Capacitance Of Electrode Research Articles

Initial Study of Reduced Graphene Oxide Foams Modified by Mn and Bi as Capacitive Electrode Materials

In a view of application of porous materials in wearable electronics and self-powered systems, reduced graphene oxide (rGO) foams modified by Mn or/and Bi were produced in this study to be used as electrodes for supercapacitors. The hydrothermal method and the freeze-drying processes were used for the preparation of the materials further morphologically, elementally and structurally analyzed. Based on the electrochemical characterization, Bi-modified rGO foam was found to be more a promising material for capacitive electrodes in comparison to the other prepared materials.

Synergistic Bimetallic Effects of BiSb Anodes Enable Long‐Stable Sodium Storage

AbstractAlloy‐type anodes are of interest for their resource‐rich and high theoretical capacity performance in sodium‐ion batteries (SIBs). However, severe volume expansion may lead to rapid capacity decay and electrode pulverization. In this work, metallic Bi with better structure stability is rationally selected as a skeleton to form a 2D BiSb alloy to alleviate the volume expansion. Interestingly, by combining in‐situ XRD and ex‐situ TEM characterizations, a reversible multi‐step alloying sodium storage mechanism of BiSb ↔ Na(Bi, Sb) ↔ Na3(Bi, Sb) in Bi0.4Sb0.6 anode is elucidated, and the partial amorphization and expanded interlayer spacing of BiSb alloy is also revealed, which greatly alleviate volume expansion thereby enhancing electrochemical stability. Furthermore, density functional theory and kinetic calculations demonstrate that Bi0.4Sb0.6 demonstrates lower Na+ adsorption energy and Na+ diffusion energy barriers, ensuring fast electron and ion transportation during sodium storage. Benefiting from the synergistic effects of binary alloy, Bi0.4Sb0.6 exhibits a high reversible capacity and cycling stability of 446 mAh g−1 at 0.1 A g−1, and 70% high capacity after 1100 cycles at 0.5 A g−1. This work provides new insights and opportunities to develop advanced precise alloy‐type anode materials for SIBs.

Li-ion solvation structure at electrified solid-liquid interface: Understanding solvation structure dynamics and its role in electrochemical energy storage through binary ethylene carbonate and dimethyl carbonate solvent.

Binary solvent electrolytes can provide interpretations for designing advanced electrolytes of next generation batteries. This study investigates the adsorption mechanisms of solvated lithium ions in binary solvents near charged electrodes. Molecular dynamic simulations are performed for lithium hexafluorophosphate (LiPF6) in ethylene carbonate and dimethyl carbonate (EC:DMC) solvent sandwiched between two electrodes. Results show that lithium ions form a tetrahedral solvation structure with two EC and two DMC molecules. The solvated lithium ion shows anti-electrostatic interaction with electrodes. This can be attributed to the electrostatic attraction of the polar end of the DMC molecule, which keeps the cation anchored to the positive electrode. Meanwhile, the solvation structure adopts a fix orientation at the negative electrode, which leads to unchanged electrostatic interaction at high charge density. Finally, EC molecules are swapped by DMC molecules near the negative electrode at high charge density. This leads to a decrease in local relative permittivity and, therefore, a decrease in differential capacitance. The differential capacitance of the positive electrode continuously decreases with increasing charge density. This is caused by the partial anchoring of solvent molecules holding the cations, which cancels the adsorption of anions near the positive electrode. This study provides insights into designing better electrolytes for efficient battery performance.

Impedance Spectroscopy for Bacterial Cell Monitoring, Analysis, and Antibiotic Susceptibility Testing.

Conventional approaches for bacterial cell analysis are hindered by lengthy processing times and tedious protocols that rely on gene amplification and cell culture. Impedance spectroscopy has emerged as a promising tool for efficient real-time bacterial monitoring, owing to its simple, label-free nature and cost-effectiveness. However, its limited practical applications in real-world scenarios pose a significant challenge. In this review, we provide a comprehensive study of impedance spectroscopy and its practical utilization in bacterial system measurements. We begin by outlining the fundamentals of impedance theory and modeling, specific to bacterial systems. We then offer insights into various strategies for bacterial cell detection and discuss the role of impedance spectroscopy in antimicrobial susceptibility testing (AST) and single-cell analysis. Additionally, we explore key aspects of impedance system design, including the influence of electrodes, media, and cell enrichment techniques on the sensitivity, specificity, detection speed, concentration accuracy, and cost-effectiveness of current impedance biosensors. By combining different biosensor design parameters, impedance theory, and detection principles, we propose that impedance applications can be expanded to point-of-care diagnostics, enhancing their practical utility. This Perspective focuses exclusively on ideally polarizable (fully capacitive) electrodes, excluding any consideration of charge transfer resulting from Faradaic reactions.

Novel Binders for Aqueous Electrode Processing of Electrochemical Capacitors.

This work studies the use of epoxy and polyurethane formulations as binders for the aqueous processing of activated carbon (AC) electrodes used as positive and negative electrodes in Electrochemical Double Layer Capacitors (EDLCs). The use of amine and carbodiimide as crosslinkers is also evaluated. The mechanical properties of those different binders have been investigated, looking towards aqueous processable and flexible electrodes. Microstructural analysis of the fabricated AC electrodes has been carried out to understand the pore-blocking effect exhibited by certain polymers. Furthermore, electrochemical characterization of all the systems has been performed by cyclic voltammetry, electrochemical impedance spectroscopy, and constant current charge/discharge measurements at different current densities. The obtained results show that polyurethane outperforms in terms of energy and power density the CMC:SBR reference system. Moreover, the studied polyurethanes maintain close to 100% of their initial capacitance after 2500 cycles under a current density of 5 A g-1 and a discharge time of 20 s.

Tuning solvation behavior within electric double layer via halogenated MXene for reliable lithium metal batteries

Solid electrolyte interphase (SEI)/electrolyte interface is critical in determining the lithium (Li) plating/stripping behavior. The solvation structure of Li-ion is well understood in the bulk electrolyte. Still, the mechanism of how SEI components affect the Li-ion solvation structure and desolvation energy barrier at the SEI/electrolyte interface is still unclear. Herein, Ti3C2 Maxine with single halogenated terminations (−Cl, −Br, −I) are synthesized and used as a model system, because their surface terminations induce a double halide-rich SEI formation (LiF and LiCl/LiBr/LiI). We examine the influence of the interaction strength between different Li halides and Li-ion on coordination number of Li ions and distribution of Li ions within the inner Helmholtz plane (IHP). A solvation sheath with a low solvent coordination number forms near the IHP of the LiBr interphase, improving the kinetics of Li deposition. Accordingly, half-cells utilising Li-carbon fiber/Ti3C2Br2 electrodes exhibit a long lifespan of 12,000 h (1 mA cm−2, 1 mAh cm−2). A pouch cell comprising Li-carbon fiber/Ti3C2Br2 anode and LiFePO4 cathode displays a capacity retention rate of 97 % after 300 cycles even at a low negative to positive electrode capacity ratio of 2.26. Our research provides crucial principles for the design of SEI components in Li metal batteries.

Enhanced Oxidation Resistance and Interface Stability of Atomic-Layer-Deposited MoNx Electrodes via TiN Passivation for DRAM Cell Capacitor Applications.

The continuous miniaturization of dynamic random-access memory (DRAM) capacitors has amplified the demand for electrode materials featuring specific characteristics, such as low resistivity, high work function, chemical stability, excellent interface quality with high-k dielectrics, and superior mechanical properties. In this study, molybdenum nitride (MoNx) films were deposited using a plasma-enhanced atomic layer deposition (PEALD) employing bis(isopropylcyclopentadienyl)molybdenum(IV) dihydride and NH3 plasma for DRAM capacitor electrode applications. Depending on the deposition temperatures of the PEALD MoNx films ranging from 200 to 400 °C, the Mo/N ratio and crystal structure varied, transitioning from the cubic NaCl-B1-type MoN phase with Mo/N ratio of 1.4 to the cubic γ-Mo2N phase with Mo/N ratio of 1.9. Notably, MoNx films grown at 400 °C exhibited low resistivity (435 μΩ·cm), a high work function (5.28 eV), and superior mechanical hardness (11.3 GPa) compared to ALD TiN films. Despite these excellent properties, the PEALD MoNx electrode demonstrated insufficient chemical stability, particularly in terms of oxidation resistance and interface quality with ALD HfxZr1-xO2 (HZO) films. This resulted in poor morphology and the formation of significant oxygen-deficient HZO layers (such as HfO2-x), leading to considerable degradation in the electrical performance of metal-insulator-metal (MIM) capacitors. To mitigate this issue, a thin (2.5-14 nm) ALD TiN layer was introduced as a passivation layer between the MoNx bottom electrode and HZO dielectric. The TiN-passivated MoNx (TiN/MoNx) electrode showed substantially enhanced oxidation resistance and reduced interfacial reactions with the HZO dielectric. Consequently, MIM capacitors with TiN/MoNx bottom electrodes demonstrated outstanding electrical performance, including excellent dielectric properties, low leakage current density, and high mechanical strength. Hence, this study proposes a promising candidates for storage nodes in the next-generation DRAM capacitors.

Sodium and Potassium storage behaviour in AgNbO3 Perovskite

In this work, we report on the investigation the perovskite‐type AgNbO3 as a model negative electrode for sodium and potassium systems. We demonstrated that during the initial discharge, regardless of the inserted cation, the material undergoes an activation mechanism that induces a crystalline‐to‐amorphous transition. This transition, in turn, leads to an enhancement of the electrode capacity. At 5A.g‐1 sodium‐ion intercalated AgNbO3 and Potassium‐ion intercalated AgNbO3 display capacities of 81mAh.g‐1 and 60mAh.g‐1, respectively. Furthermore, both electrodes display good cycling stability and efficiency over 350 cycles at 1A g−1.

Quasi-Homogeneous Bromine Phase in Zinc-Bromine Batteries with Advanced Energy Efficiency and Energy Density

Abstract Regarding energy density, kinetics, and reversibility, the zinc-bromine batteries (ZBBs) exhibit advantages comparable to the conventional metal hydride nickel batteries as aqueous systems. However, the development of ZBBs has been impeded by two critical challenges: the self-discharge of Br-Br species cross-over and the short circuit caused by zinc dendrites. Achieving high energy density necessitates a large areal capacity electrode and tight battery assembly, which introduces additional hurdles. Addressing these challenges, we have successfully implemented a novel quasi-homogeneous bromine phase. Our optimized approach has realized ZBBs with a remarkable energy efficiency (EE) of 92.7% based on an areal capacity of 12 mA h cm-2 in a period duration of 13 h, an energy density of whole battery (EDB) of 80 W h L-1 with average EE of 92.5% for an extended cycle life of approximately 500 cycles, and a maximum EDB of 186 W h L-1 without pre-added zinc metal. This innovative work holds practical significance for developing ZBBs and providing insights and solutions to critical challenges.

Designing nano-heterostructured nickel doped tin sulfide/tin oxide as binder free electrode material for supercapattery

New generation of electrochemical energy storage devices (EESD) such as supercapattery is being intensively studied as it merges the ideal energy density of batteries and optimal power density of supercapacitors in a single device. A multitude of parameters such as the method of electrodes preparation can affect the performance of supercapattery. In this research, nickel doped tin sulfide /tin oxide (SnS@Ni/SnO2) heterostructures were grown directly on the Ni foam and subjected to different calcination temperatures to study their effect on formation, properties, and electrochemical performance through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and electrochemical tests. The optimized SnS@Ni/SnO2 electrode achieved a maximum specific capacity of 319 C g− 1 while activated carbon based capacitive electrode exhibited maximum specific capacitance of 381.19 Fg− 1. Besides, capacitive electrodes for the supercapattery were optimized by incorporating different conductive materials such as acetylene black (AB), carbon nanotubes (CNT) and graphene (GR). Assembling these optimized electrodes with the aid of charge balancing equation, the assembled supercapattery was able to achieve outstanding maximum energy density and power density of 36.04 Wh kg− 1 and 12.48 kW kg− 1 with capacity retention of 91% over 4,000 charge/discharge cycles.

Experimental and theoretical investigation of high-performance green-synthesized NaTiO2/AC nanocomposite as high-capacity electrodes for next-generation sodium-ion capacitors

Experimental and theoretical investigation of high-performance green-synthesized NaTiO2/AC nanocomposite as high-capacity electrodes for next-generation sodium-ion capacitors

One-Step laser induced molybdenum carbide/graphene hybrid electrode for supercapacitor

Transition metal carbides (TMCs) have garnered significant attention in various energy applications owing to their outstanding conductive and electrochemical properties. Despite these advantages, challenges persist in terms of non-toxicity and efficient fabrication methods. In this study, a Mo3C2/laser-induced graphene (LIG) heterostructure was synthesized via one-step CO2 laser induced conversion process. The specific area capacitance of the Mo3C2/LIG hybrid electrode reached 23.5 mF cm−2, which is 2.5 times higher than that of pure Mo3C2 and 9 times greater than pure LIG electrodes. Moreover, the hybrid electrode exhibited robust cycling stability, maintaining 98.4 % of its initial capacitance after 10,000 charge–discharge cycles. Theoretical simulation also revealed superior hydrogen adsorption and high electrical conductivity of the Mo3C2/LIG hybrid electrode. This work presents a promising approach for developing advanced molybdenum carbide-based composites and offers an alternative strategy for enhancing the electrochemical performance of capacitive electrodes.

An Antiferroelectric‐Coated Metal Foam Infiltrated with Liquid Metal as a Dielectric Capacitor

Nickel metal foams serve as both a substrate and bottom electrode for a dielectric capacitor using atomic‐layer deposition (ALD) and a eutectic gallium–indium (EGaIn) liquid metal (LQM) counter electrode. The conformal dielectric has a composition of 6.25% Al–HfO2 in the antiferroelectric phase, confirmed with polarization versus electric field measurements. Liquid EGaIn is pressure‐infiltrated within the coated foams to form the dielectric capacitor. Capacitances up to 4 μF are realized. Calorimetry of the infiltrated capacitor shows a 60 J g−1 latent heat upon melting a frozen EGaIn electrode, suggesting that the phase change can alleviate thermal deviations from pulsed power capacitor operation. Infiltrated capacitors are also shown to survive bending and freeze–thaw cycles. The metal foam–ALD dielectric–LQM capacitor shows a combined set of thermal and electrical properties not available in other classes of capacitors.

Hierarchical nickel phosphide/carbon nanofibers for high performance pseudocapacitors

Nickel phosphide (Ni3P)/Carbon nanofibers (CNFs) with controllable sizes and morphologies are synthesized using micro arc oxidation method combined with thermochemical vapor deposition, with adjustment of different annealing temperatures to control the dimension of CNFs. In this study, we report the in situ formation of transition metal phosphide nanoparticles through the conversion of 1D Ni5TiO7 nanowires. This fabrication strategy ensures the high growth density of CNFs. The initially formed Ni3P nanoparticles boost the catalytic growth of CNFs, which feature a high specific surface area and excellent conductivity. Together with redox electrolyte, the specific capacitance of Ni3P/CNFs based pseudocapacitor (PC) is 114.6 mF cm−2 at a scan rate of 10 mV s−1 and maintains 95.0 % of initial capacity after 10,000 cyclic charging/discharging test. Moreover, such composite based symmetric PCs offer an energy density of as high as 31.6 Wh kg−1 accompanied with a power density of 10.3 kW kg−1. The performance of formed PC devices is comparable to market-available (Li-/Na-) batteries. Therefore, Ni3P/CNFs composite film is a suitable capacitor electrode material for constructing high performance symmetric carbon material based PCs.

Supercapacitor electrodes derived from ultra-high surface area activated carbon spheres synthesized by fluidized activation

This study thoroughly investigated the effects of activation conditions on pore structure development using response surface methodology with a central composite design. The activated carbon sphere (ACS) derived from phenolic formaldehyde resins by carbonization and fluidized activation was examined and characterized. The pore size distribution of ACS samples was all in the microporous and mesoporous scales. ACS with an ultra-high specific surface area of 3142 m2 g−1 and total pore volume of 1.513 cm3 g−1 was successfully obtained at 900 °C for 4 h. Electric double-layer capacitor (EDLC) electrodes derived from ACS with different activation conditions were examined by using cyclic voltammetry and galvanostatic charge/discharge to comprehend the influence of surface area, pore volumes, and the amount of binder on the electrochemical performance. The optimal EDLC electrode was obtained using ACS with the largest specific surface area and pore volume with 5 wt% of binder addition. The specific capacitance was 143.7 F g−1 in a 1 M H2SO4 solution. The cyclical stability of the carbon electrode was also examined under 5000 cycles, and the charge/discharge efficiency remained nearly 100 % without deterioration. This study provides insights into fabricating ultra-high surface area ACS and their potential application as supercapacitors.

Phase change-mediated core-sheath 3D printing of hollow microlattice pseudocapacitive aerogel electrode with favorable electrochemical properties

Channel-interconnected regulation within 3D-printed pseudocapacitive electrode architecture to generate high active material loading/utilization and fast ion transport is pivotal but challenging for implementing high-performance pseudocapacitance system. Herein, we demonstrated an innovative phase change-mediated core-sheath direct ink writing (DIW) 3D printing strategy for controllably constructing pseudocapacitive hollow-microlattice graphene/NiCo2O4 aerogel (HGNA) electrode, with regular hollow channels in printed filaments and abundant well-interconnected hierarchical pores built by jointing tortuous pseudocapacitive graphene nanosheets. The unique architectural features facilitated highly efficient diffusion and infiltration of substance throughout the entire thick filaments from both “interior-exterior” and “exterior-interior” directions, thereby enabling high-level yet effective loading of active materials as well as unimpeded ion transport across the printed bulk-structured electrode. Kinetics analysis revealed that the capacitance of pseudocapacitive HGNA electrode was primarily contributed from fast kinetic process. An asymmetric device assembled with DIW-printed HGNA electrode boasted a high energy storage performance with capacitance of 3.43 F cm−2 and energy density of 1.01 mWh cm−2, while featuring remarkable cycling stability (87% after 8000 cycles) and superior capacity even at large electrode thickness. This work opens a promising route for processing rational pseudocapacitive electrode architectures toward high-capacity, fast-kinetics devices.

Surface chemo-mechanics coupling of MnO2/Au layered composites under electrochemical environment

The intersection of surface mechanics and electrochemistry has gradually become a prominent topic in the realm of new energy research. To explore the influence of the electrochemical process on the stress of energy storage electrode composite, supercapacitor material manganese dioxide (MnO2) was selected as the coating and the MnO2/Au composites were prepared by the electrochemical deposition. The surface stress of MnO2/Au composites under different electrochemical modes and the stress variation law of MnO2 with varying thicknesses were determined. The addition of MnO2 could alter the stress response and the strain magnitude of the gold electrode with varied electrochemical potential. The reversible tensile strain within the Au surface during 0.3 ∼ 0.8 V charging was induced by the absorption of SO42−, while the compressive strain of the MnO2/Au composites was related to the extraction of Na+ ions resulting from the redox pseudocapacitance of MnO2. Notably, the produced stress exhibited a linear correlation with the capacitance. And the long-cycle tests revealed that as the specific capacitance of electrodes decreased, the induced tensile stress progressively diminished. This study emphasized the surface chemo-mechanics coupling of both the Au layer and MnO2/Au composites, which would provide a new approach to regulating surface strain in the solid–liquid interface.

Fabrication of asymmetric supercapacitors by laser processing of activated carbon-based electrodes produced from rice husk waste

The development of supercapacitors (SCs) by using carbon electrodes obtained from biomass waste simultaneously promotes the optimized use of the renewable energy by its high-powered storage, and the reduction of contamination in nature. Such industrial sector would be an excellent opportunity also for the developing nations, promoting their economic growth by the conversion of biowaste into added value goods. However, such carbon may not reach the desired performance for SCs. In this work, we used laser processing technology for enhancing the capacitance of SC electrodes composed of activated carbon obtained from rice husk produced in Nigerian farmlands. The activated carbon powder was synthesized by conventional carbonization-chemical activation processes and treated with microwaves. Afterwards, the CO2 laser processing of thin film electrodes composed of a mixture of the carbon powder with carbon black (conductive additive), and precursors as urea (for doping of the activated carbon with nitrogen), or manganese nitrate (for the crystallization of pseudocapacitive Mn3O4 nanoparticles on the carbon surface) was carried out for obtaining enhanced positrodes and negatrodes. The resulting hybrid electrodes exhibited a 3-fold increase of the capacitance (up to 134 F/g @ 10 mV/s) as compared to the raw carbon in the [0, 0.8] V potential window. Asymmetric SC devices integrated by carbon (-)//carbon-Mn3O4 (+) laser-treated electrodes, operating at 1.2 V voltage, revealed up to 300 × higher energy and power densities than symmetric SCs composed of raw carbon electrodes.

Operando tracking of ion population changes in the EDL electrode of a lithium-ion capacitor during its charge/discharge

This study elucidates in-pore ion population changes in an activated carbon (AC)-based electrode operating within an extended potential range, akin to the positive electrode of a lithium-ion capacitor (LIC). Molecular dynamics (MD) simulations applied to a battery-type electrolyte (1 mol L−1 LiPF6 in EC:DMC), both in bulk and adsorbed within a model porous carbon, reveal partial solvation of Li⁺ cations within the pores and complete desolvation of PF6⁻ anions in both states. Operando electrochemical dilatometry (ECD), in situ potentiostatic electrochemical impedance spectroscopy, and operando Raman spectroscopy on AC electrodes confirm: (i) ionic exchange followed by anion adsorption during initial hole injection from the point of zero charge (PZC) to 4.5 V vs. Li/Li⁺; (ii) desorption and peak liberation of trapped PF6⁻ at 3.2 V vs. Li/Li⁺ during hole withdrawal; (iii) perm-selective adsorption of partially solvated Li⁺ during electron injection down to 2.2 V vs. Li/Li⁺; (iv) cation desorption during electron withdrawal up to PZC followed by similar ionic exchange and anion adsorption (as described in (i)) at potentials above the PZC, however with peak liberation of trapped Li⁺ at 3.8 V vs. Li/Li⁺. The high polarization required to extract trapped ions from the pores may explain the reduced lifespan of LICs, requiring further work to eliminate trapping by optimizing porous texture.

Functionalized biobased carbon electrodes for selective phosphorus removal by capacitive deionization: Application and theory study

Capacitive deionization (CDI) emerges as a viable and efficient strategy for the removal and recovery of phosphorus from wastewater. However, the economic feasibility and complex synthesis of current electrode materials restrict its broader industrial application. To overcome the limitation, we fabricated aminated biobased electrode materials (MRSCN) from rice straw, forming active sites and hydrogen bonding interaction interfaces throughout the bulk phase by the nitrogen sites and peripheral amino groups in MRSCN, thereby enhancing the rapid enrichment and selective adsorption of phosphates. The phosphate adsorption capacity of MRSCN electrode reached up to 5.03 mg P/g at 1.2 V. In the presence of competing anions (Cl-, NO3– and SO42-), MRSCN exhibited markedly improved selective adsorption for phosphorus. Furthermore, density functional theory (DFT) calculations revealed that the incorporation of nitrogen active sites optimized the electronic structure of MRSCN. Meanwhile, H2PO4- and HPO42- anions served as hydrogen bond donors to the amino groups, leading to a more robust binding affinity between MRSCN and phosphates relative to other anions. The synergistic interaction between nitrogen sites and amino groups in facilitating selective phosphate removal was validated at the molecular scale. This study demonstrated the considerable potential of modified biobased carbon materials for the application in phosphate removal utilizing the CDI technique.