Voltage Range Research Articles

Understanding the Correlation between Electrochemical Performance and Operating Mechanism of a Co-free Layered-Spinel Composite Cathode for Na-Ion Batteries.

Compositing different crystal structures of layered transition metal oxides (LTMOs) is an emerging strategy to improve the electrochemical performance of LTMOs in sodium-ion batteries. Herein, a cobalt-free P2/P3-layered spinel composite, P2/P3-LS-Na1/2Mn2/3Ni1/6Fe1/6O2 (LS-NMNF), is synthesized, and the synergistic effects from the P2/P3 and spinel phases were investigated. The material delivers an initial discharge capacity of 143 mAh g-1 in the voltage range of 1.5-4.0 V and displays a capacity retention of 73% at the 50th cycle. The material shows a discharge capacity of 72 mAh g-1 at 5C. This superior rate performance by the material could be by virtue of the increased electronic conductivity contribution of the incorporated spinel phase. The charge compensation mechanism of the material is investigated by in operando X-ray absorption spectroscopy (in a voltage range of 1.5-4.5 V vs Na+/Na), which revealed the contribution of all transition metals toward the generated capacity. The crystal structure evolution of each phase during electrochemical cycling was analyzed by in operando X-ray diffraction. Unlike in the case of many reported P2/P3 composite cathode materials and spinel-incorporated cobalt-containing P2/P3 composites, the formation of a P'2 phase at the end of discharge is absent here.

Durability Investigation of Low Pt-Loaded PEM Fuel Cells with Different Catalyst Layer Morphologies

This study investigates the durability of proton exchange membrane fuel cells against the Pt-dissolution degradation mechanism using a triangular accelerated stress test (AST) within the voltage range of 0.6-1 V. The electrochemical active surface area and polarization curves are reported throughout the AST for three different catalyst layers (CL), all featuring 0.1 mg/cm2 Pt loading but with different morphologies, which include the Pt/C weight percentages, dilution ratio, and thickness. In addition, a numerical model is employed to simulate the electrochemical performance of these samples at the beginning and end of life, considering the variations in the oxygen transport resistances and catalyst structure.

A high current efficiency rail-to-rail operational amplifier

ABSTRACT This paper proposes a new single stage high current efficiency rail to rail amplifier (HCE-RTR). Due to the combination of a new constant transconductance control circuit and local common mode feedback (LCMFB) technique, the proposed rail to rail amplifier not only achieves improvements in unity-gain bandwidth (GBW) and slew rate (SR), but also ensures input stage transconductance constancy within the rail to rail voltage range. Based on the SMIC 180 nm process, the post-layout simulation results show that the proposed amplifier achieves rail-to-rail input/output. The simulated open loop AC response shows the DC gain, GBW, and PM are 66.2 dB, 8.2 MHz, and 60.97 o , respectively. When the driving load capacitance is 70 pF, the transient response simulation results show that the proposed amplifier achieves 0.039 µs average 1% settling time, and about 5.73 V/µs average slew rate. Note that under the condition of 1.8 V power supply, the power consumption is only 122.4 µW, proving the proposed amplifier can achieve high current efficiency while maintaining stability.

Enhanced Low-Temperature Resistance of Lithium-metal Rechargeable Batteries Based on Electrolyte Including Ethyl Acetate and LiDFOB Additives.

To meet the demand for higher energy density in lithium-ion batteries and expand their application range, coupling lithium metal anodes with high-voltage cathodes is an ideal solution. However, the compatibility between lithium metal batteries and electrolytes affects their applicability. In this study, proposes a locally concentrated electrolyte based on ethyl acetate (EA) as the solvent, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the lithium salt, and lithium difluorooxoborate (LiDFOB) as a sacrificial agent to enhance the low-temperature and high-voltage endurance of Li//Lithium cobalt oxide (LCO) batteries. The Li//LCO battery can operate within the voltage range of 3 to 4.5 V, with an initial discharge specific capacity of 174.5 mAh g-1 at 20 oC. At -40 oC, after 200 cycles, the capacity retention rate is 87.7%. It can operate under extreme conditions of -70 oC, with a discharge specific capacity of 112.6 mAh g-1. Additionally, LCO//HC batteries using this electrolyte demonstrate excellent performance. Present work provides a new perspective for the optimization of electrolytes for low-temperature lithium-ion batteries.

Investigation of Bandgap Properties of a Piezoelectric Phononic Crystal Plate Based on the PDE Module in COMSOL

Investigation of Bandgap Properties of a Piezoelectric Phononic Crystal Plate Based on the PDE Module in COMSOL

Experimental investigation of the polarity-switching process with different bipolar ionic liquid thruster operating frequencies

The bipolar ionic liquid thruster employs ionic liquid as a propellant to discharge positively and negatively charged high-energy particles under an alternating current (AC) power source, effectively suppressing electrochemical reaction and ensuring charge neutrality. Determining an optimal AC supply power source frequency is critical for sustained stable thruster operation. This study focuses on the emission characteristics of the ionic liquid thruster under varied AC conditions. The AC power supply was set within the frequency range of 0.5–64 Hz, with eight specific frequency conditions selected for experimentation. The experimental results indicate that the thruster operates steadily within a voltage range of ±1470 to ±1920 V, with corresponding positive polarity current ranging from 0.41 to 4.91 μA and negative polarity current ranging from −0.49 to −4.10 μA. During voltage polarity switching, an emission delay occurs, manifested as a prominent peak signal caused by circuit capacitance characteristics and a minor peak signal resulting from liquid droplets. Extended emission test was conducted at 16 Hz, demonstrating approximately 1 h and 50 min of consistent emission before intermittent discharge. These findings underscore the favorable impact of AC conditions within the 8–16 Hz range on the self-neutralization capability of the ionic liquid thruster.

OPTIMIZATION OF THE PEROVSKITE SOLAR CELL STRUCTURE

An experimental perovskite solar cell (PSC) with the structure Au/Spiro-MeOTAD/CH3NH3PbI3/PEDOT:PSS/ITO was fabricated. The measurements of main photovoltaic characteristics were provided. The current-voltage dependences (I-V curves) were measured conducted in the voltage range from -1V to 1V. During the measurements, the corresponding values were calculated of the short-circuit current density(Jsc) and open-circuit voltage(Uoc) were obtained as 1.23 mA/cm² and 0.19 V, respectively. Subsequently, an analytical model corresponding to this structure was formulated. For modeling the parameters of the perovskite solar cell, the Comsol Multiphysics environment was used, this environment is based on the finite element method. The relevant computations were provided to obtain the corresponding values of the short-circuit current density and open-circuit voltage as 3.29 mA/cm² and 0.2 V, respectively, with the maximum theoretically calculated power of this structure being 0.11 W. The experimental outcomes were juxtaposed with the predictions of the analytical computations, and the modeling results were empirically validated. An analytically accomplished model of the same structure was built by adding an electron transport layer (ETL). An organic material BCP (Bathocuproine) was used as an supplementary ETL layer. During the optimization of the PSC, the main datums were mathematically counted. Such values as the short-circuit current density of 10.17 mA/cm², open-circuit voltage of 1.2 V, and the maximum power value of Au/BCP/Spiro-MeOTAD/CH3NH3PbI3/PEDOT:PSS/ITO structure, which is 3.21 W were rated. A comparison of the volt-ampere characteristics of perovskite cells in dark and light modes was conducted for primary and optimized structures. The main parameters, obtained during the modeling of the experimental sample and subsequent model optimization, were compared. Specifically one of the key parameters of solar cell heterostructures the fill factor was evaluated and found to have increased from 16.52% to 25.00%, respectively. The light-sensitive behavior of the perovskite cell were visibly enhanced.

Study of conduction mechanisms of InSeSb nano-chalcogenide alloys.

The electrical conduction mechanisms for bulk samples of In0.1Se0.9-xSbx (x= 0, 0.04, 0.08 and 0.12) nano-chalcogenide system, synthesized by the melt-quenching technique are investigated through current-voltage (I-V) characteristics. For the detailed study of conduction mechanism pellets of bulk samples are prepared. A thorough examination of electrical conductivity is done in the temperature range of 295-318 K and 0-50 V voltage range. From I-V measurements it is observed that samples are showing ohmic nature at lower field and non-ohmic nature at relatively higher field values. The temperature dependence of DC conductivity is analyzed using the Arrhenius relationship which is found to increase with Sb content. The value of activation energy and pre-exponential factor are calculated, which revealed that the conduction is due to the hopping of charge carriers among the localized states. Different parameters of Mott's variable range hopping such as degree of disorder T0, density of localized states N(EF), hopping distance (Rhop), and hopping energy (W) are calculated. For the high field conduction process Poole-Frenkel, and Schottky processes are studied.

Stabilizing High-Voltage Performance of Nickel-Rich Cathodes via Facile Solvothermally Synthesized Niobium-Doped Strontium Titanate.

Ni-rich layered ternary cathodes are promising candidates thanks to their low toxic Co-content and high energy density (∼800 Wh/kg). However, a critical challenge in developing Ni-rich cathodes is to improve cyclic stability, especially under high voltage (>4.3 V), which directly affects the performance and lifespan of the battery. In this study, niobium-doped strontium titanate (Nb-STO) is successfully synthesized via a facile solvothermal method and used as a surface modification layer onto the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode. The results exhibited that the Nb-STO modification significantly improved the cycling stability of the cathode material even under high-voltage (4.5 V) operational conditions. In particular, the best sample in our work could provide a high discharge capacity of ∼190 mAh/g after 100 cycles under 1 C with capacity retention over 84% in the voltage range of 3.0-4.5 V, superior to the pristine NCM811 (∼61%) and pure STO modified STO-811-600 (∼76%) samples under the same conditions. The improved electrochemical performance and stability of NCM811 under high voltage should be attributed to not only preventing the dissolution of the transition metals, further reducing the electrolyte's degradation by the end of charge, but also alleviating the internal resistance growth from uncontrollable cathode-electrolyte interface (CEI) evolution. These findings suggest that the as-synthesized STO with an optimized Nb-doping ratio could be a promising candidate for stabilizing Ni-rich cathode materials to facilitate the widespread commercialization of Ni-rich cathodes in modern LIBs.

Determination of gas discharge plasma potential by Langmuir probe using different methods

In a hollow cathode discharge in helium at reduced pressure, the profile of the plasma potential Up in the cathode-anode region was measured with a single Langmuir probe. A digital technique was used to control and analyze the experimental results. The probe current-voltage characteristic was generated by applying a voltage with a spectrum with an equal probability distribution in the measured voltage range. Three methods were compared: (1) differentiation of the probe current-voltage characteristic (IVC) by the Langmuir-Druyvesteyn (LD) method with the Savitsky-Golay (SG) filter; (2) definition of the position of the noise maximum in the experimental IVC; (3) determination of the voltage corresponding to the intersection of the asymptotes of different range of the IVC. Methods (2) and (3) were used both as alternatives to method (1) for measuring the potential Up and as additional ones when choosing free parameters of the SG filter for plasma diagnostics by method (1).

Design Approaches and Electromechanical Modeling of Conformable Piezoelectric‐Based Ultrasound Systems

AbstractPainless, needleless delivery of drugs through the skin can be realized through aphenomenon called sonophoresis by applying an ultrasound field to the biological tissue. Development of wearable embodiments of such systems demands comprehensive characterization of both the physical mechanism of sonophoresisas well as wearability parameters. Here, we present a framework for analyzing disk‐type piezoelectric transducers in a polymeric substrate to create acoustic cavitation in a fluid coupling medium for sonophoresis applications. The device design and operating parameters such as the working frequency, applied voltage range, acoustic pressure distribution, and transducer spacing were determine dusing a finite element methods (FEM),and verified with experimental measurements. The influence of the surrounding water and tank reflections on the acoustic pressure field, and the interaction between the elements in the array structure were also studied.Finally, the impact of skin and the substrate geometry on the acoustic pressure fields was characterized to simulate the invivo use‐case of the system. These analytical models can be used to guide critical parameters for device design such as the separation distance of the piezoelectric transducer from the skin boundary. We envision that this tool boxwill support rapid design iteration for realization of wearable ultrasound systems.

Variable Switching Frequency for ZVS over Wide Voltage Range in Dual Active Bridge

The Dual Active Bridge (DAB) converter is known for its advantageous characteristics, including bidirectionality, galvanic isolation, and soft-switching operation. However, achieving Zero Voltage Switching (ZVS) across the complete operation range is not guaranteed, particularly through a wide input–output voltage ratio. This paper explores the integration of the switching frequency as a control variable in the DAB converter to ensure ZVS operation across a wide voltage range, employing Single Phase Shift (SPS) modulation. The study evaluated the RMS and reactive currents under variable switching frequency, presenting the advantages of this approach. Moreover, it includes a design-oriented analysis of the ZVS limits and their relationship with the switching frequency, aiming to ensure ZVS at any operating point. Experimental results validated the theoretical analysis, while presenting the main advantages of variable switching frequency implementation.

Optimization of Temperature Modulation for Gas Classification Based on Bayesian Optimization.

This study proposes an optimization method for temperature modulation in chemiresistor-type gas sensors based on Bayesian optimization (BO), and its applicability was investigated. As voltage for a sensor heater, our previously proposed waveform was employed, and the parameters determining the voltage range were optimized. Employing the Bouldin-Davies index (DBI) as an objective function (OBJ), BO was utilized to minimize the DBI calculated from a feature matrix built from the collected data followed by pre-processing. The sensor responses were measured using five test gases with five concentrations, amounting to 2500 data points per parameter set. After seven trials with four initial parameter sets (ten parameter sets were tested in total), the DBI was successfully reduced from 2.1 to 1.5. The classification accuracy for the test gases based on the support vector machine tends to increase with decreasing the DBI, indicating that the DBI acts as a good OBJ. Additionally, the accuracy itself increased from 85.4% to 93.2% through optimization. The deviation from the tendency that the accuracy increases with decreasing the DBI for some parameter sets was also discussed. Consequently, it was demonstrated that the proposed optimization method based on BO is promising for temperature modulation.

4670‐PPI OLEDoS pixel circuit design for wide data voltage range in a 5 V 0.13 μm CMOS process

AbstractOLEDoS displays hold great promise for AR/VR applications, but the ultra‐high pixel density required for microdisplays, exceeding several thousand PPI, presents significant challenges for pixel circuit design. Above all, the maximum OLED current of each OLEDoS sub‐pixel is extremely low, on the order of several nanoamperes or less, resulting in a data voltage range narrower than a few hundred millivolts. Consequently, for example, when expressing 10‐bit grayscale, designing data driver circuits to divide the data voltage range into 1024 levels becomes exceedingly challenging. Furthermore, circuit techniques that compensate for variations in transistor characteristics are nearly inapplicable due to the ultra‐small pixel area. This paper proposes a pixel circuit design method to expand the data voltage range for a 4670‐PPI OLEDoS display while considering current uniformity. The effectiveness of the proposed pixel circuit was verified through measurements on 40 × 120 pixel arrays fabricated in a 5 V 0.13 μm CMOS process.

A solid-state pulse power sub-nanosecond SiC DSRD-based generator with high-voltage and high repetition frequency for pulse discharge water treatment

Water treatment is one of the most important issues for all walks of life around the world. The unique advantages of the solid-state power electronic pulses in water treatment make it attractive and promising in practical applications. The output voltage, rising time, repetition rate, and peak power of output pulses have a significant impact on the effectiveness of water treatment. Especially in pulse electric field treatment and pulse discharge treatment, the pulse with fast rising time achieves the advantage of generating plasma without corona, which can avoid water heating effect and greatly improve the efficiency of the pulse generator. High repetition rate can significantly reduce the peak power requirement of the pulse in water treatment application, making the equipment smaller and improving the power density. Therefore, the study developed a high-voltage high frequency sub-nanosecond pulse power generator (PPG) system for wastewater treatment. It adopts SiC DSRD (Drift Step Recovery Diode) solid-state switches and realize modular design, which can achieve high performance and can be flexible expanded according to the requirements of water treatment capacity. Finally, an expandable high-voltage PPG for water treatment is built. The output parameters of the PPG include output pulse voltage range from 1 to 5.28 kV, rise time <600 ps (20%–90%), repetition up to 1 MHz. The experiment results of PPG application for pulse discharge water treatment is presented. The results indicate that the proposed generator achieves high-efficiency degradation of 4-Chlorophenol (4-CP), which is one of the most common chlorophenol compounds in wastewater. From experiment, the homemade system can degrade 450 mL waste water containing 500 mg/L 4-CP in 35 min, with a degradation rate of 98%. Thereby, the requirement for electric field intensity decreased. Through the further quantitative analysis, the impact of frequency, voltage, and electrode spacing on the degradation effect of 4-CP is confirmed.

Highly flexible and uniform switching of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)based RRAM achieved through Ag NWs embedded for high-density storage

A super-flexible resistive random access memory (RRAM) based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) embedded with Ag nanowires (Ag NWs) is fabricated on a piece of aluminum foil. In the design, the aluminum foil is used as the substrate as well as the electrode, which not only solves the flexibility of the device, but also greatly reduces the volume of the device, helpful to realize high-density integration. The uniformity of the device is greatly improved after the modification of the Ag NWs. The fluctuation range of the Set voltage (Vset) / Reset voltage (Vreset) is reduced from 0.9~2.78 V/ −0.45∼-1.25 V to 1.14∼1.35 V/-1 ∼0.5 V. What’s more, the average Vset / Vreset is decreased from 2.5 V/-1.25 V to 1.2 V/-0.7 V. Also, the multilevel switching potential of the device is confirmed by controlling the reset voltage((-0.5, −0.7, and −1.0 V). After repetitive 1000 bendings of the device with a radius of 6 mm, a stable memory window of more than 103 is still detected during 300 continuous cycles. No degradation is observed from the two resistance states at 85 °C after 104 s. These results clearly demonstrate that the device has a broad application prospect in the future application of flexible electronics due to its simple and thin structure, low cost, excellent flexibility and good uniformity.

Unveiling the potential of Na2FePO4F@PEG composite as cathode material for sodium-ion batteries

The economic and environmental advantages of Na2FePO4F fluorophosphate have positioned it as a highly promising cathode material for sodium-ion batteries (SIBs). This recognition stems from its demonstrated potential to address key challenges in energy storage systems, making it a subject of extensive research and studies.In this paper, the preparation of Na2FePO4F powder through a simplified, upscaling, and cost-effective approach that involves the direct use of phosphoric acid is described, aiming to evaluate its electrochemical performance. The obtained orthorhombic structure (S.G. Pbcn) is mixed with varying percentages of polyethylene glycol as a carbon source (15% and 20%) to generate large specific surfaces, improve electronic conductivity, and achieve an optimized carbon content for these materials. The 15% and 20% PEG-coated Na2FePO4F are evaluated at a 2 - 4 V voltage range at C/15 in Na-half cells using two electrolyte formulations: 5% FEC 1 M NaClO4:PC and 1 M NaPF6:PC. The NaPF6/FEC electrolyte exhibits better electrochemical characteristics and high cycling stability, especially in the case of the 15% PEG-coated material. These findings are also supported by the data from differential plots and rate capabilities, highlighting the potential of the coated material for applications in high-performance energy storage applications.

Wide Voltage Swing Potentiostat with Dynamic Analog Ground to Expand Electrochemical Potential Windows in Integrated Microsystems.

Electrochemical measurements are vital to a wide range of applications such as air quality monitoring, biological testing, food industry, and more. Integrated circuits have been used to implement miniaturized and low-power electrochemical potentiostats that are suitable for wearable devices. However, employing modern integrated circuit technologies with low supply voltage precludes the utilization of electrochemical reactions that require a higher potential window. In this paper, we present a novel circuit architecture that utilizes dynamic voltage at the working electrode of an electrochemical cell to effectively enhance the supported voltage range compared to traditional designs, increasing the cell voltage range by 46% and 88% for positive and negative cell voltages, respectively. In return, this facilitates a wider range of bias voltages in an electrochemical cell, and, therefore, opens integrated microsystems to a broader class of electrochemical reactions. The circuit was implemented in 180 nm technology and consumes 2.047 mW of power. It supports a bias potential range of 1.1 V to -2.12 V and cell potential range of 2.41 V to -3.11 V that is nearly double the range in conventional designs.

Effect of voltage gradients on EK-PRB remediation: Experimental and molecular dynamics simulations

Electrokinetic-Permeable Reaction Barrier (EK-PRB) coupled remediation technology can effectively treat heavy metal-contaminated soil near coal mines. This study was conducted on cadmium (Cd), a widely present element in the soil of the mining area. To investigate the impact of the voltage gradient on the remediation effect of EK-PRB, the changes in current, power consumption, pH, and Cd concentration content during the macroscopic experiment were analyzed. A three-dimensional visualized kaolinite-heavy metal-water simulation system was constructed and combined with the Molecular Dynamics (MD) simulations to elucidate the migration mechanism and binding active sites of Cd on the kaolinite (001) crystalline surface at the microscopic scale. The results showed that the voltage gradient positively correlates with the current, power consumption, and Cd concentration during EK-PRB remediation, and the average removal efficiency increases non-linearly with increasing voltage gradient. Considering power consumption, average removal efficiency, and cost-effectiveness, the voltage range is between 1.5 and 3.0 V/cm, with 2.5 V/cm being the optimal value. The results of MD simulations and experiments correspond to each other. Cd2+ formed a highly stable adsorption structure in contrast to the Al–O sheet on the kaolinite (001) crystalline surface. The mean square displacement (MSD) curve of Cd2+ under the electric field exhibits anisotropy, the total diffusion coefficient DTotal increases and the Cd2+ migration rate accelerates. The electric field influences the microstructure of Cd2+ complexes. With the enhancement of the voltage gradient, the complexation between Cd2+ and water molecules is enhanced, and the interaction between Cd2+ and Cl− in solution is weakened.

Isolated Bidirectional DC-DC Converter: A Topological Review

Bidirectional DC-DC converters (BDCs) are certainly an important power electronic converter for managing bidirectional power flow in various applications. It offers the ability to flow power in both directions, which is useful in systems with renewable energy sources and energy storage. BDCs are becoming increasingly important in various applications, including renewable energy systems, electric vehicles, and energy storage. The development of new BDC topologies and control strategies is expected to further improve their efficiency and performance. Non-Isolated Bidirectional DC-DC Converters (NBDCs) and Isolated Bidirectional DC-DC Converters (IBDCs) are the two main types of BDCs with different isolation properties and trade-offs in terms of size, cost and performance. Topological classification of BDCs further distinguishes various BDC types based on their configurations and voltage-boosting techniques. IBDCs are preferred over NBDCs due to high-power applications, and wide voltage range with higher efficiency; the performance of IBDCs is improving day by day. To provide a framework for comparison in implementing novel configurations or identifying the best converter for a given application, this study is concentrated on each topology and its usual applications. Soft switching converters are also discussed pointed to Resonant Power Converters (RPCs) for the application into Electric Vehicles (EVs). It is worth noting that the choice of BDC depends on the specific requirements of the application, such as power level, voltage range, efficiency, and cost. A detailed comparison, application, advantage and disadvantage table can be useful in comparing the characteristics of different BDCs and selecting the most suitable one.