High Electrochemical Capacitors Research Articles

Elevating Platinum to Volumetric Capacitance: High Surface Area Electrodes through Reactive Pt Sputtering.

Platinum is the most widespread electrode material used for implantable biomedical and neuroelectronic devices, motivating exploring ways to improve its performance and understand its fundamental properties. Using reactive magnetron sputtering, PtOx is prepared, which upon partial reduction yields a porous thin-film form of platinum with favorable properties, notably record-low impedance values outcompeting other reports for platinum-based electrodes. It is established that its high electrochemical capacitance scales with thickness, in the way of volumetric capacitor materials like IrOx and poly(3,4-ethylenedioxythiophene), PEDOT. Unlike these two well-known analogs, however, it is found that PtOx capacitance is not caused by reversible pseudofaradaic reactions but rather due to high surface area. In contrast to IrOx, PtOx is not a reversible valence-change oxide, but rather a porous form of platinum. The findings show that this oxygen-containing form of Pt can place Pt electrodes on a level competitive with IrOx and PEDOT. Due to its relatively low cost and ease of preparation, PtOx can be a good choice for microfabricated bioelectronic devices.

Size Control and Antioxidant Properties of Sulfur-Rich Polymer Colloids from Interfacial Polymerization.

High sulfur content polymeric materials, known for their intriguing properties such as high refractive indices and high electrochemical capacities, have garnered significant interest in recent years for their applications in optics, antifouling surfaces, triboelectrics, and electrochemistry. Despite the high interest, most high sulfur-content polymers reported to date are either bulk materials or thin films, and there is a general lack of research into sulfur-rich polymer colloids. Water-dispersed, sulfur-rich particles are anticipated to broaden the range of applications for sulfur-containing materials. In this study, the preparation and size control parameters are presented of an aqueous dispersion of sulfur-rich polymers with the sulfur content of dispersed particles exceeding 75wt%. Employing polymeric stabilizers with varying hydrophilic-lipophilic balance (HLB), along with changing the rank of inorganic polysulfides, allow for the control of particle size in the range of 360nm - 1.8µm. The sulfur-rich colloid demonstrates antioxidant properties in water, demonstrating the potential for the use of sulfur-rich polymeric materials readily removable, heterogeneous radical scavengers.

Doping effect and oxygen vacancy engineering in nickel-manganese layered double hydroxides for high-performance supercapacitors

Design of electrode materials with high electrochemical capacitance and long lifetime remains a challenging issue for high-performance supercapacitors. Herein, we successfully synthesized a binder-free composite electrode comprising oxygen vacancy-abundant NiMnMg-layered double hydroxides grown on 3D graphene foam (Vo-NiMnMg-LDH@3DG) by Mg doping during hydrothermal process and subsequently Ar plasma etching. Thanks to the incorporation of electrochemically inert Mg element, the enhanced charge transfer capability, and enriched active sites that induced by plentiful oxygen vacancies, Vo-NiMnMg-LDH@3DG manifests a high specific capacity of 374.8 mAh g−1 at a current density of 1 A g−1 and satisfactory rate performance (74.26% at 20 A g−1). Furthermore, the asymmetric supercapacitor (ASC) assembled with Vo-NiMnMg-LDH@3DG cathode and activated carbon anode exhibits a specific capacitance up to 171 F g−1 at 1 A g−1, achieving a maximum energy density of 53.62 Wh kg−1 and the highest power density of 7500 W kg−1. This work not only provides innovative approaches for preparing oxygen vacancy-rich LDH materials, but also offers insights for the design and improvement of energy storage devices based on transition metal-based LDH.

Publisher Correction: Vertical-Aligned and Ordered-Active Architecture of Heterostructured Fibers for High Electrochemical Capacitance

Publisher Correction: Vertical-Aligned and Ordered-Active Architecture of Heterostructured Fibers for High Electrochemical Capacitance

Investigation of Hybrid Electrodes of Polyaniline and Reduced Graphene Oxide with Bio-Waste-Derived Activated Carbon for Supercapacitor Applications.

Graphene-based materials have been widely studied in the field of supercapacitors. However, their electrochemical properties and applications are still restricted by the susceptibility of graphene-based materials to curling and agglomeration during production. This study introduces a facile method for synthesizing reduced graphene oxide (rGO) nanosheets and activated carbon based on olive stones (OS) with polyaniline (PAni) surface decoration for the development of supercapacitors. Several advanced techniques were used to examine the structural properties of the samples. The obtained PAni@OS-rGO (1:1) electrode exhibits a high electrochemical capacity of 582.6 F·g-1 at a current density of 0.1 A·g-1, and an energy density of 26.82 Wh·kg-1; thus, it demonstrates potential for efficacious energy storage. In addition, this electrode material exhibits remarkable cycling stability, retaining over 90.07% capacitance loss after 3000 cycles, indicating a promising long cycle life. Overall, this research highlights the potential of biomass-derived OS in the presence of PAni and rGO to advance the development of high-performance supercapacitors.

Boosting the cycle stability of nickel-rich ternary materials at high voltage by coating mixed conductor Li7.5La3Zr1.5Co0.5O12

Ni-rich NCM materials have the high electrochemical capacities and low costs. However, the disadvantage of poor cycle performance severely limits their large-scale use. In this work, the nanoscale ion-electron mix-conductor Li7.5La3Zr1.5Co0.5O12 was prepared by ball milling and used to directly mix LiNi0.83Co0.11Mn0.06O2. After annealing, a mixed conductive protective layer could be formed on the surface of the NCM. The coating layer can protect the structural integrity of the NCM particles during cycling. At a current density of 1C between 2.8 and 4.5 V, the modified sample exhibited a capacity of 196 mAh g−1, and the capacity retention rate was as high as 85.7 % after 200 cycles, which was a significant improvement of 23.8 % over the pristine sample. The lithium-ion diffusion coefficient is enhanced and the charge transfer resistance is reduced by the mixed conductor cladding. The modified material shows an excellent rate performance. The specific capacity at 5C was 181 mAh g−1. The proposed modification method is simple in process and suitable for large-scale applications. The method has reference significance for the modification of other cathode materials.

Vertical-Aligned and Ordered-Active Architecture of Heterostructured Fibers for High Electrochemical Capacitance

Vertical-Aligned and Ordered-Active Architecture of Heterostructured Fibers for High Electrochemical Capacitance

Solution Processable Polyaniline with High Electrochemical Charge Capacity

Polyaniline (PANI) is a charged polymer well-known for its high charge storage capacity and moderate electrical conductivity. PANI is often prepared by chemical or electro-polymerization, however, these polymerization methods limit options for substrate material, electrode/device geometry, and polymer morphology. To address these limitations, it is attractive to form PANI films by solution-casting. In this study, we examine the electrochemical properties of solution-cast PANI films formed from a commercially available PANI suspension containing excess dinonylnaphthalenesulfonic acid (DNNSA). Films prepared by solution casting of PANI-DNNSA have been previously characterized in terms of conductivity, morphology, and optical properties, however the electrochemical behavior of these films has been largely unexplored. Here, we present an electrochemical analysis of these solution-cast PANI films using quartz crystal microbalance, electrochemical impedance spectroscopy, and cyclic voltammetry. As cast, we find that the polymer exhibits limited electrochemical activity, but that postprocessing the material with electrolyte and crosslinking solutions increases the charge capacity up to 95 mAh/g – 86% of the charge capacity typically reported for electrodeposited PANI films. Ion-exchange processes, electrochemical capacitance, and energy storage capabilities of the chemically treated solution-cast films are assessed and compared to those of electro-deposited and chemically oxidized PANI. We demonstrate redox-active PANI films on both (a) conductive and insulating, and (b) planar and porous substrates. Finally, symmetric faradaic supercapacitor devices were constructed using spin-coated PANI electrodes in aqueous electrolyte, and the stability of these devices was examined by repeat galvanostatic charging/discharging at low current, achieving up to 88% capacity retention after 500 charge-discharge cycles.

Novel hemp biomass-derived activated carbon as cathode material for aqueous zinc-ion hybrid supercapacitors: Synthesis, characterization, and electrochemical performance

This research paper investigates the use of aqueous electrolytes in multivalent zinc-ion hybrid supercapacitors, highlighting their advantages over traditional supercapacitors in terms of increased energy density, cost-effectiveness, and enhanced safety. The study focuses on synthesizing activated carbon materials from hemp biomass through hydrothermal synthesis and KOH chemical activation. The resulting activated carbon possesses a highly porous structure essential for efficient energy storage. Herein, various advanced techniques were employed to examine the structural properties of the activated carbon material, such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) analysis, Fourier-Transform Infrared (FTIR) spectroscopy, Energy-Dispersive X-ray spectroscopy (EDS), and X-ray Photoelectron Spectroscopy (XPS). On the other flip side, the hemp-derived carbon cathode exhibits a high electrochemical capacity of 220 F/g and an energy density of 65 Wh/kg, highlighting its potential for efficient energy storage. Moreover, the cathode material demonstrates remarkable cycling stability, retaining over 98 % of its capacity after 2000 charge/discharge cycles, indicating a promising long cycle life. Overall, this study emphasizes the potential of aqueous electrolytes and hemp biomass-derived carbon materials in advancing the development of high-performance multivalent zinc-ion hybrid supercapacitors.

Prolonging cycling life of AB3-type superlattice alloys by adjusting hydrogen absorption/desorption behaviors of [A2B4] and [AB5] subunits

AB3-type La-Mg-Ni-based hydrogen storage alloys are known for their high electrochemical hydrogen storage capacity. However, their practical application has been hindered by fast capacity degradation. Herein, we managed to improve their cycle life by synchronizing the hydrogen absorption/desorption behaviors of [A2B4] and [AB5] subunits based on a series of AB3-type single-phase La0.60R0.12Mg0.28Ni3 (R = La, Pr, Nd, Gd) superlattice alloys. This is achieved by the preferable occupation of Pr, Nd and Gd in [A2B4] subunits rather than [AB5] subunits compared to La, which decreases the volume difference between [A2B4] and [AB5], significantly reducing the mismatch between [A2B4] and [AB5] during hydrogen absorption/desorption. Resultantly, the microstrain of the R = Gd alloy is only half that of the R = La alloy, leading to enhanced anti-pulverization and anti-oxidation/corrosion resistance, as well as an improved cycle stability. The S100 of the R = Gd alloy is more than 15 % higher than the R = La alloy. Moreover, the plateau pressure is adjusted to a proper level, enabling an increase in the high-rate dischargeability (HRD1500) from 53.6 % (R = La) to 66.4 % (R = Gd). This work provides impressive insights into developing high-performance superlattice hydrogen storage alloys.

Two-step electrodeposition synthesis of lamellar Ni@NiCo phosphate heterostructures as cathodes for high-performance hybrid supercapacitors

Porous structures grown in situ increase the electrode contact area with the electrolyte, reduce ion diffusion distance, and enhance electrode material electrochemical properties. In this paper, we have adopted a dual-channel electrodeposition strategy with simultaneous electrodeposition and phosphorylation to construct metal-semiconductor contact heterostructures by depositing Ni@NiCo phosphate microspherical nanostructures directly on a copper foam (CF) (Ni@NiCoP/CF) framework at room temperature. The results show that Ni@NiCoP/CF has excellent electrochemical performance with a high specific capacity of 200 mAh g–1 at 1 A g–1, 147.2 mAh g–1 at 20 A g–1 and 93.6 % after 5000 cycles, showing excellent ration performances and cycling stability. In addition, the hybrid supercapacitor composed of Ni@NiCoP/CF as the positive electrode and activated carbon as the negative electrode achieves a high energy density of 48.7 Wh kg−1 at 874 W kg−1 and has excellent cycling stability with 113.23 % capacity retention after 30,000 charge/discharge cycles at a high current density of 10 A g–1. This study serves as a guide for the development of high-performance capacitor cathode materials with high electrochemical activity and capacity.

A Flexible Supercapacitor Based on Niobium Carbide MXene and Sodium Anthraquinone-2-Sulfonate Composite Electrode.

MXene-based composites have been widely used in electric energy storage device. As a member of MXene, niobium carbide (Nb2C) is a good electrode candidate for energy storage because of its high specific surface area and electronic conductivity. However, a pure Nb2C MXene electrode exhibits limited supercapacitive performance due to its easy stacking. Herein, sodium anthraquinone-2-sulfonate (AQS) with high redox reactivity was employed as a tailor to enhance the accessibility of ions and electrolyte and enhance the capacitance performance of Nb2C MXene. The resulting Nb2C-AQS composite had three-dimensional porous layered structures. The supercapacitors (SCs) based on the Nb2C-AQS composite exhibited a considerably higher electrochemical capacitance (36.3 mF cm-2) than the pure Nb2C electrode (16.8 mF cm-2) at a scan rate of 20 mV s-1. The SCs also exhibited excellent flexibility as deduced from the almost unchanged capacitance values after being subjected to bending. A capacitance retention of 99.5% after 600 cycles was observed for the resulting SCs, indicating their good cycling stability. This work proposes a surface modification method for Nb2C MXene and facilitates the development of high-performance SCs.

Synergistically Driven CoCr-LDH@VNiS2 as a Bifunctional Electrocatalyst for Overall Water Splitting and Flexible Supercapacitors.

Utilizing alternative energy sources to fossil fuels has remained a significant issue for humanity. In this context, efficient earth-abundant bifunctional catalysts for water splitting and energy storage technologies like hybrid supercapacitors have become essential for achieving a sustainable future. Herein, CoCr-LDH@VNiS2 was synthesized by hydrothermal synthesis. The CoCr-LDH@VNiS2 catalyst entails 1.62 V cell voltage to reach the current density of 10 mA cm-2 for overall water splitting. The CoCr-LDH@VNiS2 electrode illustrates a high electrochemical specific capacitance (Csp) of 1380.9 F g-1 at a current density of 0.2 A g-1 and an outstanding stability with 94.76% retention. Moreover, the flexible asymmetric supercapacitor (ASC) achieved an energy density of 96.03 W h kg-1@0.2 A g-1 at a power density of 539.98 W kg-1 with remarkable cyclic stability. The findings provide a new approach toward the rational design and synthesis of bifunctional catalysts for water splitting and energy storage.

Facile synthesis of Co3O4@SeNPs grafted MWCNTs Nanocomposite for high energy density supercapacitor and antimicrobial applications

Herein for the first time, intertwined nanocomposite (Co3O4@Se NPs/MWCNTs) of cobalt oxide nanoparticles (Co3O4 NPs) adsorbed on selenium nanoparticles (Se NPs) (designated as Co3O4@Se NPs) and thiol (–SH) functionalized multiwalled carbon nanotubes (MWCNTs) was synthesized by a simple hydrothermal method to achieve excellent capacitive and microbicidal performance. The surface morphology, microstructure and functional group studies ensures that the existence of Co3O4@Se NPs onto MWCNTs. The electrochemical studies (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD)) were performed and demonstrated the Supercapacitive performance of Co3O4@Se NPs/MWCNTs nanocomposite. Higher electrochemical capacitance (356 F/g) with better coulombic efficiency of 84% was acquired. Also, it exhibited an admirable antimicrobial study and illustrated that the pathogens were more susceptible to Co3O4@Se NPs/MWCNTs nanocomposite. The superior electrochemical and antimicrobial activity was achieved owing to the specific inherent properties of thiol (–SH) groups opt binding and stabilizing Co3O4@Se NPs against its aggregation on the surface of MWCNTs. The thiol (–SH) group influences the enrichment of Co3O4@Se NPs onto MWCNTs and facilitates in enhancement of energy storage and microbicidal performance the nanocomposite. These attained outcomes put forward the applicability of the synthesized active nanocomposite towards supercapacitor and antibacterial agents against pathogens.

A perpendicular micro-hole array for efficient ion transport in a thick, dense MoS2-based capacitive electrode

Two-dimensional (2D) nanosheets with a high electrochemical capacitance, density, and electrical conductivity are promising for assembling thick and dense films for supercapacitors with a high volumetric energy density. However, 2D nanosheet-based films with cascading nanochannel networks are not ideal for efficient ion transport due to the tortuous pathways. We used a micro-stamping method to create a perpendicular micro-hole array in a thick, dense MoS2-based electrode without lowering its density. Our nuclear magnetic resonance measurement and computational simulations reveal that the micro-hole array can serve as ion reservoirs and provide shortcuts in the cascading nanochannel network, greatly improving the ion accessibility to MoS2-based electrodes in both the adsorption and charging processes. A MoS2-based film electrode with 2-3 times the density of a conventional carbon electrode, shows almost thickness independent capacitance performance with a mass loading up to 18.6 mg cm−2. The electrode has a volumetric capacitance of 469.5 F cm−3 and the assembled device a volumetric energy density of 80.5 Wh L−1 in an ionic liquid electrolyte. This micro-stamping strategy is easy to scale up and may pave the way for the development of 2D materials-based compact energy storage systems.

Flexible CoFe2O4 nanoparticles/N-doped carbon nanofibers membrane as self-standing anode for lithium-ion batteries

The development of new generation wearable electronic devices requires the power supply with high power density, long-term cycling performance, and excellent flexibility and mechanical stability that would enhance the durability of flexible devices during use. Herein, we designed a novel strategy for the preparation of flexible self-supporting nanofiber membrane with highly dispersed CoFe2O4 nanoparticles embedded in one-dimensional (1D) N-doped carbon nanofibers (denoted as [email protected]) by electrospinning and subsequent thermal treatment process, which possesses unique hierarchical structure containing zero-dimensional [email protected] carbon nanospheres and cross-linked three-dimensional (3D) fiber network. The rational combination of the nano-sized CFO particles with high theoretical capacity and a N-doped carbon nanofiber conductive skeleton with interconnected 3D open microstructure facilitates the robust penetration of electrolyte into the electrode, improves the overall electrical conductivity of the electrode, shortens the diffusion pathways of Li+ ions, and buffers the volume change of active materials during lithiation/delithiation. As a consequence, the optimized [email protected] exhibits relatively high electrochemical reversible capacity (611.4 mA h g−1 at 100 mA g−1 after 100 cycles) and good cycling stability, as well as satisfactory rate capability.

Synthesis and Nanostructure Investigation of Hybrid β‐Ga2O3/ZnGa2O4 Nanocomposite Networks with Narrow‐Band Green Luminescence and High Initial Electrochemical Capacity (Small 18/2023)

Network Materials In article number 2207492, Niklas Wolff, Ion Tiginyanu, Lorenz Kienle, and co-workers report on the synthesis and structural characterization of a hybrid wide-band-gap semiconductor nanocomposite network of interconnected hollow microtubes composed of β-Ga2O3/ZnGa2O4 phases using X-ray powder diffraction and transmission electron microscopy. The aero-network morphology shows ZnGa2O4-dominated narrow band green light emission under UV light excitation and high initial electrochemical capacity versus Li-ion loading.

The Effect of Y Content on Structural and Sorption Properties of A2B7-Type Phase in the La-Y-Ni-Al-Mn System.

Metal hydrides are an interesting group of chemical compounds, able to store hydrogen in a reversible, compact and safe manner. Among them, A2B7-type intermetallic alloys based on La-Mg-Ni have attracted particular attention due to their high electrochemical hydrogen storage capacity (∼400 mAh/g) and extended cycle life. However, the presence of Mg makes their synthesis via conventional metallurgical routes challenging. Replacing Mg with Y is a viable approach. Herein, we present a systematic study for a series of compounds with a nominal composition of La2-xYxNi6.50Mn0.33Al0.17, x = 0.33, 0.67, 1.00, 1.33, 1.67, focusing on the relationship between the material structural properties and hydrogen sorption performances. The results show that while the hydrogen-induced phase amorphization occurs in the Y-poor samples (x < 1.00) already during the first hydrogen absorption, a higher Y content helps to maintain the material crystallinity during the hydrogenation cycles and increases its H-storage capacity (1.37 wt.% for x = 1.00 vs. 1.60 wt.% for x = 1.67 at 50 °C). Thermal conductivity experiments on the studied compositions indicate the importance of thermal transfer between powder individual particles and/or a measuring instrument.

Effect of tension during stabilization on carbon fiber multifunctionality for structural battery composites

Here we demonstrate carbon fibers with tailorable multifunctional properties for energy storage composites. Carbon fibers made from the same precursor but with different processing tensions are investigated. The applied tension during the stabilization/oxidation stage of fiber manufacturing determines the microstructure and the resulting mechanical and electrochemical performance. Understanding of the interconnected effects enables tailoring of fibers to function as electrodes in structural battery composites. The study reveals that both amorphous and crystalline phases affect the electrochemical capacity, as higher capacity is achieved by larger d-spacing as well as higher void content. Further, the study confirms the trade-off between high tensile strength and high electrochemical capacity that needs to be taken into consideration when designing multifunctional carbon fibers.

Properties of AB5 type hydrogen storage alloy after α-AlH3 alloying

AB5 type hydrogen storage alloys have been widely used in Ni-MH batteries due to their high electrochemical capacity, excellent rate performance, and low pollution. However, the high activation difficulty limited their development in the solid-state hydrogen storage field. Mechanical alloying to synthesize composites is an effective way to reduce activation energy. In this paper, the structure and hydrogen storage properties of the LaNi5+nAlH3 (n = 0, 1, 3 wt.%) composites were investigated. The results show that with the incremental of AlH3 alloying content, the lattice constant a, b, and c and the volume (V) of the LaNi5 unit cell tend to increase, the hydrogen absorption platform pressure of the composite material gradually decreased, and the hydrogen release platform pressure gradually increased. It resulted in a reduction in the hysteresis factor (Hf) of the composite from 0.66 to 0.35. This will reduce energy waste during energy conversion. In addition, the activation property of the alloy was improved after AlH3 alloying. This will facilitate the application of AB5 type hydrogen storage alloys.