Metal Electrodes Research Articles

Unconventional Thick Cobalt Telluride Electrodes Enable Homogeneous Ion Flow for High Capacity, Fast and Safe Potassium Storage

The demand for high-energy density, fast-charging, and safe potassium-ion batteries (PIBs) is crucial for large-scale applications in electric vehicles and grid systems. Despite the potential of thick electrode designs by a conventional technique (CTEs) to boost energy density, they often encounter challenges such as reduced capacity, limited cycling lifespan, and localized short circuits. Here, we present a novel cobalt telluride composite anode by a simple tellurization and subsequent heat reduction, featuring Co1.67Te2 nanoparticles uniformly embedded within an N-doped carbon layer on a trace amount of reduced graphene oxide (CT@NC/rGO). By constructing low tortuosity electrodes (LTEs), a homogeneous distribution of potassium ions and current density is achieved, resulting in enhanced potassium storage performance. The CT@NC/rGO LTEs demonstrate excellent discharge capacities: 311.7, 276.5, and 243.7mAh g-1 after 500 cycles at 0.25Ag-1 for mass loadings of 1.4, 1.9, and 2.8mgcm-2, respectively. At a higher current density of 0.5Ag-1, discharge capacities after 650 cycles are 245.3, 175.6, and 159.2mAh g-1 for mass loadings at 1.6, 2.4, and 3.0mgcm-2, respectively. These improvements are attributed to enhanced pseudocapacitive behavior, reduced charge resistance, and accelerated ion diffusion kinetics, as evidenced by experimental and simulation studies. The proposed strategy for synthesizing high-density electrodes holds promise for developing high-performance metallic compound electrodes for PIBs and potentially extending to other types of energy storage systems.

A Systematic Study of Methyl Carbodithioate Esters as Effective Gold Contact Groups for Single-Molecule Electronics.

There are several binding groups used within molecular electronics for anchoring molecules to metal electrodes (e.g., R-SMe, R-NH2, R-CS2-, R-S-). However, some anchoring groups that bind strongly to electrodes have poor/unknown stability, some have weak electrode coupling, while for some their binding motifs are not well defined. Further binding groups are required to aid molecular design and to achieve a suitable balance in performance across a range of properties. We present an in-depth investigation into the use of carbodithioate esters as contact groups for single-molecule conductance measurements, using scanning tunnelling microscopy break junction measurements (STM-BJ) and detailed surface spectroscopic analysis. We demonstrate that the methyl carbodithioate ester acts as an effective contact for gold electrodes in STM-BJ measurements. Surface enhanced Raman measurements demonstrate that the C=S functionality remains intact when adsorbed on to gold nanoparticles. A gold(I) complex was also synthesised showing a stable C=Sׄ→AuI interaction from the ester. Comparison with a benzyl thiomethyl ether demonstrates that the C=S moiety significantly contributes to charge transport in single-molecule junctions. The overall performance of the CS2Me group demonstrates it should be used more extensively and has strong potential for the fabrication of larger area devices with long-term stability.

Exploring Metal Electroplating for Energy Storage by Quartz Crystal Microbalance: A Review

AbstractThe development and application of Electrochemical Quartz Crystal Microbalance (EQCM) sensing to study metal electroplating, especially for energy storage purposes, are reviewed. The roles of EQCM in describing electrode/electrolyte interface dynamics, such as the electric double‐layer build‐up, ionic/molecular adsorption, metal nucleation, and growth, are addressed. Modeling of the QCM sensor is introduced and its importance is emphasized. Challenges of metal electrode use, including side reactions and dendrite formation, along with their mitigation strategies are reviewed. Numerous factors affecting the electroplating processes, such as electrolyte composition, additives, temperature, and current density, and their influence on the electroplated metals’ mass, structural, and mechanical characteristics are discussed. Looking forward, the need for deeper fundamental understanding and advancing simulations of the QCM signal response as a result of electroplating metal nanostructures is stressed. Further development and integration of innovative EQCM‐strategies will provide unique future means to fundamentally understand and optimize metal electroplating for energy storage and application alike.

Piezoelectric and elastic properties of Al0.60Sc0.40N thin films deposited on patterned metal electrodes

Sc-doped aluminum nitride (AlScN) allows for piezoelectric devices with large electromechanical coupling and the benefits increase with larger Sc doping in the film. However, with a larger Sc concentration, the process window narrows, and it is necessary to fine-tune the deposition parameters to achieve a good film. In this paper, we investigate depositions of highly doped AlScN (40% Sc) on unpatterned and patterned metal layers, to show how it is possible to maintain a good film quality on a metal electrode. We find how high-temperature deposition of the metal improves the AlScN film quality, how the gas mixture allows to reduce defects, and how film quality changes with thickness. We show that extreme care must be taken in the apparently trivial step of photoresist cleaning. Finally, we extract the mechanical, electrical, and piezoelectric properties of our optimized layer from a batch of fabricated resonators, obtaining a 5× improvement of piezoelectric coupling compared to undoped AlN and a 1.5× improvement from 32% doped AlScN.

Radical Polymer-based Positive Electrodes for Dual-Ion Batteries: Enhancing Performance with γ-Butyrolactone-based Electrolytes.

Dual-ion batteries (DIBs) represent a promising alternative for lithium ion batteries (LIBs) for various niche applications. DIBs with polymer-based active materials, here poly(2,2,6,6-tetramethylpiperidinyl-N-oxyl methacrylate) (PTMA), are of particular interest for high power applications, though they require appropriate electrolyte formulations. As the anion mobility plays a crucial role in transport kinetics, Li salts are varied using the well-dissociating solvent γ-butyrolactone (GBL). Lithium difluoro(oxalate)borate (LiDFOB) and lithium bis(oxalate)borate (LiBOB) improve cycle life in PTMA||Li metal cells compared to other Li salts and a LiPF6- and carbonate-based reference electrolyte, even at specific currents of 1.0Ag-1 (≈10C). Further, the use of LiDFOB reveals a superior rate performance, i.e., ≈90% capacity at 5.0Ag-1 (≈50C). This is attributed to faster charge-transfer/mass transport, enhanced pseudo-capacitive contributions during the de-/insertion of the anions into the PTMA electrode and to lower overpotentials at the Li metal electrode.

Can Aluminum Cations Promote Nucleation for THF Hydrate Growth?

Rapid nucleation of tetrahydrofuran (THF) hydrate is essential for developing a THF hydrate-based cold storage technology. Earlier works have hypothesized the role of aluminum complexes in initiating the nucleation of clathrate hydrates using aluminum metal electrodes and substrates. This study investigates if the nucleation promotional effect of hydrate can be achieved using the aluminum salt, AlCl3, due to the formation of aluminum aqua complexes in water. Metal chlorides NaCl and MgCl2 are also utilized to evaluate the effect of cation type in initiating nucleation, i.e., the effect of charge/radius ratio. The induction time is measured in a stirred reactor at various subcoolings and concentrations of 0.05, 0.1, 0.5, 1, and 2 wt %. The nucleation time is studied in two reactor configurations based on the nature of salt introduction in the THF solution, i.e., salt premixed in solution and salt injected inside the solution. The sudden rise in the reactor temperature due to hydrate formation is used as an indicator of hydrate formation. Results indicate that AlCl3 promotes hydrate nucleation as AlCl3 reduces induction time by 92.2% at 0.05 wt % concentration compared with water. Nearly instantaneous nucleation is also achieved by directly injecting AlCl3. MgCl2 and NaCl do not show a similar effect on induction time as AlCl3. The pH and Raman spectra measurements with and without salts are carried out to explain the effect of cations on the THF-water solution.

Interfacial engineering with a ferrocene derivative for air-stable inverted perovskite solar cells with high fill factor of 83.57 %

Perovskite solar cells have demonstrated exceptional photovoltaic performance, but stability remains a challenge due to insufficient interfaces. In this work, a UV-resistance ferrocene derivative, 1,1′-bis (diphenylphosphine) ferrocene (DPPF), is introduced between the electron transport layer and the perovskite, reducing defect density by interaction with undercoordinated Pb2+, suppressing non-radiative recombination of charge carriers, and enhancing electron extraction. Desirable interfacial properties and homogeneous perovskite grains are formed, resulting in a champion power conversion efficiency (PCE) of 20.82 % and a significantly improved fill factor of 83.57 %. Moreover, DPPF can optimize the interfaces, provide a brand-new morphology with exceptional air durability, cover the active layer to restrain water and oxygen intrusion, and suppress metal electrode corrosion. Resultant devices without encapsulation have remained above 80 % of their initial PCE for 1400 h under 25 °C air and 50–60 % relative humidity conditions.

Deterministic Orientation Control of Ferroelectric HfO2 Thin Film Growth by a Topotactic Phase Transition of an Oxide Electrode.

The scale-free ferroelectricity with superior Si compatibility of HfO2 has reawakened the feasibility of scaled-down nonvolatile devices and beyond the complementary metal-oxide-semiconductor (CMOS) architecture based on ferroelectric materials. However, despite the rapid development, fundamental understanding, and control of the metastable ferroelectric phase in terms of oxygen ion movement of HfO2 remain ambiguous. In this study, we have deterministically controlled the orientation of a single-crystalline ferroelectric phase HfO2 thin film via oxygen ion movement. We induced a topotactic phase transition of the metal electrode accompanied by the stabilization of the differently oriented ferroelectric phase HfO2 through the migration of oxygen ions between the oxygen-reactive metal electrode and the HfO2 layer. By stabilizing different polarization directions of HfO2 through oxygen ion migration, we can gain a profound understanding of the oxygen ion-relevant unclear phenomena of ferroelectric HfO2.

Multifunctional robot skin based on liquid metal composites and electrode arrays

While human skin regulates body temperature and protects the organism, robots also need multifunctional skin that can protect their internal electronics. Currently, most of the research on robotic skin focuses on the limbs with the aim of improving their sensory functions. There is a lack of a robotic skin with protective features that can be applied to the whole body. In some complex working environments, too high or too low temperatures can directly jeopardize the operation of the robot's internal circuitry. In addition, ubiquitous electromagnetic waves can damage the electronic system of robots. Therefore, an e-skin that protects the robot from external factors was desired. In this study, with reference to the structure of human skin, a gallium-based liquid metal and a bismuth-based low-melting-point alloy were combined to prepare a highly thermally conductive e-skin that can withstand both thermal shock and low temperature. This skin not only features thermal management, but also touch positioning and electromagnetic shielding. The development of multifunctional robot skin (MFR skin) will extend the service life of robots, broaden their application areas, and enable future robots to replace humans to accomplish more complex and operationally difficult tasks.

Soft-metal bonding-enabled recyclable and anti-interference flexible multilayer piezoelectric sensor for tractor tire strain monitoring

Real-time efficient sensing of machine-soil interactions, especially precise tire-ground contact information, plays a critical role in cultivation, seeding, and harvesting for smart agriculture. However, the complicated agricultural environment poses a considerable challenge to traditional rigid sensors, which cannot suffer from both large deformation and electromagnetic interference. Here, we report a novel soft-metal BiInSn bonding-enabled recyclable and anti-interference flexible multilayer piezoelectric sensor for monitoring tractor tire strain. The printed BiInSn-ink electrode fully wraps the surface fibers of porous BaTiO3/PVDF-HFP electrospun films only through a low pressure at low temperature due to its unique thermal-softening effects, which of the adhesion strength is superior to the intrinsic tension limit of the film. The compact multilayer piezoelectric sensor is thus easily prepared, remarkably increasing the output voltage compared to a single-layer case (up to 300% for three layers). Benefiting from the low melting point of the BiInSn alloy, the sensors are easily recyclable compared to conventional metal electrodes prepared with copper, silver, and gold. In addition, its high electrical conductivity also enables the shielding layer to achieve ultrahigh shielding effectiveness of 2100 dB mm−1. This sensor can be demonstrated for tire strain sensing under complex operating conditions such as plowing, harrowing, and fertilizer application. These findings serve as a foundation for accelerating the development of smart agriculture.

The Bell-Evans-Polanyi relation for hydrogen evolution reaction from first-principles

The versatile Bell-Evans-Polanyi (BEP) relation stipulates the kinetics of a reaction in terms of thermodynamics. Herein, we establish the BEP relation for the hydrogen evolution reaction (HER) from fundamental electrochemical principles leveraging the Butler-Volmer relation for a one-step, one-electron process and the transition state theory. Based on first-principles investigations of HER mechanisms on fourteen metal electrodes, we firmly justify the BEP relation solely using an easy-to compute hydrogen adsorption free energy and universal electrochemical constants.

Effect of A/B ratio on the dielectric properties and insulation resistance of barium titanate sintered in a reducing atmosphere

The effect of the A/B ratio on the dielectric properties and insulation resistance of barium titanate (BaTiO3) sintered in a reducing atmosphere was investigated in this study. The increased demand for high capacitance, miniaturized, and reliable base metal electrode multilayer ceramic capacitors (BME MLCCs) has emphasized improving insulation properties. This study added Y2O3, MgO, Mn2O3, and SiO2 to tailor the barium titanate properties. We investigated how changes in the A/B ratio affect the microstructure, defect chemistry, and Y3+ ion occupation in BaTiO3, affecting dielectric properties and insulation resistance. It was observed that the activation energies for grain and grain boundary conductivity are dominated by oxygen vacancy and (VBa″−VO··) defect pair, respectively. The Ti3+ and oxygen vacancy concentrations were directly proportional to the room and high-temperature resistivities, respectively. The sample with an A/B ratio of 1.002 had the lowest oxygen vacancy and Ti3+ ratio, resulting in a higher resistance and lower thermally stimulated depolarization current (TSDC).

Physical insight into turn‐on transient of silicon carbide gate turn‐off thyristor

AbstractSilicon Carbide (SiC) Gate Turn‐off (GTO) thyristor is regarded as a promising option for pulsed power applications; however, the formation of high di/dt has been constrained by the slow current rise transient phase and the turn‐on current heterogeneity over the chip device. In this paper, a practical integrated multi‐cell simulation is performed to physically characterize the turn‐on transient of SiC GTO thyristor. Through examining electrical coupling between adjacent cells caused by both parasitics of electrode metallization and carrier travelling via SiC, the current distributions are observed, and the carrier transport dynamics are analyzed in detail. Furthermore, physical mechanisms dominating the current heterogeneity among multi‐cells are discovered in depth. It is revealed that the current heterogeneity during the turn‐on transient is primarily resulted from the Gate signal delay caused by the Gate Runner metallization, and the lateral interaction from adjacent semiconductor regions adds to this inhomogeneity; however, this situation can be improved once the electrical distance between each Anode contact and the Anode electrode gets lowered. Design method for turn‐on performance improvement is also proposed accordingly. Besides, based on the analysis conducted on the multi‐cell simulation results, the possible reason of the extremely slow current rise transient phase is speculated and experimentally verified. The improvement in the comprehension of SiC GTO's turn‐on transient, which cannot be obtained from the traditional investigation from the viewpoint of one elementary cell, will provide guiding principles helping in directing future efforts to advance the improvement of device design technology.

High-performance Schottky-barrier field-effect transistors based on two-dimensional GaN with Ag or Au contacts

The performance of two-dimensional (2D) monolayer GaN Schottky barrier field effect transistors (SBFETs) with four different metals (Ag, Au, Al, and Pt) as electrodes were studied by using ab initio simulations. The N-type Schottky contact is formed on Ag-GaN, Au-GaN, and Pt-GaN, characterized by electron Schottky barrier heights (SBH) of 0.6, 0.5, and 0.38 eV, respectively. Whereas, Al-GaN contact formed P-type Schottky contact with hole SBH of 1.42 eV. The 5.1 nm GaN SBFETs with four metal electrodes all could overcome the short-channel effect. Additionally, GaN SBFETs with Ag and Au electrodes have excellent performance, whose ON-currents are 1151.1 μA/μm and 1258.9 μA/μm, respectively. They could satisfy the demands of International Technology Roadmap for Semiconductors for high-performance transistor. Furthermore, research indicates that the device's current increases with increasing temperature. Notably, under the constant bias and gate voltage, the current is unaffected by temperature variations between the left and right electrodes.

Stable Zinc Electrode Reaction Enabled by Combined Cationic and Anionic Electrolyte Additives for Non-Flow Aqueous Zn─Br2 Batteries.

Aqueous zinc-bromine batteries hold immense promise for large-scale energy storage systems due to their inherent safety and high energy density. However, achieving a reliable zinc metal electrode reaction is challenging because zinc metal in the aqueous electrolyte inevitably leads to dendrite growth and related side reactions, resulting in rapid capacity fading. Here, it is reported that combined cationic and anionic additives in the electrolytes using CeCl3 can simultaneously address the multiple chronic issues of the zinc metal electrode. Trivalent Ce3+ forms an electrostatic shielding layer to prevent Zn2+ from concentrating at zinc metal protrusions, while the high electron-donating nature of Cl- mitigates H2O decomposition on the zinc metal surface by reducing the interaction between Zn2+ and H2O. These combined cationic and anionic effects significantly enhance the reversibility of the zinc metal reaction, allowing the non-flow aqueous Zn─Br2 full-cell to reliably cycle with exceptionally high capacity (>400mAh after 5000 cycles) even in a large-scale battery configuration of 15×15cm2.

Innovative Ethanol Sensors Utilizing Organic Material Patterned Surface Acoustic Wave Detection

In this paper, sensor based on surface acoustic waves for ethanol vapors detection, was fabricated and studied. For room temperature detection of the volatile compound, a novel carbyne nanofilm was deposited on the surface of a SAW transducer. The conventional electrodes were replaced by conductive polymeric coting of poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) to minimize the microstructural and elemental difference between the electrode and gas sensitive material. The experimental results showed that the sensors had a good response to ethanol at room temperature. The maximum response of the sensors was at 600 ppm, where the time delay between the output and the input signals of the transducer was ~ 160 μs. The parasitic contact resistance and interface capacitance were found insufficient to affect the accuracy of the measurement, although their values are higher as compared to the sensors with metal electrodes.

Ionic Conductivity Analysis of NASICON Solid Electrolyte Coated with Polyvinyl-Based Polymers

The global environmental crisis necessitates reliable, sustainable, and safe energy storage solutions. The current systems are nearing their capacity limits due to the reliance on conventional liquid electrolytes, which are fraught with stability and safety concerns, prompting the exploration of solid-state electrolytes, which enable the integration of metal electrodes. Solid-state sodium-ion batteries emerge as an appealing option by leveraging the abundance, low cost, and sustainability of sodium. However, low ionic conductivity and high interfacial resistance currently prevent their widespread adoption. This study explores polyvinyl-based polymers as wetting agents for the NASICON-type NZSP (Na3Zr2Si2PO12) solid electrolyte, resulting in a combined system with enhanced ionic conductivity suitable for Na-ion solid-state full cells. Electrochemical impedance spectroscopy (EIS) performed on symmetric cells employing NZSP paired with different wetting agent compositions demonstrates a significant reduction in interfacial resistance with the use of poly(vinyl acetate)—(PVAc-) based polymers, achieving an impressive ionic conductivity of 1.31 mS cm−1 at room temperature, 63.8% higher than the pristine material, notably reaching 7.36 mS cm−1 at 90 °C. These results offer valuable insights into the potential of PVAc-based polymers for advancing high-performance solid-state sodium-ion batteries by reducing their total internal resistance.

Soft Monolithic Shielded Sensors to Measure Shear and Normal Forces for Local Slip Detection

AbstractSoft force sensors enable closed loop control or autonomous operation of compliant robot systems. A stretchable force sensing surface containing an array of independent sensor units is reported. This design allows for the measurement of local shear and normal forces at multiple locations, independently, providing real‐time, multi‐axis force information at each unit. The sensor array is based on capacitive strain sensing, using liquid metal electrodes and air microchannel for high sensitivity. Electromechanical interference between adjacent sensor units is addressed and eliminated through design optimization and the use of compliant electrical shield layers. A 1D sensor array is applied to gripping tasks, where the independent sensor readings enable detecting local and partial slipping. This study illustrates how the device can be used to explore the dynamics of local forces during the stages of pick up, slip, and release.

Density functional model of threshold voltage shifts at High-K/Metal gates

A density functional analysis of oxide dipole layers used to set the threshold voltages in high-K/metal CMOS gate stacks is given in terms of the band alignments and chemical trends of these component oxide layers. The oxides SrO, La2O3, HfO2 and Al2O3 are found to have similar band gaps and form a ‘staircase’ of band alignments, allowing them to shift the metal electrode Fermi level in both n-type and p-type directions. This analysis supersedes previous largely empirical models based on metal oxide ion densities or electronegativity scales.

Beyond Metallic Electrode: Spontaneous Formation of Fluidic Electrodes from Operational Liquid in Highly Functional Droplet-Based Electricity Generator.

The droplet-based electricity generator (DEG) has facilitated efficient droplet energy harvesting, yet diversifying its applications necessitates the incorporation of various to the DEG. In this study, we first propose a methodology for advancing the DEG by substituting its conventional metallic electrode with electrically conductive water electrode (WE), which is spontaneously generated during the operation of the DEG with operating liquid. Due to the inherent conductive and fluidic nature of water, the introduction of the WE maintains the electrical output performance of the DEG while imparting functionalities such as high transparency and flexibility. So, the resultant WE applied DEG (WE-DEG) exhibits high optical transmittance (∼ 99%) and retains its electricity-generating capability under varying deformations, including bending and stretching. This innovation expands the versatility of the DEG, and especially, a sun-raindrop dual-mode energy harvester is demonstrated by hybridizing the WE-DEG and photovoltaic (PV) cell. This hybridization effectively addresses the weather-dependent limitations inherent in each energy harvester and enhances the temperature-induced inefficiencies typically observed in PV cells, thereby enhancing the overall efficiency. The introduction of the WE will be poised to catalyze new developments in DEG research, paving the way for broader applicability and enhanced efficiency in droplet energy harvesting technologies. This article is protected by copyright. All rights reserved.