High Current Density Conditions Research Articles

The art of Lithiation Revisited: Solvent-free room temperature reaction

The lithiation reaction holds immense significance across various branches of chemistry, particularly in the realm of electrochemical energy storage. Here, we report a new method that enables a solvent-free process at room temperature, exhibiting remarkably swift reaction kinetics. Through this process, the chemical integration of Li+ into charged materials based on transition metals is achieved using lithium iodide, LiI. An evident application of this method lies in advancing the direct recycling of cathode materials reclaimed from spent batteries. Notably, the process facilitates the efficient and direct recycling of spent Li(1-x)FePO4 cathode material, sourced from a commercial LIB, without the need for any solvents or heat treatments. The regenerated material exhibits a fully reversible capacity of approximately 168 mAh/g against Li metal, even under high current density conditions, with a consistently stable coulombic efficiency surpassing 99 % over 45 cycles. This regenerative approach holds the potential for seamless extension to other LIB cathode materials, including but not limited to LMFP, LMO, LCO and NMC.

Effects of ultrasonic power on the electrochemical characteristics of high-performance nanosized zinc–cobalt oxide electrodes for asymmetric supercapacitors

This study reports the preparation of ZnCo2O4 oxide (ZCO) electrode materials with favorable microstructure and porosity arrangement via ultrasonic electrodeposition-calcination. The application of ultrasonic waves at a power of 200 W (using ZCO-2) led to the development of a smooth and flat microstructure, characterized by the presence of numerous micropores. The lattice constant of ZnCo2O4 in the ZCO-2 oxide electrode material was determined to be 0.428 nm via TEM analysis. Furthermore, the XRD analysis of ZCOs demonstrated the effective synthesis of ZnCo2O4 electrode materials. The main lattice diffraction planes of ZCOs were observed at (111), (220), (311), (400), (511), and (440), with corresponding diffraction angles of 29.8°, 36.4°, 42.9°, 45.2°, 62.3°, and 66.5°, respectively. The application of 200 W ultrasonic power during electrochemical experiments significantly improved the electrochemical performance of ZCO-2. The ZCO-2 oxide electrode demonstrated remarkable area capacitance and negligible electrical impedance. At a current density of 3 mA/cm2, the area capacitance was measured to be 1.803 F/cm2. The ZCO-2 oxide electrode showed remarkable capacitance retention of 67.3 % even under high current density conditions. Furthermore, the asymmetric supercapacitor composed of ZCO-2 and AC (ZCO-2/AC ASC) showed outstanding electrochemical performance. The ZCO-2/AC ASC showed a capacitance of 5.721 F/cm3 at a current density of 0.5 mA/cm2. Furthermore, it demonstrated an energy density of 68.2 Wh/kg at a power density of 250 W/kg. The capacitor showed consistent performance and retained 63.8 % of its initial capacitance even after undergoing 24,000 cycles. Furthermore, the findings of this research provide substantial implications for the combination of ultrasonic electrodeposition with capacitors, while also presenting an innovative concept for electrode materials in high-performance supercapacitors.

Low humidification effect on performance of proton exchange membrane fuel cells under high current density conditions

To enhance water management in proton exchange membrane fuel cells, the influence of drying and flooding on performance in different voltage ranges is investigated by experiment. The current density attenuates as the voltage decreases in the concentration polarization range. Through the analysis of the performance curves under different conditions, the performance attenuation is due to the high current and overpotential at low voltage, which leads to the temperature rising and drying up. At high flow rates, the current attenuates at low voltages, indicating that the current density attenuation is not because of flooding and insufficient reactants. According to calculations, the anode water content is low due to more protons and water being transferred from anode toward cathode at the high current, which causes the current density to attenuate. From the current ratio, the cell can generate an additional current density of 3.2% at 0.1 V voltage, which can evaluate the degree of carbon corrosion and water electrolyzation due to the insufficient supply of reactants. In addition, the voltage undershoot of switching to high current is great, and the fuel cell has a high demand for water. Finally, reducing temperature and increasing humidification can alleviate the attenuation of current density.

Lattice Boltzmann simulation of oxygen removal from anode porous transport layer in proton exchange membrane electrolyzer

The anode porous transport layer (PTL) plays a crucial role in improving the performance of proton exchange membrane (PEM) electrolyzer. However, oxygen accumulation may cover the interface between the anode catalytic layer and PTL, decreasing mass transfer and electrolysis efficiency. In this study, we employed a comprehensive simulation approach, combining lattice Boltzmann simulation with the Immersed Boundary Method (IBM) and Phase Field Model (PFM), to investigate oxygen removal from the anode PTL. The simulation can accurately capture bubble morphology and gas saturation, demonstrating the four stages of gas removal: invasion, exhaust, breakup and retraction. Notably, the invasion stage contributes to approximately 3/4 of the total gas removal time, whereas the invasion time is significantly influenced by the critical throat in PTL. Removing the critical throat may lead to a 20% reduction in the invasion time. To determine the critical throat, we further simulate the breakthrough of a single pore by a bubble. At lower current densities (1.4 A/cm2), reducing interfacial tension facilitates bubble penetration through smaller pores but weakens the longitudinal permeability, leading to a longer invasion stage. However, at higher current densities (14 A/cm2), the breakthrough is predominantly governed by the critical throat. This suggests that optimizing the PTL structure is more effective in mitigating bubble coverage than adjusting interfacial tension under high current density conditions. These findings may provide some guidelines for enhancing the performance of PEM electrolyzer under high current density conditions.

The Coupled Temperature Field Model of Difficult-to-Deform Mg Alloy Foil High-Efficiency Electro-Rolling and Experimental Study

In response to the challenging difficult-to-deform of magnesium foils, a high-efficiency and high-precision electro-rolling temperature field coupled model is established. This model is designed to simulate the non-annealing electric rolling (NAER) process of Mg foils under conditions of high current density, rapid temperature rise rates, and large temperature gradients. Firstly, a coupled temperature field difference model for the guide roller, roll, and Mg foil is established, based on the equipment for NAER and the electrification conditions. The Joule heat, distortion heat, and friction heat in the electric rolling process were precisely considered. Secondly, considering the peculiarity of the heat source and the heat transfer mechanism during NAER, the influence of the dynamic boundary conditions on the instantaneous temperature of the Mg foil was analyzed, which was closer to the actual situation. The experimental results show that the original model can accurately simulate the transient temperature change in Mg foils during NAER, and the error between the predicted value and the measured value is within 7.1%. According to the calculation of the model, the microstructure of completely recrystallized magnesium foil with a grain size of 4.61 μm and a texture strength of 11.3 can be obtained at an inlet temperature of 250 °C.

Rare-Earth-Modified NiS2 Improves OH Coverage for an Industrial Alkaline Water Electrolyzer.

The low coverage rate of anode OH adsorption under high current density conditions has become an important factor restricting the development of an industrial alkaline water electrolyzer (AWE). Here, we present our rare earth modification promotion strategy on using the rare earth oxygen-friendly interface to increase the OH coverage of the NiS2 surface for efficient AWE anode catalysis. Density functional theory calculations predict that rare earths can enhance the coverage of surface OH, and the synthesis reaction mechanism is discussed in the synthesis process spectrum. Experimentally, by preparing a series of rare-earth-modified NiS2, the relationship between OH coverage, active site density, and catalytic activity was established by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, time-resolved absorption spectra, and so on. The unique oxygenophilic properties of rare earths enhance OH coverage, thereby increasing the density of active sites for efficient catalysis. Furthermore, Eu2O3/NiS2 was assembled into the AWE equipment and operated stably for over 240 h at a current density of 300 mA cm-2 under industrial conditions of 80 °C and 30% KOH. Rare-earth-modified NiS2 exhibits better catalytic activity than traditional non-noble metal anode catalysts Ni(OH)2 and NiS2, providing a new approach for rare earth promotion to solve the problem of low OH coverage in the AWE anode.

Experimental study on voltage instability of proton exchange membrane fuel cell: Types and boundaries

ABSTRACT This paper presents an experimental study on the voltage instability in proton exchange membrane fuel cells operating at high current densities, which is important for improving their reliability and durability. Based on experimental findings regarding transparent fuel cells, a method is proposed to identify different types of voltage instability via statistical results of linear changing rate and oscillation amplitude. The types and boundaries of voltage instability are elucidated while evaluating the impact of cathode relative humidity and flow rate on voltage instability. The findings reveal that (1) the voltage instability is greatly influenced by the cathode-side relative humidity and flow rate, (2) there are three typical types of voltage instability: voltage decline, voltage oscillation, and both, and (3) voltage decline occurs at low cathode humidity, while voltage oscillation becomes more severe at large cathode humidity and low flow rate; (4) Reduction of water content in the membrane leads to voltage decline, while an increase in water content in the catalyst layer, gas diffusion layer, and channels leads to voltage oscillation. A full-condition map diagram demonstrating voltage instability during high current density conditions is presented. The method for creating this map for voltage instability will be employed to enhance fuel cell performance.

Low hydrogen permeability and high durability proton exchange membrane with three-dimensional acid-base crosslink structure for water electrolysis

Introducing a acid–base cross-linked network structure and reinforcement layer into a proton exchange membrane (PEM) can effectively improve its performance, durability, and hydrogen permeability for high-pressure PEM water electrolysis (PEMWE). Here, a hyperbranched polymer containing imidazole terminal groups (HBP-MZ) is designed and prepared, then is used to form a novel PEM possessing a cross-linked network structure consisting of HBP-MZ, perfluorosulfonic acid (PFSA) and reinforced with a poly(ether-ether-ketone) (PEEK) mesh. The microstructure of the PEM is characterized using thermal performance analysis. Benefiting from the acid–base crosslinked structure, the obtained PEM has a more compact structure, induces a drastic increase in dimensional stability, mechanical properties, proton conductivity and stability in water. The HBP-MZ/PFSA@PEEK membrane exhibits excellent water electrolysis performance, low high-frequency impedance, and superior stability: the HBP-MZ/PFSA@PEEK membrane provides an electrolytic performance of up to 1.76 V at 2.0 A cm−2 and 1.84 V at 3.0A cm−2 (60 °C, with an IrO2 loading of 1.0 mg cm−2), and exhibits a 6.2 μV h−1 average voltage degradation rate during durability testing. Benefiting from the characteristics of HBP and the existing cross-linked structures, the obtained HBP-MZ/PFSA@PEEK membrane exhibits a lower hydrogen crossover current density of 1.06 mA cm−2 and maintains a lower hydrogen content in oxygen under conditions of high current density and high pressure. This work provides a promising way to prepare a PEM with high durability and low gas permeability that could be applied in high-pressure water electrolysis.

Te-doped-WSe2/W as a stable monolith catalyst for ampere-level current density hydrogen evolution reaction.

The development of efficient electrocatalysts for the hydrogen evolution reaction (HER) holds immense importance in the context of large-scale hydrogen production from water. Nevertheless, the practical application of such catalysts still relies on precious platinum-based materials. There is a pressing need to design high-performing, non-precious metal electrocatalysts capable of generating hydrogen at substantial current levels. We report here a stable monolith catalyst of Te-doped-WSe2 directly supported by a highly conductive W mesh. This catalyst demonstrates outstanding electrocatalytic performance and stability in acidic electrolytes, especially under high current conditions, surpassing the capabilities of commercial 5% Pt/C catalysts. Specifically, at current densities of 10 and 1200 mA cm-2, it exhibits a minimal overpotential of 79 and 232 mV, along with a small Tafel slope of 55 mV dec-1, respectively. The remarkable catalytic activity of Te-WSe2 can be attributed to the exceptional electron transfer facilitated by the stable monolithic structure, as well as the abundant and efficient active sites in the material. In addition, density functional theory calculations further indicate that Te doping adjusts H atom adsorption on various positions of WSe2, making it closer to thermal neutrality compared to the original material. This study presents an innovative approach to develop cost-effective HER electrocatalysts that perform optimally under high current density conditions.

Effect of Hydrophilic and Hydrophobic Composite Microporous Layer Coated Gas Diffusion Layers on PEFC Performance

In order to widen the market application of the polymer electrolyte fuel cell (PEFC), the output power of the PEFC system must be increased. One of the barriers is the cell voltage loss under high current density conditions. This is mainly caused by the deteriorated reactant mass transport, which is blocked by the water flooding at the catalyst layer (CL), microporous layer (MPL), and gas diffusion layer (GDL). Modifying the MPL coated on the GDL is an accessible way to provide better water management for PEFCs to elongate the operating range of the cell, so a novel MPL-coated GDL should be developed to realize the goal. Previously, we evaluated double MPL-coated GDLs, which coated a thin hydrophilic layer on the hydrophobic MPL-coated GDL in the through-plane direction. The extra hydrophilic layer was influential in promoting the introduction of water into the small pores of the hydrophobic MPL, enhancing the ability to reduce flooding, and the oxygen transport resistance under high humidity conditions can be declined.The present study evaluates a novel composite MPL that the hydrophobic and hydrophilic pores are randomly allocated in the same layer. Excess water is expelled from the hydrophilic pores while maintaining gas transport by the hydrophobic pores. To determine the appropriate hydrophobic and hydrophilic compositions, we first evaluated the most commonly used hydrophobic polytetrafluoroethylene (PTFE) binder, and the contact angle of PTFE-MPL was 136°. Polyvinyl alcohol (PVA) was chosen as the hydrophilic binder, and the contact angle of PVA-MPL was 105°. The slurry containing PTFE, PVA, carbon black, and distilled water was mixed using a mixer and then spread on the carbon paper substrate by a bar coating machine. The temperature was heated at 350°C to sinter the MPL on the substrate. However, the sintering temperature of PVA should be lower than 150°C, so the PVA in the composite MPL was burned and led to a similar contact angle as the PTFE-MPL. Meanwhile, the performance enhancement could not be obtained compared with a PTFE-MPL-coated GDL. Oppositely, when decreasing the sintering temperature to 150C°, the PTFE-PVA composite MPL demonstrated strong hydrophilicity with a small contact angle value, and the performance was exacerbated than the PTFE-MPL. Therefore, to coordinate the lower sintering temperature of PVA, polyvinylidene difluoride (PVDF) was selected as the hydrophobic binder. The contact angle of PVDF-MPL was 143°. After the PVA was preserved, the unexpectedly strong hydrophilicity was exhibited in PVDF-PVA composite MPL, aggravating the liquid water accumulation in the MPL and without performance improvement. Finally, the Nafion ionomer with relatively weak hydrophobicity was used for the composite MPL. As a hydrophilicity complement, titanium dioxide (TiO2) particles were added to the slurry to control hydrophilicity. The contact angle of Nafion/TiO2-MPL was 113°. Similarly, the Nafion/TiO2-PVDF composite MPL indicated a contact angle of 114°, and the water permeability test proved that separate hydrophobic and hydrophilic pores were generated.The oxygen transport resistances were measured based on the limiting current density values of polarization curves to evaluate the ability of the MPL-coated GDL to reduce flooding under high humidity conditions. The active area of the MEA was 1.0 cm2, and the cell temperature was kept at 35°C. Pure hydrogen and diluted oxygen (2 vol% O2 and 98 vol% N2) gases were supplied at the anode and cathode, respectively, and the flow rates were set at 1000 cm3 min-1. The relative humidity of gases supplied to the anode and cathode was 200%RH, and the gas backpressure was set at zero. The oxygen transport resistance of the Nafion/TiO2-PVDF composite MPL-coated GDL was lower than that obtained with a commercial SGL-22BB GDL. Thus, an appropriate composite MPL-coated GDL effectively enhanced PEFC performance under high humidity conditions.

Improving PEMFC Performance with Customized Catalyst Combinations and Advanced Mixing Techniques

Proton Exchange Membrane Fuel Cells (PEMFCs) are a popular choice for use in vehicles and buildings because they can operate at relatively low temperatures and have a simpler system compared to other types of fuel cells. The performance and durability of PEMFCs are influenced by the membrane electrode assembly (MEA).The cathode, where the oxygen reduction reaction occurs, is the component of the MEA that has the greatest influence on performance. The factors that affect high power performance are catalyst activity, proton conductivity, and mass transport resistance of fuels and products.Pt catalysts and PtCo catalysts have advantages and disadvantages at different current densities in PEMFCs. In low current density conditions, PtCo catalysts have been shown to exhibit higher catalytic activity compared to Pt catalysts for the oxygen reduction reaction (ORR). This can result in a more efficient fuel cell operation. However, in high current density conditions, the activity of PtCo catalysts can be reduced compared to Pt catalysts because of their larger particle sizes, which can limit their performance.The properties of the carbon support, such as its hydrophobicity and surface area, can also play an important role in determining the performance of the fuel cell. Hydrophobic carbon supports can facilitate gas diffusion and prevent flooding which can occur when water accumulates in the pores of the electrode and limits reactant transport. Moreover, such supports can limit the contact area between the water and catalyst, leading to prolonged catalyst activity and lifespan. On the other hand, high surface area supports can increase the number of sites available for catalyst anchoring and enlarge the electrode's effective surface area. However, achieving both hydrophobicity and high surface area can be challenging due to the trade-off between these properties.Because each catalyst has advantages and disadvantages at different current densities or operating conditions in PEMFCs, combining different catalystscan achieve improved performance across a wider range of operating conditions. However, each catalyst and carbon support has different affinity with ionomer. Therefore, it is impossible to achieve even ionomer distribution through simple mixing. This means that it is difficult to express the advantages of each catalyst through simple mixing because the transport properties of protons can be influenced by the distribution of the ionomer.To address this, two catalysts were mixed into thecathode electrodes separately, and it was confirmed that this approach improved their performance across a range of current densities. In particular, their high power characteristics were enhanced. To confirm these results, the MEA was tested using H2/air polarization curves, EIS analysis, and limit current density tests, and the porosity in the electrode structure was measured by the BET method and Mercury intrusion porosimetry (MIP).In conclusion, Pt and PtCo catalysts have unique advantages and disadvantages at different current densities in PEMFCs. The properties of the carbon support also play a crucial role in determining the fuel cell performance. Combining different catalysts can enhance the fuel cell's performance but achieving even ionomer distribution through simple mixing is challenging. Applying the two catalysts separately through a distribution process improved the fuel cell's performance across different current densities, especially high power characteristics.

Investigation on the microstructure evolution and mechanical properties of electromagnetic rail material in a launch environment

The failure issue of electromagnetic railgun rails is a widely researched problem, but effective research methods are lacking in studying the microstructure of rail materials. The high current and high strain rate tensile (HCHST) testing platform was designed to simulate the high current density and high strain rate deformation service conditions of pure copper rails used in electromagnetic guns. The microstructural and mechanical properties of commercially pure copper were analyzed using TEM and EBSD under high current density (2680 A/mm2) and various high strain rates (ε̇=3404s−1,ε̇=6808s−1)using the HCHST test platform. The obtained results were then compared with those obtained from the as-received state and the quasi-static current-assisted tensile (QCAT) test. The findings indicate that the deformation mechanism of pure copper specimen under HCHST is similar to that of QCAT, where dislocation and slip are the main mechanisms. However, distinct differences in microstructure were observed. Specifically, a significant number of dislocation walls were present in the grains under QCAT, whereas numerous dislocation cells were formed in the grains under HCHST. In the high-current density environment of 2680 A/mm2, as the strain rate increased, the number of dislocation cells increased while their size decreased. The grains became extremely refined, and the KAM value also increased. Furthermore, the Vickers hardness of pure copper significantly improved after undergoing the HCHST. Based on the experimental findings, it was observed that during the service process of the pure copper rail in electromagnetic railguns (under the influence of high current density and high strain rate deformation), the surface of the rail material experienced significant dislocation entanglement. This resulted in a significant increase in the strength and hardness of the surface of the rail with high strain rate deformation. However, the uneven distribution of strength and hardness throughout the surface layer of the rail eventually made it more susceptible to deformation and failure.

A nonlinear contraction channel design inspired by typical mathematical curves: Boosting net power and water discharge of PEM fuel cells

The next-generation fuel cell needs to fit high current density operating conditions, necessitating improved flow fields with superior capabilities in mass transfer and drainage. This study introduces four innovative nonlinear contraction channels aimed at enhancing net power and mitigating waterflooding under high current density. This design draws inspiration from classical mathematical curves, which can provide targeted mass transfer enhancement contingent upon species distribution. Multiple quantitative indicators are employed to evaluate the efficacy of nonlinear structures in cross-scale mass transfer, drainage, temperature uniformity, and power consumption. Numerical results indicate that the exponential-like curve channel exhibits notably superior overall performance. Its nonlinear contraction region induces purge airflow at the tail of channel, facilitating drainage and boosting the local mass transfer flux in oxygen-starved region by 48.75%. The utilization of nonlinear contraction structures alters the diffusion-convection distribution mechanism and increases the convective mass transfer proportion. Under conditions of high current density, there is a noticeable rise in the Peclet number. Considering the pumping power loss, the hyperbolic tangent, quarter-ellipse, parabolic, and exponential-like curve flow channels can enhance the net power by 3.10%, 6.82%, 8.57%, and 10.04% over straight channels. Additionally, the exponential-like curve channel enhances temperature uniformity in the catalyst layer under rated working conditions, whereas the hyperbolic tangent flow channel demonstrates superior uniformity in higher current density.

Iodine-containing additive engineering for rejuvenating inactive lithium and constructing highly stable lithium metal anodes

Inactive (‘dead’) lithium and conventional fragile solid-electrolyte interphase (SEI) usually cause performance degradation and safety hazards in Li-metal batteries. Recovering inactive lithium and constructing stable SEI are urgently required to enhance the capacity and lifespan of lithium metal batteries. Herein, we have designed a novel dual-additives electrolyte containing an I3−/I− redox couple for reviving the inactive lithium, and caffeic acid (CA) that can be anion-polymerised to modulate the composition and improve stability of the SEI. It’s found that the generated I3−/I− redox couple can turn the inactive Li2O into soluble Li+, and prompt the formation of SEI composed of inorganic LiI, Li3N and organic RCOOLi with high stability. Density functional theory (DFT) calculations indicate that the diffusion potential barrier of Li+ is significantly lower on the LiI-rich SEI interface, which can not only accelerate the transport of Li+ at the interface, but also effectively prevent I3− from attacking Li metal. Benefiting from this elaborate dual-additives electrolyte design, the symmetrical-cells present a superior electrochemical performance, i.e., high critical current density up to 10 mA cm−2, ultra-long lifespan over 7000 h at 1 mA cm−2, and over 2500 cycles under harsh conditions of high temperature (50 °C) and high current density (5 mA cm−2). In addition, as a proof of concept for practical applications of Li-metal batteries, Li|LiFePO4 full cell delivers excellent cycle stability and rate performance with low hysteresis voltage at a high cathode loading of 17.4 mg cm−2.

Evaluation of Ni–B alloy electroplated with different anionic groups

In order to study the effects of the main nickel salt on the electroplated nanocrystalline Ni–B alloy coating, the deposition rates, surface morphology, crystallinity, grain sizes, hardness, and corrosion resistance of the Ni–B films electrodeposited with plating baths containing separately nickel sulfate (NS) and nickel sulfamate (NSA) under various temperatures and current densities were compared. Under all conditions, the NSA bath system offered higher deposition rates and lower B contents than the NS counterpart because of the formation of Ni-ammonium complex, which can be adsorbed faster than nickel ions. These two groups of coatings had similar surface morphology and crystallinity under all plating conditions except for those plated with the NS bath system at 60 °C, wherein significant changes in surface texture and preferred crystal orientation as well as an abrupt increase in grain size occurred. The coating hardness was optimized by reducing the grain size and increasing the boron content because of the combined effects of grain refinement strengthening and solid solution strengthening. The differences between the two main salt systems can be explained by the presence of ammonium ions in the NSA bath, which not only increased the deposition rate but also maintained the preferred orientation in Ni (111) at high temperature. Our results indicate that, under high current density and high temperature operation conditions, the NSA main salt plating system is a more favorable option for obtaining higher quality Ni–B alloy coatings.

High-Areal Capacity, High-Rate Lithium Metal Anodes Enabled by Nitrogen-Doped Graphene Mesh.

Hosts hold great prospects for addressing the dendrite growth and volume expansion of the Li metal anode, but Li dendrites are still observable under the conditions of high deposition capacity and/or high current density. Herein, a nitrogen-doped graphene mesh (NGM) is developed, which possesses a conductive and lithiophilic scaffold for efficient Li deposition. The abundant nanopores in NGM can not only provide sufficient room for Li deposition, but also speed up Li ion transport to achieve a high-rate capability. Moreover, the evenly distributed N dopants on the NGM can guide the uniform nucleation of Li so that to inhibit dendrite growth. As a result, the composite NGM@Li anode shows satisfactory electrochemical performances for Li-S batteries, including a high capacity of 600 mAh g-1 after 300 cycles at 1 C and a rate capacity of 438 mAh g-1 at 3 C. This work provides a new avenue for the fabrication of graphene-based hosts with large areal capacity and high-rate capability for Li metal batteries.

Investigation of the operation characteristics and optimization of an alkaline water electrolysis system at high temperature and a high current density

Increasing the operating temperature of water electrolysis is an effective way to improve its performance. When the available region of the operating current density is extended, the stack can generate an increased amount of hydrogen. This can directly contribute to green hydrogen being highly competitive compared to other kinds of hydrogen. In this study, numerical analysis was conducted to investigate and optimize the operational characteristics of alkaline water electrolysis (AWE) under high temperature and high current density conditions. The numerical model of the AWE developed in our previous study has been upgraded by considering the crossover of hydrogen gas through the membrane to more accurately determine the Faraday efficiency of hydrogen production and the available safe operating range. Simulation results show that saturated vapor generation significantly affected the performance of both stack and system components in high-temperature environments. Therefore, pressurization is important to ensure the high efficiency of high-temperature water electrolysis, but it must be appropriately adjusted in consideration of gas crossover. In this study, the highest efficiency of 78.52% was captured at 120 °C and 10 bar for 1 A/cm2 operation.

Growth of mesoporous carbon supported (bimetallic) phosphides derived from Prussian blue for supercapacitors

In the context of supercapacitor energy storage, maintaining high cycle stability while enhancing energy density and coulomb efficiency is crucial. In this investigation, NiCo Prussian blue analogue (PBA) electrode materials were synthesized using the coprecipitation method, and subsequently modified via sulfurization and phosphating to obtain oxides (PBAO), sulfides (PBAS) and phosphides (PBAP) derived from Prussian blue cubes. The microphysical structure of PBA was engineered to enhance conductivity and electrochemical performance, with an in-depth exploration of the effects of sulfurization and phosphating. Additionally, mesoporous carbon (SAC) was doped into the previously prepared PBA, leading to the successful preparation of [email protected] electrode material with exceptional electrochemical performance. By utilizing electrochemical testing and various characterization techniques, the underlying sources of the observed performance differences were analyzed both experimentally and through electrochemical mechanisms. Furthermore, the addition of 0.01 M potassium ferricyanide to the 3 M KOH electrolyte significantly improved the coulomb efficiency of the material under the condition of high current density and long cycle time. Finally, an asymmetric supercapacitor (ASC) was constructed using industrial activated carbon as the negative electrode with the prepared [email protected] electrode material, and its electrochemical performance was evaluated to explore the practical application potential and prospects of this material.

Interlayer expanded SnS/N-doped carbon/SnS ultra-thin composite driven from layered tin chalcogenides as advanced anode for lithium and sodium ion battery

The unique 2D-layered structure of tin (II) sulfide (SnS) compounds has led to the emergence of strong intensities, showcasing their significant potential in lithium (LIBs) and sodium (SIBs) ion batteries. However, the commercialization process of SnS compounds remain hindered due to the poor cycle stability caused by its substantial volume expansion during cycling in battery applications. In this study, a simple and scalable synthesis of ultra-thin composite with a well-connected structure SnS/N-doped carbon/SnS (SnS/NC/SnS) is reported. The structure is directly derived from layered tin chalcogenides (A2Sn3S7·xH2O, where A represents an organic cation). Within this configuration, SnS nanosheets are decorated on the N-doped carbon material. The composite exhibits an expanded layer of 9.7 Å, enabling rapid movement of Na+ ions (approximately 7 times the diffusion coefficient of bulk SnS). This expansion also aids in accommodating volume changes during the discharging and charging processes. Concurrently, theoretical calculations demonstrate that the structure maintains a relatively stable state at the interlayer spacing mentioned. The SnS/NC/SnS composite material exhibited significant potential for application in both SIBs and LIBs. In SIBs, it demonstrated excellent long-term cyclic stability, maintaining a capacity of 190 mA h g−1 even under high current density conditions of 2.5 A g−1 after 300 cycles. In LIBs, it exhibit a superior discharge capacity of 990 mA h g−1 and retains 94.1 % of its capacity after 150 cycles at 0.2 A g−1. Notably, this synthesis method is versatile, as the interlayer spacing can be adjusted by varying the type of organic cations used in the process.

High current density charging of zinc-air flow batteries: Investigating the impact of flow rate and current density on zinc electrodeposition

Rechargeable zinc-based batteries (RZABs) show much promise over a wide range of applications due to their scalability, safety, and low cost. However, achieving stable and uniform zinc electrodeposition, particularly at high current densities, remains a significant challenge. Herein, the mechanism of charging zinc-air flow batteries under high current density conditions is investigated in detail. Through a combination of experimental and computational methods, both the individual and combined effects of current density and electrolyte flow rate on zinc electrodeposition are studied. Critical aspects of zinc electrodeposition, including ion concentration gradients, overpotential, mass transfer impedance, and gas evolution are scrutinized. Findings demonstrate that flow velocity profoundly affects current density regulation and mass transfer, while bubble formation at high current densities has implications for induced overpotential and overall charging performance. The surface morphology of electrodeposited zinc, as well as the formation and motion of bubbles, are evaluated using both in-situ and ex-situ microscopic imaging techniques. Optimal uniformity of zinc deposition is achieved by combining a current density of 60 mA cm−2 with a flow rate of 0.021 m s−1. Applying these conditions to a zinc-air battery results in excellent durability, maintaining commendable performance throughout 78 h of charge/discharge cycling. This research provides valuable insights into the correlation between operating parameters and surface properties of zinc electrodeposition, thus supporting the development of high-performance rechargeable zinc-based energy storage devices incorporating flow systems.