion) and electron (tel) for the highest conducting composite polymer electrolyte (CPE) are recognized to be 0.971 and 0.029, respectively. The linear sweep voltammetry (LSV) revealed that the electrochemical stability window for the CPE is 2.15 V. These high values of tion and potential stability established the suitability of the synthesized systems for EDLC application. Cyclic voltammetry (CV) offered nearly rectangular shape with the lack of Faradaic peak. The specific capacitance and energy density of the EDLC are nearly constant within 1000 cycles at a current density of 0.5 mA/cm2 with average of 155.322F/g and 17.473 Wh/Kg, respectively. The energy density of the EDLC in the current work is in the range of battery specific energy. The EDLC performance was found to be stable over 1000 cycles. The low value of equivalent series resistance reveals that the EDLC has good electrolyte-electrode contact. The EDLC exhibited the initial high power density of 4.960 × 103 W/Kg.

Preparation of layered-porous carbon from coal tar pitch narrow fractions by single-solvent extraction for superior cycling stability electric double layer capacitor application

Coal tar pitch (CTP) with high carbon content and wide source of raw materials was an excellent precursor for the preparation of porous carbons (PCs). CTP was composed of polycyclic aromatic hydrocarbons (PAHs) with complex molecular size and chemical structure, the separation of CTP into several fractions with relatively narrow molecular weight by solvent extraction was of significance for CTP utilization. In this paper, CTP was treated by single-solvent extraction (carbon disulfide, acetone and ethyl acetate), and the six fractions were used as raw materials to prepare PCs as electrode material for electric double layer capacitor. The fractions were well characterized and the effect of mass distribution of different narrow fractions on structure property and electrochemical performance of the PCs was studied. The PCs prepared by carbon disulfide extract, acetone raffinate and ethyl acetate extract, containing more PAHs, exhibited the excellent specific capacitance performance in comparison with its residual components. The remarkable performance might contribute in the enhanced transport of electrolyte ions via the molecular graphene structure of PAHs. Additionally, the PC prepared by carbon disulfide raffinate showed outstanding cycling performance (99.7% at 2 A g−1 after 15,000 cycles) which was related to its unique layered porous structure.

Electrical, thermal, and structural studies on highly conducting additive-free biopolymer electrolytes for electric double-layer capacitor application

Biopolymer electrolytes consisting of poly(vinyl alcohol) (PVA) and lithium trifluoromethanesulfonate (LiTf) were prepared by solution casting technique. The ionic conductivity of polymer electrolyte is increased about seven orders of magnitude which is from 3.53 ± 0.01 × 10−10 to 2.87 ± 0.01 × 10−3 S cm−1 at ambient temperature with the addition of 40 wt% of LiTf. All the polymer electrolytes follow Vogel–Tamman–Fulcher (VTF) relationship which is associated with free volume theory. The complexation between PVA and LiTf salt is proven by Fourier transform infrared spectroscopy (FTIR) study. The glass transition temperature (Tg) of polymer electrolyte was decreased with the addition of LiTf as shown in differential scanning calorimetry (DSC) thermogram. The potential difference of the polymer electrolyte showed wider range, up to 4.6 V, as proven in linear sweep voltammetry (LSV) study. Electric double-layer capacitor (EDLC) cell was assembled using prepared polymer electrolytes and two identical activated carbon-based electrodes and its electrochemical properties were also investigated. The specific capacitance of 0.37 F g−1 was obtained for the EDLC with the most conducting polymer electrolyte.

Investigation of plasticized ionic conductor based on chitosan and ammonium bromide for EDLC application

Abstract Chitosan-based polymer electrolytes incorporated with ammonium bromide (NH4Br) and glycerol were produced via solution casting technique. Characteristics of these electrolytes were examined using impedance technique, transport number measurement (TNM) and linear scan voltammetry (LSV). Based on the results obtained from impedance measurement, the sample with 40 wt.% glycerol achieved the highest ac and dc conductivies at room temperature. Dielectric behavior of the electrolytes was found to be improved upon incorporation of 40 wt.% glycerol, suggesting their relation with the conductivity trend. Result of TNM revealed that the conductivity has a huge contribution from ions. LSV analysis at 5 mV/s sweep rate showed that the best conducting sample is suitable for electrical double layer capacitor (EDLC) application. Specific capacitance (Cs) of the single carbon based electrode was determined from cyclic voltammetry (CV) technique.

1,1-Dimethylpyrrolidinium tetrafluoroborate as novel salt for high-voltage electric double-layer capacitors

A novel quaternary ammonium salt—1,1-dimethylpyrrolidinium tetrafluoroborate (DMPBF4), tetraethylammonium tetrafluoroborate (TEABF4), and spiro-(1,1′)-bipyrrolidinium tetrafluoroborate (SBPBF4) were prepared and dissolved in acetonitrile (ACN) and propylene carbonate (PC) for electrolyte systems of electric double-layer capacitors (EDLC). Physical properties such as thermal stability, solubility, and ionic conductivity were determined and six different electrolyte systems with 1 M concentration were electrochemically evaluated by linear sweep voltammetry, cyclic voltammetry, galvanostatic charge-discharge, and float test. To investigate the origin of the physical and electrochemical properties at the molecular level, quantum calculations for the chemical species in the electrolytes were also carried out. Compared to the standard electrolytes TEABF4 and SBPBF4, the novel DMPBF4 electrolyte exhibits a higher gravimetric capacitance, superior rate capability, and improved cycling stability. The energy and power density of EDLCs using DMPBF4 in the ACN electrolyte reach 40.61 Wh kg−1 and 8.09 kW kg−1, respectively, at the working voltage of 3.0 V. Moreover, EDLCs with DMPBF4 in ACN (PC) retain 87.9% (87.5%) of their initial capacitance after 1000 h of float testing at 3.0 V. The results indicate that DMPBF4 can be a promising electrolyte salt for EDLC application.

Preparation of thin-film electrolyte from chitosan-containing ionic liquid for application to electric double-layer capacitors

A novel thin-film electrolyte (TFE) based on chitosan (CS) with 1‑ethyl‑3‑methylimidazolium tetrafluoroborate (EMImBF4) was prepared by a new procedure for use as a solid electrolyte in electric double-layer capacitors (EDLCs). In this system, EMImBF4 plays important roles as both a dissolving solution and a charge carrier for EDLC application. By analyzing and characterizing the obtained products, the CS-TFEs showed a surface without CS/EMImBF4 phase separation and with high thermal stability and good tensile properties. The electrochemical properties were measured as the charge–discharge performance, the discharge capacitance, and alternating-current impedance. A test cell with CS-TFE with a calculated dry thin-film content of 80 wt% EMImBF4 showed a comparable IR drop and higher discharge capacitance than a liquid-phase EMImBF4 system and also showed low electrode/electrolyte interfacial resistance. Consequently, this novel CS-TFE is suitable for high-performance EDLCs and improves the safety of such devices.

Oxygen-rich Hierarchical Porous Carbon Derived from Coal Tar Pitch for Superior Electric Double Layer Capacitor Application

Oxygen-rich Hierarchical Porous Carbon Derived from Coal Tar Pitch for Superior Electric Double Layer Capacitor Application