Redox Additive Electrolyte Research Articles

A redox additive electrolyte boosted supercapacitive energy density of wrinkled RGO sheets

Redox additive (RA)-based electrolytes have emerged as a promising approach to enhance the performance of carbon-based supercapacitors (SCs) as they bestow the additional pseudocapacitance to carbon and enhance its energy density (Ed). The present study demonstrates the enhanced supercapacitive Ed of reduced graphene oxide (RGO) electrodes by employing an RA of 0.05 M K4[Fe(CN)6] (KFC) in 0.5 M K2SO4 (K2) electrolytes. To enhance the active surface area (confirmed by N2 absorption- desorption) with minor agglomeration (confirmed by morphological analysis) and less defective (confirmed by Raman analysis) wrinkled RGO sheets were synthesized through thermal reduction of GO. The RGO electrode obtained 3 times higher specific capacitance (CS) in K2+ KFC as compared to the K2 electrolyte. The assembled RGO-based symmetric aqueous device shows CS of 79.5 F/g and 66 mAh/g of specific capacity (CPS) at 5 mV/s with 36.8 Wh/kg Ed, 1.2 kW/kg of Pd at 15 mA, and 134 % capacitance retention over 5000 galvanostatic charge-discharge cycles in K2 + KFC electrolyte. The obtained results demonstrated the incorporation of a tiny amount of RA in supporting electrolytes can significantly enhance the electrochemical performance and pave the way for future advanced energy storage technology.

Doable high energy density supercapacitors using rice husk-derived carbon in dihydroxybenzenes as redox-additive electrolytes

Though activated carbon made from various bio wastes is quite affordable and plentiful, the energy density of these electrodes in aqueous electrolytes is still questionable. Therefore, increasing the energy density of activated carbon for use in supercapacitors is a challenging issue. The ideal way to boost the energy density of supercapacitors in aqueous electrolytes is by using redox-additive electrolytes. Redox-additive electrolytes are the impeccable solution for thriving the energy density of supercapacitors in aqueous electrolytes. Here, three additives namely 1, 2-benzene diol, 1, 3-benzene diol, and 1, 4-benzene diol were utilized as redox-additives with 1 M H2SO4 to study the influence of the position of OH on their redox activity and electrochemical performance. The activated carbon derived from rice-husk delivered a high specific capacitance of 1414 F/g at 4 A/g with 1, 4-benzene diol/H2SO4 among the three redox additives. A symmetric supercapacitor was fabricated, which exhibited a remarkable energy density of 38 Wh/kg at 2 A/g with 1, 4-benzene diol/H2SO4, which is almost 4 times superior to the energy density of the same electrode with H2SO4 (10.6 Wh/kg at 2 A/g).

Studies on sustainable CuO/ZnO@MWCNT electrodes and their supercapacitive performances in redox additive electrolyte

Supercapacitive performances of copper oxide and zinc oxide loaded multiwalled carbon nanotube (CuO/ZnO@MWCNT - CZM) nanocomposites (NCs) in redox additive electrolyte were reported. CZM NCs were hydrothermally synthesized and calcinated at 500 °C for 5 h. The structural characteristics of the prepared NCs were examined using powder X-ray diffraction analysis. Scanning electron microscopy and vibrational spectroscopy techniques were employed to analyse the surface features and molecular interactions of the prepared NCs, respectively. The working electrodes were fabricated using CZM NCs and tested in pure 3 M potassium hydroxide (KOH) and 0.2 M potassium ferrocyanide added 3 M KOH electrolytes (K4[Fe(CN)6] – RAE). Fabricated electrode exhibited the specific capacitances of 199.4 Fg−1 (at 8 Ag−1) in KOH and 1829.43 Fg−1 (at 15 Ag−1) in RAE, respectively. Furthermore, an asymmetrical-type supercapacitor was constructed using CZM NCs and activated carbon-coated Ni foil as the working and counter electrodes, respectively. Fabricated device demonstrated 18.5 W h kg−1 and 1875 W kg−1 of energy and power densities, respectively, with 83.05 Fg−1 of specific capacitance in RAE. Electrochemical studies confirmed that the prepared CZM NCs demonstrated superior performances in RAE.

Effect of Redox Additive in Aqueous Electrolyte for Electrochemical Energy Storage Applications of A and B Site Ordered LaCaCoCrO6 Double Perovskite

The surge in demand for energy storage devices has increased research interest in electrochemical energy storage. Herein, a novel LaCaCoCrO6 double perovskite using a one‐step hydrothermal process for energy storage applications is synthesized. X‐ray diffraction analysis confirms the pure orthorhombic phase of A and B site ordered LaCaCoCrO6 with Pbnm symmetry. Scanning and transmission microscopy images reveal that the synthesized material forms spheres composed of nanocrystallite aggregates. The electrochemical analysis reveals the faradaic redox behavior of LaCaCoCrO6 in redox additive electrolyte and 6 m KOH aqueous electrolyte, with a specific capacitance of ≈511 and ≈114 F g−1, respectively, at 2 A g−1. As compared to the conventional KOH electrolyte, the value of specific capacitance is substantially improved. These findings suggest that LaCaCoCrO6 has the potential as an electrode material for the development of efficient and reliable energy storage devices.

Redox additives dependent supercapacitor performances of ZnO/SnO2@MWCNT nanocomposites

The poor cyclic stability arose from the low conductivity and strong electrostatic interaction between the ions remain the formidable challenge on the development of ZnO/SnO2 based electrodes for high-performance supercapacitor devices. Herein, an effective strategy was developed to achieve the higher conductivity by the growth of ZnO/SnO2 nanocomposites (NCs) on multiwalled carbon nanotube (MWCNT) through hydrothermal approach. Physiochemical characteristics of the synthesized ZnO/SnO2@MWCNT (ZSM) NCs were investigated by the XRD, FT-IR, SEM, HR-TEM, and XPS analyses. The fabricated working electrodes performances were examined for supercapacitor devices under pure 1 M Na2SO4 (NSE) and 0.1 M K4[Fe(CN)6] added redox additive electrolytes (RAE). The fabricated working electrode showed 297 Fg−1 specific capacitance in NSE and it was increased to 3885 Fg−1 under RAE. The fabricated working electrode possessed the cyclic retention of 81.15 % even after consecutive 5000 GCD cycles and it was enhanced up to 84.42 % in RAE. Also, incorporation of redox additives, greatly enhanced the energy and power densities of the fabricated device and they were found to be 22.50 Whkg−1 and 3200 Wkg−1, respectively in RAE. It confirmed that the incorporation of MWCNT in electrode material and RAE, greatly improved the overall efficiency of the ZnO/SnO2 based supercapacitors.

Improved electrochemical performance of nanostructured binder free Cu2CoSnS4 electrode using redox additive electrolyte

Improved electrochemical performance of nanostructured binder free Cu2CoSnS4 electrode using redox additive electrolyte

Zeolitic Imidazolate Framework-8 and redox-additive electrolyte based asymmetric supercapacitor: A synergetic combination for ultrahigh energy and power density

In the present work, the electrochemical study of the synthesized electrode (ZIF-8 at 300 °C named as Z1) material was done in a three- and two-electrode (device) assembly using non redox-additive (6 M NaOH) and redox-additive (0.35 M K4(Fe(CN)6).3H2O in 6 M NaOH) electrolyte (RAE). X-ray diffraction (XRD) of Z1 sample confirmed the cubic phase with I -43 m space group. The hexagonal-type morphology was revealed by high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) analysis. The formation of narrow mesopores with average pore diameter of 1.53 nm and a large specific surface area of 1272 m2/g was confirmed by Brunauer-Emmett-Teller (BET) examination. The thermal stability of pristine ZIF-8 is investigated by Thermogravimetric analysis (TGA). In the three-electrode system, the Z1 sample as electrode reveals the pseudocapacitive (in NaOH) and battery-like redox behavior (in RAE). The fabricated electrode provides the specific capacitance of 30.6 F/g (1 A/g) and 33.1 F/g (10 mV/s) in NaOH. Moreover, the Z1 electrode exhibited an excellent specific capacity of 500.0C/g (at 10 A/g) and 532.5C/g (at 10 mV/s) in RAE. Additionally, an asymmetric supercapacitor (ASSC) device was assembled via RAE with activated carbon (AC) as an anode and Z1 as a cathode to investigate the practical feasibility. The constructed device in 0.0–2.0 V voltage window provides a significant power density of 20,000 W/Kg (for an energy density of 38.89 Wh/kg at 40 A/g) and an outstanding energy density of 75 Wh/kg (for a power density of 10,000 W/kg at 20 A/g). It exhibits good capacitance retention (80 % at 20 A/g) after 1500 cycles. Furthermore, three ASSC devices are connected in series to illuminate green, yellow, white, and red Light Emitting Diodes, thus demonstrating the potential realistic advantage of the current research work in supercapacitive energy storage devices.

Enhanced Electrochemical Performance of BiOCl Nanoflower-RGO Based Supercapacitor in the Presence of Redox Additive Electrolyte

Bismuth oxychloride (BiOCl) nanoflowers and bismuth oxychloride/reduced graphene oxide (BiOCl/rGO) composites with different weight percentage were prepared by solvothermal method. BiOCl/rGO hybrids electrode based symmetric solid state supercapacitor was fabricated by sandwiching alkaline polyvinyl alcohol (PVA/KOH) gel electrolyte in presence and absence of potassium iodide (KI). It delivered maximum specific capacitance of 611 F g−1 in presence of PVA/KOH+KI gel electrolytes, increasing by 8.75% compared to the PVA/KOH based supercapacitor. The energy and power density of the supercapacitor in presence of PVA/KOH+KI were reached 21.21 Wh kg−1 and 1.37 kW kg−1 respectively. The supercapacitor exhibits 90% capacitance retention even after 10 000 cycles.

Investigating the effect of electrolyte and its concentration dependence on WO3 nanosheet as an efficient electrode for supercapacitors: Effect of Redox Additive

This research aimed to synthesize non-uniform nanosheet-like tungstate oxide (WO3) using a simple hydrothermal process, which would result in an effective and environment-friendly material for use in supercapacitors (SCs). The resulting materials are thoroughly examined using physio-chemical techniques. The supercapacitive properties of the WO3–Ni-Foam (NF) were examined using 1 M KOH, NaOH, and LiOH electrolytes and further, the electrochemical performance of the WO3–NF electrode was assessed by changing the concentration of KOH electrolytes from 1 to 4 M respectively. The WO3–NF electrode demonstrated the highest specific capacity (Csp) of 70 mAh/g and capacitance (Cs) of 563 F/g with a high energy density of 16 Wh/kg, and power density of 281 W/kg in 2 M KOH electrolyte respectively. Additionally, the WO3–NF electrode showed excellent Columbic efficiency of 98% and long-term capacitive retention of 88% over 5000 cycles in 2 M KOH electrolyte. Additionally, the effect of redox additive (0.01 M of potassium ferrocyanide) improves the electrochemical performance of WO3–NF; the Csp and Cs values were 137 mAh/g, 618 F/g and 100 mAh/g, 800 F/g at 5 mV/s and 5 mA/cm2, respectively. Furthermore, the WO3–NF electrode exhibits good stability retention of 94% over the 2000 cycles. The electrochemical performance of WO3 nanosheets for energy storage applications was improved by this straightforward hydrothermal method and evaluating the effect of redox additive electrolyte.

High-performance carbon-fiber-based supercapacitors: Enhanced performance through the porosity modification of electrodes containing a redox mediator

Carbon-fiber-based supercapacitors (CFS) are emerging as a prospective option for innovative wearable energy storage devices by reason of their safety, environmental compatibility, and high power density. However, the limited practical application of CFS is attributed to its poor energy storage performance, which is caused by the carbon fiber electrode's limited specific surface area and low wetting ability. To address this, this study developed a CFS with micro-meso porous carbon fibers electrodes and a redox additive electrolyte (CFS-MMRE). The CFS-MMRE showed exceptional energy storage capaability, high specific capacitance of 876 mF cm−2 at 70 μA cm−2, respectively, cycling stability over 5,000 cycles with 70 % capacitance retention at 400 μA cm−2. Moreover, CFS-MMRE possesses mechanical pliability, high achievability, and remarkable energy storage performance, which make them a viable choice for wearable electronic devices.

Designing and fabricating high-performance supercapacitor based on defective mesoporous carbon as electrode and Disperse Blue 6 as novel redox additive electrolyte

Designing and fabricating high-performance supercapacitor based on defective mesoporous carbon as electrode and Disperse Blue 6 as novel redox additive electrolyte

Enhanced electrochemical performance of CuCo2O4 nanowire arrays based solid-state symmetric supercapacitor by K3[Fe(CN)6] redox additive electrolyte

The redox additive in an aqueous gel electrolyte is reported as one of the efficient methods to improve the electrochemical supercapacitor performance. Here, we report the role of redox additive, potassium ferricyanide((K3[Fe(CN)6]), referred to as KFCN) for improving the electrochemical performance of binder-free, CuCo2O4 (CCO) nanowire arrays (NWs) based solid state symmetric supercapacitors (SSCs). The crystal structure and morphology of prepared CCO films are confirmed by X-ray diffraction (XRD) and field emission-transmission electron microscopy (FE-TEM). The elemental composition of CCO films is estimated as Cu0.5Co2.77O3.82 via energy-dispersive X-ray spectroscopy (EDS) analysis. Surprisingly, the areal capacitance (or energy density at 5 mAcm−2) is significantly improved from 0.58 F cm−2 (or 0.016 mWh cm−2) to 10.5 F cm−2 (or 0.296 mWh cm−2), respectively, after the addition of KFCN to aqueous KOH electrolyte, as compared to bare KOH. Furthermore, CCO exhibits decent cyclic stability with 90 % capacitance retention up to 5000 CV cycles at the scan rate of 100 mV s−1. Moreover, 2-terminal CCO NWs-based SSCs, employed with PVA-KOH-KFCN gel electrolyte, demonstrate a wider potential window of −0.9 to 0.9 V (1.8 V) with a 7-fold increase of energy density from 9.1 to 65 Wh kg−1, as compared with that of PVA-KOH gel electrolyte. As practical validation, the operation of Red-LED for 3 min is demonstrated with PVA-KOH-KFCN gel-based SSC, manifesting that adding redox substance in aqueous electrolytes is one of the promising strategies for portable and wearable energy storage systems.

Synthesis and characterization of polyaniline nanotube supported nanocomposite of RuO2 as electrode material for application in supercapacitor device

With the rapid development of nanotechnology, the study of nanocomposites as electrode materials has significantly enhanced the scope of research towards energy storage applications. Exploring electrode material with superior electrochemical properties is still a challenge for high-performance supercapacitors. In the present research article, the synthesis and characterization of a novel nanocomposite of RuO2 nanoparticles grown over supported matrix of polyaniline nanotube (PNT) is reported. The nanocomposite (PNT/RuO2) is structurally characterized by X-ray diffraction (XRD) which reveal that the formed nanocomposite is highly amorphous in nature which is beneficial for the permeation of electrolytic ions through the electrodic matrix. Thermograms suggest that 25% of RuO2 nanoparticles are adsorbed on PNT's surface, with PNT serving as the supporting matrix. The composition of PNT/RuO2 is found to be ∼ 3:1. TEM micrographs show that PNT is acting as a supporting matrix having length ∼2-4μm and diameter ∼125 nm for the growth of RuO2 nanoparticles in PNT/RuO2 nanocomposite. The globular shaped RuO2 nanoparticles with diameter ∼220 nm are formed which are highly interconnected with each other. The surface morphology is characterized by Scanning Electron Microscope (SEM) which shows that the PNT/RuO2 nanocomposite is of dense morphology and RuO2 nanoparticles has enfolded the PNT throughout due to which it is anaalysed that the interconnectivity between the chains of PNT has also increased. The electrochemical characterization carried out in three electrode cell shows that the PNT/RuO2 nanocomposite shows specific capacitance ∼1140 F/g at 5 mV/s. Further, the electrochemical characterizations are also carried out in redox additive electrolyte hydroquinone/H2SO4 where hydroquinone acts as redox additive. The result show that the specific capacitance of PNT/RuO2 nanocomposite is ∼ 828 F/g at 5 mV/s retaining good rate capability, ∼ 45 % decay has been observed as the scan rate increases from 5 to 100 mV/s. These characteristic suggest that it could be used as potential electrode material for supercapacitor.

Fabrication of ultrahigh-performance asymmetrical supercapacitor with pristine Zeolitic Imidazolate Framework-8 and a redox additive electrolyte

In the present work, Zeolitic Imidazolate Framework-8 (ZIF-8) was prepared at room temperature using a simple solvothermal method. X-ray diffraction revealed the formation of a cubic phase with I −43 m space group. Scanning Electron Microscopy and High Resolution Transmission Electron Microscopy analysis showed the hexagonal-type morphology of as prepared pure ZIF-8. Brunauer–Emmett–Teller analysis, confirmed the formation of a narrow mesopores having surface area (877 m2/g) and average pore diameter (1.16 nm). The prepared ZIF-8 as electrode material investigated in aqueous (i.e. 2 M LiOH, 6 M KOH, and 6 M NaOH) and redox additive electrolytes RAE1 and RAE2 (i.e. 0.35 M [K4(Fe (CN)6)].3H2O in 6 M NaOH and 0.17 M [K4(Fe (CN)6)].3H2O in 1 M Na2SO4) for electrochemical analysis. The fabricated pristine ZIF-8 shows battery-type redox behavior in the three-electrode system in presence of redox additive electrolyte (RAE) and ultrahigh specific capacity (637.5 C/g) is obtained in RAE1 at a current density of 10 A/g. Furthermore, this electrode could maintain about 75% of its initial capacitance at 20 A/g after 1500 repeated charge-discharge cycles. In addition, an asymmetric supercapacitor (ASSC) device was constructed with graphene nanoplatelets (GNPs) as a negative electrode and pure ZIF-8 as a positive electrode. In the presence of RAE1, the fabricated device offers a significant energy density E of 36.91 Wh/kg at a power density P of 4429.08 W/kg in a wide voltage window range (0.0–1.9 V). The ASSC device retains 87% of its capacitance after 3200 galvanostatic charge-discharge cycles. Moreover, two asymmetric devices are joined in series to light up red and green LEDs for a practical utility.

Defective mesoporous carbon coupled with a redox additive electrolyte for high performance supercapacitor

Defective mesoporous carbon coupled with a redox additive electrolyte for high performance supercapacitor

Role of various redox additive electrolytes on the electrochemical performances of mixed metal oxide loaded multiwalled carbon nanotube based supercapacitors

Electrochemical performances of the Zinc oxide/Nickel oxide loaded multi-walled carbon nanotubes (ZnO/NiO@MWCNT - ZNC) were evaluated under different electrolytes. ZNC nanocomposites (NCs), has been successfully synthesized by a simple one-step hydrothermal method and calcinated at 500 °C. The crystalline phases of ZnO, NiO, and MWCNT, present in the prepared NCs were studied by the X-ray diffraction (XRD) analysis and their structural characteristics were revealed. The calcinated samples were further characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopic (FT-IR) techniques to evaluate the morphological and functional behaviours, respectively. ZNC NCs modified working electrodes were fabricated using the doctor blade technique and their electrochemical performances were tested using different electrolytes (pure and redox additive added electrolytes), such as 1 M KOH, 1 M KOH + 0.1 M K4[Fe(CN)6], 1 M Na2SO4 and 1 M Na2SO4 + 0.1 M K4[Fe(CN)6]. Among these electrolytes, ZNC NCs modified working electrode possessed the superior electrochemical performance with the specific capacitance value of 1988.8 Fg−1 under 0.1 M K4[Fe(CN)6] added 1 M Na2SO4 aqueous electrolyte and achieved a superior specific capacitance retention of 97.2 % after 2000 GCD cycles. The fabricated asymmetrical type supercapacitors possessed the superior energy and power densities of 43.59 W h kg−1 and 4000 W kg−1, respectively under the freshly prepared redox additives added Na2SO4 aqueous electrolyte.

Significance of Redox Additive Electrolyte over Energy and Power Densities of Mixed Metal Vanadate-Based Supercapattery Device

Significance of Redox Additive Electrolyte over Energy and Power Densities of Mixed Metal Vanadate-Based Supercapattery Device

Enhanced supercapacitor performance of ZnO/SnO2:rGO nanocomposites under redox additive electrolyte

Supercapacitor performances of ZnO/SnO2 mixed metal oxides (ZS) and mixed metal oxides loaded reduced graphene oxide (ZnO/SnO2:rGO - ZSR) nanocomposites (NCs) were reported. A simple one-pot hydrothermal method was adopted to prepare ZS and ZSR NCs and the prepared NCs were analytically characterized by XRD, SEM, FT-IR, XPS and HRTEM analyses. XRD analysis confirmed the presence of hexagonal-structured ZnO and orthorhombic-structured SnO2 nanoparticles in ZS and ZSR NCs, respectively. The presence of ZnO nanospheres and SnO2 nanorods loaded rGO nanosheets were identified by SEM and HRTEM analyses. The electrochemical characteristics of the ZS and ZSR NCs were tested under 1 M Na2SO4 (NS) and redox additive electrolytes (RAE). The ZSR NCs modified working electrodes possessed the superior specific capacitance of 3238 Fg−1 in RAE with the electrochemical capacitance retention of 91.54% after 5000 GCD cycles. Similarly, the fabricated ZSR NCs-based asymmetrical supercapacitors revealed the highest specific capacitance of 89.19 Fg−1 with the energy and power density values of 17.34 W h kg−1 and 2000 W kg−1, respectively under redox additive electrolytes.

Self-supporting electrode for flexible supercapacitors: NiCo-layered double hydroxide derived from metal organic frameworks wrapped on graphene/polyaniline nanotubes@cotton cloth

Nowadays, constructing hetero-structure materials is an efficacious procedure to uplift the electrochemical performance of layered double hydroxide (LDH) materials. The logical design of such elegant nanostructures is still challenging. Herein, NiCo-LDH nanosheets derived from Co-ZIF grown on graphene/polyaniline nanotube (G/PANI-NT)@cotton cloth (CC) was synthesized by a facile and novel two-step strategy for supercapacitors. Such hetero-structures give a 30.63 m2 g−1 surface area and more subjected electrochemical active sites. The supercapacitor performance results exhibit that the NiCo-LDH/G/PANI-NT@CC electrode has the best supercapacitor performance when it is used as a pseudocapacitor. By the ratio of Ni/Co = 2:1 in the precursor solution, the electrode shows an areal specific capacitance of 88.15 mF cm−2 at a current density of 0.075 mA cm−2. The electrochemical performance of the electrodes was perused using a redox-additive electrolyte. The electrochemical performance of the NiCo-LDH/G/PANI-NT@CC electrode was amended using K2S2O8 in a 3 M KOH solution. Considerably, the areal specific capacitance of NiCo-LDH/G/PANI-NT@CC (181.17 mF cm−2) increased to 431.30 mF cm−2, by changing the K2S2O8 concentration in KOH solution at a current density of 0.075 mA cm−2. Long-term stability test demonstrates that 84.05 % of the original capacitance remains after 10,000 cycles at the current density of 0.2 mA cm−2. The results indicate that NiCo-LDH/G/PANI-NT@CC will be an appropriate candidate for high-performance supercapacitors. The NiCo-LDH/G/PANI-NT@CC//NiCo-LDH/G/PANI-NT@CC flexible solid-state supercapacitor was assembled with the PVA/KOH gel electrolyte.

Nanoarchitectonics with beetroot peel waste derived activated carbon for improved electrochemical performances in supercapacitors using redox additive electrolyte

• For the first time, we formulated a high surface area activated carbon from beetroot peel waste (BDC-700) using chemical activation method. • A high-energy symmetric supercapacitor was fabricated using 1 M H 2 SO 4 and HQ redox additive electrolyte. • The fabricated symmetric supercapacitor with HQ/1M H 2 SO 4 electrolyte delivered a maximum energy and power density of 36 Wh/ kg and 8000 W/kg, respectively. Supercapacitors are presumed to be ideal for electrochemical energy storage high power applications because they are an intermediate between conventional capacitors and batteries. Various bio-derived activated carbon was venerated for enhanced supercapacitor application and the electrochemical performance of carbon-based materials in aqueous electrolytes was further enhanced to a greater extent with the incorporation of redox additives. In this work, the activated carbon obtained from beetroot is explored as the electrode material for supercapacitors with redox additives in electrolytes. The chemical functionalities and elements present in the prepared activated carbon were confirmed using FT-IR and XPS, respectively. The electrochemical energy storage behavior of the prepared activated carbon was analyzed with hydroquinone (HQ) as a redox additive. The specific capacity of the prepared electrode in 0.01 M HQ/H 2 SO 4 at 3 A/g is 2589 C/g. The calculated power and energy density of the fabricated symmetric cell with HQ/H 2 SO 4 at 3 A/g are 2356 W/kg and 36 Wh/kg, which is superior to the mere 1 M H 2 SO 4 electrolyte with the gravimetric power and energy density of 1800 W/kg and 13.5 Wh/kg, respectively.