High Voltage Research Articles

Application of sulfur hexafluoride in electrical engineering. Historical past, current state and prospects in future

A pressing issue today is the analysis of the possibilities of using SF6 gas and its possible limitations of use from the point of view of harmful effects on the environment. The article, based on free sources of information, systematizes the historical facts of the development of SF6 gas, the main stages of the formation of the SF6 gas environment as insulation for electrical equipment. Comparative characteristics of electrical strength for various insulating substances are presented. Research has been carried out on modern examples of the use of SF6 gas in medium and high voltage circuit breakers. Examples of the use of SF6 gas and its mixtures as gas insulation for high-voltage power lines are analyzed. It is shown that a promising direction for the development of SF6 gas is its use in gas-insulated power lines. Design features and examples of practical application of high-voltage gas-insulated power lines are presented. The features of using SF6 insulation in electrical equipment of different voltage classes are determined. Current environmental problems associated with the use of SF6 gas are analyzed and possible directions for overcoming them are established. The elements of SF6 gas decomposition products that are toxic and pose the greatest danger are considered. The characteristics of SF6 gas as a greenhouse gas are given and promising ways to reduce its use are shown. It has been established that by using not pure SF6 gas, but gas mixtures based on it, it is possible to significantly reduce the percentage of SF6 gas use. Promising directions for further development of gas insulating medium for electrical equipment without the use of SF6 gas have been established.

Experimental Investigation of Modified Level Shift PWM with Capacitor Voltage Balancing on Single Phase Modular Multilevel Converter

Modular Multilevel Converters (MMCs) are a prominent voltage source converter topology that is rapidly gaining popularity in medium/high power/voltage applications, including high-voltage DC transmission systems and electric vehicle systems. However, MMC has the critical issue of unbalanced submodule capacitor voltages and circulating current. The MMC distributes DC-link energy evenly among its submodule capacitors, rather than storing it in a large capacitor like conventional voltage source converters. In MMC, the submodule floating capacitors interface the DC input voltage and AC output voltage. Therefore, capacitor voltages must be balanced. The existing capacitor voltage control struggles to handle many gate pulses at medium and high voltages. An effective control scheme is needed to solve the issues mentioned earlier. This paper presents a performance analysis of a 1-Φ MMC using a modified level shift PWM technique based on Universal Control Modulation Scheme (UCMS) and a sorting-based capacitor voltage balancing algorithm. MATLAB/Simulink software implements the proposed control method for a 1-Φ , seven-level MMC. The outcomes of the simulation demonstration reveal that phase disposition PWM offers less harmonic distortion of output phase voltage than the other level shift PWM techniques, such as phase disposition PWM and alternate phase disposition PWM. The simulation results also demonstrate the effective use of the sorting-based capacitor balancing algorithm to regulate the voltages of the submodule capacitors. Finally, the real-time GUI tool validates the simulation results using an experimental prototype of 1-Φ MMC with the dSPACE MicroLabBox 1202.

Study of the thermal state of the transformer depending on the operating mode

Accurate analysis and prediction of the transformer's thermal condition depending on the operating mode, for example, in cold winters with a shortage of electricity, allows for effective planning of regular maintenance. In the course of the work, mathematical models were created to analyze the thermal state of the transformer, in particular, models for finding the temperature of the upper layers of oil and the highest temperature on the transformer winding. The data from these mathematical models were verified by comparing them with an already identified analog model. It was determined that the difference between the results is no more than 7 %. It has been established that the thermal state of the transformer is influenced by the ambient temperature much more than by the load. This is due to the fact that without cases of overload and emergencies, the load on the transformer, depending on the season, does not change significantly. It has been determined that the highest time utilization and the highest temperature on the high and low voltage windings are observed in August, which coincides with the peak ambient temperature. The lowest temperature on the windings and the lowest life utilization of the transformer are observed in January, which also correlates with the lowest ambient temperature. It is determined that under such operating conditions, given that the nominal service life of the transformer is 20 years, the actual service life will be approximately 90 years. It was also found that the reduction in service life in winter is 5 times less than in summer. This allows us to predict a reduction in maintenance needs during the cold months and more intensive maintenance in the summer. In addition, such models can predict potential problems and emergencies, which can significantly reduce the risk of unforeseen outages and increase the reliability of power supply. Regular monitoring and analysis of the thermal condition of the transformer makes it possible to respond quickly to changes in operating conditions and make timely maintenance decisions, which helps to optimize costs and increase the efficiency of power grids.

Microfluidic carbon cloth-based enzymatic glucose biofuel cell for sustainably powering a microelectronic circuit *

Enhancing enzymatic microfluidic biofuel cells (EBFCs) devices has garnered significant attention due to the development of microfluidic ultra-low power energy-gathering techniques. To facilitate the ability to create microfluidic EBFCs, a carbon cloth (CC) has been considered since they are effective renewable energy sources and utilized as the ideal paper-based substitute for traditional power supplies for a variety of tiny devices due to their inherent qualities and exceptional performance. The developed microfluidic EBFC utilized glucose as a fuel, carbon cloth as the bioelectrode, Glucose oxidase for the anode, and laccase for the cathode. The maximum stable open circuit voltage of CC-EBFC was measured to be 475 mV with a peak power density of 85 µW cm−2 at 300 mV and a current density of 484 µA cm−2. The power performance of the device was improved by bovine serum albumin and a booster circuit, which was also coated and connected to the load to stabilize the performance. The novelty of the work is that using a flexible substrate of carbon cloth, with a microfluidic channel, has an added advantage in the biofuel cell. LTC3108EDE DC–DC booster was used to increase energy and attain a high charging voltage of 5 V to operate a digital watch up to 3 V. With minimal weight and flexibility; this minuscule device opens up new possibilities to sustainably power wearable and portable microelectronic devices.

Synergistic structure engineering and electrochemical activation modulating vanadium oxide cathode toward superior zinc-ion storage

Aqueous zinc-ion batteries (ZIBs) have emerged as competitive systems for grid-scale energy storage due to their high safety and low cost. However, the lack of suitable high-performance cathode composites limits the practical progress of ZIBs. Herein, a novel cathode material, ammonium cation-inserted and oxygen vacancy co-modulated VO2 (named NVE), was firstly synthesized through the ethylene glycol (EG) sacrificial solvent-assisted structure transformation with the ammonium vanadate (named NV) as the precursor. The sacrificial solvent promotes the structural transformation of ammonium vanadate to NH4+-intercalated vanadium oxide and enhances the number of oxygen vacancies in the resulting material. Moreover, the electrochemical activation process was performed for in-situ construction of NH4+-inserted hydrated vanadium oxide (V2O5·nH2O) material. The electrochemical activation process with high anodic voltage enables multiple electron reactions, increasing the utilization of vanadium elements and achieving high capacity. Additionally, the formed hydrogen bonds between the V-O host and inserted NH4+ ions can enhance the structural integrity, while the oxygen vacancies decrease the interaction between the V-O host and inserted Zn2+ ions to boost ion diffusion. Consequently, the resulting activated cathode demonstrates higher capacity (441 mAh/g at 0.1 A/g), superior cycling durability (85.6 % retention over 4000 cycles), and exceptional rate capability (205 mAh/g at 20 A/g). Besides, the fabricated devices based on the activated NVE cathode show decent capacity and excellent flexible stability. Furthermore, the reversible electrochemical Zn2+ storage mechanism upon battery cycling was evaluated by several kinetic measurements and in/ex-situ characterizations. This work provides novel perspectives for the fabrication of advanced cathode materials for superior aqueous ZIBs.

Enhanced electrochemical performance of a cost-effective Sm2O3-coated spinel LiNi0.5Mn1.5O4 cathode for high-voltage lithium-ion batteries

Spinel LiNi0.5Mn1.5O4 (LNMO) has gained significant attention as a promising cathode material for lithium-ion batteries due to its high working voltage (>4.7 V) and energy density. However, challenges such as electrolyte decomposition-induced material interface erosion and transition metal dissolution under high operating voltage hinder its commercial use. In this study, a thin and uniform Sm2O3 layer has been successfully deposited on the surface of LNMO using a wet chemical method. A comprehensive investigation of surface morphology, crystal structure, and electrochemical performance of the modified LNMO is conducted. The results demonstrate that the Sm2O3 surface modification acts as a robust multifunctional protective layer, effectively shielding against hydrofluoric acid-induced chemical attack and enhancing the migration efficiency of lithium ions. Notably, the capacity retention rate of LNMO@Sm2O3 (3 wt%) remains up to 88 % after 280 cycles, significantly surpassing the uncoated counterpart. The coated material exhibits a capacity of 114 mAh g−1 even under 10 C rate conditions. Moreover, the AC impedance values and manganese dissolution of the modified material in the organic electrolyte are considerably lower than those of the uncoated counterpart. Theoretical calculations strongly support the experimental findings, revealing higher Mn vacancy formation energy and density of states at the Fermi energy level for the Sm2O3-modified electrodes. This research contributes to the field of surface modification and paves the way for further enhancements in the electrochemical performance of other high-voltage manganese-based lithium-ion batteries (LIBs).

Electromechanical Performances of Polyvinyl Chloride Gels Using (Polyvinyl Chloride-co-Vinyl Acetate) (P(VC-VA)) Synergistic Plasticization

The current polyvinyl chloride (PVC) gel flexible actuators are facing challenges of high input voltage and an insufficient elastic modulus. In this study, we conducted a detailed study on the properties of PVC gel prepared by introducing the modifier polyvinyl chloride-vinyl acetate (P(VC-VA)). We compared a modified PVC gel with the traditional one in terms of the relative dielectric constant, mechanical modulus, and electromechanical actuation performance. Experimental results demonstrated that the introduction of P(VC-VA) enhanced the dielectric constant and reduced the driving electric field strength of PVC gels. The dielectric constant increased from 4.77 to 7.3. The electromechanical actuation performance increased by 150%. We employed the Gent model to fit the experimental results, and the actual experimental data aligned well with the expectations of the Gent model. The research results show that this type of plasticizing method effectively balanced the mechanical and electrical performance of PVC gels. This study summarizes the experimental results and performance analysis of PVC gels prepared using innovative plasticization methods, revealing the potential engineering applications of polymeric gels.

Strain‐Engineered Unified SiNx Deposition for Device Passivation and Capacitance Dielectric in GaN Monolithic Microwave Integrated Circuit

Silicon nitride (SiNx) is used for device passivation and capacitance dielectric in GaN monolithic microwave integrated circuits. However, this is a conflicting requirement as passivation requires SiNx to cause tensile strain, and capacitance dielectric primarily demands a high breakdown voltage and large dielectric constant for SiNx, leading to a damaged AlGaN surface during deposition. Two independent SiNx depositions under two different conditions (silicon‐ and nitrogen‐rich) are usually carried out to meet both requirements. Herein, a solution for a unified deposition through interfacial strain analysis on an AlGaN/GaN heterostructure grown on 6H‐SiC imposed by thin film silicon nitride (SiNx), deposited using inductively coupled plasma chemical vapor deposition system is proposed. The strain analysis is done using Raman spectroscopy. The surface morphology of the SiNx is studied using atomic force microscopy. The breakdown characteristics are ascertained from measurements on high electron mobility transistors and metal–insulator–metal capacitors.

Single‐Atom 3d Transition Metals on SnO2 as Model Cell for Conversion Mechanism: Revealing Thermodynamic Catalytic Effects on Enhanced Na Storage of Heterostructures

Since the discovery in 2000, conversion‐type materials have emerged as a promising negative‐electrode candidate for next‐generation batteries with high capacity and tunable voltage, limited by low reversibility and severe voltage hysteresis. Heterogeneous construction stands out as a cost‐effective and efficient approach to reducing reaction barriers and enhancing energy density. However, the second term introduced by conventional heterostructure inevitably complicates the electrochemical analysis and poses great challenges to harvesting systematic insights and theoretical guidance. A model cell is designed and established herein for the conversion reactions between Na and TMSA‐SnO2, where TMSA‐SnO2 represents single atom modification of eight different 3d transition elements (V, Cr, Mn, Fe, Co, Ni, Cu or Zn). Such a model unit fundamentally eliminates the interference from the second phase and thus enables independent exploration of activation manifestations of the heterogeneous architecture. For the first time, a thermodynamically dependent catalytic effect is proposed and verified through statistical data analysis. The mechanism behind the unveiled catalytic effect is further elucidated by which the active d orbitals of transition metals weaken the surface covalent bonds and lower the reaction barriers. This research provides both theoretical insights and practical demonstrations of the advanced heterogeneous electrodes.

10 kV nanosecond pulse generator with high voltage gain and reduced switches

10 kV nanosecond pulse generator with high voltage gain and reduced switches

High-Concentrated Binary-Salt Ether Electrolytes for High-Voltage Lithium Metal Batteries with Ni-Rich Cathode.

The incompatibility of ether electrolytes with a cathode dramatically limits its application in high-voltage Li metal batteries. Herein, we report a new highly concentrated binary salt ether-based electrolyte (HCBE, 1.25 M LiTFSI + 2.5 M LiFSI in DME) that enables stable cycling of high-voltage lithium metal batteries with the Ni-rich (NCM83, LiNi0.83Co0.12Mn0.05O2) cathode. Experimental characterizations and density functional theory (DFT) calculations reveal the special solvation structure in HCBE. A solvation structure rich in aggregates (AGGs) can effectively broaden the electrochemical window of the ether electrolyte. The anions in HCBE preferentially decompose under high voltage, forming a CEI film rich in inorganic components to protect the electrolyte from degradation. Thus, the high-energy-density Li||NCM83 cell has a capacity retention of ≈95% after 150 cycles. Significantly, the cells in HCBE have a high and stable average Coulombic efficiency of over 99.9%, much larger than that of 1 M LiPF6 + EC + EMC + DMC (99%). The result emphasizes that the anionic-driven formation of a cathode electrolyte interface (CEI) can reduce the number of interface side reactions and effectively protect the cathode. Furthermore, the Coulombic efficiency of Li||Cu using the HCBE is 98.5%, underscoring the advantages of using ether-based electrolytes. This work offers novel insights and approaches for the design of high-performance electrolytes for lithium metal batteries.

Progress of GaN-Based E-mode HEMTs

Abstract With the continuous improvement of the power density and operating frequency in power conversion systems, it is necessary to develop the new power electronic products with better performances than the conventional semiconductors. As a typical representative of the wide-bandgap semiconductors, gallium nitride (GaN)-based heterostructure has unique high-density two-dimensional electron gas (2DEG) and hence can be used to fabricate the fast high electron mobility transistors (HEMTs) with low power loss. Therefore, they are considered as a promising candidate for the next-generation power devices to improve the switching efficiency and speed. Compared with the depletion mode (D-mode, also known as normally-on) devices, the enhancement-mode (E-mode, also known as normally-off) devices have the advantages of safety, energy-saving, and better circuit topology design, making them more attractive for industry applications. In this paper, the different structure schemes and fabrication technologies of the GaN-based E-mode HEMTs are reviewed and summarized. Their technical characteristics are systematically compared. The influences of material epitaxial structure, ohmic contact, material etching, field plate design, and passivation process on the device performances are discussed in detail wherein the fabrication process of the recessed-gate MIS-HEMTs are emphatically illustrated, focusing on the interface treatment technology and dielectric engineering. In addition, the complicated reliability issues and physical mechanisms in the E-mode HEMTs induced by high temperature, high voltage, and high frequency switching are introduced and discussed. Finally, the potential technical solutions are proposed and the future application fields of GaN-based E-mode HEMTs are prospected.

Automated Scanning Dielectric Microscopy Toolbox for Operando Nanoscale Electrical Characterization of Electrolyte‐Gated Organic Transistors

AbstractElectrolyte‐gated organic transistors (EGOTs) leveraging organic semiconductors' electronic and ionic transport characteristics are the key enablers for many biosensing and bioelectronic applications that can selectively sense, record, and monitor different biological and biochemical processes at the nanoscale and translate them into macroscopic electrical signals. Understanding such transduction mechanisms requires multiscale characterization tools to comprehensively probe local electrical properties and link them with device behavior across various bias points. Here, an automated scanning dielectric microscopy toolbox is demonstrated that performs operando in‐liquid scanning dielectric microscopy measurements on functional EGOTs and carries out extensive data analysis to unravel the evolution of local electrical properties in minute detail. This paper emphasizes critical experimental considerations permitting standardized, accurate, and reproducible data acquisition. The developed approach is validated with EGOTs based on blends of organic small molecule semiconductor and insulating polymer that work as accumulation‐mode field‐effect transistors. Furthermore, the degradation of local electrical characteristics at high gate voltages is probed, which is apparently driven by the destruction of local crystalline order due to undesirable electrochemical swelling of the organic semiconducting material near the source electrode edge. The developed approach paves the way for systematic probing of EGOT‐based technologies for targeted optimization and fundamental understanding.

High-Performance Aqueous Zinc-Organic Battery with a Photo-Responsive Covalent Organic Framework Cathode.

Covalent organic framework (COF) materials, known for their robust porous character, sustainability, and abundance, have great potential as cathodes for aqueous Zn-ion batteries (ZIBs). However, their application is hindered by low reversible capacity and discharge voltage. Herein, a donor-acceptor configuration COF (NT-COF) is utilized as the cathode for ZIBs. The cell exhibits a high discharge voltage plateau of ≈1.4V and a discharge capacity of 214 mAh g-1 at 0.2 A g-1 when utilizing the Mn2+ electrolyte additive in the ZnSO4 electrolyte. A synergistic combination mechanism is proposed, involving the deposition/dissolution reactions of Zn4SO4(OH)6·4H2O and the co-(de)insertion reactions of H+ and SO4 2- in NT-COF. Meanwhile, the NT-COF with a donor-acceptor configuration facilitates efficient generation and separation of electron-hole pairs upon light exposure, thereby enhancing electrochemical reactions within the battery. This leads to a reduction in charging voltage and internal overvoltage, ultimately minimizing electricity consumption. Under ambient weather conditions, the cell exhibits an average discharge capacity of 430 mAh g-1 on sunny days and maintains consistent cycling stability for a duration of 200 cycles (≈19 days) at 0.2 A g-1. This research inspires the advancement of Zn-organic batteries for high-energy-density aqueous electrochemical energy storage systems or photo-electrochemical batteries.

A processable high thermal conductivity epoxy composites with multi-scale particles for high-frequency electrical insulation

The solid-state transformer (SST) in the renewable energy grid is developing in the way of high voltage and high frequency, which often results in a sharp increase in heat production of the equipment and accelerates the failure of the insulating materials. Epoxy resin (EPR) is commonly used as an insulation material for SST due to its excellent electrical insulating properties, processing performance (viscosity), and low price. However, the thermal conductivity of EPR is only about 0.2 W/(m·K), which leads to poor insulating performance under high frequency and temperature. To enhance thermal conductivity, a substantial quantity of highly thermally conductive particles is incorporated into the EPR, accompanied by a severe increase in electrical insulation defects and viscosity. This study utilized a multi-scale particle-filled approach to investigate the thermal conductivity, processing characteristics, and high-frequency electrical insulation performance of composites. The composite, filled with 25 µm BN and 5 µm SiO2 particles, enhances thermal conductivity to 0.732 W/(m·K) and demonstrates superior electrical insulating properties at both 10 kHz and 20 kHz bipolar square waves (with an increase of 131.76% and 163.97% in relative EPR, respectively), as well as good processability. Meanwhile, it is found that the dielectric loss, thermal conductivity, and electric field distribution of the composite are the main factors affecting the electrical insulating properties from 10 to 20 kHz under high voltage.Graphical

Ultra‐High Peak Power Generation for Rotational Triboelectric Nanogenerator via Simple Charge Control and Boosted Discharge Design

AbstractCurrently, enhancing the output power of rotational‐mode triboelectric nanogenerators (TENGs) using various complicated systems is a contentious issue; however, this is a challenging process owing to the inherent characteristics of TENGs, namely, low output currents as opposed to high voltages. Thus, this study proposes a simple and innovative strategy for ultra‐high output peak power generation of TENGs called a self‐boosted rotational electrostatic‐discharge TENG (SRE‐TENG). The SRE‐TENG mechanism is unique as it is based on charge control and boosted discharge design, thereby achieving a remarkable peak power of 1103.8 W, peak power density of 140.6 Kw m−2, low optimum resistance of 100 Ω, and broad peak power generation range of 10 Ω to 1 GΩ. Diligent measurements and analyses of the peak and root‐mean‐square voltage and current outputs of the SRE‐TENG are conducted for various design variables and circuit configurations. The proposed SRE‐TENG mechanism is validated using experimental and multiphysics simulation results. The high‐output performance of the SRE‐TENG is demonstrated via the lighting of 3,000 LEDs and a 60‐W lamp array, continuous driving of a commercial sensor array, and hydrogen/oxygen generation via water electrolysis.

Stabilizing high temperature operation and calendar life of LiNi0.5Mn1.5O4

Severe capacity degradation at high operating voltages and poor interphase stability at elevated temperature have thus far precluded the practical application of LiNi0.5Mn1.5O4 (LNMO) as a cathode material for lithium-ion batteries. Addressing these challenges through a combination of experimental and theoretical methods in this work, we demonstrate how a fluorinated carbonate electrolyte enables both high-voltage and high temperature operation by mitigating the traditional interfacial reactions observed in electrolytes with conventional carbonate solvents. Computational studies confirm the exceptional oxidation stability of fluorinated carbonate electrolyte which reduces deprotonation at high voltage. The mitigated deprotonation will then minimize the formation of HF acid which corrodes the LNMO surface and leads to phase transformation and poor interphases. With fluorinated carbonate electrolyte at elevated temperature, it was found on LNMO’s subsurface a reduced amount of Mn3O4 phase which can block Li+ transfer and result in drastic cell failure. Leveraging this approach, LNMO/graphite full cells with a high loading of 3.0 mAh/cm2 achieve excellent cycling stability, retaining ∼84 % of their initial capacity at room temperature (25 °C) after 200 cycles and ∼68 % after 100 cycles at 55 °C. This advanced electrolyte also shows promise for improving calendar life, retaining >30 % more capacity than the carbonate baseline after high temperature storage. These results indicate that electrolytes based on fluorinated carbonates are a promising strategy for overcoming the remaining challenges toward practical commercial application of LNMO.

ВПЛИВ ВЕЛИЧИНИ ЄМНОСТІ ПОСЛІДОВНОГО РЕЗОНАНСНОГО КОНТУРУ НА ПОТУЖНІСТЬ ЕЛЕКТРОТЕХНІЧНИХ СИСТЕМ РЕЗОНАНСНОГО ТИПУ ДЛЯ МОНІТОРИНГУ ІЗОЛЯЦІЇ ВИСОКОВОЛЬТНОГО ОБЛАДНАННЯ

It were analyzed the processes of charging the capacitive electro-technical storage (CES), which can be the electrical insulation of modern high -voltage equipment (in particular power cables) during the current monitoring of its techni-cal condition by the value of leakage currents when applying high voltage to insulation. The transformerless electro-technical system (ETS) of a resonance type, in which resonant inductive-capacitive circuit (ICС) with a high Q -factor carried out a multiple increase in AC voltage, was used to generate such voltage. Analytical expressions were obtained for the steady-state voltage on such CES and transient currents in the ETS circuit its charging. Simulation modeling of transient processes in the circuits of such ETS during CES charging was performed using the LTSpice software pack-age. It is shown that the dependences of the output voltage and current of the ETS on time, obtained by analytical ex-pressions, practically coincide with the results of simulation simulations. The influence of the ratio of the load capaci-tance and the resonant circuit capacitance on the relative load charging time and, accordingly, on the ETS power was studied. It was found that in order to increase the power of high -voltage transformerless ETS of the specified reso-nance type, it is necessary to increase the ratio of the CES capacity to the ICС capacity of the resonant circuit of the ETS. This approach can be used when using ETS with resonant ICCs to create powerful electric discharge installations (EDIs) for the implementation of technologies for obtaining electro-spark micro- and nanopowders with unique opera-tional properties. When creating powerful EDIs, it is suggested to use the value of the above-mentioned ratio at least 10. References 31, figures 5.

–C≡N functionalizing polycarbonate-based solid-state polymer electrolyte compatible to high-voltage cathodes

Solid-state polymer electrolytes (SPEs) capable of withstanding high voltage are considered to be key for next-generation energy storage devices with inherent safety as well as high energy density. This study involves the rational design of solid-state –C≡N functionalized P(VEC1-CEA0.3)/LiTFSI@CE SPEs and its synthesis by in-situ free radical polymerization of vinyl ethylene carbonate (VEC) and 2-cyanoethyl acrylate (CEA). In situ polymerization yields electrode/electrolyte interfaces with low interfacial resistance, forming a stable SEI layer enriched with LiF, Li3N, and RCOOLi, ensuring stable Li plating/stripping for over 1400 h. The –C≡N moiety renders the αH on the adjacent αC positively charged, thereby endowing it with the capability to anchor TFSI−. Simultaneously, the incorporation of –C≡N moiety diminishes the electron-donating ability of the C=O, C–O–C, and –C≡N functional groups, facilitating not only the ion conductivity enhancement but also a more rapid Li+ migration proved by DFT theoretical calculations and Raman spectroscopy. At room temperature, tLi+ of 0.60 for P(VEC1-CEA0.3)/LiTFSI@CE SPEs is achieved when the ionic conductivity σLi+ is 2.63 × 10−4 S cm−1 and the electrochemical window is expanded to 5.0 V. Both coin cells with high-areal-loading cathodes and the 6.5-mAh pouch cell, exhibit stable charge/discharge cycling. At 25 °C, the 4.45-V Li|P(VEC1-CEA0.3)/LiTFSI@CE|LiCoO2 battery performs stable cycling over 200 cycles at 0.2 C, with a capacity retention of 82.1%.

Ion-dipole regulation based on bidentate solvent for stabilizing high-voltage lithium metal batteries

The poor compatibility of ester electrolytes with lithium metal anode severely limits its use in high voltage lithium metal batteries (LMBs). In this work, a bidentate solvent 1,2-diethoxyethane (DEE) is introduced into ester electrolyte to regulate the ion-dipole interactions to enhance the solubility of LiNO3, which enables compatibility with Li anode and maintains the high voltage cathode stability. In the designed electrolyte, the steric effect of DEE facilitates the participation of NO3- and PF6− anions in the Li+ solvation structure, thus promoting the generation of inorganic-rich solid electrolyte interphase (SEI). And the low viscosity of DEE also ensures that the ester electrolyte poses good interfacial wettability. As a result, our designed electrolyte enables the high-loading Li||NCM622 and Li||NCM811 (∼3 mA h cm-2) full cells to achieve stable cycling over 200 cycles, 8 times longer than that of a conventional ester electrolyte. This work suggests that regulation of intermolecular interactions in conventional ester electrolytes is a scalable and effective approach to achieve excellent electrochemical performance of LMBs.