Electrode Structure Research Articles

Tracking the Evolution of Ionomer Film and Catalyst Material to Unravel PEMFC Performance Degradation

Abstract Several characterization techniques were performed on a proton exchange membrane fuel cell (PEMFC) to relate the performance degradation induced by the membrane-targeted accelerated stress test (AST) to the evolution of electrochemical and physical properties of the electrode. This works investigated the ionomer structure and the proton transport properties. Electron microscopy and small angle neutron scattering analysis provided access to the electrode’s nanoscale structure, the distribution of the platinum particle size, the structure of the 2-3 nm thick ionomer film, as well as the location of the water uptake by the electrode. A newly-developed technique using proton desorption under diluted O2 allows to distinguish effectively used active sites for oxygen reduction reaction. Proton transport and dioxygen diffusivity properties were measured using impedance spectroscopy and limiting current technique respectively. The Membrane-AST leads to an increase in the water uptake of the electrode due to a modification of the global structure of the electrode, a reduced platinum surface area, and corrosion of carbon particles. However, it does not alter the ionomer structure. The decrease in performance is partially attributed to the increase in proton resistivity, but mainly due to the limitation of dioxygen transport fostered by the electrode structure modifications.

Advanced characterization of confined electrochemical interfaces in electrochemical capacitors.

The advancement of high-performance fast-charging materials has significantly propelled progress in electrochemical capacitors (ECs). Electrochemical capacitors store charges at the nanoscale electrode material-electrolyte interface, where the charge storage and transport mechanisms are mediated by factors such as nanoconfinement, local electrode structure, surface properties and non-electrostatic ion-electrode interactions. This Review offers a comprehensive exploration of probing the confined electrochemical interface using advanced characterization techniques. Unlike classical two-dimensional (2D) planar interfaces, partial desolvation and image charges play crucial roles in effective charge storage under nanoconfinement in porous materials. This Review also highlights the potential of zero charge as a key design principle driving nanoscale ion fluxes and carbon-electrolyte interactions in materials such as 2D and three-dimensional (3D) porous carbons. These considerations are crucial for developing efficient and rapid energy storage solutions for a wide range of applications.

Hierarchical Reactions Involving Dynamic Structural Changes in Lithium-Ion Batteries during Overcharge Using Advanced Analytical Techniques

Abstract High-Ni cathode materials are promising for lithium-ion batteries compared to conventional cathode materials because of relatively high energy density and low cost. High-Ni cathodes are inherently thermally unstable, and when used in large scale batteries, they can cause serious problems such as thermal runaway and associated destruction of the internal structure. For practical use, it is necessary to understand the internal phenomena when they are incorporated into large scale batteries. We examined the stacked electrode structural change inside pouch cells with approximately 1 Ah capacity during over charging, which includes LiNi0.8Mn0.1Co0.1O2, LiNi0.6Mn0.2Co0.2O2, and LiCoO2 athodes, by using synchrotron-based operando X-ray radiography. In addition, the bulk crystalline, electronic, and local structures of these materials as well as surface electronic structure changes during overcharging were also analyzed. We found that as the amount of Ni-content in the cathodes increase, destabilization of surface oxygen and structural phase transitions occur at smaller state of charge, leading to faster and more severe collapse of the stacked electrode structure inside the pouch cells. This finding of a relationship of hierarchical structural changes from the cathode surface to the pouch cell is useful for the safe use of lithium-ion batteries with high energy density containing high-Ni cathodes.

Insight into electrochemical cutting using flexible electrode: electrode structure design, dynamic deformation analysis, and experimental verification

Insight into electrochemical cutting using flexible electrode: electrode structure design, dynamic deformation analysis, and experimental verification

High-Performance Supercapacitors Enabled by Coral-like Organic-Inorganic PPy/FeCoN Electrode Structures for Sustainable Energy Storage

High-Performance Supercapacitors Enabled by Coral-like Organic-Inorganic PPy/FeCoN Electrode Structures for Sustainable Energy Storage

Ethylene glycol-mediated dispersion enhancement of oxidized MWCNTs for improved electrochemical performance in flexible, free-standing OCNT/LMO electrode

The rapid advancement of flexible electronics and wearables necessitates high-capacity flexible batteries that adapt to various shapes and movements. Carbon nanotubes (CNTs), with their exceptional electrical conductivity, mechanical flexibility, and structural stability, are promising candidates. However, achieving a well-dispersed and uniform distribution of CNTs and heavy active materials like lithium manganese oxide (LMO) particles in different matrices is challenging due to issues with agglomeration and quick sedimentation. This study uses ethylene glycol (EG) as a dispersing solvent to form strong hydrogen bonds with oxidized CNTs, enhancing dispersion stability and preventing re-aggregation. Its higher viscosity compared to water helps in better stabilizing and dispersing LMO particles within the oxidized CNT suspension by reducing sedimentation. The OCNT/LMO-EG electrode shows a higher discharge capacity of 128 mAh/g with Coulombic efficiency of 99.6% after 200 cycles, compared to the OCNT/LMO-W2 electrode, which uses water for dispersion and achieves 108 mAh/g with 99.6% efficiency. These results highlight ethylene glycol's potential to improve CNT and LMO dispersion, resulting in a homogeneous electrode structure with enhanced conductivity and higher capacity.

A PVDF-HFP/YSZ nanofiber composite solid-state electrolyte by in-situ polymerization of 1,3-dioxolane for 4.5 V high-voltage NCM811 battery

Solid lithium metal batteries with solid polymer electrolytes have advantages in terms of high energy density and safety. However, their application is still hindered by unstable solid electrolyte interfaces (SEI and CEI) and uncontrolled dendrite growth. Here, a composite skeleton loaded with dielectric filler yttrium stabilized zirconia nanoparticles (YSZ) on the surface of PVDF-HFP nanofiber filaments is designed, and a novel composite solid electrolyte (CSE) is prepared by in-situ polymerization of DOL (1,3-dioxolane) on this framework to achieve safe and stable high-voltage lithium metal battery (LMB). The dual stable electrode interfaces (CEI and SEI) constructed by in-situ can effectively suppress the generation of lithium dendrites and suppress the degradation of the high-voltage NCM811 positive electrode structure and the generation of cracks in NCM811 particles, endowing the battery with extraordinary performance. The as-obtained CSE exhibits high ionic conductivity of 1.01 × 10−3 S cm−1 at 30 °C, the enlarged electrochemical window of 6.0 V, and the Li+ transference number is 0.72. The assembled Li|NCM811 battery is capable of stable cycling for 400 cycles at a cut-off voltage of 4.5 V and current density of 1C, with a capacity decay of only 0.074 % per cycle. .

Influence of ion mobility and electrode structure effects on supercapacitors with CaO, MgO, and SiO2

Influence of ion mobility and electrode structure effects on supercapacitors with CaO, MgO, and SiO2

Comprehensive review for zinc powder anodes: Significance, optimizing design, and industrial feasibility in zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) have emerged as promising candidates for sustainable energy storage systems, due to their low cost, enhanced safety, and high-power density. Nevertheless, practical applications are still hampered by inherent challenges related to the zinc (Zn) foil anode, including dendrite formation and interfacial parasitic reactions. As an alternative, Zn powder (Zn-p) presents significant potential, owing to its cost-efficiency, large-scale processability, versatility, and industrial applicability. Notably, the amount of Zn-p can be accurately regulated, enhancing Zn anodes utilization efficiency and facilitating industrial applications. Nevertheless, the unique spherical microstructure of Zn-p introduces specific challenges, such as complex ion pathways, uneven Zn deposition, and a complicated electrode manufacturing process, which directly impact the battery performance, safety, and lifespan. In pursuit of a deeply comprehensive relationship between electrode structure and electrochemical performance for Zn-p-based anodes, this review provides a detailed examination of the working mechanisms of Zn-p-based anodes, while also identifying both the opportunities they present and the unique challenges they face. Moreover, the latest research progress is summarized, with a focus on innovative design strategies for optimizing Zn-p-based anodes. The relationship between these structural aspects and the resulting electrochemical performance, including safety, cycle life, and capacity, is thoroughly examined to provide a deeper understanding of how to achieve optimal battery system design and performance. Meanwhile, the fabrication processes and potential for practical flexible applications of Zn-p-based batteries were detailed. Finally, prospects for achieving high performance and practical utilization of Zn-p-based anodes are offered, providing scientific guidance for their practical application.

Comprehensive insight of charge storage and ion transport in bioinspired nanostructure electrode-patterned supercapacitors by multiscale investigation

Supercapacitors with bioinspired leaves-on-branchlet hybrid carbon nanostructure-patterned electrodes show high areal capacitance and outstanding rate capability. However, the fundamental mechanisms of charge storage and ion transport in such a bioinspired supercapacitor at multiple length scales remain little explored. Herein, we develop a multi-scale model to comprehensively explore the mechanism of charge storage and ion transport, in which the finite-element-based Nernst-Planck-Poisson calculations are used for the macro-scale understanding, and molecular dynamics simulations for the atomic-scale investigation. High-throughput simulations are conducted to quantify the effect of the bioinspired structure, thermal influence, and size effect on the electrochemical performance of supercapacitors. An in-depth analysis of the simulation and experimental results demo some design advice are concluded, (1) engineering the hierarchical ordered electrode structure with sharp edges to promote charge storage and transfer, (2) designing the channel architecture with a width of ∼4 nm for avoiding size effect and improving the ion transport and storage performance. This work explores the electrochemical performance and structure properties of the devices which probably provide the designing and optimizing bases for achieving high-performance supercapacitors.

Cyanoethyl cellulose-enabled cathodes with interpenetrating electron transport and ion transport paths via phase inversion method for high energy density lithium metal batteries

Binders need to exhibit high bonding strength, sufficient mechanical properties, and electrolyte insolubility to help achieve uniform and stable porous structure and conductive network in electrode composites. Traditional binders like polyvinylidene fluoride offer good electrochemical stability but suffer from poor adhesion performance and weak mechanical flexibility, resulting in unstable electrode structures. To address these issues, a cyanoethyl cellulose-based binder was used to prepare a cyanoethyl cellulose-based cathodes with interpenetrating electron transport and ion transport paths via phase inversion method for high energy density lithium metal batteries. The polar groups (CN, C-O-C, and –OH) on the cyanoethyl cellulose chains could promote the transport of Li-ions through electrostatic interactions. The interpenetrating electron transport and ion transport paths enabled fast Li-ion and electron transport in the cyanoethyl cellulose-based cathodes, resulting in a higher Li-ion diffusion coefficient of to 3.74 × 10−10 cm2·s−1. Hence, the cyanoethyl cellulose-based cathodes enabled batteries with an energy density of 419.8 Wh·kgcathode−1 (mass loading of 16.6 mg·cm−2). This study provided a new strategy to achieve uniform and stable porous structure and conductive network in electrode composites high energy density batteries.

Self-Powered Wearable Displacement Sensor for Continuous Respiratory Monitoring and Human-Machine Synchronous Control.

Flexible wearable electronic devices play a vital role in daily monitoring, medical diagnosis, and human-computer interaction, and such devices have a great demand for portability, integration, comfort, and self-power. In this study, a triboelectric nanogenerator integrated into a flexible chest belt is proposed as a displacement sensor to monitor the displacement and frequency of thoracic expansion. Based on three parallel interpolation electrode structures with phase differences, the Triboelectric Nanogenerators's(TENG) output signal pulse number can characterize the sliding displacement, with a resolution of more than 1mm and a durability of more than 700,000 cycles. Based on the flexible printed circuit processing technology, the volume of the sensor is less than 8.5cm3, and the weight is less than 3.2g, which improves the portability of the device. Based on wireless radio frequency technology, the collected signals are transmitted to the upper computer, and then the monitoring of respiratory physiological signals and the human-machine synchronous control of the ventilator are achieved within the overshoot of 1.5% and the control error of 5% through a simulation machine. This work provides a sensing method for daily and medical respiratory monitoring and demonstrates the enormous potential of frictional electric sensors in intelligent medical applications.

Modeling Battery Cell Reversible Expansion Using the Discrete Element Method

Intercalation type electrodes experience a volume change due to insertion of guest species in the host lattice.1 For lithium-ion batteries, and in particular the anode electrode, this volume change can be significant and is necessary to consider2,3 when designing these batteries, in order to link the cell level volume change to pack and system level implications4. For graphitic anodes, volume expansion can range from zero to ten percent as charging occurs5,6. Silicon based anodes, which comparatively offer a much higher theoretical energy density, can expand up to four hundred percent of its initial size7,8. If the design of the cells does not allow enough space for these expansions to occur, resultant stress on the electrode structure can cause fracturing of the active material. This leads to capacity loss9,10, reducing performance of the cell and driving other destructive behaviors during electrochemical operation. Numerical simulation can be used to predict volumetric expansion of the electrodes and the resultant stresses in the electrode structure as lithiation occurs. One simulation method used for capturing this volume expansion is the discrete element method (DEM), which can include hundreds of particles with unique dimensions and tracks what happens in the particle phase as expansion occurs. Through use of DEM simulations we are able to capture electrode strains at a microscale level, and extrapolate these results to a cell level response. This is coupled with experimental measurements that quantify electrode level volume expansion to increase accuracy of the simulation results. In this work, we present the expansion for a composite Active Material-Binder electrode structure and the resultant stress-strain behavior observed. Expansion of the electrode is linked to the half-cell potential11 and state-of-lithiation as well as design properties, which are quantified to give a full picture of the resultant electrode-electrolyte continuum. References T. R. Garrick, K. Kanneganti, X. Huang, and J. W. Weidner, J. Electrochem. Soc., 161, E3297 (2014). T. R. Garrick, X. Huang, V. Srinivasan, and J. W. Weidner, J. Electrochem. Soc., 164, E3552 (2017). T. R. Garrick et al., J. Electrochem. Soc., 164, E3592 (2017). T. R. Garrick, Y. Zeng, J. B. Siegel, and V. R. Subramanian, J. Electrochem. Soc., 170, 113502 (2023). D. J. Pereira et al., J. Electrochem. Soc., 167, 080515 (2020). T. R. Garrick et al., J. Electrochem. Soc., 170, 060548 (2023). D. J. Pereira, A. M. Aleman, J. W. Weidner, and T. R. Garrick, J. Electrochem. Soc., 169, 020577 (2022). D. J. Pereira, J. W. Weidner, and T. R. Garrick, J. Electrochem. Soc., 166, A1251 (2019). S. Pannala, H. Movahedi, T. R. Garrick, A. G. Stefanopoulou, and J. B. Siegel, J. Electrochem. Soc., 171, 010532 (2024). T. R. Garrick, Y. Miao, E. Macciomei, M. Fernandez, and J. W. Weidner, J. Electrochem. Soc., 170, 100513 (2023). T. R. Garrick, J. Gao, X. Yang, and B. J. Koch, J. Electrochem. Soc., 168, 010530 (2021).

Understanding the Mechanism of Evaporation-Induced Islands during the Formation of Catalyst Layers and Their Influence on the Alkaline Oxidation Evolution Reaction

Advancements in anode development substantially reduce the cost and enhance the performance of water electrolysis. The strategic configuration of nano-sized catalyst materials on anode supports is a pivotal factor in the expansion of the production of catalyst layers and has a significant influence on their electrochemical performance [1–3]. Therefore, it is essential to understand the structure formation mechanisms during electrode fabrication. This contribution aims to explore the inherent drying mechanisms in the coating process and their subsequent influence on the morphological evolution of anodes, ultimately establishing a linkage between these morphological changes and electrochemical performance and stability metrics. The initial phase of the study involved a detailed characterization of commercial nickel cobalt oxide nanoparticles via advanced analytical techniques, including transmission electron microscopy and energy-dispersive X-ray spectroscopy [4]. Subsequently, a stable ink was formulated by dispersing the catalyst alongside a binder in a solvent, which was then uniformly applied to a conductive nickel plate utilizing an ultrasonic spray coater. Prior to application, the catalyst inks underwent optimization based on the Hansen solubility parameters of catalyst materials [5, 6] and subsequent visualization of their stability and dispersibility characteristics through transmittogram analysis [7]. The drying process of the coating was conducted at two distinct temperatures, 50 °C and 150 °C, to investigate the effect of temperature on solvent evaporation. Morphological and structural analyses of the anodes were subsequently performed using scanning electron microscopy (SEM), laser scanning microscopy (LSM), and atomic force microscopy (AFM), providing insight into the alterations induced by the drying process. The analyses conducted in this study elucidate significant modifications in the morphology of the layer structures attributable to variations in drying temperatures as illustrated in Figure 1. Specifically, lower temperature resulted in reduced evaporation rates that facilitated the formation of larger, isolated regions/islands on the anode support. These are indicative of a non-uniform coating distribution. In contrast, a higher temperature promoted rapid evaporation, resulting in a quite homogeneous distribution of smaller islands accompanied by the emergence of voids within the anode layer. Electrochemical analysis revealed that these morphological changes are of vital importance: they govern the wetting behaviour and the dynamics of bubble formation which are important for the electrochemical performance and durability of the catalyst layers. Moreover, the insights gleaned from this study are instrumental in identifying optimal configurations of catalyst layer structures, i.e., features that should be maintained during scale-up. In conclusion, this study significantly advances the field by revealing novel principles governing the design and optimization of electrode structures for the oxygen evolution reaction. In particular, the complicated relationship between drying temperatures and morphological evolution, which significantly influences electrochemical performance is explained.

Correlating the 3D Morphology of Polymer-Based Battery Electrodes with Effective Transport Properties.

Polymer-based batteries represent a promising candidate for next-generation batteries due to their high power densities, decent cyclability, and environmentally friendly synthesis. However, their performance essentially depends on the complex multiscale morphology of their electrodes, which can significantly affect the transport of ions and electrons within the electrode structure. In this paper, we present a comprehensive investigation of the complex relationship between the three-dimensional (3D) morphology of polymer-based battery electrodes and their effective transport properties. In particular, focused ion beam scanning electron microscopy (FIB-SEM) is used to characterize the 3D morphology of three polymer-based electrodes which differ in material composition. The subsequent segmentation of FIB-SEM image data into active material, carbon-binder domain and pore space enables a comprehensive statistical analysis of the electrode structure and a quantitative morphological comparison of the electrode samples. Moreover, spatially resolved numerical simulations allow for computing effective properties of ionic and electronic transport. The obtained results are used for establishing analytical regression formulas which describe quantitative relationships between the 3D morphology of the electrodes and their effective transport properties. To the best of our knowledge, this is the first time that the 3D structure of polymer-based battery electrodes is quantitatively investigated at the nanometer scale.

Addressing Fundamental Challenges of Si/Gr Electrodes with High Silicon Contents Using Innovative Bilayer Electrode Structure Design

Addressing Fundamental Challenges of Si/Gr Electrodes with High Silicon Contents Using Innovative Bilayer Electrode Structure Design

Time and cost efficient post-synthesized core-shell NiCo-MOFs electrode for solid-state supercapacitors

Designing electrode materials with a core-shell structure proves to be an efficient strategy for achieving high conductivity and surface area in supercapacitors (SCs), facilitating improved charge transfer and faradaic reactions. Leveraging the advantages of core-shell architectures for SCs, we synthesized binder-free Co-MOFs (CMFS) and core-shell NiCo-MOFs (NCMFS) electrodes through a facile chemical process on stainless steel substrates. Morphological analysis reveals interconnected leaf-like structures for CMFS and a porous sheet-like morphology for NCMFS electrodes. Further, the structural, morphological, and compositional analysis reveals the existence of a core-shell NiCo structure in the NCMFS electrode. This unique architecture significantly enhances electrochemical properties, as evidenced by a specific capacitance of 1016 F/g, substantially surpassing that of CMFS (557 F/g) at 2 A/g. Impressively, both materials demonstrate excellent cycling stability, a critical parameter for real-time SCs applications. Furthermore, symmetric solid-state SCs NCMFS//NCMFS device exhibited an energy density of 8.19 Wh/kg, a power density of 2117 W/kg at 4 A/g, and a 67% retention rate over 3000th cycles. The study highlights the importance of core-shell structures in enhancing the performance of SCs. Moreover, it demonstrates the efficacy of post-synthesis methodologies in surpassing traditional hydrothermal and solvothermal approaches for producing advanced energy storage devices. This approach offers significant advantages in terms of time efficiency and cost-effectiveness.

Design of a Contact-Type Electrostatic Spray Boom System Based on Rod-Plate Electrode Structure and Field Experiments on Droplet Deposition Distribution

Spraying is currently one of the main methods of pesticide application worldwide. It converts the pesticide solution into fine droplets through a sprayer, which then deposit onto target plants. Therefore, in the process of pesticide application, improving the effectiveness of spraying while minimizing or preventing crop damage has become a key issue. Combining the advantages of electrostatic spraying technology with the characteristics of ground boom sprayers, a contact-type electrostatic boom spraying system based on a rod–plate electrode structure was designed and tested on a self-propelled boom sprayer. The charging chamber was designed based on the characteristics of the rod–plate electrode and theoretical analysis. The reliability of the device was verified through COMSOL numerical simulations, charge-to-mass ratio, droplet size, and droplet size spectrum measurements, and a droplet size prediction model was established. The deposition characteristics in soybean fields were analyzed using the Box–Behnken experimental design method. The results showed that the rod–plate electrode structure demonstrated its superiority with a maximum spatial electric field of 2.31 × 106 V/m. When the spray pressure was 0.3 MPa and the charging voltage was 8 kV, the droplet size decreased by 26.6%, and the charge-to-mass ratio reached 2.88 mC/kg. Field experiments showed that when the charging voltage was 8 kV, the spray pressure was 0.3 MPa, the traveling speed was 7 km/h, and the number of deposited droplets was 8517. This study provides some basis for the application of electrostatic spraying technology in large-scale field operations.

Analysis of the Radial Force of a Piezoelectric Actuator with Interdigitated Spiral Electrodes.

The actuator is a critical component of the micromanipulator. By utilizing the properties of expansion and contraction, the piezoelectric actuator enables the manipulator to handle and grasp miniature objects during micromanipulation. However, in piezoelectric ceramic disc actuators with conventional surface electrode configurations, the actuating force generated in the radial direction is relatively limited. When used as the actuation element of the manipulator, achieving regulation over a wide range of operating strokes becomes challenging. Therefore, altering the electrode structure is necessary to generate a greater radial force, thus enhancing the positioning and grasping capabilities of the operating arm. This paper investigates a piezoelectric actuator with interdigitated spiral electrodes, featuring a constant pitch between adjacent electrodes. The radial force was tested under mechanical clamping conditions, and the influence of the electrical signal was examined. The characteristics of the electrode structure were described, and the working principles of the piezoelectric actuators were analyzed. Theoretical equations were derived for the macroscopic characterization of the radial clamping force of the actuator, based on the piezoelectric constitutive equation, geometric principles, and Bond matrix transformation relationships. A finite element model was developed, reflecting the features of the electrode structure, and finite element simulations were employed to verify the theoretical equations for radial force. To prepare the samples, encircled interdigitated spiral electrode lines were printed on the PZT-52 piezoelectric ceramic disc using a screen printing method. The clamping force experimental platform was established, and experiments on the clamping radial force were conducted with electrical signals of varying waveforms, frequencies, and voltages. The experimental results show that the piezoelectric ceramic disc actuator with an interdigitated spiral electrode line structure, when excited by a stable sine wave operating at 200 V and 0.2 Hz, generated a peak force of 0.37 N. It was 1.76 times greater than that produced by a previously utilized piezoelectric disc with conventional electrode structures.

Rectifying solid electrolyte interphase structure for stable multi-dimensional silicon anodes

Electrolyte engineering is a promising strategy to stabilize electrode structure. However, the high active material utilization of Si anode accompanied by inevitable huge volume expansion makes higher requirements than regulating Li metal deposition behaviors from dendrite growth. Herein, we rectified the solid electrolyte interphase (SEI) layer on Si surface to maintain the electrode integrity during repeated cycling. In our design, an oligomeric buffer layer (CHO2-/CH3O-) derived from FEC and an inorganic pillar (LiF/Li3N) derived from LiFSI/LiNO3 weave into organic-inorganic crosslinking SEI during the initial activation process. Leveraging COMSOL modeling reveals the small stress and strain of the Si particle under the protective effect of concrete SEI layers. Moreover, synchrotron X-ray 3D nano-computed tomography comprehensively elucidates the structural integrity of Si particles during cycling. With this merit, various silicon-based anodes show remarkable cycling stability. Notably, the Si/C || LiFePO4 full battery still affords a capacity retention ratio exceeding 95 % at 1 mA cm−2 after 300 cycles. This interphase engineering design strategy provided in our work advances the understanding of how to cope with devastating volume variation by leveraging the SEI characteristic perspective.