Composite Electrode Structure Research Articles

Manufacturing Shape-Controllable Flexible PEDOT/rGO Composite Electrodes for Planar Micro-Supercapacitors.

Flexible electronic products, with their characteristics of flexibility and wearability, have attracted significant attention and have become an important direction in the research and development of the electronics industry. Planar micro-supercapacitors (MSCs) with flexible composite electrodes can provide reliable energy support for these products, propelling their further development. The research employed a quick, effective, and environmentally friendly method of laser scribing to create shape-controllable flexible composite electrodes on composite films of Poly(3,4-ethylenedioxythiophene) and graphene oxide (PEDOT/GO), which were subsequently assembled into MSCs. An analysis of the composite electrode morphology, structure, and elemental distribution was conducted through the utilization of SEM, TEM, and XPS techniques. Following this, a comprehensive evaluation of the electrochemical performance of the flexible MSCs was carried out, which included cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and assessment of cyclic stability. The analysis of the CV results indicated that the MSCs achieved the areal capacitance of 5.78 mF/cm2 at 5 mV/s. After 5000 cycles at a current density of 0.05 mA/cm2, the capacitance retention rate was 85.4%. The high areal capacitance and strong cycle stability of MSCs highlight the potential of PEDOT/reduced graphene oxide (PEDOT/rGO) electrodes in electrode applications.

Cell Performance Prediction of the Particle Structure of All-Solid-State Batteries By Numerical Simulation and Machine Learning

All-Solid-State Battery (ASSB) is expected to be commercialized for electric vehicle applications. However, the correlation between the electrode structure and the cell performance is unknown, and no design theory has been established. Especially the effect of contact stress on solid-solid interface is important. And the ununiform reaction area cause the exsess current concentration. In our previous study, we developed various simulation model to understand the effect of heterogeneous structure and the effect of volume expansion on dynamic structure change during charging-discharging cycle from the viewpoint of durability. In this study, we developed new simulation model with stress calculation and electrochemical reaction, Moreover, the simulation results were used to create training dataset for machine learning. By using these approaches, we tried to develop new method to predict cell performance from composite electrode structure to cell performance.The stress estimation was performed using the discrete element method (DEM) [1]. The various material parameters are used such as, particle diameter (average and standard deviation), Young's modulus, Poisson's ratio and density. The distribution of the stresses on each particle was calculated from the DEM calculation results and confirmed to be approximately Gaussian.To simulate electrochemical reaction and mass transport in electrode layer, we used multi-network model (MNM)[6]. The schematic image of this model is shown in Fig.1, we used various network grid of active material network, solid electrolyte network and interface network. Basic equations of Li concentration, Li potential and electron potential were calculated in these networks. In this study, with DEM and MNM, we developed new simulation model shown in Fig.2.A convolutional neural network (CNN) [7] was used as the model for machine learning, and various structural parameters, including the DOD, cell potential, and stress on each particle calculated by DEM, were identified to create a dataset. 250 images were used for training, 150 of which were used for training, 50 for validation, and 50 for testing. The coefficient of determination (R²) of the standard deviation of DOD and potential is almost 0.7 in each condition, and the cell performance can be predicted by the machine learning model. The contact area of the electrochemical reaction interface, AM-SE, was calculated from the stress on the contact surface calculated by DEM and Hertzian contact theory [8]. Thus, we can express the relationship between interface mechanical stress on solid-solid and effective reaction, and this effect can be predicted with various structure of composite electrode layer by using machine learning. It was possible to predict the cell performance and effective contact area in the electrode layer of the all-solid-state battery.Acknowledgement:This research was carried out under the project (Grant Number JPMJMI21G4) supported by the JST-Mirai Program, Japan.

Preparation and electrochemical properties of carboxylated graphene-supported NiO nanosheets for supercapacitors

Nickel oxide (NiO) with the advantages of inexpensive, non-toxic, environmentally friendly and high theoretical specific capacitance, is a potential electrode material for supercapacitors. In this work, the synthesized NiO exhibited a stacked state of nanosheets with wavy patterns and a high specific surface area. Additionally, the carboxylated graphene/nickel oxide (CG/NiO) composite electrodes were prepared through the electrostatic self-assembly technique. The CG/NiO composite electrode was systematically characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller measurements. More excitingly, the BET surface area of the CG/NiO composite electrode is 138.14 m2/g, which is three times higher than that of the pure NiO. The high surface area and unique mesoporous structure of composite electrodes facilitated rapid ion transport and sufficient redox reactions. As a result, the CG/NiO composite electrode displayed a high specific capacity of 175.5 C g−1 at 1 A/g and satisfying cycling stability (55.4 % retention after 5000 cycles at 5 A/g).

Rational design of MXene/Boron Carbon Nitride nanotube composite electrode for supercapacitors with improved electrochemical properties

3D structures obtained using 1D and 2D materials are promising materials in energy storage. Optimizing the interlayer spacing of 2D MXene through flexible conductive materials is an important step in synthesizing 3D composite electrodes. In this study, flexible and conductive MXene/BCN nanotube composite film electrodes were prepared by vacuum filtration using BCN nanotubes in different weight ratios (10 %, 20 %, and 30 %) in mixed and sandwiched structures. The mixed MXene/BCN10 (m-MX/BCN10) composite film electrode structure attained a specific capacitance of 678 F g−1, the highest of all tested electrodes, and exhibited remarkable cycle stability by retaining 95 % of its capacitance even after 10,000 charge/discharge cycles. In the symmetric supercapacitor (SSC), the cell exhibited a specific capacitance of 97 % after 10,000 charge/discharge cycles. Moreover, SSC showed an energy density of 32 Wh kg−1 and a power density of 11.5 kW kg−1. The composite electrodes made of 2D Ti3C2Tx MXene and 1D BCN nanotube materials open up a new avenue for synthesizing promising materials for energy storage in transition metal carbides and 1D nanotubes or nanowires.

Application of Diluted Electrode Method to Sodium-ion Insertion into Hard Carbon Electrode

Herein, the diluted-electrode method is applied to a hard carbon (HC) electrode to estimate sodium-ion (Na+) insertion kinetics. As metallic nickel (Ni) particles do not accommodate Na+ ions in the potential range of 0–2.0 V vs. Na+/Na, the HC powder electrode is diluted by adding inert Ni particles, enabling the adjustment of the HC concentration while maintaining the composite electrode structure. By examining the rate capabilities of the HC electrodes with different dilutions, we confirm that the Na+ insertion rate for the highly diluted electrode is 10 times higher than that for the undiluted electrode. These improved kinetics can be attributed to the alleviation of Na+ depletion, which results in insignificant concentration polarization under dilute conditions. For a highly diluted electrode, the Na+ insertion kinetics must be controlled by the Na+ mobility in the HC particles and across the HC/electrolyte interface. Therefore, our study reveals that the inherent kinetics of Na+ insertion into HC are very high and provides a basis for developing high-power Na-ion batteries.

Titanium Nitride Nanorods Array-Decorated Graphite Felt as Highly Efficient Negative Electrode for Iron-Chromium Redox Flow Battery.

Iron-chromium redox flow batteries have attracted widespread attention because of their low cost. However, the performance of these batteries is still lower than that of vanadium redox flow batteries due to the poor electrochemical activity of Cr3+ /Cr2+ redox couples on graphite felt electrodes. Herein, binder-free TiN nanorods array-decorated 3D graphite felt composite electrode-is demonstrated. The dendrite-like TiN nanorods array increases the specific surface area of the electrode. The nitrogen and oxygen elements on the surface provide more adsorption sites and electrochemically active sites for Cr3+ /Cr2+ . The contact resistance of the composite electrode is effectively reduced and its homogeneity and stability are improved by avoiding the use of a binder and mixing process. A battery prepared using the TiN nanorods array-decorated 3D graphite felt electrode has enabled the maximum power density to be 427 mW·cm-2 , which is 74.0% higher than a battery assembled with TiN nanoparticles bonded to graphite felt. At a current density of 80 mA·cm-2 , the TiN nanorods battery exhibits the highest coulombic efficiency of 93.0%, voltage efficiency of 90.4%, and energy efficiency of 84.1%. Moreover, the battery efficiency and composite electrode structure remains stable during a redox flow battery cycle test.

Unraveling kinetics and mechanism of electrocatalytic hydrodechlorination of chlorinated PPCPs by nickel-cobalt metal organic framework supported palladium composite electrode

In this work, a nickel-cobalt bimetallic organic framework (NiCo-MOF) was introduced as an intermediate layer to synthesize a Pd/NiCo-MOF/Nickel foam composite electrode, which was applied for electrocatalytic hydrodechlorination (ECH) of chlorinated pharmaceuticals and personal care products (PPCPs). The introduction of the NiCo-MOF structure dramatically improved the catalytic activity compared with the common Pd/Nickel foam electrode. Combined with transmission electron microscope and X-ray absorption fine structure analysis, catalyst on Pd/NiCo-MOF/Nickel foam surface had smaller particle size. The removal of the Pd/NiCo-MOF/Nickel foam electrode for chloramphenicol (CAP) reached more than 95 % at 40 min, while the removal of the Pd/Nickel foam electrode was only approximately 55 %. In this study, the active atomic hydrogen (H*) adsorbed on the Pd and NiCo-MOF structures is the critical active species to remove chlorinated PPCPs by Pd/NiCo-MOF/Nickel foam electrode. Density functional theory (DFT) was used to calculate and investigate the adsorption strength of the composite electrode structure for CAP, the product and H*. This work provided a new method to achieve higher catalytic performance and reactivity operability and longevity of catalytic materials through the synergism of a NiCo-MOF interlayer with Pd particles.

Mesoporous Gold Film with Surface Sulfur Modification to Enable Dendrite-Free Lithium Plating/Stripping for Long-Life Lithium Metal Anodes.

The formation of a lithiophilic phase is an effective method to inhibit the growth of lithium dendrites and obtain high-performance Li metal anodes (LMAs). Nonetheless, previous studies have overlooked the underlying mechanistic studies that modulate the structure of the lithiophilic phase as well as lithiophilicity. A self-supporting sulfur-modified mesoporous gold film on nickel foam (SMGF@NF) for LMAs is created with mesoporous structure, which can provide sufficient active sites for uniform lithium deposition. The synergistic promotion of lithiophilic gold and sulfurleads to uniform lithium nucleation and induces consistent lithium removal during lithium stripping. The doping of S promotes the decomposition of bistrifluoromethanesulfonimide lithium saltto generate lithium fluorde, thus forming a more stable solid electrolyte interface. Combining the multifaceted advantages of SMGF@NF, its lithium-plated electrode can achieve ultralong cycle life in symmetrical batteries (over 1000h at 0.5mA cm-2 and 1 mAh cm-2 ) and ultralow overpotential (≈10mV). Meanwhile, the Li-SMGF@NF||LiFePO4 full cell achieves a high cycling performance and rate capability (92.4% capacity retention after 1000 cycles at 5 C). The study probes into the composite electrode surface composition and structure, revealing the mechanism of high-performance LMAs.

Effect of Graphite Morphology on the Electrochemical and Mechanical Properties of SiOx/Graphite Composite Anode

Mixing SiOx materials with graphite materials has become a key technology to improve their performance, but it is still unclear what kind of graphite materials help to construct a stable electrode structure. The purpose of this study is to explore the effect of graphite morphology on the structure and performance of SiOx/C composite electrodes (850 mAh g−1). For the SiOx/C59 composite electrode constructed by the lamellar graphite (C59) with a big aspect ratio and SiOx particles, the SiOx particles agglomerate in the pores of C59 particles. This uneven electrode structure could lead to excessive stress and strain of the electrode during cycling, which causes the anode electrode structure failure and cycling performance deterioration. While the small-size lamellar graphite (SFG15) with random orientation helps to construct stable electrode structure with uniform particle distribution and pore structure, which could reduce the stress and strain change of the electrode during cycling. Thus, the composite electrode (SiOx/SFG15) exhibits better cycling performance compared with SiOx/C59 composite electrode. This work reveals the structure-activity relationship of graphite morphology, electrode structure and the mechanical and electrochemical performance of the electrode, and provides a guide to the design and development of the high capacity SiOx/C composite electrode structure.

Consecutive Ink Writing of Conducting Polymer and Graphene Composite Electrodes for Foldable Electronics-Related Applications.

For foldable electronic devices of the future, most components should have very good flexibility and reliability to maintain electrical properties even under repeated deformation. In this study, two types of inks for conducting polymer and graphene were simultaneously printed on flexible plastic substrates via the newly developed consecutive ink writing (CIW) process for the formation of composite electrodes of foldable electronic devices. To consecutively print conducting polymer ink and graphene ink, a conventional three-dimensional (3D) printer was modified by installing two needles in the printer head, and the two inks were printed through the nozzle in the same route with a time interval. By adjusting several printing conditions (ink concentration, printing parameters, printing time intervals between the two inks, etc.), various structures of composite electrodes, such as layered or fused 2D or 3D structures were developed on the glass substrate. Furthermore, by changing the printing order of the two inks and 3D printer bed temperature, the composite electrodes with a higher printing resolution were successfully printed on the flexible polyimide substrate. The printed composite electrodes via CIW process exhibit the lowest surface electrical resistance of 0.9 kΩ and high flexibility, and stable resistance values were maintained after 1000 cycles of the folding test. Consequently, the CIW process developed in this study applies to the production of the electrical parts and components for various flexible devices, such as foldable and wearable electronics.

Effects of Composite Electrode Structure on Performance of Intermediate-Temperature Solid Oxide Electrolysis Cell

The composite electrode structure plays an important role in the optimization of performance of the intermediate-temperature solid oxide electrolysis cell (IT-SOEC). However, the structural influence of the composite electrode on the performance of IT-SOEC is not clear. In this study, we developed a three-dimensional macroscale model coupled with the mesoscale model based on percolation theory. We describe the electrode structure on a mesoscopic scale, looking at the electrochemical reactions, flow, and mass transport inside an IT-SOEC unit with a composite electrode. The accuracy of this multi-scale model was verified by two groups of experimental data. We investigated the effects of operating pressure, volume fraction of the electrode phase, and particle diameter in the composite electrode on electrolysis reaction rate, overpotential, convection/diffusion flux, and hydrogen mole fraction. The results showed that the variation in the volume fraction of the electrode phase had opposite effects on the electrochemical reaction rate and multi-component diffusion inside the composite electrode. Meanwhile, an optimal range of 0.8–1 for the particle diameter ratio was favorable for hydrogen production. The analysis of IT-SOEC with composite electrodes using this multi-scale model enables the subsequent optimization of cell performance and composite electrode structure.

Structure and Properties of Composite Electrodes Based on Thermally Expanded Graphite Produced from Lignin

Structure and Properties of Composite Electrodes Based on Thermally Expanded Graphite Produced from Lignin

The Silicon Electron Multiplier sensor

The Silicon Electron Multiplier (SiEM) is a novel sensor concept for minimum ionising particle (MIP) detection which uses internal gain and fine pitch to achieve excellent temporal and spatial resolution. In contrast to sensors where the gain region is induced by doping (LGADs, APDs, SPADs), amplification in the SiEM is achieved by applying an electric potential difference in a composite electrode structure embedded within the silicon bulk using MEMS fabrication techniques. Since no gain-layer deactivation is expected with radiation damage, such a structure is expected to withstand fluences of up to 1016 neq/cm2. Various geometries and biasing configurations are studied, within the boundaries imposed by the fabrication process being considered. The effective gain, the field in the sensor, the leakage current and breakdown conditions are studied for cell sizes in the range of 6–15µm. Simulations show that gains in excess of 10 can be achieved, and studies of the time structure of the induced signals from a charge cloud deposited in the middle of the sensor show that time resolutions similar to other sensors with internal gain can be expected. Plans for the manufacture of a proof-of-concept sensor and for its subsequent characterisation are discussed.

High-Performance Flexible Sulfur Cathodes with Robust Electrode Skeletons Built by a Hierarchical Self-Assembling Slurry.

The electrochemical performance of lithium–sulfur batteries is fundamentally determined by the structural and mechanical stability of their composite sulfur cathodes. However, the development of cost‐effective strategies for realizing robust hierarchical composite electrode structures remains highly challenging due to uncontrollable interactions among the components. The present work addresses this issue by proposing a type of self‐assembling electrode slurry based on a well‐designed two‐component (polyacrylonitrile and polyvinylpyrrolidone) polar binder system with carbon nanotubes that forms hierarchical porous structures via optimized water‐vapor‐induced phase separation. The electrode skeleton is a highly robust and flexible electron‐conductive network, and the porous structure provides hierarchical ion‐transport channels with strong polysulfide trapping capability. Composite sulfur cathodes prepared with a sulfur loading of 4.53 mg cm−2 realize a very stable specific capacity of 485 mAh g−1 at a current density of 3.74 mA cm−2 after 1000 cycles. Meanwhile, a composite sulfur cathode with a high sulfur loading of 14.5 mg cm−2 in a lithium–sulfur pouch cell provides good flexibility and delivers a high capacity of 600 mAh g−1 at a current density of 0.72 mA cm−2 for 78 cycles.

New Insights on Electrochemical Parameters in Battery Modeling through 3D Digital Twin Structural Analysis

Electrochemical parameters such as chemical diffusion coefficients and exchange current densities are very critical in simulating electrochemical battery models. However, conventional experimental methods have not reflect actual status of composite electrodes and cells due to the limitation in analyzing their micro-structures. To address these challenges, we attempted to draw 3D digital twin structures of composite electrodes and cells and then quantify veiled parameters like active surface area. As a result, we could obtain more correct chemical diffusion coefficients and exchange current densities and improve the reliability of electrochemical battery models. In this work, we will introduce how to build and use 3D digital twin structures of composite electrodes for lithium-ion batteries.[References]1. J. Park, Y. M. Lee et al., Energy Storage Materials, 19 (2019) 124-1292. J. Park, Y. M. Lee et al., Advanced Energy Materials, 10(35) (2020) 20015633. J. Kim, J. Park, Y. M. Lee et al., ACS Energy Letters, 5(9) (2020) 2995-30044. J. Kim, S. Jung, Y. M. Lee et al., Advanced Energy Materials , Online published (2021)

Effect of Binder Content on Silicon Microparticle Anodes for Lithium-Ion Batteries

Electrode formulation directly influences the resulting composite electrode structure and properties, ultimately impacting the electrode performance and durability. Although there have been many significant advancements in the development and understanding of novel and effective binder materials for silicon anodes1–4, few studies report more than one formulation, or ratio of active material to conductive additive to polymeric binder5,6.In this study, we focus on investigating the impact of polyimide binder weight ratio in silicon microparticle electrodes. Electrode adhesion to the current collector, cohesion, porosity, electrical resistivity, and electrical tortuosity were characterized in pristine electrodes. These properties were then correlated to electrode cycle life and rate performance in Si-NMC622 full cells. We show that there is an optimal binder weight ratio for a given type of polymer binder. Increasing binder weight ratio improves electrode adhesion and cohesion, resulting in improved cycle life. However, increased binder weight ratio decreases electrical conductivity and porosity, leading to poorer silicon particle utilization, capacity, and rate performance.In the formulations we investigated, the silicon to carbon weight ratio was fixed, while binder content was varied. The optimal binder ratio maximizes silicon particle utilization, achieving 1084 ± 25 mAh/gSi gravimetric capacity after the formation cycles. When binder content was increased three-fold, the discharge capacity decreased by 27%, which was correlated to lower electrode porosity and lower initial coulombic efficiency. We hypothesize that insufficient porosity limits lithium-ion access to the silicon particles, thus reducing the capacity at the given C-rate. We also hypothesize that the decreased coulombic efficiency indicates that the polyimide binder contributes to the consumption of available lithium.In contrast, capacity retention improved with additional binder content. This is partly due to increased electrode cohesion with the added binder and partly due to lower overall capacity in the silicon particles, resulting in less volumetric strain. In electrodes with the binder content reduced by one-third, capacity retention dropped dramatically. We hypothesize that there is a lower limit of binder content, below which the electrode lacks sufficient structural integrity to withstand volume strains during cycling.These findings point towards important design principles for the optimization of binder content in silicon electrode formulations.

The hierarchical synthesis of tungsten disulfide coated vertically aligned boron carbon nitride nanotubes composite electrodes for supercapacitors

This study investigated the specific capacitance, energy density and cyclic stability parameters of a WS2 coated vertically aligned BCN nanotubes (VA-BCN-NTs) composite electrode structure. The specific capacitance of VA-BCN-NTs was found to be 364Fg−1 at a current density of 0.5Ag−1. This electrode had 97% of their initial specific capacitance after 10,000 cycles at a current density of 20Ag−1, exhibiting excellent cyclic stability. In the three-electrode cell, the specific capacitance of the VA-BCN-NT@WS2 electrode at a current density of 0.5Ag−1 was calculated to be 690Fg−1. After 5000 cycles at a current density of 20Ag−1, the electrode structure had a capacitance value of 74%, showing good stability. In the two-electrode cell, the specific capacitance of the VA-BCN-NT@WS2 symmetrical supercapacitor at a current density of 1Ag−1 was found to be 170Fg−1. It was observed to have retained 85% of its capacitance after 10,000 cycles over a 1 V potential range. While the energy density of this structure was 23.6Whkg−1, the power density was 4250Wkg−1.

Attenuation of Microwave Radiation by Post-Anode Plasma in a Composite Grid Electrode Structure

This paper presents a new composite grid electrode structure for the generation of plasma that is suitable for modeling microwave radiation transmission through atmospheric plasma. The new grid anode-composite cathode (GA-CC) structure is to be contrasted with the ordinary grid anode-cathode plate (GA-CP) structure. It is found that the breakdown voltage of the new GA-CC electrode structure is lower than that of the GA-CP structure and is a bit shifted to the right on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Pd</i> -axis. An advantage of the GA-CC structure over the GA-CP structure is that it requires a lower voltage to generate the same current. It is found that plasma generated by the new GA-CC structure selectively strengthens electromagnetic waves attenuation in the frequency range of 9–12 GHz.

Biomass waste-derived hierarchical porous composite electrodes for high-performance thermally regenerative ammonia-based batteries

Thermally regenerative ammonia-based battery (TRAB) is an electrochemical device for converting low-grade waste heat into electrical energy. To improve the power generation of TRAB, the biomass waste-derived hierarchical porous composite electrode is prepared through the corrosion method and the electroplating for the high specific surface area for electrochemical reactions and the hierarchical porous structure for mass transfer in this study. The use of the hierarchical porous composite electrodes induced a 77.4% higher maximum power density of TRAB (81.6 W m−2) compared with that of TRAB with copper foam electrodes (46.0 W m−2). As to the electrode preparation, the composite electrode structure is jointly influenced by the ratio of KOH and fungus bran pre-carbonized products (FBPC) and the electrodeposition time, affecting the battery performance. The optimal ratio of the KOH/FBPC and the optimal electrodeposition time are 1.0 and 20 min, respectively. In addition, the porous composite electrode is also applicable for bimetallic thermally regenerative ammonia-based batteries, in which the highest reported power density (848.2 W m−2) is obtained.

Incorporation of Fe3O4 nanoparticles in three-dimensional carbon nanofiber/carbon nanotube aerogels for high-performance anodes of lithium-ion batteries

Recently, Fe3O4 based materials have been widely investigated to serve as anode materials of lithium-ion batteries (LIBs) because of the high theoretical capacity (924 mA h g−1). Unfortunately, the actual capacity of these materials are low and they suffer from poor cycling stability. Herein, carbon nanotube/carbon nanofiber composite aerogels (CA) were used as scaffold to fabricate Fe3O4-CA composites for anode materials. Fe3O4 nanoparticles were evenly presented on the external surface and internal channel of the 3-dimensional (3D) CA network. The 3D conductive network can buffer the volume expansion of anode materials. Additionally, such structure can prevent the aggregation of Fe3O4. Therefore, the structure of the Fe3O4-CA composite electrode can be maintained during lithiation/delithiation processes. The Fe3O4-CA composites delivered a high reversible capacity of 825.1 mA h g−1 after 100 cycles. Additionally, an ultra-high coulombic efficiency closed to 100% was obtained. The excellent performance of the Fe3O4-CA composites may be due to the synergistic effect of the Fe3O4 nanoparticles and 3D conductive network structure.