High Voltage Conditions Research Articles

Strongly solvating triglyme-based electrolyte realizes stable lithium metal batteries at high-voltage and high-temperature

The electrolyte in lithium-metal batteries (LMBs) plays a pivotal role in stabilizing the surface of the lithium metal anode (LMA) and high-voltage cathode. However, currently widely studied ether-based electrolytes, although it has good compatibility with LMA due to their lower reactivity, are facing significant challenges related to poor oxidation resistance and cathode/electrolyte interface (CEI) instability when combined with the high-voltage cathode, particularly at elevated temperatures. Therefore, there is an urgent need to design advanced electrolytes capable of maintaining high stability under high-voltage and high-temperature conditions. Here, we have developed an ultra-stable localized high-concentration electrolyte (LHCE) by introducing triethylene glycol dimethyl ether (TG), which exhibits strong solvation ability. Computational and experimental results demonstrate that the designed TG-based dilute high-concentration electrolyte (TG-DHCE) possesses a stable solvation structure, high oxidation resistance, and thermal stability, making it ideal for LMBs. Furthermore, the unique solvation structure of TG-DHCE promotes the preferential decomposition of anions while facilitating the formation of stable, inorganic-rich electrode/electrolyte interfaces on the anode and cathode. Consequently, equipped with TG-DHCE, Li||Li cells (more than 1600 h) and Li||NCM523 cells (80.6%, 250 cycles) show superior stability and also demonstrate remarkable performance even at elevated temperatures (60 °C). Additionally, under the harsh conditions of ultrahigh loading NCM523 cathode (19.7 mg/cm2) and limited Li reservoir (twice excess Li was deposited on Cu, Li@Cu) (N/P = 2), Li@Cu||NCM523 cells still maintain stable operation. This work pioneers a new path by choosing strongly solvating solvents, effectively enhancing the cycle life of LMBs under high-voltage and high-temperature conditions.

A Highly-Fluorinated Lithium Borate Main Salt Empowering Stable Lithium Metal Batteries.

Traditional lithium salts are difficult to meet practical application demand of lithium metal batteries (LMBs) under high voltages and temperatures. LiPF6, as the most commonly used lithium salt, still suffers from notorious moisture sensitivity and inferior thermal stability under those conditions. Here, we synthesize a lithium salt of lithium perfluoropinacolatoborate (LiFPB) comprising highly-fluorinated and borate functional groups to address the above issues. It is demonstrated that the LiFPB shows superior thermal and electrochemical stability without any HF generation under high temperatures and voltages. In addition, the LiFPB can form a protective outer-organic and inner-inorganic rich cathode electrolyte interphase on LiCoO2 (LCO) surface. Simultaneously, the FPB- anions tend to integrate into lithium ion solvation structure to form a favorable fast-ion conductive LiBxOy based solid electrolyte interphase on lithium (Li) anode. All these fantastic features of LiFPB endow LCO (1.9 mAh cm-2)/Li metal cells excellent cycling under both high voltages and temperatures (e.g., 80 % capacity retention after 260 cycles at 60 °C and 4.45 V), and even at an extremely elevated temperature of 100 °C. This work emphasizes the important role of salt anions in determining the electrochemical performance of LMBs at both high temperature and voltage conditions.

A Highly‐Fluorinated Lithium Borate Main Salt Empowering Stable Lithium Metal Batteries

AbstractTraditional lithium salts are difficult to meet practical application demand of lithium metal batteries (LMBs) under high voltages and temperatures. LiPF6, as the most commonly used lithium salt, still suffers from notorious moisture sensitivity and inferior thermal stability under those conditions. Here, we synthesize a lithium salt of lithium perfluoropinacolatoborate (LiFPB) comprising highly‐fluorinated and borate functional groups to address the above issues. It is demonstrated that the LiFPB shows superior thermal and electrochemical stability without any HF generation under high temperatures and voltages. In addition, the LiFPB can form a protective outer‐organic and inner‐inorganic rich cathode electrolyte interphase on LiCoO2 (LCO) surface. Simultaneously, the FPB− anions tend to integrate into lithium ion solvation structure to form a favorable fast‐ion conductive LiBxOy based solid electrolyte interphase on lithium (Li) anode. All these fantastic features of LiFPB endow LCO (1.9 mAh cm−2)/Li metal cells excellent cycling under both high voltages and temperatures (e.g., 80 % capacity retention after 260 cycles at 60 °C and 4.45 V), and even at an extremely elevated temperature of 100 °C. This work emphasizes the important role of salt anions in determining the electrochemical performance of LMBs at both high temperature and voltage conditions.

A bimetal strategy for suppressing oxygen release of 4.6V high-voltage single-crystal high-nickel cathode

High-voltage cathode materials, such as single-crystal high-nickel layered oxide materials, are a necessary condition for achieving high energy density lithium-ion batteries, but they have to be accompanied by the structural instability and irreversible release of lattice oxygen during operation, posing serious safety hazards. Here, to solve the lattice oxygen release issue of single-crystal high-nickel cathode, we propose an improved strategy for overall cathode by synchronously addressing interface and lattice instability, ensuring stable operation at a high voltage up to 4.6 V. By Al-doping, in the bulk phase, we intensify the charge transfer between transition metals and oxygen, and the columnar effect caused by doped atoms effectively alleviates internal strain, thereby significantly limiting lattice shrinkage and then suppressing oxygen release. On the other hand, the protective layer of LiNbO3 as the fast ion conductor formed at the cathode interface suppresses parasitic reactions and hinders lattice oxygen loss caused by dissolution of transition metals. Therefore, after 200 cycles at a cut-off voltage of 4.6 V, our cathode material still maintains a capacity retention rate of 89.1%. Density functional theory (DFT) calculations predict the effective suppression of oxygen release for the modified cathode materials, which has been further confirmed by differential electrochemical mass spectrometry (DEMS) tests. This work provides a new perspective for solving the problem of oxygen release under high cut-off voltage conditions for single crystal high nickel cathode.

Sb-Doped Biphasic P2/O3-Type Mn-Rich Layered Oxide Cathode Material for High-Performance Sodium-Ion Batteries.

Mn-rich P2-type layered oxide cathode materials suffer from severe capacity loss caused by detrimental phase transition and transition metal dissolution, making their implementation difficult in large-scale sodium-ion battery applications. Herein, we introduced a high-valent Sb5+ substitution, leading to a biphasic P2/O3 cathode that suppresses the P2-O2 phase transformation in the high-voltage condition attributed to the stronger Sb-O covalency that introduces extra electrons to the O atom, reducing oxygen loss from the lattices and improving structural stability, as confirmed by first-principle calculations. Besides, the enhanced Na+ diffusion kinetics and thermodynamics in the modified sample are associated with the enlarged lattice parameters. As a result, the proposed cathode delivers a discharge capacity of 142.6 mAh g-1 at 0.1C between 1.5 and 4.3 V and excellent performance at a high mass loading of 8 mg cm3 with a specific capacity of 131 mAh g-1 at 0.2C. Furthermore, it also possesses remarkable rate capability (90.3 mAh g-1 at 5C), specifying its practicality in high-energy-density sodium-ion batteries. Hence, this work provides insights into incorporating high-valent dopants for high-performance Mn-rich cathodes.

Enhancement in the electrochemical stability at high voltage of high nickel cathode through constructing ultrathin LiCoPO4 coating

The challenge of commercial layered-structure nickel-rich cathodes in lithium-ion batteries (LIBs) are the rapid capacity/voltage degradation at high rate capability and thermal runaway. The wide operational voltage range and excellent electrochemical stability of the coating material are key points to improve electrochemical performance and thermal stability at high voltage and high rate conditions. The uniformly olivine-type LiCoPO4 (LCP) coatings were successfully prepared on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode combining sol–gel method and heat treatment. The capacity retention and operating voltage stability of the cathode at high cutoff voltage of 4.6 V were dramatically improved due to the ultrathin and stable interface is designed. The modified NCM811 exhibited a high cycling capacity of 157.7 mAh·g−1 at 5 C with a capacity loss of only 12.1 %. In high nickel cathode coating modification, LCP as the thinnest phosphate coating effectively improves the capacity decay of the cathode at high rate. The interface reconstruction provided a stable channel of Li+ transport, which suppressed the cathode/electrolyte interface reaction to enhance the stability. The formation of strong covalent PO bonds at the interface significantly reduced the oxidizing activity on the NCM811 surface, further inhibiting the oxygen release and irreversible phase transition.

Design and characterization of an antiproton deceleration beamline for the PUMA experiment

We report on the design and characterization of an antiproton deceleration beamline, based on a pulsed drift tube, for the PUMA experiment at the Antimatter Factory at CERN. The design has been tailored to high-voltage (100kV) and ultra-high vacuum (below 10−10mbar) conditions. A first operation achieved decelerating antiprotons from an initial energy of 100keV down to (3898±3)eV, marking the initial stage in trapping antiprotons for the PUMA experiment. Employing a high-voltage ramping scheme, the pressure remains below 2×10−10mbar upstream of the pulsed drift tube for 75% of the cycle time. The beamline reached a transmission of (55±3)% for antiprotons decelerated to 4keV. The beam is focused on a position sensitive detector to a spot with horizontal and vertical standard deviations of σhoriz=(3.0±0.1)mm and σvert=(3.8±0.2)mm, respectively. This spot size is within the acceptance of the PUMA Penning trap.

Defect engineering unveiled: Enhancing potassium storage in expanded graphite anode

Expanded graphite (EG) stands out as a promising material for the negative electrode in potassium-ion batteries. However, its full potential is hindered by the limited diffusion pathway and storage sites for potassium ions, restricting the improvement of its electrochemical performance. To overcome this challenge, defect engineering emerges as a highly effective strategy to enhance the adsorption and reaction kinetics of potassium ions on electrode materials. This study delves into the specific effectiveness of defects in facilitating potassium storage, exploring the impact of defect-rich structures on dynamic processes. Employing ball milling, we introduce surface defects in EG, uncovering unique effects on its electrochemical behavior. These defects exhibit a remarkable ability to adsorb a significant quantity of potassium ions, facilitating the subsequent intercalation of potassium ions into the graphite structure. Consequently, this process leads to a higher potassium voltage. Furthermore, the generation of a diluted stage compound is more pronounced under high voltage conditions, promoting the progression of multiple stage reactions. Consequently, the EG sample post-ball milling demonstrates a notable capacity of 286.2 mAh g-1 at a current density of 25 mA g−1, showcasing an outstanding rate capability that surpasses that of pristine EG. This research not only highlights the efficacy of defect engineering in carbon materials but also provides unique insights into the specific manifestations of defects on dynamic processes, contributing to the advancement of potassium-ion battery technology.

Electrolyte Regulation in Stabilizing the Interface of a Cobalt-Free Layered Cathode for 4.8 V High-Voltage Lithium-Ion Batteries.

The cobalt-free layered oxide cathode of LiNi0.65Mn0.35O2 is promising for high-energy-density lithium-ion batteries (LIBs). However, under high-voltage conditions, severe side reactions between the Co-free cathode and electrolyte, as well as grain boundary cracks and pulverization of particles, hinder its practical applications. Herein, an electrolyte regulation strategy is proposed by adding fluoroethylene carbonate (FEC) and LiPO2F2 as electrolyte additives in carbonate-based electrolytes to address the above issues. As a result, a homogeneous and dense organic-inorganic hybrid cathode electrolyte interface (CEI) film is formed on the cathode surface. The CEI film consists of C-F, LiF, Li2CO3, and LixPOyFz species, which is proven to be highly conductive and effective in suppressing structure damage and alleviating the interfacial reactions between the cathode and electrolyte. With such a CEI film, the interfacial stability of the Co-free cathode and the high-voltage cycling performance of Li||LiNi0.65Mn0.35O2 are greatly improved. A reversible capacity of 155.1 mAh g-1 and a capacity retention of 81.3% over 150 cycles are attained at a 4.8 V charge cutoff voltage with the tamed electrolyte, whereas the cell without the additives only retains 76.1% capacity retention. Therefore, our work demonstrates the synergistic effect of FEC and LiPO2F2 in stabilizing the interface of Co-free cathode materials and provides an alternative strategy for the electrolyte design of high-voltage LIBs.

Research on the Reliability of Threshold Voltage Based on GaN High-Electron-Mobility Transistors.

With the development of high-voltage and high-frequency switching circuits, GaN high-electron-mobility transistor (HEMT) devices with high bandwidth, high electron mobility, and high breakdown voltage have become an important research topic in this field. It has been found that GaN HEMT devices have a drift in threshold voltage under the conditions of temperature and gate stress changes. Under high-temperature conditions, the difference in gate contact also causes the threshold voltage to shift. The variation in the threshold voltage affects the stability of the device as well as the overall circuit performance. Therefore, in this paper, a review of previous work is presented. Temperature variation, gate stress variation, and gate contact variation are investigated to analyze the physical mechanisms that generate the threshold voltage (VTH) drift phenomenon in GaN HEMT devices. Finally, improvement methods suitable for GaN HEMT devices under high-temperature and high-voltage conditions are summarized.

Investigation on different materials after pulsed high field conditioning and low-energy H- irradiation

During operation, the radio-frequency quadrupole (RFQ) of the LINAC4 at CERN is exposed to high electric fields, which can lead to vacuum breakdown. It is also subject to beam loss, which can cause surface modification, including blistering, which can result in reduced electric field holding and an increased breakdown rate. First, experiments to study the high-voltage conditioning process and electrical breakdown statistics have been conducted using pulsed high-voltage DC systems in order to identify materials with high electric field handling capability and robustness to low-energy irradiation. In this paper, we discuss the results obtained for the different materials tested. To complement these, an investigation of their metallurgical properties using advanced microscopic techniques was done to observe and characterize the different materials and to compare results before and after irradiation and breakdown testing.

Design, characterization and installation of the NEXT-100 cathode and electroluminescence regions

NEXT-100 is currently being constructed at the Laboratorio Subterráneo de Canfranc in the Spanish Pyrenees and will search for neutrinoless double beta decay using a high-pressure gaseous time projection chamber (TPC) with 100 kg of xenon. Charge amplification is carried out via electroluminescence (EL) which is the process of accelerating electrons in a high electric field region causing secondary scintillation of the medium proportional to the initial charge. The NEXT-100 EL and cathode regions are made from tensioned hexagonal meshes of 1 m diameter. This paper describes the design, characterization, and installation of these parts for NEXT-100. Simulations of the electric field are performed to model the drift and amplification of ionization electrons produced in the detector under various EL region alignments and rotations. Measurements of the electrostatic breakdown voltage in air characterize performance under high voltage conditions and identify breakdown points. The electrostatic deflection of the mesh is quantified and fit to a first-principles mechanical model. Measurements were performed with both a standalone test EL region and with the NEXT-100 EL region before its installation in the detector. Finally, we describe the parts as installed in NEXT-100, following their deployment in Summer 2023.

A low-voltage alternant direct current electroporation chip for ultrafast releasing the genome DNA of Helicobacter pylori bacterium.

Nucleic acid detection, as an important molecular diagnostic method, is widely used in bacterial identification, disease diagnosis. For detecting the nucleic acid of bacteria, the prerequisite is to release nucleic acids inside the bacteria. The common means to release nucleic acids is thechemical method, which involves complex processes, is time-consuming, and remains chemical inhibitors. Compared with chemical methods, electroporation as a physical method has the advantages of easy operation, short-time consumption, and chemical reagents free. However, the current works using electroporation often necessitates high-frequency or high-voltage conditions, entailing bulky power devices. Herein, we propose a low-voltage alternant direct current (LADC) electroporation chip and the corresponding miniature device for ultrafast releasing thegenome DNA from Helicobacter pylori (H. pylori)for detection. We connected a micrometer-interdigital electrode in the chip with a 20V portable battery to make the miniature device. Using this low-voltage device, our chip released genome DNA of H. pylori within only 5ms, achieving a cell lysis rate of 99.5%. We further combined this chip with acolorimetric loop-mediated isothermal amplification assay to visually detect H. pylori within ~ 25min at 10CFU/μL. We detected 11 clinical samples using the chip, and the detection results were consistent with those of the clinical standard. The results indicate that the LADC electroporation chip is useful for ultrafast release of genome DNA from bacteria and is expected to promote the development of nucleic acid detection in POCT and other scenarios.

Research on the Production of Turquoise Hydrogen from Methane (CH4) through Plasma Reaction

Turquoise hydrogen is produced through a process of separating carbon into solid carbon based on fossil fuels and refers to hydrogen that does not produce carbon dioxide. In this study, the characteristics of turquoise hydrogen production through a methane thermal cracking reaction using an arc plasma torch were investigated. The plasma torch operated stably under high voltage and transport gas flow conditions. The composition of the gas generated from the methane plasma reaction was analyzed using an online IR gas analyzer and GC-FID. The experimental results show that the hydrogen yield decreased to 16.4% as the methane feed rate increased but increased to 58.8% as the plasma power increased. Under these conditions, the yield of solid carbon, a valuable byproduct, was also shown to increase to 62.9%. In addition, solid carbon showed high-temperature heat-treated characteristics based on its generation location. Carbon oxides such as CO and CO2 are rarely generated under any experimental conditions. Consequently, it can be considered that plasma thermal cracking is a promising technology for CO2-free hydrogen production and a valuable solid carbon.

Localized Medium Concentration Electrolyte with Fast Kinetics for Lithium Metal Batteries.

Localized high-concentration electrolyte is widely acknowledged as a cutting-edge electrolyte for the lithium metal anode. However, the high fluorine content, either from high-concentration salts or from highly fluorinated diluents, results in significantly higher production costs and an increased environmental burden. Here, we have developed a novel electrolyte termed "Localized Medium-Concentration Electrolyte" (LMCE) to effectively address these issues. This LMCE is designed and produced by diluting a medium concentration (0.5 M-1.5 M) electrolyte which is incompatible with lithium metal anode before diluting. It has ultralow concentration (0.1 M) and demonstrates remarkable compatibility with lithium metal anode. Surprisingly, our LMCE, despite having an ultralow concentration (0.1 M), exhibits excellent kinetics in Li/Cu, Li/Li, LiFePO4 /Li, and NCM811/Li batteries. Additionally, LMCE effectively inhibits the corrosion of the Al current collector caused by LiTFSI salt under high voltage (>4 V) conditions. This groundbreaking LMCE design transforms the seemingly "incompatible" into the "compatible", opening up new avenues for exploring various electrolyte formulations, including all liquid electrolyte-based batteries.

Localized Medium Concentration Electrolyte with Fast Kinetics for Lithium Metal Batteries

AbstractLocalized high‐concentration electrolyte is widely acknowledged as a cutting‐edge electrolyte for the lithium metal anode. However, the high fluorine content, either from high‐concentration salts or from highly fluorinated diluents, results in significantly higher production costs and an increased environmental burden. Here, we have developed a novel electrolyte termed “Localized Medium‐Concentration Electrolyte” (LMCE) to effectively address these issues. This LMCE is designed and produced by diluting a medium concentration (0.5 M–1.5 M) electrolyte which is incompatible with lithium metal anode before diluting. It has ultralow concentration (0.1 M) and demonstrates remarkable compatibility with lithium metal anode. Surprisingly, our LMCE, despite having an ultralow concentration (0.1 M), exhibits excellent kinetics in Li/Cu, Li/Li, LiFePO4/Li, and NCM811/Li batteries. Additionally, LMCE effectively inhibits the corrosion of the Al current collector caused by LiTFSI salt under high voltage (>4 V) conditions. This groundbreaking LMCE design transforms the seemingly “incompatible” into the “compatible”, opening up new avenues for exploring various electrolyte formulations, including all liquid electrolyte‐based batteries.

Preparation and Application of Novel Power Semiconductor Chips

This study aims to improve the triggering current and dynamic characteristics of thyristor chips by designing new gate structures and multilayer semiconductor structures. Thyristor chips are essential components in power electronic devices, widely used in fields such as power transmission, motor control, and energy conversion systems. Trigger current is a key factor in the performance of thyristor chips, which is responsible for initiating the conduction state of the thyristor and carrying high current under high voltage conditions. This study improved the triggering current and dynamic characteristics of thyristor chips by optimizing the chip structure, especially by introducing multilayer P/N semiconductor design and improving the gate structure. The research results provide important guidance for the future development of thyristor chips and also contribute to the advancement of semiconductor technology.

Surface reconstruction layer boosting interfacial stability of LiCoO2/Li6PS5Cl in bulk all-solid-state Li batteries

The study introduces a gas–solid interface reduction reaction (GSIRR) for LiCoO2 cathode reconstruction, forming a CoO/Li2CO3 layer that enhances interfacial compatibility and electrochemical performance, especially under high-voltage conditions.

Spray-assisted synthesis of ant-cave-structured Ni-rich cathode microspheres with Li-reactive coating layer for high-performance Li-ion batteries

In this study, a spray-assisted synthetic method for preparation of Ni-rich Li [NixCoyMn1-x-y]O2 (NCM) cathode microspheres is introduced. Unlike the co-precipitation method, which necessitates pH control, the use of complexing agent, and further lithiation step, the spray-assisted approach can produce Li-containing precursors with homogeneous elemental distribution in a few seconds. To overcome the high energy density loss arising from the morphological traits of the hollow/porous microspheres produced from the spray process, a two-step spraying methodology is adopted. Planetary ball milling efficiently pulverizes the spray-pyrolyzed product, which is then dispersed in an aqueous solution to form colloids. Spray drying and subsequent oxidation of the colloidal solution yield ant-cave-structured NCM microspheres with fine primary particles. By simply changing the stoichiometry of the metal salts dissolved in the aqueous solution, NCM cathodes with the desired composition (NCM622 and NCM811) are obtained. Additionally, a Li-reactive coating layer is introduced on the surface of the fine particles comprising NCM microspheres by a 10-min gas-phase coating method. The delicate design of NCM622 cathode with a coating layer enables stable cycle performance (capacity retention of 82.0 % after the 150th cycle) and high rate capability (136.8 mA h g−1 at 10 C) when operated under high-voltage conditions (2.5–4.5 V).

Liquid Structure and Anti-Corrosion Effect of Super-Concentrated Electrolyte Solution

For realizing sustainable world, Lithium-ion batteries are required to have higher energy density. Aluminum metal have been dominantly used as a current collector of positive electrode. A mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) containing 1 mol dm-3 Lithium hexafluorophosphate (LiPF6) has been used as an electrolyte solution. Aluminum forms thin passivation layer on its surface, preventing the corrosion. However, aluminum corrosion may occur due to this electrolyte solution under high voltage condition. Recently, super-concentrated electrolyte solution (SCES) [1], which consists of only two or three times as much solvent as lithium salt, has been attracting attention as a new electrolyte solution of high-voltage lithium-ion battery. Motsumoto et al. proposed that aluminum corrosion was remarkably suppressed in lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based SCES [2]. To clarify the corrosion-inhibiting factor of SCES, we investigated aluminum corrosion in the several lithium salts based SCESs [3]. And we found that lithium perchlorate (LiClO4)-based SCES could suppress corrosion of Aluminum current collector. Liquid structure of the SCES may plays an important role in corrosion suppression. In the present work, we demonstrated Raman spectroscopy and Quantum chemical calculations to reveal the liquid structure of the LiClO4-based SCES.The LiClO4 based SCES was prepared by dissolving LiClO4 into DMC as the molar ratio of 1 : 2. For comparison, DMC solution containing 1 mol dm-3 LiClO4 and neat DMC was also prepared. Raman spectroscopic experiments were conducted using Laser Raman spectrophotometer (NRS-5100, JASCO) installed a laser at 532 nm. Quantum calculations were performed using the Gaussion 9 program suite (Gaussian, USA). Geometry optimization were conducted at the B3LYP/6-311+G(d,p) level. An intensive peak is observed at approximately 915 cm-1 for neat DMC. When a small amount of LiClO4 is added to DMC (corresponding to 1 mol dm-3 LiClO4 solution), new peak is observed at approximately 932 cm-1. This peak can be assigned to ClO4 - anion. A new peak appears at approximately 950 cm-1 with increasing LiClO4 (corresponding to the SCES). According to the Quantum calculations, the new peak is assigned to aggregate in which the ClO4 - cross-links Li+. In addition, HOMO energy of a contact ion pair (CIP), in which ClO4 - coordinates to Li+, is lower than that of free ClO4 - anion. The oxidative stability of ClO4 - increases by forming CIP and aggregate. The decomposition products of ClO4 - may affect the Aluminum corrosion. The high oxidative stability of LiClO4-based SCES may prevent the Aluminum corrosion.