Open Voltage Research Articles

Enhancing the electrochemical properties of Li-rich layered oxide cathodes by a facile Fe/Ti integrated modification strategy

Li-rich layered oxide cathodes have gained much attention due to their high specific capacity, high operating voltage, and environmental friendliness. However, poor rate performance, rapid capacity and voltage decay during cycling have hindered its commercial application. In this work, a Fe/Ti integrated modification strategy is proposed to construct a LiFeTiO4 spinel phase coating on the surface of Li1.2Mn0.54Ni0.13Co0.13O2, effectively reducing interfacial side reactions and suppressing the irreversible oxygen release, while doping with Fe3+ and Ti4+ ions can effectively broaden the lithium diffusion channel and enhance the structural stability. As a result, the modified sample with 2 wt% of Fe/Ti demonstrates excellent cycling stability with a superior capacity retention of 91% after 400 cycles at 1C and good rate performance with a high specific discharge capacity of 216 mAh g−1 at 2C. Moreover, the initial Coulombic efficiency of the modified sample is also improved. This integrated modification strategy offers a new design to promote the large-scale application of Li-rich Mn-based cathode materials.

Resistive random-access memories using quasi-2D halide perovskites for wafer-scale reliable switching behaviors

In this study, we propose the (PEA)2MA3Pb4I13, a quasi-two-dimensional (2D) halide perovskite, in the realm of resistive switching memory devices. A quasi-2D perovskite film (PEA)2MA3Pb4I13, with a thickness measuring 450 nm, has been effectively fabricated on a silicon substrate coated with platinum through an all-solution process conducted at low temperatures. The constructed resistive switching memory devices, incorporating an Ag/(PEA)2MA3Pb4I13/Pt/Ti/SiO2/Si configuration, display dependable and consistent bipolar switching attributes. The device shows an ultra-low operating voltage of less than +0.1 V, an impressive high ON/OFF ratio exceeding 108, reversible resistive switching via pulse voltage operation, and the capability for multilevel data storage. In addition, there is little variation in device characteristics depending on the location on a wafer or device size.

Biomimetic Neuromorphic Sensory System via Electrolyte Gated Transistors.

Biomimetic neuromorphic sensing systems, inspired by the structure and function of biological neural networks, represent a major advancement in the field of sensing technology and artificial intelligence. This review paper focuses on the development and application of electrolyte gated transistors (EGTs) as the core components (synapses and neuros) of these neuromorphic systems. EGTs offer unique advantages, including low operating voltage, high transconductance, and biocompatibility, making them ideal for integrating with sensors, interfacing with biological tissues, and mimicking neural processes. Major advances in the use of EGTs for neuromorphic sensory applications such as tactile sensors, visual neuromorphic systems, chemical neuromorphic systems, and multimode neuromorphic systems are carefully discussed. Furthermore, the challenges and future directions of the field are explored, highlighting the potential of EGT-based biomimetic systems to revolutionize neuromorphic prosthetics, robotics, and human-machine interfaces. Through a comprehensive analysis of the latest research, this review is intended to provide a detailed understanding of the current status and future prospects of biomimetic neuromorphic sensory systems via EGT sensing and integrated technologies.

Steady‐State and Transient Analysis of LLC and iLLC Resonant DC–DC Converters with Wide Voltage Operations Using GaN Technology for Light‐Duty xEV Charging Systems

Steady‐State and Transient Analysis of LLC and iLLC Resonant DC–DC Converters with Wide Voltage Operations Using GaN Technology for Light‐Duty xEV Charging Systems

Mullite Mineral-Derived Robust Solid Electrolyte Enables Polyiodide Shuttle-Free Zinc-Iodine Batteries.

Zinc dendrite, active iodine dissolution, and polyiodide shuttle caused by the strong interaction between liquid electrolyte and solid electrode are the chief culprits for the capacity attenuation of aqueous zinc-iodine batteries (ZIBs). Herein, mullite is adopted as raw material to prepare Zn-based solid-state electrolyte (Zn-ML) for ZIBs through zinc ion exchange strategy. Owing to the merits of low electronic conductivity, low zinc diffusion energy barrier, and strong polyiodide adsorption capability, Zn-ML electrolyte can effectively isolate the redox reactions of zinc anode and AC@I2 cathode, guide the reversible zinc deposition behavior, and inhibit the active iodine dissolution as well as polyiodide shuttle during cycling process. As expected, wide operating voltage window of 2.7V (vs Zn2+/Zn), high Zn2+ transference number of 0.51, and low activation energy barrier of 29.7kJ mol-1 can be achieved for the solid-state Zn//Zn cells. Meanwhile, high reversible capacity of 127.4 and 107.6 mAh g-1 can be maintained at 0.5 and 1 A g-1 after 3000 and 2100 cycles for the solid-state Zn//AC@I2 batteries, corresponding to high-capacity retention ratio of 85.2% and 80.7%, respectively. This study will inspire the development of mineral-derived solid electrolyte, and facilitate its application in Zn-based secondary batteries.

Optimization of Pulsed Laser Energy Density for the Preparation of MoS2 Film and Its Device by Pulsed Laser Deposition.

This article aims to explore the most optimal pulsed laser energy density when using the pulsed laser deposition (PLD) process to prepare the MoS2 films. We gradually increased the pulsed laser energy density from 70 mJ·cm-2 to 110 mJ·cm-2 and finally determined that 100 mJ·cm-2 was the best-pulsed laser energy density for MoS2 films by PLD. The surface morphology and crystallization of the MoS2 films prepared under this condition are the best. The films consist of a high-crystallized 2H-MoS2 phase with strong (002) preferential orientation, and their direct optical band gap (Eg) is 1.614 eV. At the same time, the Si/MoS2 heterojunction prepared under the optimal pulsed laser energy density shows an opening voltage of 0.61 V and a rectification ratio of 457.0.

Electronic transport properties of tetracene molecular junctions formed with different metallic electrodes

Density functional theory in combination with non-equilibrium Green’s function is employed to study the electron transport properties of tetracene-based molecular junctions formed with silver, gold, copper and platinum electrodes. The physical origin of the IV curves is discussed by analyzing their density of states, molecular projected self-consistent Hamiltonian, transmission spectra, conductance trends and HOMO-LUMO gap at different operating voltages. The results indicate that till a low bias voltage of 1.4 V, the tetracene molecule shows metallic behavior with silver and copper electrodes while semi-metallic and non-metallic nature with gold and platinum electrodes respectively is observed. The zero bias conductance is found to be greatest for Ag followed by Cu and Au with the least in Pt. Furthermore, it is worth mentioning that negative differential resistance feature is observed in molecular junctions with all the electrodes except Pt, with the highest peak-to-valley current ratio of 1.283 found in Ag-Tetracene-Ag molecular junction.

Self-Driven, Monopolar Electrohydrodynamic Printing via Dielectric Nanoparticle Layer.

Electrohydrodynamic printing holds both ultrahigh-resolution fabrication capability and unmatched ink-viscosity compatibility yet fails on highly insulating thick/irregular substrates. Herein, we proposed a single-potential driven electrohydrodynamic printing process with submicrometer resolution on arbitrary nonconductive targets, regardless of their geometric shape or sizes, via precoating with an ultrathin dielectric nanoparticle layer. Benefiting from the favorable Maxwell-Wagner polarization, the reversely polarized spot brought about a significant drop (∼57% for ceramics) in the operation voltage as its induced electric field and a negligible residual charge accumulation. Thus, ordered micro/nanostructures with line widths down to 300 nm were directly written at a stage speed as low as 5 mm/s, and silver features with width of ∼2 μm or interval of ∼4 μm were achieved on insulating substrates separately. Flexible sensors and curved heaters were then high-precision printed and demonstrated successfully, presenting this technique with huge potential for fabricating flexible/conformal electronics on arbitrary 3D structures.

The Behavior of Terminal Voltage and Frequency of Wind-Driven Single-Phase Induction Generators under Variations in Excitation Capacitances for Different Operating Conditions

This paper assesses the behavior of output voltage and frequency of wind-driven self-excited induction generators with variable excitation capacitances connected to the main and auxiliary windings under different operating conditions. The optimum values of the main winding excitation capacitance for fixed terminal voltage operation under different values of shunt capacitance, load, and speed are also evaluated. The obtained results show that the terminal voltage is highly affected by changing the main winding excitation capacitance. In addition, the frequency is greatly affected by changing the auxiliary winding excitation capacitance. However, under different operating conditions, variation in the output frequency under different values of the main winding capacitance, with fixed auxiliary winding capacitance, is acceptable. Extensive simulations were conducted and the results are discussed in this publication.

Low breakdown voltage and CMOS compatible avalanche photodiode based on SOI substrate.

In this work, we present a novel, to the best of our knowledge, lateral avalanche photodiode (APD) with low breakdown voltage and high bandwidth which has the potential to serve as a core device in future large-scale advanced optoelectronic hybrid chips. By taking advantage of a silicon-on-insulator (SOI) substrate combined with a separation absorption multiplier (SAM) structure, the demonstrated APDs exhibit a high gain of 148. Furthermore, the minimum breakdown voltage of the measured device is 6.1 V, which represents the lowest breakdown voltage for Si-APD, making it compatible with the existing CMOS technology for low voltage operation. Benefiting from an ultra-thin top silicon and lateral SAM structure, the problem of edge breakdown has been completely solved. Additionally, a set of device arrays with absorption and avalanche regions of different sizes is also manufactured and compared. Our findings indicate that the proposed APD has fascinating application prospects in the CMOS process-based LIDAR chips.

All colloidal supercapattery: colloid@carbon cloth electrodes meet "water‐in‐salt" electrolyte

The pursuit of excellent electrochemical performance, nonflammability and environmental friendliness of aqueous batteries and supercapacitors has driven efforts to find high‐energy yet reliable electrode materials and electrolyte solutions. Here, all colloidal supercapattery are developed using high‐concentration "water‐in‐salt" electrolytes (LiTFSI‐KOH) and pseudocapacitive colloid@carbon cloth as both positive and negative electrodes, which showed merits of batteries and supercapacitors. Ni/Co‐colloid @carbon cloth positive and Fe‐colloid @carbon cloth negative electrodes can be synthesized by in situ electrochemical reaction. The maximum operating voltage of an aqueous colloidal supercapattery is 1.8 V, and the energy density can reach 73.98 Wh kg−1 at a power density of 1799.5 W kg‐1. The specific capacitance of the aqueous colloidal supercapattery still maintains 74.3% of the initial after 2000 cycles of charge/discharge measurement. The combination of quasi ion colloidal materials and "water‐in‐salt" electrolyte pave a profound way to achieve high energy and power ability simultaneously at the supercapattery device.

A eutectic mixture catalyzed straight forward production of functional carbon from Sargassum tenerrimum for energy storage application

Here, we present a sustainable and scalable approach for synthesizing functionalized nanomaterials directly from an abundant natural seaweed resource coupled with a green eutectic mixture. The study utilized crushed seaweed granules obtained from fresh brown seaweed Sargassum tenerrimum (ST) and a eutectic mixture generated through the complexation of urea and a metal salt, which act as both solvent and catalyst to facilitate the straightforward production of metal oxide functionalized nanomaterials. Subjecting seaweed granules and the eutectic mixture to pyrolysis at temperatures between 700 °C and 900 °C in a nitrogen (N2) atmosphere resulted in the formation of ST-derived carbon (STC) functionalized with β-MnO2. The nanoneedles thus synthesized were examined for their electrochemical properties in both three-electrode and two-electrode configurations, employing 6 M KOH and 1 M Na2SO4 as electrolytes. Within the three-electrode framework, β-MnO2 functionalized STC at 800 °C (MSTC-8) displayed a remarkable specific capacitance, of 685.1 F g−1 in alkaline electrolyte and 308.3 F g−1 in neutral electrolyte at 0.1 A g−1, demonstrating a superior performance compared to MSTC-7 and MSTC-9. Additionally, two-electrode experiments and evaluations of cyclic stability were performed on MSTC-7, MSTC-8, and MSTC-9 symmetric supercapacitors. The fabricated symmetric supercapacitor in Na2SO4 with the operational voltage window up to 1.7 V, achieved a maximum energy density of 45.5 Wh/kg and a power density of 172.66 W kg−1. Moreover, the current investigation highlights the enduring performance of MSTC-8//MSTC-8 symmetric supercapacitor, with a capacitance retention of 95 % and 80 % over 20,000 cycles in KOH and Na2SO4 electrolytes respectively.

Pilot Study on the Production of Negative Oxygen Ions Based on Lower Voltage Ionization Method and Application in Air Purification

In the current highly industrialized living environment, air quality has become an increasing public health concern. Natural environments like forests have excellent air quality due to high concentrations of negative oxygen ions originating from low-voltage ionization, without harmful ozone. Traditional negative oxygen ion generators require high voltage for corona discharge to produce ions. However, high voltage can increase electron collisions and excitations, leading to more dissociation and recombination of oxygen molecules and consequently higher ozone production. To address the challenge of generating negative oxygen ions without accompanying ozone production, this study designed and constructed a low-voltage negative oxygen ion generator based on nanometer-tip carbon fiber electrodes. The advantage of this device lies in the high curvature radius of carbon fibers, which provides high local electric field strength. This allows for efficient production of negative oxygen ions at low operating voltages without generating ozone. Experiments demonstrated that the device can efficiently generate negative oxygen ions at a working voltage as low as 2.16 kV, 28% lower than the lowest voltage reported in similar studies. The purification device manufactured in this study had a total decay constant for PM2.5 purification of 0.8967 min−1 within five minutes, compared to a natural decay constant of only 0.0438 min−1, resulting in a calculated Clean Air Delivery Rate (CADR) of 0.1535 m3/min. Within half an hour, concentrations of PM2.5, PM1, PM10, formaldehyde, and TVOC were reduced by 99.09%, 99.40%, 99.37%, 94.39%, and 99.35%, respectively, demonstrating good decay constants and CADR. These findings confirm its effectiveness in improving indoor air quality, highlighting its significant application value in air purification.

Performance optimization of green tandem OLEDs with double emitting layers

The utilization of a double emitting layer structure with well-matched energy levels has been shown to improve carrier balance and decrease operating voltages in organic light-emitting diodes (OLED). In this study, tandem OLEDs with double emitting layers (DEMLs) are successfully fabricated and optimized. Through adjusting the emitting layer thickness ratio and cavity length, the optimized green tandem OLEDs show driving voltages of 4.8 and 5.4 V, with current efficiency (CE)/power efficiency (PE) of 242.4 cd/A/158.6 lm W−1 and 237.1 cd/A/137.9 lm W−1 at 100 and 1000 cd m−2, respectively. The ultra-high CE of 242.4 cd/A is the state of the art among all reported two-units green tandem OLEDs. Meanwhile, the device at the initial luminance of 10000 cd cm−2 also displays an extremely long LT50 of 734.8 h. In addition, the tandem OLED can emit pure green light with color coordinates of (0.27, 0.71), and has the ability to adjust the color coordinates by varying the cavity length.

Influence of Electrolyte Concentration on Metal Removal Rate and Surface Finish Quality in Electrochemical Machining Masking

Electrochemical machining (ECM) is a specialized and precise manufacturing technique involving selective metal removal to achieve the desired shape or form. This article’s primary focus is examining the technical facets associated with the procedure. The elements mentioned encompass the system’s design and optimization, the electrolyte solution’s careful selection, and the precise control of the etching parameters. When considering the overall framework, it is essential to consider important factors such as the concentration of electrolytes, the operational voltage, and the value of the current flowing through the system. The main objective of this study is to evaluate the influence of different concentrations of sodium chloride electrolyte on the metal removal rate (MRR). This will be achieved by utilizing a direct current power supply. The present investigation used aluminum, steel, and stainless steel materials as the substrate for experimentation. These materials were selected to have identical dimensions for the anode and cathode. The main objective of this study is to evaluate the influence of varying concentrations (0.5, 1, 1.5, and 2 mole/liter) of sodium chloride electrolyte on the material removal rate and surface roughness. The findings have been disclosed, revealing the utmost removal rate for aluminum, steel, and stainless-steel materials across all levels of electrolyte concentration. The experimental information is currently presented, related to the rates of metal removal at various electrolyte concentrations of 2 moles per liter. The rates of mass loss observed in aluminum are comparatively higher when compared to those surveyed in steel and stainless steel. The roughness of a machined surface is inversely proportional to the concentration of the electrolyte.

Polyacrylonitrile Based Triblock Copolymer Binder Enabling Excellent Performance toward LiNi0.5Mn1.5O4 and Sulfur Based Batteries.

There is an urgent need for lithium-ion batteries with high energy density to meet the increasing demand for advanced devices and ecofriendly electric vehicles. Spinel LiNi0.5Mn1.5O4 (LNMO) is the most promising cathode material for achieving high energy density due to its high operating voltage (4.75 V vs Li/Li+) and impressive capacity of 147 mAh g-1. However, the binders conventionally used are prone to high potential and oxidation at the cathode side, resulting in a loss of the ability to bond active material and conductive agent integrity. This can lead to severe capacity fading and irreversible battery failure. This study demonstrates that incorporating acrylic anhydride and methyl methacrylate into conventional acrylonitrile through solution polymerization improves the binding energy and voltage resistance. The results indicate that the triblock poly(acrylonitrile-methyl methacrylate-acrylic anhydride) (PAMA) binder has a much higher peeling strength (0.506 N cm-1) compared to its polyvinylidene fluoride (PVDF) counterpart (0.3 N cm-1), making it a more feasible strategy. When assembled with LiNi0.5Mn1.5O4, the PAMA based electrode maintains a capacity retention of 70.7% after 800 cycles at 0.1 C, which is significantly higher than the 33.9% retention of the PVDFbased electrode. This is due to the large number of polar groups, including ─C≡N and ─C═O, on PAMA, which are conducive to adsorbing lithium polysulfide. The S@PAMA electrode is tested and maintained a capacity value of 628.7 mAh g-1 after long-term cycling, confirming its ability to effectively suppress the shuttle effect.

Investigating the efficiency of electrocoagulation using similar/dissimilar electrodes for the detoxification of Coralene Rubine dye: a cost effective approach.

Efficient treatment of textile dyeing wastewater can be achieved through electrocoagulation (EC) with minimal sludge production; however, the selection of the appropriate electrode is essential in lowering overall costs. Also, the reuse of the treated aqueous azo dye solution from this process has not been explored in detail. With these objectives, this study aims to treat synthetic azo dye solutions and achieve high colour removal efficiency (CRE%) using similar (Ti-Ti) and dissimilar (Ti-Cu) metal electrodes through EC with an attempt to reduce the cost. The aqueous Coralene Rubine GFL azo dye was used to examine the efficiency and cost of the EC process. X-Ray Photoelectron Spectroscopy was used to study the EC mechanism, while High Performance Liquid Chromatography was used to analyse the degradation of the dye and the formation of intermediate compounds. The concentration of metal ions in the treated dye solution was quantified using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), with Ti-Ti treated solution having 14.20mg/L concentration of Ti and Ti-Cu treated solution having 0.078mg/L of Ti and 0.001mg/L of Cu, respectively. Colour removal efficiency of 99.49% was obtained for both electrode sets, with a lower operating time and voltage for dissimilar metal combination. Ecotoxicity studies showed negligible toxicity of Ti-Cu treated dye samples compared to untreated solutions. Survival rate, protein estimation, and catalase activity was used to validate the treatment method's efficacy. The study found that the dissimilar electrode material exhibited reduced toxicity due to the presence of heavy metals below the permissible limit.

Towards Implantable Artificial Muscles: Epoxy Based Bilayer Thermal Actuators with Ambient Activation Temperatures

AbstractThe development of soft and biocompatible actuators is a current challenge in the fast‐growing field of soft robotics. A variety of shape‐memory and thermal actuators are currently being explored for application in these areas, especially to produce actuators that can operate at biocompatible temperatures for in vivo applications. Here we detail the synthesis of epoxy based materials, a class of materials not fully explored for soft actuators. By careful tuning of polymer composition by variation of monomer feed ratios, we show tuneable glass transition temperatures (Tgs) of these materials. Ambient temperature (30–60 °C) thermal actuators were then realised by casting of bilayers of epoxy resins with varying Tgs. Differences in thermal expansion when the Tg was reached lead to actuation in a specific direction. With optimisation, actuation in both the external‐heated and joule‐heated NiChrome‐epoxy actuators were able to occur at physiological temperatures (36–40 °C), previously unreported in the literature. For the joule‐heated NiChrome–epoxy actuators surface temperatures remained under 40 °C during actuation at low operating voltages (<2 V). Higher force and power output could be achieved in a repeatable fashion at higher driving voltages without loss of displacement, but also leading to higher surface temperatures. These materials and the actuation approach present an exciting opportunity to develop future implantable actuators to solve significant challenges related to quality of life and an ageing population.

In Operando Study of Microsupercapacitors with Gel Electrolytes Using Nano‐Beam Synchrotron X‐ray Diffraction

AbstractSynchrotron radiation X‐ray diffraction (XRD) with nanoscale beam size was used here for in situ and in operando study of micro‐supercapacitors (MSC) with gel electrolyte and MXene Ti3C2Tx electrodes. The electrode structure was characterized as a function of applied voltage and distance from the gap separating electrodes using microscopic cells with cylindrical shape designed for transmission mode XRD. The devices with gel electrolytes based on H2SO4 (with H2O/PVA and DMSO/PVA) showed stable performance with no changes in MXene structure under voltage swaps between positive and negative values. Experiments with KI‐based electrolytes demonstrated changes of MXene structure correlated with decrease of energy storage parameters under conditions of increased operation voltage starting from 0.8 V. The optimal performance of the MSCs was observed when the MXene structure remained unchanged upon switching the applied voltage polarity. The changes of inter‐layer distance of MXene upon swap of applied voltage correlate with decrease of device performance and are undesirable for stable operation of MSC's. We also tested feasibility of X‐ray fluorescence (XRF) for characterization of electrolyte ion migration in MSCs using 2D element mapping. Irreversible sorption of iodine by MXene was found using XRF mapping of charged electrodes using standard in‐plane MSC device and KI electrolyte.

Statistical analysis of vertically stacked nanosheet complementary FET based on polycrystalline silicon with multiple grain boundaries

In this study, a complementary field-effect transistor (CFET) based on a polycrystalline silicon (poly-Si) stacked-nanosheet (NS) structure with a grain boundary (GB) is designed and analyzed using a technology computer-aided design (TCAD) simulation. The advantage of the CFET using a poly-Si is that the active cell region can be reduced by 50 % because the p-type transistors are vertically stacked on the n-type transistors. In addition, it is possible to replace the conventional CMOS process and fabricate a three-dimensional vertically stacked structure at a low cost. To consider the effect of the GB in poly-Si, we assumed that there is a single GB at the center of the body region. By optimizing the geometrical parameters of the proposed CFET, the transfer characteristics of the NMOS and PMOS transistors, such as the threshold voltage (Vth), on current (Ion), off current (Ioff), and subthreshold swing (SS), are symmetrical. The proposed CFET demonstrated a superior logic performance of NML = 0.299 V and NMH = 0.297 V at an operation voltage of VDD = 0.65 V. To consider random GBs in the poly-Si, we assumed that five GBs existed in the proposed CFET, and the variation in CMOS logic inverter characteristics are statistically analyzed. As a result, the RSDs for Vm of the NMOS and PMOS transistors are 2.067 % and 0.293 %, and the RSDs of the pull-down delay time (tpHL) and pull-up delay time (tpLH) are 5.320 % and 3.244 %, respectively. An acceptor-like traps with high trap density are dominant in the proposed CFET, and this trend is similar across the 1024 samples. Nevertheless, most of the differences are within 5 % and the proposed CFET exhibited stability against GBs and the potential to replace the conventional CMOS logic inverters.