Electrolyte Distribution Research Articles

Influence of Electrolyte Saturation on the Performance of Li-O2 Batteries.

Electrolyte saturation can strongly affect the Li-O2 battery performance. However, it is unclear to what extent saturation reduction will impact the battery capacity. In this study, we investigated the influence of electrolyte saturation and distribution within a porous positive electrode on the deep discharge-charge capacities and cycling stability. The study used both models and experiments to investigate the change of electrolyte distribution, double-layer capacitance, ohmic resistance, and O2 concentration in the positive electrode at different electrolyte saturations. Results revealed that electrodes with 60% electrolyte saturation achieved almost the same maximum discharge (6.38 vs 6.76 mAh/cm2) and charge (5.52 vs 5.65 mAh/cm2) capacities with fully saturated electrodes. The partially wet positive electrode (40% saturation) obtained more cycles than the electrode with 100% saturation before the discharge capacity dropped below the cutoff point. However, the electrode with 40% saturation had a low average charging efficiency of 88.76%, whereas the fully saturated electrode obtained 98.96% charging efficiency. Moreover, the fully wet positive electrode had the lowest overpotential during cycling (1.26-1.39 V). The measured electrochemically active surface areas showed that even 40% saturation could sufficiently wet the positive electrode surface and obtain a double-layer capacitance (18.12 mF) similar to that with 100% saturation (20.4 mF). Furthermore, a considerable increase in O2 concentration at wetted surface areas was observed for the electrolyte saturation of less than 60% due to the significantly higher O2 diffusivity in the gas phase.

Correlating Catalyst Growth with Liquid Water Distribution in Polymer Electrolyte Fuel Cells.

This study investigates the impact of liquid water distribution in a polymer electrolyte fuel cell (PEFC) on the spatially heterogeneous platinum (Pt) catalyst degradation. The membrane electrode assemblies (MEAs) are aged using accelerated stress tests (ASTs) in varied cathode gas environments (N2 and air) to instigate Pt catalyst degradation. The study employs high-resolution neutron imaging and synchrotron micro-X-ray diffraction (micro-XRD) to map liquid water distribution and Pt particle size, respectively. Neutron radiographs reveal liquid water accumulation primarily within the diffusion media, especially under flow field lands, due to thermal resistance differences between channels and lands. Aged MEAs exhibit increased water retention, likely due to increased hydrophilicity of the diffusion media with aging. Synchrotron micro-XRD maps unveil significant heterogeneity in Pt particle size distribution in the aged MEAs, correlated with preferential liquid water accumulation under flow field lands. This study highlights the critical role of flow field design and water distribution in catalyst degradation, underscoring the need for innovative strategies to enhance fuel cell durability and performance.

Evaluation of Postoperative Electrolyte Imbalance of Oral Squamous Cell Carcinoma Patients: A Study in a Tertiary Level Hospital

This cross-sectional observational study was performed to evaluate the post-operative electrolyte imbalance in oral squamous cell Carcinoma patients, and it was conducted at the Department of Oral & Maxillofacial Surgery in Dhaka Dental College & Hospital, Dhaka, Bangladesh during June 2022 to June 2023. A total of 100 patients who were clinically and histo-pathologically diagnosed as OSCC patients were enrolled in this study. The collected data were edited, coded processed for computer data entry. The data were analyzed using Statistical Package for Social Sciences (SPSS) software, version-23.0. Descriptive analysis was performed and the results were presented as tables and graphs. Unpaired t tests, Chi-square, Spearman’s rho correlation tests were performed to compare the mean and ratio correlation of the study variables where P<0.05 with 95%CI. The ethical clearance of this study was obtained from the Ethics Committee of Department of Oral & Maxillofacial Surgery in Dhaka Dental College & Hospital, Dhaka, Bangladesh. A total of 100 oral squamous cell carcinoma (OSCS) patients were enrolled in this study. The mean age of the patients was 56.63 ± 9.54 years. The mean BMI of the patients was 18.20 ± 0.60 kg/m2. The majority of the patients were male and it was 54% while female was 46%. 64% patients belonged to lower socio-economic class. 52% patients had the habit of betel nut which was the highest while 39 % had the habit of betel nut with tobacco. The majority, 32% of patients had Stage-I. The mean surgery duration was 5.45± 0:91 hours and 7.2±: 0:15 minutes. The mean blood required for the surgery 1.44±0.68 units. According to the distribution of the post-operative variations of electrolyte imbalances, Sodium (Na+) was observed, hypo 25(25%) and hyper0(0%) on day-1 and hypo 31(31%), and hyper 4(4%) was observed on day 3 and followed by Potassium (K+) hypo 5(5%) and hyper 2(2%) on day- 1 and hypo 7(7%) and, hyper2(25) on day- 3. In comparison of ratio between hypo and hyper of day1 and day-3, showed statistically significant relationship observed (p<0.05). According to postoperative electrolyte distribution, on day-1, mean Sodium (Na+) was observed 136.68±2.69 mmol/L whereas on day-3, mean Sodium (Na+) was observed 133.81±4.21 mmol/Land followed by on day-1 mean Potassium (K+),3.86±0.46mmol/L, day-3, mean Potassium (K+),3.74 ±0.45 mmol/L on day-1. Among the postoperative electrolyte, except, Potassium (K+), all were observed statistically significant (P<0.05). In conclusion, hypocalcaemia, hyponatremia, and hypomagnesaemia are the relatively common after maxillofacial surgeries. Beside this BMI could affect electrolyte abnormalities after maxillofacial surgery.

Redox flow battery:Flow field design based on bionic mechanism with different obstructions

All-vanadium redox flow batteries (VRFBs) are pivotal for achieving large-scale, long-term energy storage. A critical factor in the overall performance of VRFBs is the design of the flow field. Drawing inspiration from biomimetic leaf veins, this study proposes three flow fields incorporating differently shaped obstacles in the main flow channel. These designs aim to enhance the electrolyte diversion into branches, achieving a more uniform electrolyte distribution. Among these, the structure featuring circular obstacles demonstrated superior performance, exhibiting the lowest charging voltage and the highest discharging voltage. It also achieved the highest concentration uniformity of the active species (0.903). In comparison, at the flow rate of 3ml/s and the current density of 40mA cm−2, the efficiency based on pump power saw a maximum increase of 1.7 % and the efficiency based on output power experienced a maximum improvement of 2.5 %. This work offers a new direction in studying biomimetic flow field design and holds considerable potential for practical engineering applications.

Weakened functional group activity enables the uniform distribution of the gel electrolyte to achieve the high-performance of Li-ion batteries

Electrolyte gelation is considered to be one of the main routes to solve the safety problem of liquid electrolytes. However, the distribution of gel polymer electrolyte (GPE) on the surface of electrodes and the mechanism of their effect on the performance of battery are still unknown. Here, methyl methacrylate (MMA) containing methyl (-CH3) and methyl-2-cyanoacrylate (MCA) containing cyanide (-CN) are employed as representative monomers to explore the relationship between gel distribution and battery performance. Due to the stronger electron-withdrawing properties, PMCA gel has shorter chain length and greater shrinkage, showing many cracks on the electrode surface, while PMMA gel can evenly cover the surfaces of electrodes. As a result, the capacity retention rate of 1.4 Ah NCM811/Gr pouch cells with PMMA is 93.5% for 500 cycles at 25 °C and 91.5% for 600 cycles at 60 °C, which these of the cells with PMCA are 58.8% for 266 cycles at 25 °C and 69.1% for 327 cycles at 60 °C. XPS analysis of the electrode sheets before and after cycling reveal that the PMCA-electrode has a large number of rzero valent lithium element precipitation, whereas the PMMA-electrode has the more stable interface film. This study indicates that the uniform distribution of gel electrolyte with -CH3 functional group on the electrode surface can improve the electrochemical performance of NCM811/Gr battery, which has the guiding significance.

An Analytical Model for Predicting the Rate Performance of Battery Cells Under Mixed Kinetic Control

The prediction of battery performance conventionally relies on resource-intensive numerical simulations based on the porous electrode theory. For computational speedup, simplified physics-based models have proven attractive as they still capture the underlying reaction mechanisms to a certain degree. In this class of models, physical complexity is usually reduced by assuming a single rate-limiting reaction. For example, the single particle model describes battery cells limited only by the solid diffusion pathway [1]. On the flipside, our previous analytical model exploited inefficiency of electrolyte transport, particularly in thick electrodes [2]. With advancement in both electrode and electrolyte technologies, however, it becomes challenging for these models to handle more realistic batteries.In this work, we propose an improved physics-based analytical model that enables mixed control of both kinetic processes, reflecting both salt depletion and particle size effect. An extension to our uniform reaction (UR) model, the new model uses salt distribution in electrolyte to probe the accessible lithium in the electrode level. The added solid diffusion module calculates the equilibrium potential at particle surface, lithium concentration at particle surface (Cs), and in turn the particle-level depth of discharge. We refer to the model as the URCs model, recognizing its two components. The model features higher tunability as it now accepts function-valued electrode and electrolyte properties. It also allows for prediction of discharge voltage curves and energy output of the cell.The model is compared with numerical simulation over a wide range of cell parameters. It shows good agreement with simulated results in rate performance test, specific energy output test, and discharge voltage curves. Better alignment is observed for the NMC/Li half cell than the NMC/Gr full cell, likely due to mixed reaction type in the graphite anode. Figure 1 shows the comparison of voltage curves across various C rates for a half cell with 70um NMC electrode and particles of 4um radius. Additionally, the cells are optimized for their specific capacity against electrode thickness and porosity. The optimal parameters predicted by the model lie closely to the global optimum from numerical simulation. Figure 2 shows the optimization results for a full cell with particles of 4um radius, overlaid on contour lines generated from the URCs model.The model offers a speed up of over 500 times compared with state-of-art P2D solvers [3]. Furthermore, its compatibility with gradient-based optimization algorithms opens possibilities for more efficient global optimization schemes, in which the number of function calls can be reduced. The high efficiency and the analytical nature of the URCs model render it a powerful tool for both on-board applications and battery cell design.[1] Doyle, M. and Newman, J., 1997. Analysis of capacity–rate data for lithium batteries using simplified models of the discharge process. Journal of Applied Electrochemistry, 27, pp.846-856.[2] Wang, F. and Tang, M., 2020. A quantitative analytical model for predicting and optimizing the rate performance of battery cells. Cell Reports Physical Science, 1(9).[3] Sulzer, V., Marquis, S.G., Timms, R., Robinson, M. and Chapman, S.J., 2021. Python battery mathematical modelling (PyBaMM). Journal of Open Research Software, 9(1). Figure 1

(Invited) Operando Visualization of the Electrolyte Distribution in Vanadium Redox Flow Electrodes

Electrolyte transport losses are among the main factors that limit the performance of Vanadium Redox Flow Batteries (VRFBs)1. The electrolyte must percolate into the electrode and reach the reaction sites with minimum resistance to reduce such losses. The optimized electrolyte flow ensures that the reactants and products are transported to and away from the reaction sites freely and decreases the pumping losses of the electrochemical cell, increasing the overall efficiency of the battery system.The electrolyte distribution in a porous electrode is crucial for the stability and performance of the electrode. The presence of gas bubbles in the electrode reduces the electrochemically active surface, resulting in cell potential fluctuations. In addition, the gas bubbles cause poor contact between the electrolyte and the electrode, and the ionic conductivity could be locally blocked2. These effects lead to inhomogeneous potential distribution (spikes), accelerating the electrode material's corrosion. Gas bubbles are very common in VRFBs, and they result from parasitic side reactions, such as carbon corrosion, hydrogen evolution (HER), or incomplete electrode wetting3.Synchrotron X-ray imaging is a powerful tool for tracking these bubbles in porous carbon materials. We have designed an experimental setup resembling an operating VRFB cell to image the flow through the porous carbon electrode. With its modular structure, the setup offers excellent flexibility to evaluate different designs and operational aspects of VRFBs4, 5. The findings of our investigations over the years will be discussed in this presentation. References J. Kim and H. Park, Journal of Power Sources, 2022, 545, 231904. K. Krause, C. Lee, J. K. Lee, K. F. Fahy, H. W. Shafaque, P. J. Kim, P. Shrestha and A. Bazylak, ACS Sustainable Chemistry & Engineering, 2021, 9, 5570-5579. M.-A. Goulet, M. Skyllas-Kazacos and E. Kjeang, Carbon, 2016, 101, 390-398. L. Eifert, N. Bevilacqua, K. Köble, K. Fahy, L. Xiao, M. Li, K. Duan, A. Bazylak, P.-C. Sui and R. Zeis, ChemSusChem, 2020, 13, 3154-3165. K. Köble, L. Eifert, N. Bevilacqua, K. F. Fahy, A. Bazylak and R. Zeis, Journal of Power Sources, 2021, 492, 229660. Figure 1

Insights Toward Thermal Stability and Electrolyte Distribution: A Hybrid Metrology Approach

Gas evolution in Li and Na ion batteries is a key problem as it is a sign of electrode degradation and electrolyte reduction. Gas evolution is caused by breakdown of electrolyte solvents and can release flammable gases leading to thermal runaway. As new and more stable electrodes, electrolyte, or electrolyte additives are implemented, it is crucial to monitor their performance and ensure thermal safety. Covalent Metrology is an analytical service lab based in Sunnyvale CA that serves as an extension of your battery R&D team. First, I will describe Covalent Metrology’s expertise, capabilities, and flexible workflows. I will then highlight some well-established analytical methods, such as GCMS and NMR to characterize volatile and non-volatile breakdown products of the electrolyte. Lastly, I will discuss the use of Scanning Acoustic Microscopy (SAM) and Glow Discharge Optical Emission Spectroscopy (GD-OES) to investigate the spatial distribution of electrolyte in a battery. We believe this hybrid metrology approach can provide important feedback toward developing better batteries more safely.

Measuring the Electrolyte Distribution in Silver Gas Diffusion Electrodes during CO2 Electroreduction Using Operando Synchrotron Tomography

Electrochemical CO2 reduction (eCO2R) has emerged as a promising technology to support the shift away from fossil fuels in the chemical industry. When coupled with renewable energies it allows for an overall carbon-negative process, while enabling CO2 as a carbon source for the production of commodity chemicals. Efficient eCO2R requires gas diffusion electrodes (GDEs) that provide a large wetted surface area inside the porous system, while also preserving gaseous diffusion pathways for CO2 mass transport through their hydrophobicity. Under the high cathodic overpotential in eCO2R, electrowetting diminishes the hydrophobicity of the GDE and can lead to excessive flooding of the porous system [1]. This severely hinders the CO2 mass transport and thus gives rise to the competing hydrogen evolution reaction (HER), lowering the Faradaic efficiency of the process. Therefore, understanding the flooding behavior of GDEs is of major interest for further development of the process.Mathematic models can be applied here to describe the flooding state under the influence of electrowetting and elucidate its influence on the gas transport through the GDE. The validation of such models requires direct experimental measurements of the electrolyte saturation during eCO2R, which can be accomplished with the use of synchrotron radiation [2].In this work, experimental results for the direct measurement of the electrolyte saturation during eCO2R in sprayed silver GDEs are presented. In a first, these measurements were obtained in operando synchrotron tomography experiments, utilizing a high beam energy to penetrate through the 3 mm diameter GDE in the in-plane direction. The results indicate a higher beam absorption towards the gas side of the GDE, as well as higher absorption at increased current density. Key to the interpretation of these results is the disentanglement of the effects of concentration increase due to migration in the electric field and the actual increase in electrolyte saturation. The experimental results are used to validate a continuum model for a sprayed silver GDE in eCO2R which includes the effect of electrowetting on flooding behavior by introducing capillary pressure – saturation and contact angle – potential correlations [3]. A good agreement between model and tomography results is reached, showing an interplay between concentration increase and flooding effects.[1] Bienen, F., Paulisch, M. C., Mager, T., Osiewacz, J., Nazari, M., Osenberg, M., Ellendorff, B., Turek, T., Nieken, U., Manke, I., & Friedrich, K. A., Investigating the electrowetting of silver‐based gas‐diffusion electrodes during oxygen reduction reaction with electrochemical and optical methods. Electrochemical Science Advances (2022) e2100158.[2] Hoffmann, H., Paulisch, M. C., Gebhard, M., Osiewacz, J., Kutter, M., Hilger, A., Arlt, T., Kardjilov, N., Ellendorff, B., Beckmann, F., Markötter, H., Luik, M., Turek, T., Manke, I., & Roth, C., Development of a Modular Operando Cell for X-ray Imaging of Strongly Absorbing Silver-Based Gas Diffusion Electrodes. Journal of The Electrochemical Society 169 (2022) 044508.[3] Osiewacz, J., Löffelholz, M., Turek, T., Modeling the Influence of Electrolyte Distribution in Silver Gas Diffusion Electrodes for CO2 Electroreduction. ECS Meeting s 01 (2023) 1727. Figure 1

Addressing Mass Conservation in Two-Dimensional Modeling of Lithium Metal Batteries with Electrochemically Plated/Stripped Interfaces

Several previous studies have aimed to develop mathematical models based on the moving boundary approach for predicting changes in lithium morphology during the cycling of lithium metal batteries under different operating conditions. These modeling frameworks play a crucial role in enhancing our fundamental understanding of the transport and reaction mechanisms and guide experimentalists in developing safer and more efficient lithium metal anodes. In this work, using a simple two-dimensional model for the lithium metal battery, we aim to bring attention to the bulk convection in the liquid electrolytes induced by the movement of the lithium metal surface modeled as a moving boundary. The back-and-forth motion of the lithium metal surface during the plating and stripping of lithium introduces a weak fluid motion in the liquid electrolyte that should be incorporated in the model equations and corresponding boundary conditions (Figure 1). The results for the electrochemical signatures and morphology evolution thus obtained by solving a coupled fluid model are compared with the case where the velocity distribution in the liquid electrolyte is ignored. This work extends our previously reported perspective on the convective flux correction to rectify the mass conservation failures at moving boundaries in one-dimensional models to two dimensions. This careful implementation of the correct boundary conditions ensures the mass conservation of lithium in two-dimensional simulations for predicting the morphological evolution of lithium metal electrodes over cycles. These revised battery models with accurate mass and charge conservation are crucial for predicting the performance of the battery over cycles. Additionally, these relative fluxes at the moving and fixed boundaries are sometimes ignored by assuming a bulk concentration condition at the far end, especially at the cathode/separator interface. While it may not affect overpotential signatures at the anode, it leads to mass conservation issues with implications for the accuracy of cycling simulations. Thus, with the help of a two-dimensional electro-convection model, this study addresses the role of bulk convection in liquid electrolytes and the importance of ensuring mass conservation in lithium metal battery models.

Operando Visualization of Redox Flow Batteries Using Fluorescence Spectroscopy with Alizarin Red S Electrolyte

Redox flow batteries (RFBs) charge and discharge by transferring electrons between two pairs of redox species separated by a proton exchange membrane. Unlike traditional batteries that store energy in redox-active materials within an enclosed cell, RFBs store energy in liquid electrolytes housed in external reservoirs1. These electrolytes are pumped through the cell, enabling redox reactions on the surface of electrodes. The energy storage capacity of RFBs is determined by the concentration of the active species and the size of the reservoirs, making them a promising technology for large-scale energy storage applications2. While RFBs possess advantages such as long lifetime, flexible design for battery capacity and power, and rapid response, they suffer from drawbacks like low energy density, power density, and energy efficiency3. Efforts to address these issues have primarily focused on modifications to the electrode materials or the flow field4 , 5. However, evidence supporting performance enhancements often relies on global parameters such as energy efficiency, energy density, and voltage drop, lacking detailed mechanistic and microscopic studies. Real-time observation of the electrode-electrolyte interface during redox reactions and the transport of redox species in the flow field holds the potential to significantly contribute to understanding the electrode structure and mass transport phenomena in RFBs6. This understanding, in turn, facilitates prediction and purposeful enhancement of battery performance by developing desirable structures for both electrode and flow fields. Microscopy, particularly confocal microscopy, serves as a powerful tool for observing microscopic structures. Confocal microscopes yield sharper images with higher resolution than widefield microscopy, enabling rapid acquisition of high-resolution images.In this study, we employed a confocal laser scanning microscope for operando visualization of RFBs. We designed a transparent framework for the battery, allowing light to pass through, and covered its surface with a glass cover to visualize the porous carbon electrode. We selected a fluorescent redox-active species, Alizarin Red S to enable visualization using fluorescence spectroscopy. Leveraging its unique fluorescence properties, we established a correlation between fluorescence intensity and the state of charge. This innovative approach enables us to observe the distribution of electrolytes, the dynamics of redox reactions on the electrode surface (with fast speed of imaging ＜0.2s), the mass transfer behavior of the electrolyte on the electrode surface, and the uniformity of electrolyte flow in the flow field, including areas of stagnation or recirculation. Zhang, J. et al. An all-aqueous redox flow battery with unprecedented energy density. Energy Environ. Sci. 11, 2010–2015 (2018).Rubio-Garcia, J., Kucernak, A. & Charleson, A. Direct visualization of reactant transport in forced convection electrochemical cells and its application to redox flow batteries. Electrochem. commun. 93, 128–132 (2018).Tolmachev, Y. V. Flow Batteries From 1879 To 2022 And Beyond. Qeios 1–79 (2023).Wang, R. et al. Gradient-distributed NiCo2O4 nanorod electrode for redox flow batteries: Establishing the ordered reaction interface to meet the anisotropic mass transport. Appl. Catal. B Environ. 332, 122773 (2023).Kumar, S. & Jayanti, S. Effect of flow field on the performance of an all-vanadium redox flow battery. J. Power Sources 307, 782–787 (2016).Wong, A. A., Rubinstein, S. M. & Aziz, M. J. Direct visualization of electrochemical reactions and heterogeneous transport within porous electrodes in operando by fluorescence microscopy. Cell Reports Phys. Sci. 2, 100388 (2021).

Design and Characterization of Porous Electrodes for Redox Flow Batteries

The commercialization of redox flow batteries as large-scale energy storage systems depends on lowering the capital and operating costs which depend on achieving maximum power density. Optimizing electrode design parameters and flow field-electrode combinations is critical to minimize losses and maximize active material utilization. Modeling the current drawn from an electrode offers a means to interpret electrode structure based on the electrolyte distribution driven by internal design. However, direct imaging methods (such as in-situ fluorescence microscopy and X-ray tomography) and numerical methods for current to potential prediction (3D Lattice Boltzmann modeling) are specific to individual electrode structures and possess limited predictable value to obtain an ideal electrode design. In this work, we present an electrode impedance spectroscopy (EIS)-based approach for determining electrode design parameters and devise a general method for determination of effective diffusion layer thickness. Using COMSOL modeling we verified the development of slug flow behavior in highly randomized porous electrode systems, indicating that the mass transport properties are dictated by inter-fiber distance. An analytical model to predict current as a function of applied overpotential is presented which allows us to vary structural parameters of the porous electrodes to study the influence of surface area, inter-fiber distances and diffusion layer thickness on the RFB performance. This model is a highly flexible tool applicable to any electrochemical system using a porous electrode and identifies critical variables affecting electrode design to characterize optimal electrode structure to minimize mass transport losses and optimize operational parameters.

The effect of pin-type flow field plate design on the current distribution in a H2-fed polymer electrolyte fuel cell

The flow field plate (FFP) design is a key factor for enhancing the electrochemical performance of Polymer Electrolyte Fuel Cells (PEFCs) through optimal reactants’ distribution, low-pressure drops, and efficient water removal. The effect of geometrical features of the pin-type FFP design on the electrochemical performance of a 48 cm2 H2-fed Fuel Cell (FC) was assessed through polarization curves recording and current and temperature distribution maps along the electrode active area. The study was performed by changing excess air stoichiometry and cathode relative humidity (RH). Low-pressure drops were measured using pin-type FFPs; regardless of geometrical features, they were one order of magnitude lower than those of a single-channel serpentine FFP. Channel width and number of pins greatly influenced the current distribution along the active area and, consequently, the electrochemical performance of FCs. In particular, the best electrochemical performance was reached at air stoichiometry 4 and cathode RH = 100 % by using FFP with the highest coverage factor (65 %) and the lowest channel width (1 mm). Current distribution maps demonstrated that this FFP geometry led to an almost homogeneous current distribution and efficient water removal also at high current density values. On the contrary, low coverage factor (45 %) and high channel width led to worse electrochemical performances due to an uneven reactants distribution and an inefficient water removal, causing cell flooding.

Machine-learning assisted analysis on coupled fluid-dynamics and electrochemical processes in interdigitated channel for iron-chromium flow batteries

This study explores the impact of interdigitated flow channel spacing on electrolyte distribution and flow velocity in porous electrodes, thereby affecting pump consumption and system efficiency. Utilizing a 3D electrochemical flow-coupled model, the research investigates the electrochemical performance and energy efficiency across various channel spacings, specific flow rates, and current densities. It elucidates the mechanisms by which interdigitated channel spacing influences battery performance. Through controlled trial-and-error, the optimal spacing for flow channels in Iron-Chromium Redox Flow Batteries (ICRFBs) was determined to be 4 mm. At a current density of 140 mA/cm2, the voltage efficiency reached 86.3 %, and the pump-based voltage efficiency achieved 85.9 %. To quickly and efficiently explore the impact of each individual parameter on battery efficiency and identify the optimal operating conditions, this study further developed a multi-task machine learning (ML) model. Initially trained on simulation data, the model achieved high predictive accuracy (R2 > 0.88) and effectively linked the interdigitated flow field design of ICRFBs with current density, specific flow rate, and channel spacing. The ML model was then validated through further investigation to ensure its accuracy and to achieve optimum performance efficiency as recommended by the model. This integrated approach offers a comprehensive understanding of RFBs performance under varying conditions, driving advancements in RFBs technology.

Flow field design and simulation in electrochemical machining for closed integral components

Using closed integral components (CICs) not only simplifies the structure and reduces the weight of aeroengine components but also reduces the number of parts and improves overall engine performance. However, there are currently few publicly available reports on the electrochemical machining (ECM) of CIC blades. The key factor influencing the stability of ECM is the flow-field, which is difficult to design for a CIC because its two sides are closed, thereby limiting the direction of electrolyte flow into the processing area. To achieve the ECM of CICs, flow modes involving either lateral or composite liquid supply (LLS or CLS) are proposed, followed by flow-field and cathode-deformation simulation analyses. The simulation results show that the CLS flow-field is more reasonably designed and its electrolyte distribution is more uniform. The maximum cathode deformation under CLS flow-field is only ca. 15 µm. The experiments were conducted to improve the efficiency of CIC ECM and compare the LLS and CLS flow-fields. During processing, the feed rate was increased from 0.2 min/mm to 0.45 min/mm, and the surface roughness (Ra) decreased from ca. 1.29 µm to ca. 0.37 µm. The experiments show that the CLS flow-field offers higher processing efficiency and better surface quality.

Numerical simulation of all-vanadium redox flow battery performance optimization based on flow channel cross-sectional shape design

This paper numerically investigates optimizing trapezoidal flow channel cross-sectional shapes to improve all‑vanadium redox flow battery performance. A 3D steady-state multiphysics model coupling fluid dynamics, mass transfer, and electrochemistry was developed in COMSOL. Eight trapezoidal and one rectangular cross-section serpentine flow fields were simulated at varied flow rates. Results showed the TCS-T06 design reduced pressure drop by 12 % and pump power by 12 % versus the RCS. The concentration distribution of VO2+ was also improved, enhancing mass transfer. At 60 mA/cm2, TCS-T06 achieved 0.9 % higher pump power-based voltage efficiency. The optimized trapezoidal cross-section was proven to minimize losses, improve electrolyte distribution, and enhance VRFB performance. This work provides guidance for optimizing trapezoidal flow channel cross-sections to improve VRFB performance via enhanced mass transfer and reduced pressure drop.

Failure of Lithium-Ion Batteries Accelerated by Gravity.

The safety concerns surrounding lithium-ion batteries (LIBs) have garnered increasing attention due to their potential to endanger lives and incur significant financial losses. However, the origins of battery failures are diverse, presenting significant challenges in developing safety measures to mitigate accidental catastrophes. In this study, the aging mechanism of LiNi0.5Co0.2Mn0.3O2||graphite-based cylindrical 18,650 LIBs stored at room temperature for two years was investigated. It was found that an uneven distribution of electrolytes can be caused by gravity, leading to temperature variations within the battery. Specifically, it was observed that the temperature at the top of the battery was approximately -0.89 °C higher than at the bottom, correlating with an increase in partial internal resistance. Additionally, upon disassembly and analysis of spent batteries, the most significant damage to electrode materials at the top of the battery was observed. These findings suggest that gravity-induced electrolyte insufficiency exacerbates side reactions, particularly at the top of the battery. This study offers a unique perspective on the safety concerns associated with high-energy-density batteries in long-term and large-scale applications.

1,3,6-Hexanetricarbonitrile as electrolyte additive to inhibit sodium dendrites in sodium-metal batteries

Sodium-metal batteries (SMBs) offer substantial competitiveness owing to their wide elemental distribution and high specific capacity. However, SMBs face safety issues such as unstable properties of the Solid Electrolyte Interphase (SEI) layer due to irregular sodium dendrites. In this paper, we constructed a stable and uniform SEI layer by introducing the 1,3,6-Hexanetricarbonitrile (HTCN) electrolyte additive, replacing the conventional, insoluble nitrate. HTCN facilitates the generation of substances like Na3N with high electrical conductivity on the Na anode surface. This accelerates Na+ shuttling and provides high-flux nucleation sites. Molecular dynamics simulations were employed to elucidate the solvated structure of electrolyte and radial distribution of Na+ after HTCN addition. Moreover, in-situ optical microscopy revealed a stable and robust SEI layer, effectively inhibiting the disorderly growth of sodium dendrites. The superior cycling performance of the Na3V2(PO4)3 (NVP)/Na full cell further demonstrates the addition of HTCN.

Experimental investigation of electrochemical machining for involute internal spline using cathode working teeth sheet with circumferential vibration

Manufacturing internal splines with complex structures in high-hardness materials poses challenges in conventional machining processes. This paper introduced a new electrochemical machining (ECM) method using an assembled tool cathode with a cathode working teeth sheet with circumferential vibration for efficient and stable shaping of involute internal splines of intricate high-hardness components. A detailed design of the assembled tool cathode is presented, accompanied by flow field simulations analysing electrolyte distribution during circumferential vibration. A specific experimental system, fixture, and a used electrolyte filter module were constructed for spline ECM experiments. The results show that with the cathode feed rate of 2.7 mm/min, and the circumferential vibration frequency of 80 Hz, the involute internal spline profiles were successfully shaped with higher precision and efficiency with less appropriate allowance.

Evaluation of serum electrolyte abnormalities in type II diabetic patients presenting in Gulab Devi hospital, Lahore

Background: The hallmark of diabetes mellitus (DM) is hyperglycemia brought on by an absolute or relative insulin shortage. Globally, the prevalence of DM is a major cause for worry. The International Diabetes Federation estimates that 26.7% of Pakistan's adult population would have diabetes in 2022, totalling over 33,000,000 cases 1. Patients with diabetes are more likely to experience electrolyte imbalances, which may be caused by an imbalance in the distribution of electrolytes. Electrolytes play a vital role in the maintenance of blood acid-base balance, composition of body fluids, blood clotting, muscle and nerve conduction. Impaired electrolytes balance in diabetics may lead to micro and macrovascular complications. Aims and objectives: The objective of this study is to investigate disturbances in serum electrolytes including Sodium (Na+), Potassium (K+) and Chloride (Cl) in Type II diabetics. Methodology: This has been a descriptive cross-sectional study where random sampling technique was used. 3cc clotted blood samples of 100 Type II diabetic patients were collected from diabetic OPD and medicine wards of Gulab Devi Chest Hospital Lahore and processed in the Pathology lab of Gulab Devi Educational Complex. Results: Out of 100 samples of type II diabetic patients, there were 65 patients in which serum sodium levels were decreased. Serum potassium and serum chloride were slightly increased in some patients. Conclusion: In this study, serum sodium levels were significantly decreased in type II diabetic patients, while no significant alteration was observed in serum potassium and chloride levels. Serum electrolytes should be routinely measured in diabetics to prevent complications.