Porous Electrodes Research Articles

Carbonized porous zeolitic imidazolate framework as promising electrode for electrochemical supercapacitors

In order to manufacture effective supercapacitors with improved electrochemical performance, it is imperative to investigate greater surface area electrode materials. This work describes the development of a cost-effective method for the carbonization of porous zeolitic imidazole framework (ZIF8) to utilize as electrode of electrochemical supercapacitors. The electrode materials were prepared by synthesizing highly porous ZIF8-P followed by pyrolysis at 500 °C (ZIF8-P-500). The pyrolysis of ZIF-8 significantly strengthened the porous behavior by maintaining their hexagonal particles and obtaining high surface to volume ratio. The measurements using constant current charge/discharge (GCD) and cyclic voltammetry (CV) were used to evaluate the electrochemical capacitance characteristics of the synthesized ZIF8-P based electrode. The supercapacitor assembly using the optimized ZIF8-P electrode exhibited a high specific capacitance of ∼423.9 Fg–1 with exceptional cycle stability by maintaining capacitance of ∼86.7 % from its initial capacitance after 5000 cycles. Thus, the results indicate that the ZIF8-P based supercapacitor offers a compelling path for creating porous carbon electrodes from MOFs using low cost pyrolysis for advancing supercapacitor technology.

A hydrophilic porous graphene aerogel electrode with a large specific surface area for high-performance all-aqueous thermally regenerative batteries

All-aqueous thermally regenerative batteries (ATRBs) have shown great potential in harvesting low-grade waste heat. In this study, a hydrophilic porous graphene aerogel (GA) electrode developed by an ice template was developed for ATRBs to enhance electricity generation. The physicochemical property of GA was analyzed by traditional characterization. The main functional group of GA was N–H, which offered ATRBs a high hydrophilic surface. As a result of the ice templates, the diameter of pores in GA was almost lower than 4 nm, which provided a high specific area and good wettability. In addition, density functional theory calculations were carried out to verify the superiority of good electrical conductivity and strong adsorption on the cupric ions. Therefore, ATRB with GA achieved a competitive performance (a peak power density of 432 W/m2), illustrating great potential in the future thermoelectricity conversion application.

Metal-organic framework derived porous nanosheets-like Co3O4 electrodes on stainless steel with high-performance for supercapacitors

In this work, three-dimensional (3D) nanoporous MOF-derived Co3O4 was successfully prepared by a facile, easy, and rapid solvothermal method on a stainless steel substrate using 1, 4-BDC organic linker and a precursor. Additionally, the effects of the Co-precursor and organic linker on the structure, composition, and morphology of the prepared MOF-derived Co3O4 samples were investigated through an XRD study, which indicated that the MOF-derived Co3O4 thin films exhibited crystalline nature upon deposition on the stainless steel substrate. FE-SEM revealed a porous nanosheet-like morphology. EDAX analysis confirmed the formation of the MOF-derived Co3O4 structure, indicating the presence of cobalt, oxygen, and carbon elements. The oxidation states of the prepared MOF-derived Co3O4 thin films were determined by X-ray photoelectron spectroscopy. Furthermore, the electrochemical performance of the MOF-derived Co3O4 samples was evaluated in a three-electrode system using 1 M KOH electrolyte. Consequently, optimized MOF-derived Co3O4 exhibited excellent electrochemical performance attributed to these advantages. The C3 sample demonstrated an outstanding specific capacitance of 1210 F/g at a current density of 0.5 mA/cm², along with remarkable cyclic stability retention of 94.30 % after 4000 charging/discharging cycles. Additionally, the MOF-derived Co3O4 (C3) electrode showed an excellent energy density of 35.70 Wh/kg and a power density of 4.5 kW/kg. As a result, the unique hierarchical porous structure of MOF-derived Co3O4 also offers effective pathways and excellent electrochemical performance, making it a promising candidate for advanced electrode materials in high-performance supercapacitors.

Bioactive Ion-Confined Ultracapacitive Memristors with Neuromorphic Functions.

The field of bioinspired iontronics, bridging electronic devices and ionic systems, has multiple biological applications. Carbon-based ultracapacitive devices hold promise for controlling bioactive ions via electric double layers due to their high-surface-area and biocompatible porous carbon electrodes. However, the interplay between complex bioactive ions and porous carbons remains unclear due to the variety of structures of bioactive ions present in biological systems. Herein, we investigate the adsorption behavior of a series of bioactive ammonium-based cations with varying alkyl chain lengths in nanoporous carbons. We find that strong physisorption results from the synergistic hydrophobic interaction and electrostatic attraction between porous carbons (with a negative zeta potential) and bioactive cations. Bioactive cations with varying alkyl chain lengths can be irreversibly physically adsorbed and confined within nanoporous carbons resulting in anion enrichment and depletion during electric polarization. This situation, in turn, results in a characteristic memristive behavior in all-carbon capacitive ionic memristor devices. Our findings highlight the relationship between the resistance state of the memristor and ion adsorption mechanisms in all-carbon capacitive devices, which hold potential for future transmitter delivery, biointerfacing, and neuromorphic devices.

Bioactive Ion‐Confined Ultracapacitive Memristors with Neuromorphic Functions

The field of bioinspired iontronics, bridging electronic devices and ionic systems, has multiple biological applications. Carbon‐based ultracapacitive devices hold promise for controlling bioactive ions via electric double layers due to their high‐surface‐area and biocompatible porous carbon electrodes. However, the interplay between complex bioactive ions and porous carbons remains unclear due to the variety of structures of bioactive ions present in biological systems. Herein, we investigate the adsorption behavior of a series of bioactive ammonium‐based cations with varying alkyl chain lengths in nanoporous carbons. We find that strong physisorption results from the synergistic hydrophobic interaction and electrostatic attraction between porous carbons (with a negative zeta potential) and bioactive cations. Bioactive cations with varying alkyl chain lengths can be irreversibly physically adsorbed and confined within nanoporous carbons resulting in anion enrichment and depletion during electric polarization. This situation, in turn, results in a characteristic memristive behavior in all‐carbon capacitive ionic memristor devices. Our findings highlight the relationship between the resistance state of the memristor and ion adsorption mechanisms in all‐carbon capacitive devices, which hold potential for future transmitter delivery, biointerfacing, and neuromorphic devices.

Hierarchical porous self-supporting graphite carbon electrodes based on the biomimetic structure for supercapacitors

Regulating pore structure, improving conductivity, and reducing the influence of binders are considered important ways to improve the performance of carbon-based electrode materials for supercapacitors. This study successfully prepares a highly graphitized hierarchical porous self-supporting carbon electrode without the need for binders, conductive agents, and current collectors using low-cost and abundant pine wood as the precursor and K2FeO4 as the activator and catalyst. The self-supporting electrode inherits the biological structure of biomass and forms a large number of micro mesopores through activation, showing an excellent 3D interconnected pore structure, and achieves a high degree of graphitization with the ID/IG ratio of being only 0.47. The self-supporting electrode facilitates the effective transport of electrolyte ions and electrons, demonstrating excellent electrochemical performance. It achieves an area specific capacitance of 3.64 F cm−2 under a current density of 5 mA cm−2. Two identical self-supporting electrodes are employed to construct a symmetric supercapacitor. The supercapacitor exhibits an energy density of 148.61 μWh cm−2 at a power density of 1 mW cm−2, with a capacity retention rate of 89.26 % after 10,000 charge-discharge cycles.

Electroanalysis of bromate at riboflavin impregnated Ketjen black porous electrode via an autocatalytic cycle with finite length diffusion

The emergence of elevated concentrations of bromate, classified as a 2B type carcinogen, in drinking water following the treatment of water supplies with ozonation and other oxidation methods has underscored the importance of developing methods for reliable and rapid screening of drinking water. In this work, we report the use of electro activated riboflavin (RF) impregnated Ketjen black (KB) modified screen-printed electrode (elRF@KB-SPE) for the determination of bromate. The sensing surfaces were subjected to morphological and structural characterization using scanning electron microscopy and Raman spectroscopy. These analyses confirmed the successful modification of the electrode with an extended elRF@KB porous coating. Based on cyclic voltammetry (CV) and electrochemical impedance spectroscopy measurements, the response of elRF@KB-SPE towards bromate can be described through a dual mechanism involving i) an autocatalytic chemical/electrochemical process that predominantly occurs in the finite length pores of KB, and ii) an RF-mediated electrocatalytic process. Notably, the data demonstrated that the advanced electrocatalytic properties of the otherwise electrocatalytically inactive absorbed RF molecules are endowed after a simple electro activation process (three CV scans). Amperometric measurements at −0.05 V vs. Ag/AgCl revealed a linear relationship between the current response and the concentration of bromates over the concentration range 0.50−18.0 μM, achieving a limit of detection (3σ/slope) of 0.04 μM. The interference effect of various electroactive species was investigated demonstrating that elRF@KB-SPE is highly selective to bromate. The analytical utility of the method was evaluated in spiked tap water samples. Recoveries were 91.2 − 106.4 %.

Designing tortuous gas diffusion path for hydrogen oxidation reaction and stability of solid oxide fuel cell: An engineered microstructural aspect in anode functional layer

Commercialization of solid oxide fuel cell (SOFC) is restricted due to long term performance degradation. SOFC is activated by diffusion of gasses through porous electrodes to the electrochemical active sites termed as triple phase boundary (TPB). Among all other parameters, tortuosity influences the functionality of TPB and is responsible for gas transport which relates its bulk diffusion and its migration through the porous electrode. The novelty of present research lies in designing of optimum tortuous gas diffusion path for effective hydrogen oxidation reaction through engineered morphology of anode functional layer. The study involves the fabrication of anode for planar SOFC using four configurations. Configuration A and B involves anode monolith synthesized through conventional route [(40 vol % Ni in dispersed-8 mol % Yttria stabilized zirconia (SZ)] and functional core-shell Ni@SZ. Configuration C (trilayer anode, TLA) is designed to have graded matrix with conventional Ni-SZ (fuel inlet side), 28 vol% Ni@SZ acting as active layer and 32 vol % Ni@SZ sandwiched in between. Configuration D consists of Ni@SZ as the active layer onto conventional Ni-SZ support. TLA is found to have minimum tortuosity (τ = 2) with maximum cell endurance for 2000 h (2.06–8.2 %/1000 h@800 °C under load). Ni@SZ with unimodal pore distribution is capable of reducing the activation barrier for charge migration (14 kJmol-1) compared to Ni-SZ (32 kJmol-1) with multimodal pores. This results in higher redox tolerance for Configuration B-D (4–7 % conductivity degradation/20 cycles) compared to Configuration A (27% conductivity degradation/20 cycles). Post mortem analyses of microstructure support the retention of core-shell morphology of Ni@SZ with lower deterioration.

Multifunctional fluorinated phosphonate-based localized high concentration electrolytes for safer and high-performance lithium-based batteries

This study introduces a novel fluorinated phosphonate-based additive, Bis(2,2,2-trifluoroethyl)(methoxycarbonylmethyl)phosphonate (BTCMP), in a localized high-concentration electrolyte (LHCE) to address key challenges in lithium metal batteries (LMBs), such as dendritic lithium growth and porous electrode morphology. The pristine LHCE forms a fluorine-rich solid electrolyte interphase (SEI) layer, primarily composed of lithium fluoride (LiF). However, the pristine LHCE suffers from severe electrolyte decomposition, forming a thicker and more resistive cathode electrolyte interphase (CEI), leading to increased impedance and reduced cyclability. Interestingly, Density Functional Theory (DFT) investigations revealed that the BTCMP inclusion modifies the solvation structure by dispersing the aggregates into smaller fragments, facilitating easier Li+ migration than the pristine LHCE. The addition of BTCMP suppresses solvent decomposition as confirmed by an increasing trend in the lowest unoccupied molecular orbital (LUMO) of corresponding LHCE molecules. Further, the presence of BTCMP results in a thinner and more stable CEI, reducing electrolyte decomposition, maintaining better ion transport, and preserving the cathode's structural integrity, as supported by TEM and XPS analysis. The BTCMP-based F-rich LHCE retained 82 % of its initial capacity while maintaining a coulombic efficiency of 99.5 % after 200 cycles in a Li||LNMO cell while the pristine LHCE only retained 47.2 % of initial capacity post-150 cycles. Additionally, the flame-retardant properties of BTCMP-based LHCE highlight its safety compared to commercial electrolytes.

Selective electro-capacitive deionization of Yb(III) by nanospherical N-doped carbon supported nickel‑iron bimetallic oxide, nitride and phosphide

The separation of rare earth elements from the mining waste water is highly important but still facing challenge. In this study, three different porous composite electrode materials were well-designed by decorating the nickel‑iron bimetallic oxide, nitride or phosphide onto nitrogen-doped carbon nanosphere, respectively (termed as NiFeO@NC, NiFeN@NC and NiFeP@NC), and utilized in capacitive deionization device for electrosorption of Yb(III) from water under the low-voltage electric field. The characterization and electrochemical results indicated that the incorporation of N or P atom lead to the reduced specific surface area and the enhanced electrochemical properties (i.e., larger specific capacitance, lower charge transfer resistance). In addition, NiFeN@NC and NiFeP@NC exhibited the excellent electrosorption capacities of Yb(III) with 105.24 mg·g−1 and 90.31 mg·g−1, respectively, under conditions of a flow rate of 20 mL·min−1, a voltage of 1.2 V, and pH of 5.0, which was extremely higher than NiFeO@NC (i.e., 50.7 mg·g−1). Moreover, all these three materials also demonstrated the remarkable electrosorption selectivity of Yb(III) from the mixed solution, and the robust durability with over 90 % of initial capacities after ten consecutive electrosorption-desorption cycles. Furthermore, the XPS characterizations and electrosorption results revealed that the electrosorption mechanism mainly depended on the synergistic effects of intrinsic Faraday redox reaction, electric double layer capacitance and active binding sites. Therefore, this work provided a feasible strategy for the separation of rare earth elements from aqueous solution, and the prospective applications related to the recovery of rare earth elements from mining wastes or spent permanent magnets in future life.

Optimising Sodium Borohydride Reduction of Platinum onto Nafion-117 in the Electroless Plating of Ionic Polymer–Metal Composites

The effects of process parameters on the electroless plating of ionic polymer–metal composites (IPMCs) were studied in this work. Specifically, the NaBH4 reduction of platinum onto Nafion-117 was characterised. The effects of the concurrent variation of NaBH4 concentration, stir time and temperature on surface resistance were studied through a full factorial design. The three-factor three-level factorial design resulted in 27 runs. Surface resistance was measured using a four-point probe. A regression model with an R2 value of 97.45% was obtained. Surface resistance was found to decrease with increasing stir time (20 to 60 min) and temperature (20 to 60 °C). These responses were attributed to increased platinisation rates, resulting in more uniform electrode deposition, confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDAX) analysis. Surface resistance decreased, going from 1% to 5% NaBH4 concentration, but increased from 5% to 10% concentration. This behaviour was attributed to surface morphology: increased grain size inducing porous electrodes, in line with findings in the literature. The maximum tip displacement, measured through a computer vision system, as well as the maximum blocking force, measured through an analytical balance setup, were obtained for all 27 samples. The varying results were discussed with regards to surface and cross-sectional SEMs, alongside EDAX analysis.

Bimolecular Salt Strategy Enhances Heteroatom Doping and Porosity Optimization of Porous Carbon for Supercapacitors.

The incompatibility between electrolyte ions and electrode pore sizes, coupled with the extensive use of activators and dopants, significantly restricts the fabrication of porous carbon materials. Consequently, developing environmentally sustainable and efficient methodologies that exploit the intrinsic properties and pretreatment of materials to facilitate self-activation and self-doping becomes crucial. In this study, potassium histidine and magnesium histidine molecular salts were synthesized as precursors, enabling specific ion activation and bimetallic template-directed tunable porosity through a one-step carbonization process. Notably, the ratio of bimolecular salts significantly influenced the porous structure of carbon, the properties of heteroatoms, and the electrochemical performance. By optimizing the ratio, the porous carbon materials exhibited high accessibility to electrolyte ions and effective ion/electron transport channels. Consequently, the optimal sample (NOSPC-2) achieved a high specific capacitance of 318 F g-1 at 0.1 A g-1 and a good capacitance retention rate of 98.8% after 50,000 cycles at 5 A g-1. In addition, NOSPC-2 also boasted high energy density and power density, reaching 22 Wh kg-1 and 25 kW kg-1, respectively. This research represents a significant stride in advancing preparation technologies for small molecule derived porous carbon materials, providing valuable insights for the rational design of carbon electrode materials for capacitive energy storage.

Design and optimization of pore structure in three-dimensional micro-nano hierarchical SnOx supercapacitor electrodes for enhanced ion diffusion

This paper introduced a novel continuous electrochemical synthesis strategy to address the challenges of slow ion/electron transport rates and low electrode reaction efficiency in Sn-based electrode materials. This approach leveraged the induction and confinement of bubble templates to assist atoms deposition, generating micron-sized tin skeletons. Subsequently, these skeletons were transformed into a secondary nanoporous structure through dissolution-deposition etching effects. From liquid-phase ions to metal skeletons to porous oxides, the sequential material transformations realized the innovative design of three-dimensional (3D) hierarchical structures. This strategy ingeniously exploited the diffusion advantages of the electrolyte in the micro-nano hierarchical structure to achieve the diffusion enhancement of ions, thus solving the “dead surface” problem in the energy storage process. This study revealed the thermodynamic and kinetic feasibility of the constructed 3D micro-nano hierarchical structure through electrochemical evaluations and theoretical calculations, and elucidated the constitutive relationship in which the electrochemical performance of the electrode materials was enhanced with decreasing pore size. In addition, design optimization of pore structures and modelling exploration of pore size limit values were conducted based on density functional theory (DFT) simulations. These simulations demonstrated the advantages of hierarchical structures with controllable pore sizes in facilitating electrolyte ion diffusion, predicting an optimal pore size of 55 μm for 3D hierarchical porous SnOx electrodes. The integration of this innovative structural design with simulation insights offered significant implications for enhancing the sluggish electrode reaction kinetics of metal oxide electrode materials, advancing the controllable fabrication of high-performance energy storage devices.

Revisiting the Electrochemical Impedance Spectroscopy of Porous Electrodes in Li‐ion Batteries by Employing Reference Electrode

AbstractElectrochemical impedance spectroscopy (EIS), characterized by its non‐destructive and in situ nature, plays a crucial role in comprehending the thermodynamic and kinetic processes occurring within Li‐ion batteries. However, there is a lack of consistent and coherent physical interpretations for the EIS of porous electrodes. Therefore, it is imperative to conduct thorough investigations into the underlying physical mechanisms of EIS. Herein, by employing reference electrode in batteries, we revisit the associated physical interpretation of EIS at different frequencies. Combining different battery configurations, temperature‐dependent experiments, and elaborated distribution of relaxation time analysis, we find that the ion transport in porous electrode channels and pseudo‐capacitance behavior dominate the high‐frequency and mid‐frequency impedance arcs, respectively. This work offers a perspective for the physical interpretation of EIS and also sheds light on the understanding of EIS characteristics in other advanced energy storage systems.

Selective adsorption of divalent and trivalent cations in porous electrodes.

The capacitive deionization technology uses the electrochemical adsorption of ions in porous electrodes to desalinate seawater or brackish water. Recently, capacitive deionization has gained significant attention as a technology for selective adsorption of ionic species from multicomponent aqueous electrolytes. To investigate the mechanism of selective adsorption at the molecular level, we performed molecular dynamics simulations of aqueous electrolytes and porous electrodes with different divalent or trivalent ions, electrode pore sizes, and applied voltages. We calculated the free energy barriers preventing ions from entering the pores of the electrode and the structure of the water molecules near the ions and the electrode surface under various conditions. Our results suggest that, when the pore and ion sizes are comparable, the steric and electrostatic interactions between the hydrated ions and electrode pores are comparable in magnitude. Moreover, the relative importance of the two interactions can be reversed by slight changes in the external conditions, such as the ion size, valence of the ions, electrode pore size, and applied voltage. Thus, by finely tuning the electrode pore size and the applied voltage, it may be possible to selectively adsorb a particular ionic species from a multicomponent electrolyte through capacitive deionization using a porous electrode.

Hydrothermal preparation of cotton-based rGO/N-doped porous carbon as electrode materials of supercapacitors

Porous carbon electrode materials are commonly used in supercapacitors due to their inexpensive raw materials, simple processing, and low pollution, aligning with the vision for green energy storage. Consequently, there is a current trend to discover porous carbon electrode materials with superior electrochemical properties. To enhance the pore volume ratio and electrochemical performance of porous carbon materials, this study proposes a hydrothermal method to pretreat the raw materials, facilitating the doping of nitrogen from urea. Moreover, graphene is introduced for its excellent conductivity, which can further improve the electrochemical properties of the material. We found a new one-step reduction Graphene Oxide (rGO)and the doping of nitrogen (N) elements were optimized by hydrothermal method, the wettability and pseudo-capacitance performance of the material are improved, and HTPC-700 shows a very excellent specific capacitance, its specific capacitance reaches 600 F g−1 at a current density of 0.5 A g−1, and it even reaches 260 F g−1 at a current density of 1 A g−1. Meanwhile the power density and energy density are respectively 74 W h kg−1 and 280 W kg−1. It also exhibits a remarkable capacitance retention rate of over 98.7 % after 5000 cycles at a current density of 1 A g−1. Additionally, it demonstrates a rich ant nest-like pore structure and good specific surface area of 2427 m2/g, and a large pore volume of 1.09 cm3/g after carbonization and KOH activation. This study offers a novel doping method and provides a unique perspective for the development of porous carbon electrodes.

Enhancing Cu2+ removal efficiency in a hybrid electrodeposition system based on vertically placed thermally regenerative batteries using gradient porous electrodes

Thermally regenerative batteries (TRB) can combine with an electrodeposition cell (EC) to develop a hybrid system (TRB-EC) for low-grade waste heat disposal and Cu2+ recovery from wastewater. To improve the Cu2+ removal efficiency in EC, a vertically placed reactor and gradient porous electrodes are proposed to remiss ammonia crossover and enhance power generation in TRB. The vertically placed reactor effectively reduced the NH3 concentration difference on the both side of anion exchange membrane, inhibiting NH3 transmembrane transport. Moreover, the gradient porous anode is used to adjust the physical and chemical distribution in anode chamber. The results indicate that the maximum power density of 14.6 W/m−2 is obtained in a TRB employing the gradient porous electrodes (the pore order is large-middle-small scale), which is 22 % better than that of electrodes with uniform-size pores. Through the strategy of flow catholyte, the maximum power density can be further increased to 19.4 W/m−2 and the cathodic coulombic efficiency is improved to 92.7 %. Due to above optimal design, the Cu2+ removal efficiency of the hybrid system can reach an impressive value of 98.4 % (87.7 % in TRBs and 10.7 % in EC), showing a promising method of heat waste and Cu2+ disposal.

Effect of Hydrogen Pressure on The Mass Transfer Characteristics of Hydrogen-Bromine Flow Battery Electrodes

The mass transfer characteristics of porous carbon electrodes in the liquid side of a hydrogen bromine redox flow battery (H2-Br2 RFB) were investigated under compressive deformation caused by operation at elevated hydrogen pressure. Here, flow cell measurements of permeability and micro-particle image velocimetry (μPIV), alongside electrochemical measurements of capacitance and battery discharge were used to characterize changes in the liquid side electrode compression, in-plane liquid flow, accessible surface area, polarization, and mass transfer scaling brought by hydrogen pressure. We studied two electrode types with different structures, carbon paper and carbon cloth, in untreated well as heat-treated forms in the pressure range 0–8 bar H2. It was found that pressure-induced compression of the liquid side electrode increases the accessible area of untreated electrodes, with little effect on heat-treated electrodes, but decreases the electrochemical performance of the battery in all cases by increasing the ohmic resistance of the cell and decreasing the mass transfer coefficient of the porous electrode. Overall, heat treatment is shown to affect the rigidity, saturation behavior, and generalized mass transfer of paper electrodes but not of cloth electrodes. Our findings will guide the selection of electrode materials and operation parameters for the H2-Br2 RFB.

Modulating the electrode pore structure using the magnetic field for reduced local-oxygen transport resistance in polymer electrolyte membrane fuel cell

We utilize a magnetic field to align the pore structure of the PEMFC cathode catalyst layer in the direction of O2 infiltration. This alignment reduces the oxygen diffusion resistance within the catalyst layer, thereby augmenting the performance of the PEMFC. Membrane Electrode Assemblies (MEAs) with magnetically aligned cathodes demonstrate a 50% reduction in O2 transfer resistance compared to conventional MEAs, as verified through electrochemical experiments and it makes a performance enhancement in the I-V curve. Beyond electrochemical experimentation, electrode pore analysis utilizing 3D reconstruction and Lattice Boltzmann Direct Numerical simulation (LB-DNS) for internal flow field analysis within pores, reveals that alignment of the electrode structure in the through-plane direction enhanced pore continuity. This continuity and the resultant minimized proportion of dead pores are identified as the causative factors for the observed performance improvements.

Tuning Electrode and Separator Sizes For Enhanced Performance of Electrical Double‐Layer Capacitors

AbstractAn electrical double‐layer capacitor (EDLC) comprises two porous electrodes sandwiching an electrolyte‐permeable separator, which prevents the electrodes from short‐circuiting. While previous studies have mainly focused on electrolyte and electrode properties of EDLCs, the device configuration in terms of electrode and separator sizes received less attention, with separators often simplistically modelled as infinitely large reservoirs of ions. Herein, we investigate how the relationship between electrode and separator thicknesses impacts EDLC charging. We find that the assumption of bulk reservoir holds only under specific conditions. Moreover, we identify a tradeoff between stored energy density and pressure variations within the separator, potentially jeopardizing the EDLC durability. We also explore the influence of ionic liquid additives on EDLC charging. While prior research has shown that trace amounts of uncharged additives with strong electrode affinity can significantly enhance energy storage, we observe this effect as negligible for electrodes and separators of comparable sizes. Instead, we show how to optimize EDLC performance by fine‐tuning the concentration of additives and separator‐to‐electrode size ratio to maximize stored energy density.