Electrode Design Research Articles

Extending the π-Conjugation of a Donor-Acceptor Covalent Organic Framework for High-Rate and High-Capacity Lithium-Ion Batteries.

Realizing high-rate and high-capacity features of Lihium-organic batteries is essential for their practical use but remains a big challenge, which is due to the instrinsic poor conductivity, limited redox kinetics and low utility of organic electrode mateials. This work presents a well-designed donor-acceptor Covalent Organic Framework (COFs) with extended conjugation, mesoscale porosity, and dual redox-active centers to promote fast charge transfer and multi-electron processes. As anticipated, the prepared cathode with benzo [1,2-b:3,4-b':5,6-b''] trithiophene (BTT) as p-type and pyrene-4,5,9,10-tetraone (PTO) as n-type material (BTT-PTO-COF) delivers impressive specific capacity (218 mAh g-1 at 0.2 A g-1 in ether-based electrolyte and 275 mAh g-1 at 0.2 A g-1 in carbonate-based electrolyte) and outstanding rate capability (79 mAh g-1 at 50 A g-1 in ether-based electrolyte and 124 mAh g-1 at 10 A g-1 in carbonate-based electrolyte). In addition, the potential of BTT-PTO-COF electrode for prototype batteries has been demonstrated by full cells of dual-ion (FDIBs), which attain comparable electrochemical performances to the half cells. Moreover, mechanism studies combining ex situ characterization and theoratical calculations reveal the efficient dual-ion storage process and facile charge transfer of BTT-PTO-COF. This work not only expands the diversity of redox-active COFs but also provide concept of structure design for high-rate and high-capacity organic electrodes.

Desolvation Effect Triggered by TiS2‐TiO2 Heterostructure for Ultrahigh‐Rate Aqueous Zinc‐Ion Batteries

AbstractAqueous Zn ion batteries (AZIBs) represent a promising candidate for the next‐generation energy storage and conversion systems due to their high safety and cost‐effectiveness. However, sluggish kinetics arising from interface desolvation processes pose challenges in achieving high‐power density and long cycle life for AZIBs. Here, it is discovered for the first time that heterostructures utilize built‐in electric field forces to promote the desolvation process at the electrode‐electrolyte interface. Density functional theory (DFT) calculations and structural characterization demonstrate that heterogeneous structures simultaneously accelerate the desolvation process and enhance ion diffusion, resulting in the outstanding rate performance (160.9 mA h g−1 at 5 A g−1) of TiS2‐TiO2 heterostructures, far exceeding that of a conventional TiS2 electrode with 14.2% capacity retention. Meanwhile, the insertion/extraction of the desolvated charge carriers reduced the volume change of TiS2‐TiO2 material during the charging/discharging processes, enabling the long‐lasting cycling stability (108.6 mA h g−1 after 2000 cycles at 0.5 A g−1). This study provides instructive electrode design strategies for the construction of fast‐charging electrochemical energy storage systems.

Design and development of green electrode using graphene oxide modified with L-hypip coated with iron NPs for enantioselective electro-organic cyanation in the presence of NaCl electrolyte

This study presents the development of a cost-effective and eco-friendly electrode for the enantioselective electro-organic synthesis of (R)-2‑hydroxy-2-phenylpropanenitriles 4(a-l) with yields ranging from 88 % to 98 %. The electrode is constructed using graphene oxide (GO) modified with (2S,3R)-3-hydroxypiperidine-2-carboxylic acid (L-Hypip) as a cheap enantioselective organic linker and coated with iron (Fe) nanoparticles, referred to as GOHypip@Fe. This design aims to facilitate the efficient synthesis of (R)-2‑hydroxy-2-phenylpropanenitrile derivatives 4(a-l). Sodium chloride (NaCl), a readily available and inexpensive electrolyte, is employed to enhance the electrochemical reaction rate. The electrode underwent thorough characterization and identification using SEM, EDS, XPS, XRD, TGA, BET, CV, and FT-IR analyses. Its cost-effectiveness and eco-friendly nature highlight its potential for sustainable electro-organic synthesis processes. The synthesized (R)-2‑hydroxy-2-phenylpropanenitriles 4(a-l) were identified and characterized through melting point, 1HNMR, and CHN analyses.

Optimization of Contact Pad Design for Silver Nanowire-Based Transparent Heater to Improve Heating Characteristics.

Transparent heaters are gaining significant attention for applications such as antifog glass, smart windows, and smart farm greenhouses. A transparent heater basically consists of transparent conducting materials that serve as a heating area and contact pad electrode to apply power. To fabricate a transparent heater, materials with excellent light transmittance and low sheet resistance are required. Among various transparent conducting materials, such as Indium Tin Oxide (ITO), carbon nanotube (CNT), graphene, and silver nanowires (AgNWs), AgNWs are particularly favored due to their good electrical, optical, and mechanical properties. However, in order to improve the heating characteristics of transparent heaters, research is essential not only on improving the properties of transparent conducting materials but also on the design of contact pad electrodes that can uniformly improve current distribution. Here, we explore various shapes of contact pad electrodes for AgNW-based transparent heaters to improve current distribution. Shapes such as line, spot, twisted, and parallel-type contact pad electrodes are designed and investigated to optimize overall heating characteristics. We analyze the heating properties of these transparent heaters with various contact pad electrodes, demonstrating how their specific shape and size affect heating characteristics and uniformity. We also investigate the optimal shape of the contact pad electrode to minimize transmission loss through UV-VIS spectroscopy. As a result, we confirm that the shape of the contact pad electrode was important for simultaneously achieving high heating characteristics of 120 °C, good heating uniformity, and over 80% transparency in an AgNW-based transparent heater.

Prussian Blue-Derived Atomic Fe/Fe3C@N-Doped C Catalysts Supported by Carbon Cloth as Integrated Air Cathode for Flexible Zn-Air Batteries.

The development of an integrated air cathode with superior oxygen reduction reaction (ORR) performance is fundamental to flexible zinc-air batteries (ZABs) for wearable electronics. Herein, a self-assembled metal-organic framework (MOF)-derived strategy is proposed to prepare a atomic Fe/Fe3C@N-doped C catalysts supported by carbon cloth (CC) catalyst for use as an air cathode of flexible ZABs. The Prussian Blue precursor, which self-assembles on the surface of the carbon cloth due to electrostatic attraction, is critical in achieving the uniform dispersion of catalysts with high density loading on carbon cloth substrates. The hollow cubic structure, N-doped carbon layer coating, and the integrated electrode design can provide more accessible active sites and facilitate a rapid electron transfer and mass transport. Density functional theory (DFT) calculation reveals that the electronic interactions between the Fe-N4 and Fe3C dual active sites can optimize the adsorption-desorption behavior of oxygen intermediates formed during the ORR. Consequently, the Fe/Fe3C@N-doped C/CC exhibits an excellent half wave potential (E1/2 = 0.903V) and superior long-term cycling stability in alkaline environments. With excellent ORR performance, ZABs and flexible ZABs based on Fe/Fe3C@N-doped C/CC air cathode demonstrate excellent overall electrochemical performance in terms of open circuit voltage, maximum power density, flexibility, and cycling stability.

Advances and Challenges of Carbon‐Free Gas‐Diffusion Electrodes (GDEs) for Electrochemical CO2 Reduction

AbstractElectrochemical CO2 reduction reaction (CO2RR) coupled with renewable electricity holds promises for efficient mitigation of carbon emission impacts on the environment and turning CO2 into valuable chemicals. One important task in CO2RR development is the design and fabrication of efficient electrodes for stable operation in the long term. Gas‐diffusion electrodes (GDEs) have been employed to continuously feed CO2 to the electrolyzers. Despite significant advances in GDE design and tailoring GDE properties, the present GDEs often suffer from the critical issue of flooding due to the electrowetting of carbon‐based substrates, which hinders the transition to industrial application. To address flooding, GDEs with intrinsically hydrophobic polymeric substrates have been recently fabricated and have shown promising performances. Herein, the advances and challenges associated with carbon‐free GDEs are reviewed for CO2RR. This review first briefly outlines GDE and electrolyzers basics. Through critical discussion around the shortcomings of conventional carbon‐based GDEs, the most recent efforts to resolve flooding are summarized. Subsequently, the advances, advantages, and challenges of carbon‐free GDEs are elaborated. Finally, priorities for future studies are suggested, with the aim to support the advancement and scale‐up of carbon‐free GDEs and extend them to other electrochemical systems where gas and the electrolyte are in contact.

Molecular Probing Coupled with Density Functional Theory Calculation to Reveal the Influence of Fe Doping on Fe-NiOOH Electrode for High Current Density of Water Splitting.

Fe-doped NiOOH electrocatalysts have attracted wide interest for the exceptional oxygen evolution reaction (OER) performance, but the precise role of Fe doping on the improved intrinsic activity remains unclear. Herein, the molecular probe technique combined with density functional theory calculation is used to reveal the influence of the Fe atom on the rate-determining step of the OER reaction, where the pre-catalyst of hierarchical self-supporting NiFe layered double hydroxide [LDH] nanosheets equipped on nickel foam (NiFe LDH/NF) is generated via a facile and industrially well-matched one-pot corrosion method. The physical characterization results reveal the reconstruction of NiFe LDH into Fe-doped NiOOH for promoted OER, which has a lower OH* adsorption energy with fast subsequent steps that help in obtaining an improved charge injection efficiency compared to NiOOH. In addition, more exposed electroactive species and facile delivery of mass/electron inside the catalytic procedure actually have a high-quality contribution to the outstanding catalytic activity. Therefore, the NiFe LDH36/NF electrocatalyst provides high catalytic activities of 241 and 320mV at 10mA cm-2 toward the OER and overall water-splitting in 1m KOH. This work provides a promising avenue for the rational design of durable self-supporting electrodes toward large-scale water splitting.

Recent Advances in electrode optimization of electrochemical energy devices using Topology Optimization

Abstract Topology optimization (TO) has emerged as a prominent trend in recent years, driven by its ability to explore optimized material distributions from scratch. Recently, there has been a significant shift in the application of TO, in optimizing systems involving complex electrochemical reactions, particularly electrode porous structures. This paper aims to examine the utilization of TO in enhancing electrodes across various electrochemical devices. It encompasses a broad spectrum of applications, including the optimization of porous electrodes through the density-based method and interfaces between electrodes and electrolytes through the level-set method. The paper will delve into the challenges and opportunities associated with employing TO in electrode design for electrochemical devices. These challenges involve addressing computational complexity, the absence of theoretical foundations for optimized structures, and the fabrication of complex structures for practical real-world applications. Additionally, beyond TO, the paper will spotlight other notable techniques in the structural design of porous electrodes using mathematical optimization. By offering insights into state-of-the-art research and developments in TO's application to electrode design, this paper provides researchers with valuable resources to navigate the evolving landscape of electrode design for electrochemical energy devices.

Theoretical and Experimental Insights into Dendrite Growth in Lithium‐Metal Electrode

AbstractA stable lithium‐metal electrode can enable the shift from the Li‐ion batteries to the next generation chemistries such as Li−S and Li−O2 with significant gains in the energy density and sustainability. This transition, however, is hindered by the dendrite formation, high chemical reactivity, and volume changes of the Li electrode. Although recent advancements in computational and experimental research have deepened our understanding of these issues, the primary obstacles to the commercialization of the lithium‐metal batteries (LMBs) still persist. To address these challenges, a synergistic approach that combines computational and experimental strategies shows great promise. In this regard, this paper reviews the current experimental and theoretical understanding of the lithium‐metal electrodes in view of the initiation and growth mechanisms of the lithium dendrites and interface instability. Leveraging the strengths of both approaches can offer a holistic insight into the LMB performance and guide the development of innovative designs for electrolytes and electrodes that can enhance the stability and performance of the LMBs.

Perspectives on Photocatalytic Paper‐Based Batteries Fueled by Alcohol

AbstractAmid growing energy demands, innovative solutions are essential to power a variety of devices. Paper‐based microfluidic fuel cells (PμFCs), powered by eco‐friendly alcohols derived from biomass, present a promising option. While lightweight and disposable, they mainly rely on costly noble‐metal catalysts for high efficiency. In this context, the concept of photo paper batteries (pPBs), utilizing affordable sunlight‐activated semiconductors to drive alcohol oxidation on paper, opens the possibility to disposable and affordable energy solutions. Our review highlights recent progress in PμFCs fueled by alcohols like methanol, ethanol, ethylene glycol, and glycerol. We explore semiconductor advancements driving anodic reactions and envision the potential of pPBs. To achieve practical pPBs, refining semiconductors, electrode design, and microfluidic engineering are pivotal. This short review highlights the transformative potential of pPBs and beckons researchers to partake in shaping this new field.

Pseudo Two-Dimensional Model for the Design of Fast-Charging Lithium-Ion Battery Electrodes

Pseudo Two-Dimensional Model for the Design of Fast-Charging Lithium-Ion Battery Electrodes

Hard X-ray Photoelectron Spectroscopy Probing Fe Segregation during the Oxygen Evolution Reaction.

NiFe electrocatalysts are among the most active phases for water splitting with regard to the alkaline oxygen evolution reaction (OER). The interplay between Ni and Fe, both at the surface and in the subsurface of the catalyst, is crucial to understanding such outstanding properties and remains a subject of debate. Various phenomena, ranging from the formation of oxides/(oxy)hydroxides to the associated segregation of certain species, occur during the electrochemical reactions and add another dimension of complexity that hinders the rational design of electrodes for water splitting. In this work, we have developed the procedure for the quantification of chemical depth profiling by XPS/HAXPES measurements and applied it to two NiFe electrodes with different porosities. The main outcome of this study is related to the surface reconstruction of the electrodes during the OER, followed at two different depths by means of X-ray photoelectron spectroscopy. We find that Fe initially segregates at the surface when exposed to ambient conditions, resulting in the formation of an inactive FeOx phase. In addition, the porosity of the catalyst plays a significant role in the segregation process and thus in the performance of the electrode. In particular, the higher porosity of the nanostructured sample is responsible for a more pronounced diffusion of Fe from the subsurface to the surface with a more effective suppression of the activity of the Ni1-xFexOOH phase. These results highlight the importance of the fact that the chemical state of the surface of a multielement system is a snapshot in time, dependent on both external parameters, such as the applied potential and the adjacent electrolyte, and the underlying bulk properties accessible with HAXPES.

Tailoring electrochemical CO2 reduction selectivity over CuSn by modulating surface oxidation state with infrared laser treatment

Infrared laser treatment was used to precisely modify the surface structure of CuSn electrodes, effectively fine-tuning the selectivity of reduction products. With increasing laser power, the metallic Cu and Sn surfaces became more oxidized, and the Sn/Cu composition ratio varied with depth and further changed post-EC reaction. The diversity of reduction products, including C1 (CO, CH4, and formate), C2 (C2H4, ethanol, acetate, acetaldehyde, and glycolaldehyde), and C3 (propanol and isopropanol) compounds, shifted towards a more selective production of C1 (CO and formate) products. These tailored behaviors are attributed to variations in interfacial electronic structures, oxidation states, composition ratios, and the interaction between CO2 and the density of states (Cu, O, and Sn) near the Fermi level. The laser treatment method enables precise tuning of electrode surfaces, modulation of reduction products, and enhancement of selectivity. Moreover, this technique presents a novel approach for electrode design in the field of CO2 reduction, offering new avenues for optimizing catalytic performance.

Optimization of electrode thickness of lithium-ion batteries for maximizing energy density

AbstractThe demand for high capacity and high energy density lithium-ion batteries (LIBs) has drastically increased nowadays. One way of meeting that rising demand is to design LIBs with thicker electrodes. Increasing electrode thickness can enhance the energy density of LIBs at the cell level by reducing the ratio of inactive materials in the cell. However, after a certain value of electrode thickness, the rate of energy density increase becomes slower. On the other hand, the impact of associated limitations becomes stronger, reducing the practical applicability of LIBs with thicker electrodes. Hence, an optimum value of thickness is of utmost importance for the practicability of thicker electrode design. In this paper, both the cathode thickness and the anode thickness of an NCM LIB cell were optimized by applying response surface methodology (RSM) with a Box-Behnken design (BBD) to maximize the energy density. Moreover, the influence of electrode porosity, together with the interaction of porosity with cathode and anode thickness, was incorporated into the optimization. A full factorial design of 3-level, 3-factor was used to generate 15 simulation conditions in accordance with the design of experiment (DoE) achieved through BBD. Then, those conditions were used to achieve 15 responses by simulating a reduced-order electrochemical model. Finally, the statistical technique analysis of variance (ANOVA) was used to analyze and validate the results of RSM. The results show that the RSM-BBD optimization method, coupled with ANOVA, has successfully optimized the thicknesses of both positive and negative electrodes for maximum energy density, despite the nonlinearity of the electrochemical system. The findings suggest an optimized cathode thickness of 401.56 µm and anode thickness of 186.36 µm for a maximum energy density of 292.22 of an NCM LIB cell, while electrode porosity is preferred to be 0.2.

Efficient Oxygen Evolution Reaction on Catalyst‐Free Acid‐Functionalized Plastic Chip Electrodes

Innovative electrode design is critical for improving the oxygen evolution reaction (OER) and meeting rising global energy demands. Despite the development of numerous carbon materials for water splitting, their potential is hampered by sluggish kinetics, primarily due to high activation energy compounded by various smaller factors, including additives or binders used in electrode modification. To address these limitations, a catalyst‐free plastic chip electrode (PCE) for OER is developed. PCE is functionalized by oxidizing it in acidic media at 1.8 V versus Ag/AgCl and eliminates the need for additives, offering a more accurate industrial representation. The oxidation process enhances the electrode's surface area and introduces electrochemically active oxygen‐containing functional groups. Characterization of the modified PCE is conducted using scanning electron microscope, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, Raman, and thermogravimetric analysis, while electrolyte analysis utilizes UV–vis spectroscopy and NMR. The PCE oxidized for 6 h (PCE@6) demonstrates improved OER performance, with an onset overpotential of 260 mV, an overpotential of 1.06 V versus reversible hydrogen electrode at 10 mA cm−2, and a Tafel slope of 494 mV decade−1. The modified PCE reduces overpotential and minimizes bubble formation, enhancing efficiency and showcasing its potential as a cost‐effective solution for alkaline water electrolysis systems.

Quantifying Lithium-Ion Battery Rate Capacity, Electrode Structuring, and Transport Phenomena Using E-I Measurements

The specific energy of lithium-ion batteries (LIBs) can be enhanced through various approaches, one of which is increasing the proportion of active materials by thickening the electrodes. However, this typically leads to the battery having lower performance at a high cycling rate, a phenomenon commonly known as rate capacity retention. One solution to this is perforating the electrode, by creating channels or corrugations in the active electrode material, either as holes or as channels. This is known to reduce the rate capacity retention effect, but in order to engineer this better, a simplified transport process analysis needs to be established. In this paper, we propose a classic electrochemical analysis based on voltage–charge cycling measurements in order to obtain a classical mass transport coefficient, hm, that is further used as a main indicator for electrode design quality assessment. We also demonstrate theoretically and experimentally how the mass transfer coefficient, hm, can be determined and how it changes as the electrode layer thickness increases, with and without electrode corrugations.

Digital Twin Reveals the Impact of Carbon Binder Domain Distribution on Performance of Lithium‐Ion Battery Cathodes

The rising demand for high‐performance lithium‐ion batteries (LIBs) emphasizes the need for precise electrode design. The carbon binder domain (CBD) within electrodes, crucial for electron transport and structural integrity, can impede lithium‐ion transport and reduce electrochemically active sites. This study leverages digital twin technology to investigate the impact of CBD distribution along the electrode thickness on LIB cathode performance. Virtual LIB cathodes with varying CBD configurations are generated, and their performance using 3D heterogeneous electrochemical modeling is evaluated. The results reveal that a steep CBD gradient significantly diminishes charge capacity compared to a mild gradient, particularly at higher current rates. This reduction is attributed to an increased tortuosity factor and an uneven distribution of electrochemical activity, which adversely affect mass transport and electrochemical reaction dynamics. These effects are more pronounced at lower porosities and higher loading levels. These findings highlight that optimizing CBD distribution is critical for advancing electrode design and enhancing LIB cathode performance.

Optimization of FeMn-MOF doped with silver nanoparticles for high-performance supercapattery devices

Supercapacitors are demanded by energy storage devices for both fast charging and discharging performance as well as extended life cycles. The design and manufacture of higher supercapacitor electrodes help a device to function much better. Ag nanoparticles were produced on Fe-MOF and Mn-MOF using the hydrothermal synthesis technique to synthesize unique composite material called FeMn-MOF/Ag (NPs). These refined composites find use in supercapacitors, hydrogen evolution reactions (HER), and electrochemical sensors. Highly conductive silver nanoparticles were added to FeMn-MOF with high rate capability. Apart from their inherent benefits of metal–organic frameworks, the as-made FeMn-MOF/Ag nanoparticles also improved electrical conductivity. When the scan rate was 3 mV s−1, the FeMn-MOF/Ag (NPs) showed a specific capacity (CV) of 1417 C g−1. Similarly, when the applied current density was 2 A g−1, it displayed a specific capacity (GCD) of 2346 C g−1. The FeMn-MOF/Ag (NPs)//AC asymmetric supercapacitor exhibited an energy density of 13 (Wh/kg) and a power density of 1685 (W/kg). For the hydrogen evolution process, the material exhibited an overpotential of 90.22 mV and a Tafel slope of 58.4 mV dec−1. Furthermore, it exhibited exceptional durability in cycling, maintaining 93.3% of its capacitance after undergoing 12,000 cycles. Therefore, these results offer crucial insights into the progress of different electrode materials. The results suggest that FeMn-MOF/Ag nanoparticles possess advantageous characteristics suitable for utilization as electrodes in supercapattery and HER (hydrogen evolution reaction) applications.

Methods for increasing productivity of AC-electrospinning using weir-electrode

The presented work brings new knowledge in the field of spinning electrodes for AC‑electrospinning technology, which is used for producing nanofibrous structures using a solution of polyvinyl butyral. It presents new types of spinning weir‑electrodes and describes research on the influence of electrode design parameters on the stability of the spinning process and the productivity of nanofiber production. The multistage spinning electrode is presented in the ratio of stages one to five. Research is also focused on the effect of the parameters of the electric signal used as a source for the spinning electrode on spinning stability and productivity. Observed parameters were voltage level, frequency and shape such as sine wave, rectangle wave and modified sine wave. An analysis of the influence of the spinning conditions on the resulting nanofibrous structure was also performed by analyzing results gained by SEM; the defects were investigated mainly. The results of the research presented in the thesis open up new possibilities for follow-up research in the field of AC-electrospinning.

Review of AEM Electrolysis Research from the Perspective of Developing a Reliable Model

This review thoroughly examines recent progress, challenges, and future prospects in the field of alkaline exchange membrane (AEM) electrolysis. This emerging technology holds promise for eco-friendly hydrogen production. It blends the benefits of traditional alkaline and proton-exchange membrane technologies, enhancing affordability and operational efficiencies by utilizing non-precious metal catalysts and operating at reduced temperatures. This study discusses key developments in materials, electrode design, and performance enhancement techniques. It also highlights the strategic role of AEM electrolysis in meeting global energy transition targets, like achieving Net Zero Emissions by 2050. An in-depth exploration of the operational fundamentals of AEM water electrolysis is provided, noting the technology’s early stage development and the ongoing need for research in membrane-electrode assembly assessment, catalyst efficiency, and electrochemical ammonia production. Moreover, this review compiles results on different cell components, electrolyte types, and experimental approaches, providing insights into operational parameters critical to optimizing AEM performance. The conclusion emphasizes the necessity for continuous research and commercialization efforts to exploit AEM electrolysis’s full potential across diverse industries.