Open Voltage Research Articles

Layered magnesium vanadate film electrodes as high-performance cathode materials for thin-film non-aqueous zinc-ion batteries

Thin-film non-aqueous zinc-ion batteries (ZIBs) are recognized as an alternative energy storage technology with large-scale application prospects. The use of organic electrolytes with a wide window of electrochemical stability to construct non-aqueous ZIBs results in high operating voltage and energy density. In this paper, magnesium vanadate (Mg0.01V2O5) films were in situ grown and annealed on indium tin oxide (ITO) conductive glass using low-temperature liquid-phase deposition, and directly assembled into thin-film ZIBs. The battery achieved a stable capacity of 137.5 mA h m−2 after 80 cycles at 167 mA m−2. In addition, it exhibited an initial capacity of 104.1 mA h m−2 at 250 mA m−2 and a capacity retention of 75.6 % after 200 cycles. Good rate performance feedback was also obtained. According to X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), the electrochemical reaction process of the Mg0.01V2O5 film electrode was analyzed and the insertion/extraction mechanism of Zn2+ was investigated. Due to the instability of the V2O5 structure, the pre-inserted layer of Mg2+ plays a role as a pillar between layers during preparation, supporting the vanadium–oxygen layer and improving structural stability and battery life. At the same time, thin-film ZIB directly composed of film, diaphragm, electrolyte and zinc sheet has good diffusion dynamics, simplicity and size controllability, making it more suitable for commercial applications. Therefore, the thin-film non-aqueous ZIBs in this work may provide new ideas for mobile novel micro power sources.

Influence of Biaxial Strain and Interfacial Layer Growth on Ferroelectric Wake-Up and Phase Transition Fields in ZrO2.

Investigations on fluorite-structured ferroelectric HfO2/ZrO2 thin films are aiming to achieve high-performance films required for memory and computing technologies. These films exhibit excellent scalability and compatibility with the complementary metal-oxide semiconductor process used by semiconductor foundries, but stabilizing ferroelectric properties with a low operation voltage in the as-fabricated state of these films is a critical component for technology advancement. After removing the influence of interfacial layers, a linear correlation is observed between the biaxial strain and the electric field for transforming the nonferroelectric tetragonal to the ferroelectric orthorhombic phase in ZrO2 thin films. This observation is supported by applying the principle of energy conservation in combination with ab initio and molecular dynamics simulations. According to the simulations, a rarely reported Pnm21 orthorhombic phase may be stabilized by tuning biaxial strain in the ZrO2 films. This study demonstrates the significant influence of interfacial layers and biaxial strain on the phase transition fields and shows how strain engineering can be used to improve ferroelectric wake-up in ZrO2.

In Situ Phase Separation-Induced Self-Healing Catalyst for Efficient Direct Seawater Electrolysis.

Direct seawater electrolysis technology for sustainable hydrogen production has garnered significant attention, owing to its abundant resource supply and economic potential. However, the complex composition and high chloride concentration of seawater have hindered its practical implementation. In this study, we report an in situ-synthesized dual-phase electrocatalyst (HPS-NiMo), comprising an amorphous phosphide protective outer phase and a crystalline alloy inner phase with supplementary sulfur active sites, to improve the kinetics of direct seawater electrolysis. The HPS-NiMo exhibits long-term stability, remaining stable for periods exceeding 120 h at 200 mA cm-2; moreover, it lowers the required operating voltage to ∼1.8 V in natural seawater. The chlorine chemistry, corrosion during direct natural seawater electrolysis, and mechanism behind the high-performing catalysts are discussed. We also investigated the possibility of recovering the anode precipitates, which inevitably occurs during seawater electrolysis.

Inhibiting the Jahn-Teller Effect of Manganese Hexacyanoferrate via Ni and Cu Codoping for Advanced Sodium-Ion Batteries.

Manganese (Mn)-based Prussian blue analogs (PBAs) are of great interest as a prospective cathode material for sodium-ion batteries (SIBs) due to their high redox potential, easy synthesis, and low cost. However, the Jahn-Teller effect and low electrical conductivity of Mn-based PBA cause poor structure stability and unsatisfactory performance during the cycling. Herein, a novel nickel- and copper-codoped K2Mn[Fe(CN)6] cathode is developed via a simple coprecipitation strategy. The doping elements improve the electrical conductivity of Mn-based PBA by reducing the bandgap, as well as suppress the Jahn-Teller effect by stabilizing the framework, as verified by the density functional theory calculations. Simultaneously, the substitution of sodium with potassium in the lattice is beneficial for filling vacancies in the PBA framework, leading to higher average operating voltages and superior structural stability. As a result, the as-prepared Mn-based cathode exhibits excellent reversible capacity (116.0 mAh g-1 at 0.01 A g-1) and superior cycling stability (81.8% capacity retention over 500 cycles at 0.1 A g-1). This work provides a profitable doping strategy to inhibit the Jahn-Teller structural deformation for designing stable cathode material of SIBs.

Enhanced electrochemical performance of a LiFePO4 cathode with an environmentally friendly pectin/polyethylene glycol binder

The advancement of lithium-ion battery technology relies on the development of materials that not only improve performance but also align with environmental sustainability. This work presents a novel water-based pectin-PEG binder for LiFePO4 cathodes that combines eco-friendliness with electrochemical innovation. The binder material is made by mixing pectin, a flexible natural substance, with polyethylene glycol through a radical copolymerization process. This combination gives the binder both flexibility and a boost in electrical performance. Our experimental results demonstrate that LFP cathodes with this binder have an intriguing self-healing ability in comparison with the conventional PVDF binder, enhanced charge-discharge capacities, improved cycling stability, and higher ionic conductivity. Specifically, electrodes utilizing the pectin-PEG binder exhibit an impressive retention of discharge capacity. They maintain roughly 150 mAh g−1 after 500 cycles at 1C with 99% retention, and about 141 mAh g−1 with 97% retention at 3C. Cyclic voltammetry (CV) confirms that the PP binder maintains its ionic diffusion properties at high sweep rates, whereas galvanostatic intermittent titration technique reveals a much higher lithium ion diffusion coefficient (DLi+) within the operational voltage range of the LFP-PP250 electrodes. These findings establish an attractive direction for the development of electrodes for high-energy density, sustainable lithium-ion batteries.

Improved high voltage operation of amorphous In–Ga–Zn–O thin film transistor by carrier density enhancement

We report on improved high voltage operation of amorphous-In–Ga–Zn–O (a-IGZO) thin film transistors (TFTs) by increasing carrier density and distributing the high bias field over the length of the device which utilizes an off-set drain structure. By decreasing the O2 partial pressure during sputter deposition of IGZO, the channel carrier density of the high voltage a-IGZO TFT (HiVIT) was increased to ∼1018 cm−3. Which reduced channel resistance and therefore the voltage drop in the ungated offset region during the on-state. To further decrease the electric field in the offset region, we applied Ta capping and subsequent oxidation to locally increase the oxygen vacancy levels in the offset region thereby increasing local carrier density. The reduction of the drain field in the offset region from 1.90 V μm−1 to 1.46 V μm−1 at 200 V drain voltage, significantly improved the operational stability of the device by reducing high field degradation. At an extreme drain voltage of 500 V, the device showed an off-state current of ∼10−11 A and on-state current of ∼1.59 mA demonstrating that with further enhancements the HiVIT may be applicable to thin-film form, low leakage, high voltage control applications.

Мodelling of Passive Coupling of Battery Units of Hybrid Energy Storage System

Due to the development of electric transport and the growth of “green” energy, electric energy storage systems (ESS) are increasingly being used in the world. The growth of the battery market in the last decade has been 20-30%. One of the ways to increase the efficiency of an electric power storage device is its hybridization, i.e. the use of heterogeneous battery units. The paper examines the features of passive coupling of lead-acid and lithium-ion batteries in a hybrid storage device. A model is presented for calculating the electrical characteristics of these units during operation. The possibility of choosing a hybrid drive structure that provides a comparable operating voltage range of the units (operation without voltage converters) is demonstrated. The modes of operation of a hybrid energy storage system are modeled both for simple parallel connection and for switching blocks according to a threshold algorithm. It is demonstrated that in order to equalize the discharge rate of the main and additional units, it is necessary to coordinate the capacity of the ESS, the degree of hybridization, the type of load and the electrical parameters of the batteries, which is impossible without modeling the system. When the threshold switching of the blocks takes place, additional control parameters, making it possible to change the discharge rate of the additional block and increase the economic efficiency of the hybrid ESS. Estimates of the economic efficiency of hybrid ESSs have been made for different values of the threshold switching voltage of the lithium-ion unit, as well as for three characteristic loads: an electric forklift truck, a 30-apartment apartment building and a 300-apartment residential complex. The results demonstrate the features and technical and economic potential of passive hybridization, can be used for the design of hybrid ESSs for small power systems with solar and wind power plants, in the calculation and design of generator – storage – consumer systems.

Iron Sulfide Microspheres Supported on Cellulose-Carbon Nanotube Conductive Flexible Film as an Electrode Material for Aqueous-Based Symmetric Supercapacitors with High Voltage.

Nanostructured iron disulfide (FeS2) was uniformly deposited on regenerated cellulose (RC) and oxidized carbon nanotube (CNT)-based composite films using a simple chemical bath deposition method to form RC/CNT/FeS2 composite films. The RC/CNT composite film served as an ideal substrate for the homogeneous deposition of FeS2 microspheres due to its unique porous architecture, large specific surface area, and high conductivity. Polypyrrole (PPy), a conductive polymer, was coated on the RC/CNT/FeS2 composite to improve its conductivity and cycling stability. Due to the synergistic effect of FeS2 with high redox activity and PPy with high stability and conductivity, the RC/CNT/FeS2/PPy composite electrode exhibited excellent electrochemical performance. The RC/CNT/0.3FeS2/PPy-60 composite electrode tested with Na2SO4 aqueous electrolyte could achieve an excellent areal capacitance of 6543.8 mF cm-2 at a current density of 1 mA cm-2. The electrode retained 91.1% of its original capacitance after 10,000 charge/discharge cycles. Scanning electron microscopy (SEM) images showed that the ion transfer channels with a pore diameter of 5-30 μm were formed in the RC/CNT/0.3FeS2/PPy-60 film after a 10,000 cycle test. A symmetrical supercapacitor device composed of two identical pieces of RC/CNT/0.3FeS2/PPy-60 composite electrodes provided a high areal capacitance of 1280 mF cm-2, a maximum energy density of 329 μWh cm-2, a maximum power density of 24.9 mW cm-2, and 86.2% of capacitance retention after 10,000 cycles at 40 mA cm-2 when tested at a wide voltage window of 1.4 V. These results demonstrate the greatest potential of RC/CNT/FeS2/PPy composite electrodes for the fabrication of high-performance symmetric supercapacitors with high operating voltages.

Efficient gradient heating-up approach for rapid growth of high-quality amorphous ZrO2 dielectric films

High-k oxide dielectric films are indispensable for low-power-consumption oxide thin-film transistors (TFTs) applied in advanced and portable electronics. However, high-quality oxide dielectric films prepared by solution process typically require sophisticated processes and long thermal annealing time, severely limiting both the throughput manufacturing and cost-effectiveness. In this study, the influence of different heating-up methods on the surface morphology and dielectric properties was systematically investigated. Gradient heating-up method could not only substantially improve the surface morphology and quality of high-k ZrO2 films but also efficiently shorten the annealing time. The gradient heating-up process was further designed on the basis of thermal behavior of the xerogel-like precursor, which successfully realize the preparation of high-quality ZrO2 films with an annealing time of 5 min (i.e. the efficiency of thermal treatment increased by about 89%). The ZrO2 film presented excellent dielectric properties, including a low leakage current density of ∼10−8 A cm−2 (at 2 MV cm−1 ), a large areal capacitance of 169 nF cm−2 and a high dielectric constant of 20.41 (1 MHz). Furthermore, InSnZnO TFT based on the ZrO2 gate dielectrics shows an acceptable device performances, such as a high carrier mobility of 2.82 cm2 V−1 s, a high on/off current ratio of ∼105 and a low subthreshold swing of 0.19 V decade −1 at a low operation voltage of 5 V. This work provide a highly promising approach to fabricate high-quality solution-processed high-k oxide dielectric films employed for large-scale and low-power-consumption electronics.

High Efficiency Flat-Type GaN-Based Light-Emitting Diodes with Multiple Local Breakdown Conductive Channels.

We investigated a flat-type p*-p LED composed of a p*-electrode with a local breakdown conductive channel (LBCC) formed in the p-type electrode region by applying reverse bias. By locally connecting the p*-electrode to the n-type layer via an LBCC, a flat-type LED structure is applied that can replace the n-type electrode without a mesa-etching process. Flat-type p*-p LEDs, devoid of the mesa process, demonstrate outstanding characteristics, boasting comparable light output power to conventional mesa-type n-p LEDs at the same injection current. However, they incur higher operating voltages, attributed to the smaller size of the p* region used as the n-type electrode compared to conventional n-p LEDs. Therefore, despite having comparable external quantum efficiency stemming from similar light output, flat-type p*-p LEDs exhibit diminished wall-plug efficiency (WPE) and voltage efficiency (VE) owing to elevated operating voltages. To address this, our study aimed to mitigate the series resistance of flat-type p*-p LEDs by augmenting the number of LBCCs to enhance the contact area, thereby reducing overall resistance. This structure holds promise for elevating WPE and VE by aligning the operating voltage more closely with that of mesa-type n-p LEDs. Consequently, rectifying the issue of high operating voltages in planar p*-p LEDs enables the creation of efficient LEDs devoid of crystal defects resulting from mesa-etching processes.

Performance Investigation of PEM Fuel Cell with Three-Pass Serpentine Flow Fields under Varying Operating Voltages

The fuel cells performance is significantly impacted by both design and operational factors. The effective distribution of reactants within the flow fields is facilitated by the design of the flow channels. Therefore, the geometry of the flow channels and the overall design of the flow field play a crucial role in determining the fuel cells performance. Among various flow field designs, the serpentine flow field demonstrates superior performance compared to others. In this research, a three-dimensional proton exchange membrane fuel cell model was developed and used to study the influence of three-pass serpentine flow field on cell performance across varying operating voltages (0.9 V, 0.7 V and 0.5 V). The purpose of this research is to simulate and evaluate the comportment of the three-pass serpentine flow channels configuration by analyzing several parameters such as channels velocity distribution, oxygen mole fraction, pressure distribution and electrolyte current density along the z-axis at the cathode under different operating voltages. Numerical simulations were conducted using the COMSOL Multiphysics software. Therefore, this software is used to solve numerically the complete three-dimensional model with the governing equations of charge conservation, species transport, momentum, and continuity. The obtained results indicate that among different operating voltages, the cell voltage of 0.5 V demonstrated the highest channels velocity distribution, pressure distribution, and electrolyte current density. Moreover, it is found that at an operating voltage of 0.5 V, there is an important decrease in oxygen concentrations indicating a significant oxygen consumption in the fuel cell which improves the overall efficiency. This work contributes valuable insights to the optimization of fuel cell performance, specifically highlighting the favorable outcomes associated with the three-pass serpentine flow field design at lower operating voltages

Bidirectional DC-DC Converter and Improved Electrical Vehicle Dynamic Response Control

Background: In automotive applications where bidirectional power flow is necessary to lighten the power system, dual active bridge (DAB) converters are frequently employed. Variations in the required output voltage, erratic input voltage, and shifting loads all have an impact on this converter. As a result, converter performance has to be improved. To increase efficiency, the current stress of the DC-DC converter must be optimised. This paper proposes a control scheme for the coupled inductor bidirectional DC-DC (CIB DC-DC) converter utilising both model predictive control (MPC) and a proportional-integral (PI) controller. The integration of these control techniques aims to enhance the performance and efficiency of the converter. Methods: The MPC algorithm is employed to predict the converter's future behaviour based on a dynamic model, taking into account system constraints and performance criteria. By optimising the control action over a finite time horizon, the MPC algorithm ensures an optimal response, considering the current state and anticipated changes. Additionally, a PI controller is incorporated to augment the control strategy. The proportional component of the PI controller enables a fast initial response to the error between the desired and actual converter outputs. The integral component eliminates steady-state errors and provides robustness against disturbances, resulting in improved overall system performance. Results: The proposed control scheme is implemented and evaluated through simulations and experimental tests on a prototype converter. The results demonstrate the effectiveness of the combined MPC and PI controller approach. Conclusion: The coupled inductor bidirectional DC-DC (CIB DC-DC) converter using MPC can provide precise control of power flow between two voltage domains, enabling efficient bidirectional power transfer. The predictive capabilities of MPC allow it to adapt to varying load conditions and respond quickly to changes, ensuring stable operation and accurate regulation of voltage and current. Overall, the coupled inductor bidirectional DC-DC converter controlled using MPC over PI offers improved performance, efficiency, and flexibility compared to traditional control methods. MPC can handle the complex dynamics response and non-linear characteristics of the converter, making it suitable for bi-directional vehicle charging applications, where precise control and high efficiency can be achieved.

Enhancing optimization accuracy in power systems: Investigating correlation effects on objective function values

This study addresses the critical yet often overlooked aspect of incorporating correlations among input stochastic variables in power system planning and scheduling optimization. While existing literature has extensively focused on uncertainty modelling, there remains a gap in fully assessing the consequences of disregarding correlations on objective function values across different power network sizes. To bridge this gap, we utilize Monte Carlo simulation with Cholesky decomposition, alongside Quasi-Monte Carlo sampling and Latin Hypercube Sampling, to effectively model uncertainty and capture correlation coefficients among input variables, including wind, solar photovoltaic, and load power. The most efficient technique is then integrated into our optimization model, which is applied to small, medium, and large power network models. Our proposed optimization model addresses conflicting objectives using a hybrid NSGAII-MOPSO, aiming to simultaneously minimize total operational cost, power loss, and voltage deviation. By implementing this model on selected power networks and comparing outcomes between cases with independent and correlated variables, we rigorously assess discrepancies in objective function values. We visualize and analyze these errors across systems of varying sizes, shedding light on the impact of neglecting variable correlations. Notably, the maximum discrepancies are observed at $3.26/h, $40.66/h, and $2754.04/h for the IEEE 30-bus, IEEE 57-bus, and IEEE 118-bus systems, respectively. Crucially, as the system size increases, so does the magnitude of these differences, underlining the escalating impact of neglecting variable correlations on optimization outcomes. We stress the importance of integrating such considerations into future planning and operational strategies to mitigate errors and enhance decision-making processes.

Understanding HZO Thickness Scaling in Si FeFETs: Low Operating Voltage, Fast Wake-Up, and Suppressed Charge Trapping

Understanding HZO Thickness Scaling in Si FeFETs: Low Operating Voltage, Fast Wake-Up, and Suppressed Charge Trapping

Low Operation Voltage, High-Temperature Reliable, and High-Yield BEOL Integrated Hf₀.₅Zr₀.₅O₂ Ferroelectric Memory Arrays

Low Operation Voltage, High-Temperature Reliable, and High-Yield BEOL Integrated Hf₀.₅Zr₀.₅O₂ Ferroelectric Memory Arrays

P‐176: New liquid crystal materials for high‐contrast displays of the fringe‐field switching mode

Since the establishment of liquid crystal display industries, larger sizes, faster response, higher contrast ratio, higher resolution and lower power consumption have become a pursuing target of various panel suppliers. Considering the marvelous viewing angle of the fringe‐field switching (FFS) mode, FFS displays with a higher contrast ratio are able to show more details in the dark pictures, resulting in a much better viewing experience. Herein, to develop the next‐generation liquid crystal (LC) materials for high‐contrast FFS panels, various high‐contrast LC (HCLC) materials were designed. By minimizing Δn and maximizing Kave, HCLCs exhibited lower light leakage in dark states, leading to a higher contrast ratio compared to the reference. Two HCLCs for improving the operation voltage, transmittance, contrast ratio and response time were developed by optimizing the properties of HCLC materials. Furthermore, FFS monitors with a contrast ratio of 2820:1 and a color gamut of 96.4% NTSC were demonstrated.

Measurement of space charge density distributions and dielectric resonance enhancement of beam deflection properties of KTN crystal

In recent years, potassium tantalum niobate (KTN) electro-optical deflection devices have gained considerable attention because of their notable advantages, such as large deflection angles, low operational voltage requirements, and compact dimensions. This study uses the phase-shifted interferometric optical path to characterize the influence of direct current (DC) voltage on charge density. An interferogram is acquired using the four-step phase-shifting technique, enabling the calculation of phase delays and deducing the variation in charge density. Experimental results demonstrate that the charge density near the cathode increases with an increase in DC voltage. Subsequently, we utilize the frequency dependence of the dielectric constant of the KTN crystal on the electric field. The dielectric constant can be enhanced when the characteristic frequency of the motion of the polar nanoscale region matches the frequency of the electric field. This field-induced enhancement effect improves the beam deflection performance of the KTN crystal. Application requirements in the field of high-speed random scanning can be realized through the mechanism of the KTN crystal co-acting with DC and alternating current electric fields.

Initiating cationic-anionic chemistry with stepwise surface-to-inner conversion in copper selenide superstructures for high-energy rechargeable magnesium batteries

Copper selenides are viewed as the most capable cathode materials for rechargeable magnesium batteries, yet suffer from unsatisfactory energy density due to their low operating voltage plateau (∼0.9 V vs. Mg/Mg2+) and insufficient reversible capacity. Herein, a stepwise conversion from surface cationic-anionic redox to inside electrochemical displacement reaction is realized in copper selenide (Cu2-xSe) superstructure cathodes. A highly reversible high-voltage platform at ∼1.6 V is discovered during discharge process. Ex-situ spectroscopy and microscopy results demonstrate that the high-voltage plateau is contributed by surface Cu2+ charge-carrier transformation and anionic Se2– redox reaction while sufficient inner Cu-Mg replacement conversion at low-voltage region. Following the favorable mechanism, the Cu2-xSe superstructure cathodes can present high specific capacity of 385.4 mAh g–1 at 0.1 A g–1 and outstanding energy density of 426.3 Wh kg–1. Moreover, the Cu2-xSe superstructure cathodes also maintain a reversible capacity of 223.6 mAh g–1 over 700 cycles with 0.0147 % capacity degradation per cycle at 1.0 A g–1 and long-term charge-discharge lifetime for 3000 cycles at 5.0 A g–1. This research reports a new Mg2+ storage mechanism for copper selenide cathodes and provides novel route to develop high-energy-density rechargeable magnesium batteries.

21‐3: Closed‐Form Expression for the Current‐Voltage Characteristics of OLEDs

The development of OLED displays is a non‐ergodic process in which there is continuous novel change; and comprehending emitters that are evolving requires new theory, or at least modification of that which is already possessed. For the first time, a new data‐validated closed‐form physics‐based expression is derived for the I‐V characteristics of OLEDs in this paper. Two parameters emerge from the new model: liminal current and liminal voltage. Both parameters are expressed in terms of device and material parameters, allowing a device engineer to intuitively design experiments to target low voltage operation OLEDs. Robust parameter extraction methods are proposed and validated with experimental data.

Hydrophobic Two-Dimensional Layered Superstructure of a Polyoxometalate Cluster as the Cathode Material for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries hold promise for sustainable energy storage, yet challenges in finding high-performance cathode materials persist. Polyoxovanadates (POVs) are emerging as potential candidates due to their structural diversity and robust redox activity. Despite their potential, issues like dissolution in electrolytes, structural degradation, and byproduct accumulation persist. This work introduces a POV-based hydrophobic two-dimensional (2D) layered superstructure that addresses these challenges. The hydrophobic nature minimizes POV dissolution, enhancing structural stability and inhibiting phase transitions during cycling. The 2D arrangement ensures a larger surface area and improved electronic conductivity, resulting in faster kinetics and higher specific capacity. The superstructure demonstrates improved cycle life and an increased operating voltage, marking a significant advancement in POV-based cathode materials for aqueous zinc-ion batteries.