High Open Voltage Research Articles

Ethyl 2-butene phosphite as a film-forming additive for high voltage lithium-ion batteries

Increasing the charge cutoff voltage can significantly improve the capacity of lithium-ion batteries. However, the structural degradation of Ni-rich cathodes and high reactivity of electrolytes at the high-potential cathodes greatly affect the cycling stability. In this paper, a new type of cathode film-forming additive, ethyl 2-butene phosphite (EBP), is synthesized based on the molecular design of phosphite by increasing the functional group of carbon-carbon double bond and ring structure. Theoretical calculation shows that EBP has a higher HOMO level and can form a cathode electrolyte interphase (CEI) on the cathode electrode surface before the electrolyte in theory. The electrochemical performance of NCM622/Li half-cells is significantly enhanced by incorporating EBP into the electrolyte, achieving 72.52% capacity retention over 100 cycles at 0.5C. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive Spectroscopy (EDS) are used to characterize the morphology of the anode and cathode, revealing that EBP forms a dense and complete CEI film on the surface of the LiNi0.6Co0.2Mn0.2O2 electrode. This film effectively blocks direct contact between the electrolyte and the cathode active material, prevents the dissolution of transition metals, improves interfacial stability, and consequently enhances the high-voltage cycling performance of the battery.

Study on the Preparation and Electrochemical Properties of LiFe0.4Mn0.6PO4 Coated with Bamboo Shaving-Based Carbon.

LiFe1-xMnxPO4 (0 < x < 1) has a high operating voltage range and theoretical energy density, but its actual capacity decreased due to its low electronic conductivity. To overcome this problem, we successfully prepared LiFe0.4Mn0.6PO4/C (LFMP/C) with a uniform carbon coating by a one-step solvothermal method using bamboo shavings as the carbon source. The results showed that heating at a reaction temperature of 180 °C for 18 h was the optimal synthesis condition to obtain LFMP/C. The addition of bamboo shaving-based carbon was effective in inhibiting excessive grain growth and reducing particle size. The disordered carbon layer enhanced the surface conductivity by connecting the surfaces of the particles. The synergistic effect of the nanoparticle size and the pores distributed around the particles increased the specific surface area and thus improved the contact area between the active substance and the electrolyte. Furthermore, there were improvements in electronic conductivity and ionic mobility. LFMP/C-16 showed initial discharge capacities of 150.1 and 143.5 mAh·g-1 at rates of 0.1 and 0.2C, respectively, with a capacity retention rate of 97.73% after 100 cycles, indicating excellent cyclic performance.

Cobalt Hexacyanoferrate Cathode with Stable Structure and Fast Kinetics for Aqueous Zinc-Ion Batteries.

Prussian blue analogues (PBAs) show great promise as cathode candidates for aqueous zinc-ion batteries thanks to their high operating voltage, open-framework structure, and low cost. However, suffering from numerous vacancies and crystal water, the electrochemical performance of PBAs remains unsatisfactory, with limited capacity and poor cycle life. Here, a simple coprecipitation method is shown to synthesize well-crystallized cobalt hexacyanoferrate (CoHCF) with a small amount of water and high specific surface area. Benefitting from two redox-active sites, CoHCF could deliver 104.6 mA h g-1 at 0.02 A g-1 and 72 mA h g-1 at 1 A g-1, with good capacity retention of 92.4% after 300 cycles at 0.5 A g-1. Several electrochemical kinetic tests indicate that the reaction is dominated by capacitive behavior and that the diffusion coefficient of Zn2+ ions is approximately 10-9 cm2 s-1. Furthermore, ex-situ XRD indicated a reversible insertion/extraction of Zn2+ ions without any phase transition.

Electrolyte Chemistry Towards Ultra‐High Voltage (4.7 V) And Ultra‐Wide Temperature (−30 to 70 °C) LiCoO2 Batteries

AbstractLiCoO2 batteries for 3 C electronics demand high charging voltage and wide operating temperature range, which are virtually impossible for existing electrolytes due to aggravated interfacial parasitic reactions and sluggish kinetics. Herein, we report an electrolyte design strategy based on a partially fluorinated ester solvent (i.e., DFEA) that achieves a balance between weak Li+‐solvent interactions, sufficient salt dissociation, high interfacial stability, and superior thermal stability to address the aforementioned challenges. The resulting high‐voltage wide‐temperature electrolyte (HWE) not only possesses low desolvation energy, fast Li+ transport, high oxidation stability, excellent thermal‐abuse tolerance and non‐flammability, but also enables the formation of both inorganic‐rich cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI). Owing to the above merits, this HWE endows the highly stable operation of LiCoO2 cathodes under an ultra‐high voltage of 4.7 V and Graphite || LiCoO2 batteries in an ultra‐wide temperature range of −30 to 70 °C. Meanwhile, a 1.7 Ah‐level 4.6 V Graphite || LiCoO2 pouch cell with a high energy density of 240 Wh kg−1 also delivers excellent cycling stability, representing a significant advancement in the design of electrolytes towards ultra‐high voltage and ultra‐wide temperature batteries.

Effects of thiols on electro-optical properties of reverse polymer-stabilised liquid crystal films

ABSTRACT Reverse-mode polymer stabilised liquid crystal (RPSLC) can maintain a transparent state without voltage and exhibit excellent light scattering haze performance when voltage is applied, making it suitable for long-term use in smart windows. However, the high operating voltage of polymer stabilised liquid crystal devices necessitates efforts to reduce the driving voltage and enhance the contrast ratio to improve their optical properties. In this paper, we demonstrate that the introduction of a small amount of the thiol monomer into acrylate polymer monomer during UV-induced homopolymerisation and copolymerisation significantly affects the crosslinking density of the polymer network, thereby influencing the electro-optic performance of RPSLC devices. As a result, we have developed a high-contrast RPSLC device with a saturation voltage below 10 V. These findings are crucial for guiding practical improvements in the performance of RPSLC device.

Operando Gravimetric and Energy Loss Analysis of Na3V2(PO4)2F3 Composite Films by Electrochemical Quartz Microbalance with Dissipation Monitoring.

The rising demand for energy storage calls for technological advancements to address the growing needs. In this context, sodium-ion (Na-ion) batteries have emerged as a potential complementary technology to lithium-ion batteries (Li-ion). Among other materials, Na3V2(PO4)2F3 (NVPF) is a promising cathode for Na-ion batteries due to its high operating voltage and good energy density. In order to further characterize the (dis)charge behavior of NVPF, the electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) was employed to track both the frequency and dissipation loss changes at the electrode/electrolyte interface. The electrode composite preparation proved to be crucial for extending the potential window to both Na3V2(PO4)2F3/Na2V2(PO4)2F3 and Na2V2(PO4)2F3/Na1V2(PO4)2F3 domains. Composites prepared with rawNVPF powder (1-20 μm particles) and polyvinylidene fluoride (PVDF) binder (raw-NVPF:PVDF) exhibited large dissipation changes during (dis)charging, attributed to the soft viscoelastic nature of the binder and substantial hydrodynamic interaction caused by the large particles. On the other hand, composites prepared by sieved NVPF particles (<1 μm particles) with sodium carboxymethyl cellulose (NaCMC) binder (sieved-NVPF:NaCMC) showed rigid properties, enabling an extended and more accurate gravimetric analysis. This allowed for the determination of a linear charge-to-mass relationship for the full potential window of NVPF, reflecting the potential independent insertion/deinsertion of bare Na ions (23 g·mol-1). Additionally, reversible dissipative changes were observed for the Na3V2(PO4)2F3/Na2V2(PO4)2F3 transition, with no further dissipative changes observed during the Na2V2(PO4)2F3/Na1V2(PO4)2F3 process.

Electrolyte Chemistry Towards Ultra-High Voltage (4.7 V) And Ultra-Wide Temperature (-30 to 70 °C) LiCoO2 Batteries.

LiCoO2 batteries for 3 C electronics demand high charging voltage and wide operating temperature range, which are virtually impossible for existing electrolytes due to aggravated interfacial parasitic reactions and sluggish kinetics. Herein, we report an electrolyte design strategy based on a partially fluorinated ester solvent (i.e., DFEA) that achieves a balance between weak Li+-solvent interactions, sufficient salt dissociation, high interfacial stability, and superior thermal stability to address the aforementioned challenges. The resulting high-voltage wide-temperature electrolyte (HWE) not only possesses low desolvation energy, fast Li+ transport, high oxidation stability, excellent thermal-abuse tolerance and non-flammability, but also enables the formation of both inorganic-rich cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI). Owing to the above merits, this HWE endows the highly stable operation of LiCoO2 cathodes under an ultra-high voltage of 4.7 V and Graphite || LiCoO2 batteries in an ultra-wide temperature range of -30 to 70 °C. Meanwhile, a 1.7 Ah-level 4.6 V Graphite || LiCoO2 pouch cell with a high energy density of 240 Wh kg-1 also delivers excellent cycling stability, representing a significant advancement in the design of electrolytes towards ultra-high voltage and ultra-wide temperature batteries.

Conductive MOF-Derived Coating for Suppressing the Mn Dissolution in LiMn2O4 toward Long-Life Lithium-Ion Batteries.

Spinel lithium manganese oxide (LiMn2O4, LMO) is a promising cathode material with nontoxicity, high operating voltage, and low cost. However, structural collapse during battery cycling ─ caused by Mn dissolution and the Jahn-Teller effect ─ is a critical disadvantage, reducing cycle retention, particularly at high temperatures. In this study, to solve these critical issues, we introduce Cu3(HITP)2 (CuHITP; HITP = 2,3,6,7,10,11-hexaiminotriphenylene), a conductive two-dimensional (2D) metal-organic framework (MOF) as a surface coating material. The CuHITP-derived coating increases the electrical conductivity and suppresses Mn dissolution by enriching the LMO surface with Mn4+. By suppressing Mn dissolution, structural stability also improves, offsetting the inherent problems. As a result, at 60 °C, CuHITP-LMO exhibits an initial capacity of 95.8 mAh g-1 at 100 mA g-1 and achieves a capacity of 42.4 mAh g-1 after 300 cycles. This research highlights the potential of conductive 2D MOFs to improve the electrochemical performances of LMO.

An aqueous zinc-ion battery with an organic-inorganic nanohybrid cathode featuring high operating voltage and long-term stability.

Cathode materials with both high capacity and high operating voltage are essential for advancing aqueous zinc-ion batteries (ZIBs). Conventional high-capacity materials, such as vanadium-based compounds, typically deliver low discharge voltages. In contrast, organic cathodes show high operating voltages but often exhibit limited capacity. The present study focuses on developing hybrid cathodes composed of organic (amino PEG amine, APA) and inorganic (ammonium vanadium oxide, NVO) components, referred to as APA-NVO, featuring a dual energy-storage mechanism specifically designed to achieve a wide operating voltage of 1.9 V and provide exceptionally durable ZIBs.

High-performance biodegradable dielectric composite: Towards minimizing electronic waste

Polymer-based dielectric capacitors are crucial in modern electronics due to their wide capacitance range, high operating voltage, lightweight nature, and graceful failure reliability. However, the predominant use of nondegradable dielectric polymers raises environmental concerns. This study addresses this issue by preparing flexible biodegradable dielectric composite films of poly(butylene adipate-co-terephthalate) (PBAT) incorporating varying amounts of nitrogen-doped and non-doped biochar derived from banana peel waste. It was found that the incorporation of biochar in the nanocomposite improved various properties such as dielectric properties, biodegradability, mechanical strength, and thermal stability. The PBAT nanocomposite with 10 wt% N-doped biochar exhibited an 83 % rise in dielectric constant compared to pure PBAT while maintaining a low dielectric loss of 0.071 at 1000 Hz. This approach offers a cost-effective and environmentally sustainable method, showing potential for advancing next-generation disposable electronic materials with enhanced performance attributes.

Electrophoretically deposited artificial cathode electrolyte interphase for improved performance of NMC622 at high voltage operation

A composite film, composed of Li6PS5Cl ion-conducting nanoparticles and a polymerized ionic liquid binder, was electrophoretically deposited onto the LiNi0.6Mn0.2Co0.2O2 cathode surface, forming an artificial cathode electrolyte interphase.

Enhanced elevated-temperature performance of LiMn2O4 cathodes in lithium-ion batteries via a multifunctional electrolyte additive

LiMn2O4 is a promising cathode material for lithium-ion batteries (LIBs) due to its low cost, environmental friendliness, and high voltage operation. However, its electrochemical performance deteriorates at elevated temperatures, primarily by reason of the structural degradation during cycling and proliferation of adverse reactions at the electrode/electrolyte interface. One of the main reasons is that the hydrolysis and decomposition of the LiPF6 at high temperatures produces HF, which leads to corrosion at the electrode/electrolyte interface and accelerates manganese dissolution. In this work, we report a multifunctional silane-based electrolyte additive, trimethoxyphenylsilane (TMPS), to solve these problems. Theoretical calculations and experimental results both demonstrate that TMPS can eliminate HF, stabilize PF5, and inhibit LiPF6 hydrolysis, thereby mitigating transition metal leaching. Additionally, TMPS improves the stability between cathode and electrolyte by constructing a highly stable and homogeneous cathode-electrolyte interfacial. The LiMn2O4//Li cell using the electrolyte containing 1 wt% TMPS retains 95.5 % and 83.7 % of its capacity after 500 cycles at 25 °C and 60 °C, respectively. Moreover, 18650-type cylindrical cells with this electrolyte also exhibit enhanced electrochemical performance at elevated temperatures. It demonstrates that TMPS is a promising multifunctional additive for manganese-based cathodes in LIBs.

Synergistic effects of co-additives in constructing a robust and Li+-conductive interphase for high-voltage LiCoO2

Elevating the charging cut-off voltage is the most effective method to improve energy density of LiCoO2 (LCO)-based lithium-ion batteries, while high-voltage operation further leads to the instability of electrolyte and electrode-electrolyte interphase. Herein, a tailored carbonate electrolyte with functional co-additives is proposed for high-voltage LCO by constructing thin and robust cathode-electrolyte interphase (CEI). The co-additives, lithium bis(oxalato)borate (LiBOB) and tris(trimethylsilyl)phosphite (TMSPi), decompose prior to the carbonate solvents to ensure the stability of the electrolyte. The later decomposition of TMSPi not only generates Li+-conductive P-containing species but also suppresses the excess decomposition of LiBOB. The synergistic effects of robust B-containing species and high Li+-conductive P-containing species in the CEI ensure excellent performance of LCO cathode under high voltage of 4.5 V (vs. Li/Li+), exhibiting a high capacity retention of 95.2% for 200 cycles and improved rate capability up to 5C with a high capacity of 146 mAh g−1. Moreover, the LCO||graphite full cell with the tailored electrolyte can maintain a capacity retention of 93.9% after 100 cycles, more than twice that of the BE electrolyte (44.3%). This co-additives strategy offers a guideline on constructing advanced CEI for practical application in high-voltage cathode.

Construction of uniform MgO nanoshells for improved high-voltage performance of Li-ion batteries.

A conformal Mg(OH)2 nanoshell was constructed through a wet-chemical process, where a gradual release of OH- as the precipitating agent was designed to ensure the heterogeneous growth of the coating species. Such a coating treatment was found to be efficient in improving the structural stability and electrochemical stability of a 5 V LiNi0.5Mn1.5O4 cathode.

Multiple Polarization States in Hf1- xZrxO2 Thin Films by Ferroelectric and Antiferroelectric Coupling.

HfO2-based multi-bit ferroelectric memory combines non-volatility, speed, and energy efficiency, rendering it a promising technology for massive data storage and processing. However, some challenges remain, notably polarization variation, high operation voltage, and poor endurance performance. Here we show Hf1- xZrxO2 (x=0.65 to 0.75) thin films grown through sequential atomic layer deposition (ALD) of HfO2 and ZrO2 exhibiting three-step domain switching characteristic in the form of triple-peak coercive electric field (EC) distribution. This long-sought behavior shows nearly no changes even at up to 125°C and after 1 × 108 electric field cycling. By combining the electrical characterizations and integrated differential phase-contrast scanning transmission electron microscopy (iDPC-STEM), wereveal that the triple-peak EC distribution is driven by the coupling of ferroelectric switching and reversible antiferroelectric-ferroelectric transition. We further demonstrate the 3-bit per cell operation of the Hf1- xZrxO2 capacitors with excellent device-to-device variation and long data retention,by the full switching of individual peaks in the triple-peak EC. The work represents a significant step in implementing reliable non-volatile multi-state ferroelectric devices.

Research on Self-Recovery Ignition Protection Circuit for High-Voltage Power Supply System Based on Improved Gray Wolf Algorithm

In order to solve the problems of traditional high-voltage power supply ignition protection circuits, such as non-essential start–stop power supply, a slow response speed, the system needing to be restarted manually, and so on, a high-voltage power supply system self-recovery ignition protection circuit was designed using an IGWO (improved grey wolf optimization) and PID control strategy designed to speed up the response speed, and improve the reliability and stability of the system. In high-voltage power supply operation, the firing discharge phenomenon occurs. Current transformers fire signal into a current signal through the firing voltage value and Zener diode voltage comparison to set the safety threshold; when the threshold is exceeded, the fire protection mechanism is activated, reducing the power supply voltage output to protect the high-voltage power supply system. When the ignition signal disappears, based on the IGWO-PID control of the ignition self-recovery circuit according to the feedback voltage, the DC supply voltage of the high-voltage power supply is adjusted, inhibiting the ignition discharge and, according to the ignition signal, “segmented” to restore the output of the initial voltage. MATLAB/Simulink was used to establish a system simulation model and physical platform test. The results show that the protection effect of the designed scheme is an improvement, in line with the needs of practical work.

Dual-Modal Dielectric Elastomer System for Simultaneous Energy Harvesting and Actuation.

Dielectric elastomers (DEs) have promising capabilities for soft electromechanical systems, including those for actuation and energy generation. However, their widespread application is restricted by electromechanical instability (EMI) and the requirement for high-voltage operation. This study presents a dual-modal DE system that effectively overcomes these limitations by leveraging a dual-membrane structure. The proposed structure not only suppresses EMI through charge sharing but also enables simultaneous energy harvesting and actuation, enhancing the overall electrical performance of the system. The system demonstrated a remarkable improvement in output performance, exceeding that of traditional single-modal DE generators by up to 30%. The practicality of the system is developed by integrating it into a mechanically powered soft robot capable of locomotion and environmental monitoring using a wireless temperature sensor. This study paves the way for the development of advanced DE-based systems with enhanced stability, functionality, and potential for diverse applications in soft robotics, energy harvesting, and other areas that require coupled electromechanical capabilities.

Mitigating Crosstalk by Slurry Additive Toward 5V Cobalt-Free LiNi0.5Mn1.5O4 Cathode.

LiNi0.5Mn1.5O4 (LNMO), with its spinel symmetry, emerges as a promising cathode material for high-voltage lithium-ion batteries (LIBs). Nonetheless, the vulnerability of LNMO to interfacial degradation, particularly electrolyte breakdown during high-voltage operation, compromises its long-term cycling performance. To overcome this longstanding challenge, a slurry additive-polyester-urethane-acrylate (PEUA)-to form a multi-functional ultra-thin electrode coating, enhancing the lifespan and energy density of LIBs is introduced. Comprehensive characterizations and theoretical analyses reveal that the PEUA slurry additive effectively maintains electrode integrity, facilitates electrons and lithium ions transport, and inhibits hazardous side reactions, thus preventing the by-products from triggering cathode-electrolyte-anode interface crosstalk. Consequently, the 5V LNMO || Li cell with PEUA slurry additive maintains a high-capacity retention of 97.8%, with improved cycling stability at high-temperature and full-cell configurations. This crosstalk-mitigation strategy offers a promising avenue for extending the lifespan and electrochemical performance of high-voltage cobalt-free cathodes, advancing the practical use of high-energy density LIB technology.

Ionic Exchange Mechanism in Electrical Double Layer Induced by Stable Passivation Film Boosts High Voltage Performance in Supercapacitors

Ionic Exchange Mechanism in Electrical Double Layer Induced by Stable Passivation Film Boosts High Voltage Performance in Supercapacitors

Rational Design of Porous Y2O3-MnOx/Carbon Heterostructures with Abundant Oxygen Vacancies for High-Efficiency and Ultrastable Zinc-Ion Storage.

Manganese oxides have been considered as the most competitive cathode materials for aqueous zinc-ion batteries (ZIBs) on account of their inherent safety, high operating voltage, environmental friendliness, and cost-effectiveness. Unfortunately, the manganese dissolution, inherently poor electronic conductivity, and the sluggish reaction kinetics of commercial manganese-based oxides severely hinder their practical applications. To address the above issues, we creatively developed hierarchical porous Y2O3-MnOx/C nanorods (named OV-YMO/C) with unique heterostructures and abundant oxygen vacancies via a facile MOF-assisted synthetic process and employed as the advanced cathode. Owing to the well-constructed porous structure, larger surface areas, abundant oxygen vacancies, and strong synergetic coupling effect at the heterogeneous interface, the as-obtained OV-YMO/C cathode exhibited a fascinating discharge capacity of 389.6 mAh g-1 at 0.1 A g-1. Simultaneously, it demonstrated remarkable rate performance (233 mAh g-1 at 4.0 A g-1) and cycling durability (90.6% capacity retention over 3000 cycles at 4.0 A g-1). The fabricated Zn//OV-YMO/C pouch cell could deliver superior flexibility and electrochemical stability under extreme bending conditions. Furthermore, the electrochemical reaction mechanism was comprehensively explored by kinetic analysis and density functional theory (DFT) calculations. The synergistic strategy by subtly combining the MOF-assisted approach, heterojunction engineering, and oxygen defects engineering provides valuable insights into the construction of cathode materials for high-rate and ultrastable aqueous ZIBs.