Electrochemical Charge Storage Research Articles

Tuning the Assembly Process of Polyaniline Nanofibers by Adjusting the Acidic Nature and Solution Acidity toward Enhancing Electrochemical Charge Storage

Tuning the Assembly Process of Polyaniline Nanofibers by Adjusting the Acidic Nature and Solution Acidity toward Enhancing Electrochemical Charge Storage

Insight on electrochemical charge storage behavior of naturally surface oxidized amorphous NiCuCoB nanosheets

Transition metal boron (TMB) nanostructures are found to be emerging materials in the field of energy conversion and storage. Despite several careful systematic researches on the TMBs and their electrochemical energy storage applications, still a comprehensive and insightful study on the charge storage mechanism, origin of the redox reaction sites on alloyed TMB surface, types of interactions of the electrolytes with respect to TMB's surface structure has not been realized. Herein, a series of TMBs nanosheets are prepared using Cu, Co, Ni and B through a simple low-cost reduction approach and explored systematically their charge storage behavior. Trimetallic NiCuCoB nanosheets over other TMBs demonstrated outstanding electrochemical energy storage performances with high-rate capability. A symmetric two-electrode coin cell device of NiCuCoB in 6.0 M KOH offers 358 F g−1 specific capacitance with 56 Wh kg−1 energy and 13,320 W kg−1 power density, with 50,000 cycling stability. Kinetically fluent faradaic redox reactions are favourably occurred by a surface-controlled mechanism with minor contribution from diffusion, which are facilitated by oxidized surface of NiCuCoB viz., metal-oxide and/or metal-oxy/hydroxide, a high surface area and high conductivity of the material, as evidenced by experiments.

Post-engineering of solution plasma-derived carbons via thermal air treatment for supercapacitor electrodes with enhanced capacitive performance

Carbon materials produced by solution plasma process (SPP) typically exhibit insufficient surface area and deficient microporosity, limiting their application in supercapacitor electrodes. Thus, post-engineering strategies are necessary to overcome this limitation. In this study, carbon nanoparticles (CNPs) were synthesized from benzene by SPP and subsequently subjected to thermal air treatment (TAT) under mild conditions (300 and 400 °C in an air atmosphere). The resulting CNPs had uniform morphology and an amorphous structure. With increasing TAT temperature, the specific surface area of CNPs increased from 171 to 575 m2 g−1 through the development of micropores and mesopores. TAT also enriched the acidic oxygen functional groups on the surfaces of the CNPs. The electrochemical charge storage properties of the CNPs were investigated using a three-electrode system in a 1 M H2SO4 electrolyte. The CNPs with TAT at 400 °C demonstrated the highest specific capacitance of 130 F g−1 at a current density of 1 A g−1, which was 5.4 times higher than that of the untreated CNPs (24 F g−1). It also exhibited stable cycling performance after 5000 charge–discharge cycles. This study demonstrates that TAT is a simple and effective post-engineering strategy for increasing the specific surface area and micro–mesoporosity of SPP-derived CNPs, as well as modifying their surface chemistry. These improvements enable the practical application of CNPs produced by SPP in the field of supercapacitors.

Hydrothermal Synthesis and Electrochemical Performance of Mesoporous La2CrMnO6 Double Perovskite for Energy Storage Applications

Mesoporous La2CrMnO6 double perovskite is successfully synthesized using the hydrothermal technique, and characterized its physicochemical properties using X‐ray diffraction, X‐ray photoelectron spectroscopy, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy, and transmission electron microscopy. The synthesized material exhibits a high surface area of 57.07 m2 g−1, providing more active sites for electrochemical charge storage. The electrochemical performance of the La2CrMnO6 as an electrode material is evaluated for the first time, which reveals an excellent specific capacitance of 1416 F g−1 at 1 A g−1 in a three‐electrode setup. Results suggest that mesoporous La2CrMnO6 double perovskite is a promising electrode material for electrochemical energy storage applications.

Iron oxide induced preparation of nanoscrolls of reduced graphene oxide for electrochemical charge storage applications

Fe3O4 - reduced graphene oxide nanoscrolls (FRGNS) are tailored for fabricating electrode material for supercapacitor applications. The scrolling of reduced graphene oxide is initiated by the magnetic field produced by the superparamagnetic iron oxide NPs. The formation mechanism and critical concentration of nanoparticles required for scroll formation is investigated by varying the weight ratio of iron oxide NPs. The nanoscroll formation is completely reversible and reproducible. The unique end open morphology of nanoscrolls facilitates the electrolytic accessibility and the Fe3O4 NPs favor the redox reactions as well. At a current density of 1Ag-1, FRGNS12 (rGO: Fe3O4 1:12) achieve a noteworthy specific capacitance value of 1498 Fg-1 within a potential ranging from 0 to −0.73 V in 1 M Na2S2O3 with exceptional energy density of 110.9 Wh Kg−1 and power density of 405 Wkg-1. A prominent cycling stability of 88% capacitance retention after 4000 cycles is also obtained. The electrochemical performance of opened as well as regenerated scrolls (RFRGNS12) are also evaluated. The specific capacitance increases to 1514 Fg-1 for RFRGNS12 due to the further exfoliation of rGO sheets take place during the unscrolling and scroll regeneration process. The unique fabrication methodology for the synthesis of graphene nanoscrolls and their utilization as electrode material for supercapacitors paves a new pathway for the advancement of novel electrode materials for supercapacitors.

Unraveling the electrochemical properties and charge storage mechanisms of lactobacillus-mediated synthesized RGO-titanium silver nanocomposite as a promising binder-free electrode for asymmetric supercapacitor device

A sustainable and scalable technique was developed to synthesize RGO-TiAg nanocomposites at room temperature, utilizing Lactobacillus sp. as an environmentally friendly reducing and stabilizing agent. This approach offers a cost-effective solution for large-scale production. The unique properties of Lactobacillus sp. allow for the reduction of metal ions while inhibiting agglomeration and preserving the stability of the resulting nanocomposites. The addition of reduced graphene oxide (RGO) sheets to the TiAg-based electrode increases its specific surface area, thereby enhancing the electrode's charge-storage capacity by promoting the formation of conductive networks. Furthermore, the hydrophilic oxygen groups of chemically reduced graphene oxide in the RGO-TiAg nanocomposites facilitate the electrolyte's access to the electrode's pores. Electrochemical analysis revealed that the RGO-TiAg NCs demonstrated the highest specific capacitances of 816.92 F/g at 1.5 A/g. An asymmetric supercapacitor device was fabricated by utilizing a composite electrode composed of RGO-TiAg NCs and activated carbon (AC). Polyvinyl alcohol-Na2SO4 (PVA-Na2SO4) was employed as the electrolyte and electrode separator. The RGO-TiAg NCs//ACarbon assisted ASC supercapacitor device demonstrated a specific capacitance of 256 F/g at 4 A/g, along with tremendous energy and power densities of 53.33 Wh kg− 1 and 2 kW kg− 1, respectively, at the same current density. The device exhibited a high-power density of 6 kW kg− 1 and an energy density of 25 Wh kg− 1, with a capacitance retention of 82% even at an ultrahigh current density of 12 A/g, after 10,000 cycles. Additionally, this work illustrates an effective method for synthesizing nanocomposites that may be used for developing prospective, high-performance supercapacitors for energy storage.

Graphitic Carbon Nitride-Induced Multifold Enhancement in Electrochemical Charge Storage of CoS-NiCo2S4 for All-Solid-State Hybrid Supercapacitors.

In order to improve the electro-microstructural physiognomics of electrode materials for applications in better efficiency supercapacitors, herein graphitic carbon nitride (GCN)-heterostructurized CoS-NiCo2S4 is designed using a controlled material growth synthesis procedure. The developed CoS-NiCo2S4/GCN possesses ample hydrophilicity, possible charge transfer between GCN and CoS-NiCo2S4, uniform phase distribution, and distinctive microstructural characteristics. The preliminary electrochemical studies in the three-electrode setup show GCN-induced lower charge transfer resistance and very unique Warburg profile corresponding to extremely low diffusion resistance in CoS-NiCo2S4/GCN as compared to pristine CoS-NiCo2S4. Furthermore, GCN is found to significantly induce surface-controlled (capacitive-type) charge storage and frequency-independent specific capacitance up to 10 Hz in CoS-NiCo2S4. Furthermore, the CoS-NiCo2S4||N-rGO and CoS-NiCo2S4/GCN||N-rGO all-solid-state hybrid supercapacitor (ASSHSC) devices were fabricated using N-rGO as the negative electrode material, and the inducing effect of GCN on the supercapacitive charge storage performance of the devices is thoroughly studied. Results demonstrate that the mass specific capacitance and areal capacitance of CoS-NiCo2S4/GCN||N-rGO are ∼2 and ∼4 times more than those of the CoS-NiCo2S4||N-rGO ASSHSC device, respectively. Furthermore, the CoS-NiCo2S4/GCN||N-rGO offers more energy density, rate energy density, and additional charge-discharge durability (over ∼10,000 cycles) than the CoS-NiCo2S4||N-rGO ASSHSC device. The multifold performance improvement of CoS-NiCo2S4 with GCN heterostructurization is ascribed to GCN-induced supplemented porosity and pore widening, ionic nonstoichiometry (Ni2±δ, Co2±δ, and Co3±δ), wettability, integrated enhancement in the conductivity, and electroactive-ion accessibility in the CoS-NiCo2S4/GCN heterocomposite. The present study offers vital physicoelectrochemical insights toward the future development of low cost and high-performance electrode materials, and their implementation in high-rate and operationally stable all-solid-state hybrid supercapacitor devices, for application in the next-generation front-line technologies.

Hybridization of Fe-O in iron doped hydroxyapatite for superior electrochemical charge storage

Hydroxyapatite (HAp) is an interesting phosphate candidate with a weak electrical conductivity that can be tuned by doping metal ions to enhance the active sites for electrochemical charge storage. HAp and Fe-doped HAp were prepared by a wet chemical method. On doping, the crystallite size reduces to 9.56 nm. The surface area of 0.01FH (0.01% Fe) is 152.17 m2/g which is ∼3 times higher compared to PH. The 0.01FH sample shows the highest specific capacitance of 351.3 F/g at 30 mA/g. While X-ray photoemission spectroscopy shows the oxidation states of Fe in 2+ and 3+, X-ray absorption indicates (i) the enhancement of unoccupied density of states of Fe, and (ii) reduced interatomic distance of Fe-O in 0.01FH. These results show that the augmentation of surface properties and hybridization of Fe-O and the modification of its local atomic structures are responsible for high electrochemical charge storage in 0.01FH.

Enhanced optoelectronic and supercapacitive performance of electrodeposited Mn3O4 thin film prepared from two-electrode: An effect of Zn-ion incorporation

Here in, we report electrodeposited Mn3O4 thin film doped with various level of Zn dopant (0≤x≤5.0,%), on a layer of indium tin oxide (ITO) on glass substrate. The deposition route involves the use of two-electrode electrochemical cell system comprising graphite and the substrate as counter and working electrodes, respectively. Some surface properties such as those of morphological, crystal structure, optical, electrical and electrochemical were studied to evaluate the films’ potentials in energy conversion and storage devices. Microstructural studies revealed the films grew with isotropic morphology of good tetragonal shaped crystal structure with even distribution and possessing required surface area on the substrate surfaces. Raman prominent peak at 659 cm −1 wave number indicates a typical A1g Raman vibrating mode of Mn2+ in a Mn3O4 spinel structure. The crystallite size and microstrain values were found varying from 38 to 43 nm and 5.6 × 10−3 to 3.2 × 10−3, with respect to increase in dopant content, respectively. Energy band gap and Urbach energy were varied from 3.28 to 2.68 eV and 1.59 to 2.17 eV with increasing level of dopant content, accordingly. Electrochemical charge storage area capacitance (12.62 to 21.35 mF cm −2)/capacity (5.1 to 8.1μAh cm −2) and rate capability of Mn3O4 electrode were found to improve with Zn dopant. The work therefore discusses the tailoring of band absorption and supercapacitive characteristic of electrodeposited Mn3O4 thin film with Zn-doping for enhanced energy application.

Engineering Multifunctionality in MoSe2 Nanostructures Via Strategic Mn Doping for Electrochemical Energy Storage and Photosensing

To achieve advanced functionalities in nanostructured MoSe2 for enhanced electrochemical charge storage and improved photosensing, here we propose an effective strategy, i.e., the substitutional doping of the heteroatom Mn. We achieve a 313% increase in specific capacitance for 6.2% of Mn doping compared to pristine MoSe2 at the scan rate of 5 mV/s in a three-electrode configuration. For a two-electrode arrangement, also superior charge-storage performance is noted. The enhanced electrode performance can be attributed to the increase of electrical conductivity arising due to an increase of electron density for the n-type nature of Mn doping realized via an X-ray photoelectron spectroscopy study and density functional theory calculation. The latter one also unveils that Mn doping introduces catalytically active sites by disrupting homogeneous charge distribution over the topology of the MoSe2 basal plane contributing to better charge-storage performance. Mn doping-induced shift in the Fermi level of MoSe2 toward the conduction band also minimizes the contact barrier height signifying its improved capabilities for a photosensor device. Additionally, Mn doping causes alleviation of the charge-recombination process resulting in increase of photocarrier separation. As a result, we observe a 187% enhancement in the photocurrent and significantly higher responsivity and detectivity for 6.2% Mn-doped MoSe2 than its pristine counterpart. Our proposed doping strategy to modulate charge storage as well as photoresponse properties demonstrates high potential for MoSe2 along with other two-dimensional transition-metal dichalcogenides in developing next-generation energy-storage and optoelectronic devices.

Intermolecular Interactions and Electrochemical Studies on Highly Concentrated Acetate-Based Water-in-Salt and Ionic Liquid Electrolytes

Water-in-salt electrolytes constitute a new class of materials that have distinct properties relative to lower-concentration solutions. A recent approach to further increase the salt concentration and decrease the water content includes the addition of an ionic liquid to a highly concentrated aqueous solution. However, the physicochemical and electrochemical properties of aqueous lithium acetate-1-ethyl-3-methylimidazolium acetate solutions as well as the molecular interactions between electrolyte species have not been characterized. Here, we investigate these properties by evaluation of the ionic conductivity, viscosity, and thermal properties as well as the electrochemical behavior of various electrodes in these electrolytes. The intermolecular interactions are probed by nuclear magnetic resonance and infrared spectroscopies. We find that the addition of the ionic liquid increases the solubility limit of lithium acetate and that with an increase in both acetate salt and ionic liquid concentration in the electrolyte and decrease in water concentration, a strong acetate-water network is formed. The electrochemical stability window increases upon addition of the ionic liquid and reaches a value larger than 5 V for a set of negative Al and positive Ti electrodes in the highest acetate salt/ionic liquid concentration. Preliminary electrochemical charge storage performance measurements of a symmetric device based on two porous carbon electrodes cycled at a current density of 25 mA g-1 delivered a specific capacitance of 20 F g-1 with a Coulombic efficiency higher than 99% using a 1.8 V voltage window.

Bimetallic Synergies Help the Application of Sodium Vanadyl Phosphate in Aqueous Sodium-Ion Batteries.

Aqueous sodium-ion batteries (ASIB) offer many potential applications in large-scale power grids since they are inexpensive, safe, and environmentally friendly. Sodium superionic conductors (NASICON), especially carbon-coated Na3 V2 (PO4 )3 (NVP), have attracted much attention due to the full use of their high ion migration speed. However, the poor cycle lifespan and capacity retention of NVP hinder its application in ASIB. Herein, a novel bimetal-doped Na3 V1.3 Fe0.5 W0.2 (PO4 )3 (NV1.3 Fe0.5 W0.2 P) cathode is designed and synthesized to achieve outstanding cycling stability (95 % of initial capacity at 50th cycle). The electrochemical behavior and charge storage mechanism of NV1.3 Fe0.5 W0.2 P are systematically investigated by various in situ and ex situ characterizations. The Fe and W codoping could stabilize the NASICON framework to suppress the proton attack on the Na site in the aqueous electrolyte, thus resulting in excellent cycling stability. DFT calculations show that bimetallic doping increases the structural stability of NVP. Moreover, an ASIB fabricated using a NV1.3 Fe0.5 W0.2 P cathode and a NaTi2 (PO4 )3 anode delivers 64 mAh g-1 at room temperature, 95 % capacity retention after 50 cycles (1 A g-1 ).

Insight into Electrochemical Performance of Nitrogen-Doped Carbon/NiCo-Alloy Active Nanocomposites.

Nanocomposites containing Ni or Co or NiCo alloy and nitrogen-doped carbon with diverse ratios have been prepared and utilized as active elements in supercapacitors. The atomic contents of nitrogen, nickel, and cobalt have been adjusted by the supplement amount of Ni and Co salts. In virtue of the excellent surface groups and rich redox active sites, the NC/NiCo active materials exhibit superior electrochemical charge-storage performances. Among these as-prepared active electrode materials, the NC/NiCo1/1 electrode performs better than other bimetallic/carbon electrodes and pristine metal/carbon electrodes. Several characterization methods, kinetic analyses, and nitrogen-supplement strategies determine the specific reason for this phenomenon. As a result, the better performance can be ascribed to a combination of factors including the high surface area and nitrogen content, proper Co/Ni ratio, and relatively low average pore size. The NC/NiCo electrode delivers a maximum capacity of 300.5 C g-1 and superior capacity retention of 92.30% after 3000 unceasing charge-discharge cycles. After assembling it into the battery-supercapacitor hybrid device, a high energy density of 26.6Wh kg-1 (at 412W kg-1 ) is achieved, comparable to the recent reports. Furthermore, this device can also power four light-emitting-diode (LED) demos, suggesting the potential practicability of these N-doped carbon compositing with bimetallic materials.

Insights into the Charge Storage Mechanism of Binder-Free Electrochemical Capacitors in Ionic Liquid Electrolytes

Electrochemical capacitors (synonymously supercapacitors) working under an electrochemical double-layer charge storage mechanism (EDLC) are widely investigated because of their excellent power density and cycle life; however, their energy density is lower than those of lithium-ion batteries. Ionic liquids (ILs) are of great interest as electrolytes for EDLCs due to their wide operational voltage window. Here, we provide a systematic investigation on the influence of anions of ILs on the charge storage mechanism and electrochemical stability of EDLC electrodes. Two IL electrolytes, viz., [1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI)], having similar cations but different anions and carbon nanotube (CNT) electrodes are chosen for this study. The CNT//BF4:TFSI//CNT-based device showed superior electrochemical performance (∼69 F·g–1 gravimetric specific capacitance, ∼949 W·kg–1 power density, and ∼139 Wh·kg–1 energy density at 0.5 A·g–1) to CNT//EMIMBF4//CNT and CNT//EMIMTFSI//CNT devices. The device using a mixture of BF4:TFSI (1:0.5) electrolytes has an operating voltage of 0–3.8 V and specific capacitance retention of ∼45% at 0.5 A·g–1 after 500 cycles. In the case of the IL mixture (BF4:TFSI), the combined anion structure and their properties play very crucial part in the improvement of the electrochemical performance of the CNT//BF4:TFSI//CNT device. The assembled Teflon Swagelok-type cell could light up green (3.3 V) and red (2.1 V) light-emitting diodes for more than 5 min.

Synthesis of Na3 Fe2 (PO4 ) 3 with NASICON-Type Structure from Ferrous Oxalate Precursor in the Presence of Colloidal Silicon Dioxide

The widespread presence of sodium in the earth’s crust, the significant stability of its compounds and its great ecological recycling possibilities are all factors that lead researchers to new structures exhibiting ion migration of sodium and high electrochemical potential. The present research shows a new way for Na₃Fe₂(PO₄)₃ synthesis with Na Super Ion Conductor structure. The use of ferrous oxalate precursor Na₃Fe(C₂O₄)₃ changes the reaction pathway of the iron-phosphate system synthesis and leads to the formation of a structure that allows ion migration that enhances electrochemical charge storage properties. At best the measured capacity was 85 mAh g-1 over a voltage range of 4.2 V to 1.5 V vs Na/Na+. It is shown that the presence of colloidal silicon dioxide helps the main phase crystallization, without entering its structure.

Synergistic Effect of Nitrogen–Sulfur Codoping on Honeycomb-like Carbon-Based High-Energy-Density Zinc-Ion Hybrid Supercapacitors

Zn-ion hybrid supercapacitors (ZHSCs) are emerging charge storage devices that inherit many of the advantages of supercapacitors and batteries. However, problems such as unsatisfactory cycling stability and low energy density need to be solved urgently, which can be accomplished by developing cathode materials with excellent properties. Herein, we report the development of performance-enhanced ZHSCs obtained by incorporating N and S heteroatoms into orange peel-based hierarchical porous carbon (NS-OPC) to facilitate Zn2+ adsorption. The results of ex situ photoelectron spectroscopy and X-ray diffraction demonstrated the presence of −OH and Zn2+ chemisorbed and Zn4SO4(OH)6·5H2O during charging and discharging, respectively. Density functional theory calculations show that double doping can promote the chemisorption/desorption kinetics of Zn2+ and thus promote the electrochemical charge storage of C materials. Impressively, when used to assemble ZHSCs, the device still has an energy density of 53.9 Wh kg–1, a high power density of 6063.75 W kg–1, and an 86.2% capacity retention after 10,000 cycles. This study not only provides a reasonable technique for developing superior C-based electrode materials but also contributes to the understanding of the charge storage process in heteroatom-doped C materials.

Anomalous electrochemical performance of binary silver–strontium phosphate-based electrode material in supercapattery

Mesoporous silver strontium phosphate (SSP) was synthesized through a facile hydrothermal technique and utilized as a positive electrode for supercapattery. Material's morphology, crystallinity, elemental composition, and homogeneity were carried out through SEM, TEM, XRD, EDS, XPS, and EDS mapping. Various electrochemical characterizations were performed in three as well as two electrode assemblies to ensure the ability of the material towards electrochemical charge storage. In fact, three-electrode results explore that the material possesses excellent performance in terms of specific capacity, lower series resistance, and negligible charge transfer resistance. After a conclusive three electrode assembly findings, an asymmetric supercapacitor was assembled by utilizing SSP as a positive electrode and as a counterpart carbon nanotube (CNT) as a negative electrode. This hybrid device reveals excellent electrochemical performance and was able to deliver a specific capacity of 240.0 C/g. Indeed, not only higher capacity was delivered by this device, nevertheless, its performance was remarkable in terms of high energy density and excellent power density. Besides, the rate capability for the supercapattery was estimated from GCD which was ∼77% at the highest current density of 12 A/g. The stability has a significant role in energy storage devices and was analyzed by charging and discharging the device, and the results demonstrate the outstanding specific capacity retention of 86.68% after 5000 cycles. Likewise, the device successfully holds coulombic efficiency of 95.79% by the end of 5000 charge-discharge cycles. Our analysis reveals that this material possesses remarkable energy performance which makes it applicable for future supercapattery devices.

Large‐Area Smooth Conductive Films Enabled by Scalable Slot‐Die Coating of Ti3C2Tx MXene Aqueous Inks

AbstractLarge‐area flexible transparent conductive electrodes (TCEs) featuring excellent optoelectronic properties (low sheet resistance, Rs, at high transparency, T) are vital for integration in transparent wearable electronics (i.e., antennas, sensors, supercapacitors, etc.). Solution processing (i.e., printing and coating) of conductive inks yields highly uniform TCEs at low cost, holding great promise for commercially manufacturing of transparent electronics. However, to formulate such conductive inks as well as to realize continuous conductive films in the absence of percolation issue are quite challenging. Herein, the scalable slot‐die coating of Ti3C2Tx MXene aqueous inks is reported for the first time to yield large‐area uniform TCEs with outstanding optoelectronic performance, that is, average DC conductivity of 13 000 ± 500 S cm−1. The conductive MXene nanosheets are forced to orientate horizontally as the inks are passing through the moving slot, leading to the rapid manufacturing of highly aligned MXene TCEs without notorious percolation problems. Moreover, through tuning the ink formulations, such conductive MXene films can be easily adjusted from transparent to opaque as required, demonstrating very low surface roughness and even mirror effects. These high‐quality, slot‐die‐coated MXene TCEs also demonstrate excellent electrochemical charge storage properties when assembled into supercapacitors.

Polyindole Embedded Nickel/Zinc Oxide Nanocomposites for High-Performance Energy Storage Applications.

Conducting polymers integrated with metal oxides create opportunities for hybrid capacitive electrodes. In this work, we report a one-pot oxidative polymerization for the synthesis of integrated conductive polyindole/nickel oxide (PIn/NiO), polyindole/zinc oxide (PIn/ZnO), and polyindole/nickel oxide/zinc oxide (PNZ). The polymers were analyzed thoroughly for their composition and physical as well as chemical properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), and thermogravimetric analysis (TGA). The PIn and its composites were processed into electrodes, and their use in symmetrical supercapacitors in two- and three-electrode setups was evaluated by cyclic voltammetry (CV), galvanostatic discharge (GCD), and electrochemical impedance spectroscopy (EIS). The best electrochemical charge storage capability was found for the ternary PNZ composite. The high performance directly correlates with its uniformly shaped nanofibrous structure and high crystallinity. For instance, the symmetrical supercapacitor fabricated with PNZ hybrid electrodes shows a high specific capacitance of 310.9 F g-1 at 0.5 A g-1 with an energy density of 42.1 Wh kg-1, a power density of 13.2 kW kg-1, and a good cycling stability of 78.5% after 5000 cycles. This report presents new electrode materials for advanced supercapacitor technology based on these results.

Flexible Solid-State Aqueous Sodium-Ion Capacitor Using Mesoporous Self-Heteroatom-Doped Carbon Electrodes

Supercapacitors find numerous applications such as in consumer electronics, peak power demands, capturing surge power, etc. Various types of carbon materials are explored as electrode material. In this work, disordered mesoporous carbon was synthesized from expired medicinal capsule covers by sulfonation and subsequent chemical activation was carried out with KOH. Powder X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, Brunauer–Emmett–Teller studies, and X-ray photoelectron spectroscopy were utilized to characterize the generated carbon which confirmed the disordered carbon had a large surface area with stratified pores. The testing for electrochemical charge storage was conducted on a three-electrode setup comprising an aqueous 1 M NaClO4 electrolyte that exhibited a high 324 F g–1 specific capacitance at 0.4 A g–1, revealing suitability for sodium-ion ultracapacitor. Consequently, CR2032 coin-type sodium-ion capacitors were fabricated using both aqueous and nonaqueous electrolytes. The laboratory prototype capacitor with the aqueous electrolyte delivered 42 Wh kg–1 specific energy at 179 W kg–1 specific power. Besides, the capacitor with the nonaqueous electrolyte showed a remarkable 54.3 Wh kg–1 specific energy at 540 W kg–1 specific power. The Coulombic efficiency exhibited by both devices was about 99% even at the 10000th charge–discharge cycle. The amplified charge storage performance of the disordered carbon was ascribed to the presence of homogeneous mesopores that led to enhanced accessibility of the electrode/electrolyte contact area. According to the results of the power law and Dunn’s approach, the mesoporous carbon electrode was found to have a considerable diffusive charge storing mode involving Na+ intercalation in the sodium-ion nonaqueous ultracapacitor. A green-light-emitting diode could run continuously for 16 min on a single charge using the laboratory prototype CR-2032 coin-type nonaqueous ultracapacitor. Interestingly, a homemade solid-state flexible sodium-ion ultracapacitor was also fabricated that impressively manifested 13.7 Wh kg–1 specific energy at 180 W kg–1 specific power in 180° bent angle.