Stack Pressure Research Articles

Modeling and Measuring the Leaked-Air Rate into the Insulation Layer of a Single-Aisle Aircraft Cabin

Leaked air from an aircraft cabin into its envelope walls through cracks can lead to a large amount of moisture condensation on inner shell skins and in insulation layers. The leaked-air rate is subject to the stack pressure difference and the geometry of the cracks. So far, the impacts of the crack sizes and positions, and the flight conditions on the resulting leaked-air rate have been unclear. This investigation adopts validated computational fluid dynamics (CFD) to model leaked flow, pressure, and temperature distribution in a single-aisle aircraft cabin. Impacts of the flight cruising altitude, crack size and position, and flow blocker on the leaked-air rate were examined. In addition, measurements were conducted in a reduced-scale cabin mockup in an environmental chamber to mimic flight conditions. Obtained test data were adopted to validate CFD modeling. Results reveal that a higher cruising altitude of a flight results in greater leaked-air rate from the cabin to the envelope walls due to the larger temperature difference. The smaller the crack size was, the lower the leaked-air rate. In addition, more cracks farther away from the neutral plane lead to a greater leaked-air rate. A flow blocker in the middle of the insulation layer reduced the leaked-air rate by 34.5%.

Crack Healing Mechanism by Application of Stack Pressure to the Carbon-Based Composite Anode of an All-Solid-State Battery

Crack Healing Mechanism by Application of Stack Pressure to the Carbon-Based Composite Anode of an All-Solid-State Battery

Conformal Pressure and Fast-Charging Li-Ion Batteries

Batteries capable of extreme fast-charging (XFC) are a necessity for the deployment of electric vehicles. Material properties of electrodes and electrolytes along with cell parameters such as stack pressure and temperature have coupled, synergistic, and sometimes deleterious effects on fast-charging performance. We develop a new experimental testbed that allows precise and conformal application of electrode stack pressure. We focus on cell capacity degradation using single-layer pouch cells with graphite anodes, LiNi0.5Mn0.3Co0.2O2 (NMC532) cathodes, and carbonate-based electrolyte. In the tested range (10–125 psi), cells cycled at higher pressure show higher capacity and less capacity fading. Additionally, Li plating decreases with increasing pressure as observed with scanning electron microscopy (SEM) and optical imaging. While the loss of Li inventory from Li plating is the largest contributor to capacity fade, electrochemical and SEM examination of the NMC cathodes after XFC experiments show increased secondary particle damage at lower pressure. We infer that the better performance at higher pressure is due to more homogeneous reactions of active materials across the electrode and less polarization through the electrode thickness. Our study emphasizes the importance of electrode stack pressure in XFC batteries and highlights its subtle role in cell conditions.

Rate-dependent deformation of amorphous sulfide glass electrolytes for solid-state batteries

Sulfide glasses are emerging as potential electrolytes for solid-state batteries. The mechanical behavior of these materials can significantly impact cell performance, and it is thus imperative to understand their deformation and fracture mechanisms. Previous work mainly reports properties obtained under quasi-static loading conditions, but very little is known about deformation under dynamic conditions. The current investigation shows that the sulfide glass mechanical behavior is dominated by viscoplasticity, differing substantially from polycrystalline oxide and sulfide solid electrolytes. Finite element modeling indicates that the sulfide glass stiffness is high enough to maintain good contact with softer lithium metal electrodes under moderate stack pressures. The observed viscoplasticity also implies that battery operating conditions will play an important role in electro-chemo-mechanical processes that are associated with dendritic lithium penetration. In general, the rate-dependent mechanical behavior of the sulfide glass electrolytes documented here offers a new dimension for designing next-generation all-solid-state batteries.

Comparison of Pretreatment Methods for Salinity Gradient Power Generation Using Reverse Electrodialysis (RED) Systems.

With the increasing concern about climate change and the energy crisis, the use of reverse electrodialysis (RED) to utilize salinity gradient power (SGP) has drawn attention as one of the promising renewable energy sources. However, one of the critical issues in RED processes is membrane fouling and channel blockage, which lead to a decrease in the power density. Thus, this study aims to improve our understanding of SGP generation by using RED by investigating the effect of pretreatment on the RED performance. Experiments were conducted by using a laboratory-scale experimental setup for RED. The low-salinity and high-salinity feed solutions were brackish water reverse osmosis (BWRO) brine from a wastewater reclamation plant, and a NaCl solution simulating seawater desalination brine. Several pretreatments were applied to the RED process, such as cartridge filter (CF), microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), activated filter media (AFM), and granular activated carbon (GAC). The results indicate that the open-circuit voltage (OCV) and the power density were similar, except for in the NF pretreatment, which removed the dissolved ions to increase the net SGP. However, the pressure in the RED stack was significantly affected by the pretreatment types. The excitation–emission matrix (EEM) fluorescence spectroscopy and the parallel factor analysis (PARAFAC) quantified the organic compounds that are related to the stack pressure. These results suggest that the removal of both colloidal and organic matters by pretreatments is crucial for improving the RED performance by reducing the pressure that is increased in the RED stack.

Operating High‐Energy Lithium‐Metal Pouch Cells with Reduced Stack Pressure Through a Rational Lithium‐Host Design

AbstractTransitioning from a liquid electrolyte to an inorganic solid electrolyte offers a potential pathway to enable highly reversible lithium‐metal anodes. However, the solid‐electrolyte‐protected lithium‐metal anode suffers from poor interfacial ionic contacts and requires an impractically high stack pressure (>1.0 MPa) to maintain the interfacial contacts. It is demonstrated here that combining a hollow silver/carbon fiber scaffold and an inorganic/organic composite electrolyte enables a highly reversible lithium‐metal anode. Since the high surface area of the electrode provides intimate contact and the hollow structure of the electrode relieves the lithium plating‐induced stress, the electrode/electrolyte interface remains stable during cycling even under mild stack pressure. This unconventional structural design is validated in practical pouch cells assembled with the 3D lithium host containing a onefold excess of lithium and a high‐nickel cathode. At a mild stack pressure of 320 kPa, the pouch cell displays 83% capacity retention for 200 cycles. The work illustrates that combining a hollow electrode architecture and a robust solid electrolyte offers a practical pathway toward rechargeable lithium‐metal anodes.

A review of solar chimney for natural ventilation of residential and non-residential buildings

The requirement for passive cooling strategies in buildings has great attention in almost all countries, where hot temperatures are predominant throughout the year. The ventilation process is a crucial necessity for a healthy lifestyle and its significance is additionally highlighted through the contemporary universal outbreak of Covid-19. One of the promising applications for cooling residential buildings is the solar chimney (SC) that is particularly convenient for hot and humid climates. The solar chimney is a natural draught passive method that utilizes available solar energy to build up the stack pressure. The solar chimney participates in elevating the cooling and heating efficiency of residential/non-residential spaces. The present article introduces an overview of the operation and performance of the SC. Studying the potential design and operating parameters influencing the SC performance for natural ventilation (NV) compared to the electrical high-energy technologies to sustain the acceptable indoor climatic conditions is important. As well, the natural ventilation for harsh climate conditions using SC only is not applicable so the enhanced solar ventilation systems are studied. Combined enhanced cooling/heating energy systems based on the solar chimney are considered as an effective strategy towards low-energy consuming buildings.

Solid-state lithium battery cathodes operating at low pressures

<h2>Summary</h2> Many studies of solid-state battery cathodes employ high stack pressures and low current densities. In practice, cells operating at current densities in the mA cm⁻² range at stack pressures of a few MPa are required. Here, we show the influence of the composite cathode components LiNi_0.83Mn_0.06Co_0.11O₂, Li₃InCl₆, and carbon nanofibers, operating at 2-MPa stack pressure and find that the overall composite cathode capacity is determined primarily by the conductivity of the solid electrolyte. Higher conductivities reduce the mass of the solid electrolyte required to access a high capacity from the active material (high utilization), enabling higher active material loadings and higher overall capacities. Cycling between 2.6 and 4.2 V rather than 4.4 V reduces the LiNi_0.83Mn_0.06Co_0.11O₂ volume change from 6% to 2.5%, achieving 94% rather than 65% capacity retention after 50 cycles for a reduction in capacity of only 14%.

Pressure-induced interfacial contacts and the deformation in all solid-state Li-ion batteries

In this paper, we use a combination of computational models and experiments to study the effects of stack pressure on interfacial contacts and deformation of solid state electrolytes in an all solid state battery (ASSB). The induced strain distributions in the LiBH 4 –LiNH 2 based all solid-state battery are measured using a combination of in-situ optical microscopy and digital image correlation (DIC) techniques, while the contact strains and stresses are computed using analytical and computational finite element models. The results show that moderate pressure improves the interfacial contacts and battery electrochemical performance characteristics with low induced strains in the electrolyte, while high pressure induces large axial and shear strains that can cause failure by yielding or cracking phenomena, in addition to the degradation of electrochemical performance characteristics. The highest room temperature conductivity of 9 × 10 −5 Scm −1 was obtained at a stack pressure of 0.26 MPa. The implications of the results are discussed for the design and fabrication of robust all solid state batteries with improved performance characteristics. • In-situ strain mapping/computational modeling of contacts and deformation. • Pressure application improves electrode-electrolyte interfacial surface contacts. • Intermediate stack pressures improve ionic conductivity without cracking. • High stack pressures induce large axial/shear strains and cracking of the electrolyte.

The effect of aspect ratio on the mechanical behavior of Li metal in solid-state cells

The Li metal anode is necessary for solid-state batteries to dramatically exceed the energy density of state-of-the-art conventional Li-ion batteries. To enable the Li metal anode, the mechanical properties of Li metal under compression in a commercially relevant cell configuration must be determined. This work examines the compression creep behavior of Li metal coupled with a relevant model solid-state electrolyte (Li 6.5 La 3 Ta 0.5 Zr 1.5 O 12 ) and current collector (Ni) as a function of applied stress (1–10 MPa) and Li foil thickness (100–700 μm). At 1 MPa applied stress, the strain rate of all Li foil thicknesses under compression was almost four orders of magnitude lower than what is predicted from tensile creep tests. Steady-state creep behavior was observed for Li foil ≥350 μm at 5 MPa and ≥250 μm at 10 MPa. Conversely, sustained creep deformation was not observed for 100 and 150 μm Li foils at any applied stress. It is suggested that friction at the Li/LLZO and Li/Ni interfaces leads to the formation of hydrostatic stress that controls Li deformation at low aspect ratios. These results have implications for battery pack stack pressure requirements, particularly relating to void formation during stripping and Li metal filament penetration during plating. • Compressive creep measurements of Li metal foils in solid-state cell configuration. • Strain and strain rate decreased with decreasing Li foil thickness. • The strain rate of Li measured in compression was lower than predicted from tension. • Friction at Li interfaces prevents substantial creep deformation for thin Li foils.

Experimental visualization of leakage current in reverse electrodialysis and its effect on inorganic scaling

In both electrodialysis (ED) and reverse electrodialysis (RED), the leakage current flowing through the feed/drain channels and liquid connections of the stack causes efficiency losses. However, there have been few reports on the effect of leakage current on inorganic scaling, a fouling phenomenon that increases the stack pressure and decreases electric power. In large-scale RED systems with high stack voltages of several tens of volts, water electrolysis is inevitable despite the presence of redox couples, and the resulting increased pH caused by the water reduction reaction leads to severe inorganic scaling. Water dissociation in a bipolar membrane (BPM) can reduce the flux of hydroxide ions across the effective working area, which allows the lateral leakage current along the BPM surface to be visualized by a specific pattern of inorganic precipitates moving from the bottom to the top of the BPM surface. In addition, the change in the area occupied by inorganic precipitates was evaluated as a function of the internal resistance of the stack and the resistance of the distributor connecting the compartment and feed channel. The findings highlight the importance of proper stack design in minimizing leakage-current-related efficiency losses and inorganic/organic fouling in real large-scale RED and ED systems.

Thermodynamic Modeling and Performance Analysis of Vehicular High-Temperature Proton Exchange Membrane Fuel Cell System.

Since the high temperature proton exchange membrane fuel cells (HT-PEMFC) stack require a range of auxiliary equipments to maintain operating conditions, it is necessary to consider operation of related components in the design of HT-PEMFC systems. In this paper, a thermodynamic model of a vehicular HT-PEMFC system using phosphoric acid doped polybenzimidazole membrane is developed. The power distribution and exergy loss of each component are derived according to thermodynamic analysis, where the stack and heat exchanger are the two components with the greatest exergy loss. In addition, ecological functions and improvement potentials are proposed to evaluate the system performance better. On this basis, the effects of stack inlet temperature, pressure, and stoichiometric on system performance are analyzed. The results showed that the energy efficiency, exergy efficiency and net output power of the system achieved the maximum when the inlet gases temperature is 406.1 K. The system performance is better when the cathode inlet pressure is relatively low and the anode inlet pressure is relatively high. Moreover, the stoichiometry should be reduced to improve the system output performance on the basis of ensuring sufficient gases reaction in the stack.

Sulfide glass solid-state electrolyte separators for Li metal batteries: using an interlayer to increase rate performance and reduce stack pressure

A range of sulfide glass electrolyte compositions were found to be insoluble in ether-based solvents. A critical current density of 3 mA cm−2 was achieved with a 0.1 MPa stack pressure and a thin ether-based liquid electrolyte interlayer.

Impact of Graphite Materials on the Lifetime of NMC811/Graphite Pouch Cells: Part II. Long-Term Cycling, Stack Pressure Growth, Isothermal Microcalorimetry, and Lifetime Projection

Part II of this 2-part series examines the impact of competitive graphite materials on NMC811 pouch cell performance using Ultra-High Precision Coulometry (UHPC), isothermal microcalorimetry, and in-situ stack growth. A simple lifetime projection of the best NMC811/graphite cells as a function of operating temperature is made. We show that graphite choice greatly impacts fractional fade, while fractional charge endpoint capacity slippage was largely unchanged due to identical cathodes. We show that an increase in graphite 1st cycle efficiency due to limited redox-active sites—favourable for minimizing Li inventory loss—is concomitant with an increase in negative electrode charge transfer resistance. Further, we demonstrate that cells with competitive artificial graphites (AG) have a lower parasitic heat flow (∼0.060 mW A−1 h−1 at 40 oC) compared to cells with natural graphites (NG), and that the cells with the AGs had minimal stack thickness change with cycling. Finally, we model SEI growth for NMC811 cells limited to 4.06 V with the square-root time model, and project that the best NMC811/graphite cells here can have decades-long lifetimes at 20 –30 °C when Li plating is avoided. Such cells are excellent candidates for grid storage applications where energy density is less important compared to long lifetime.

Influence of external stack pressure on the performance of Li-S pouch cell

The lithium-sulfur (Li-S) cell system is promising to satisfy the increasing need for cost-efficient energy storage with high theoretical energies due to the enormous theoretical gravimetrical capacity and the abundance of sulfur. Furthermore, the technology readiness level of Li-S batteries increased steadily in recent years due to extensive research, as well as the number of reported prototype cells. However, an often ignored test parameter is the application of external pressure to the cell stack. In this study, the influence of external pressure on the performance of Li-S cells is investigated. Therefore, five-layered pouch cells with solvent-free processed cathodes are assembled. These cells are tested under lean electrolyte conditions (electrolyte to sulfur ratio of 4.5 µl mg(S)−1). To evaluate the influence of the used electrolyte system either the state-of-the-art 1,2-dimethoxyethane/1,3-dioxolane electrolyte or the sparing polysulfide solvating hexyl methyl ether/1,3-dioxolane electrolyte is deployed. The impact of pressure application is evaluated electrochemically as well as by post-mortem focused ion beam-scanning electron microscopy of the cycled electrodes. Moreover, a technique for infiltration of sulfur into the carbon host matrix is presented, discussed, and successfully implemented.

Effect of electrolyte anions on the cycle life of a polymer electrode in aqueous batteries

Redox polymers are a class of high-capacity, low-cost electrode materials for electrochemical energy storage, but the mechanisms governing their cycling stability are not well understood. Here we investigate the effect of anions on the longevity of a p-dopable polymer through comparing two aqueous zinc-based electrolytes. Galvanostatic cycling studies reveal the polymer has better capacity retention in the presence of triflate anions than that with sulfate anions. Based on electrode microstructural analysis and evolution profiles of the cell stacking pressure, the origin of capacity decay is ascribed to mechanical fractures induced by volume change of the polymer active materials during repeated cycling. The volume change of the polymer with the triflate anion is 61% less than that with the sulfate anion, resulting in fewer cracks in the electrodes. The difference is related to the different anion solvation structures—the triflate anion has fewer solvated water molecules compared with the sulfate anion, leading to smaller volume expansion. This work highlights that anions with low solvation degree are preferable for long-term cycling.

Mechanical Behavior and Dendrite Resistance of closo‐Hydroborate Solid Electrolyte (Adv. Mater. Interfaces 3/2022)

Closo-Hydroborate Solid Electrolyte The solid electrolyte Na4(CB11H12)2(B12H12) at the interface with Na anode is tested as a function of battery stack pressure and current density in article number 2101254 by Matteo Brighi, Fabrizio Murgia, and Radovan Černý. Employing two different polyanions allows tuning locally the electrochemical properties while preserving structural and chemical coherence. Image credit: Xavier Ravinet & Olivier Gaumer - University of Geneva.

Enhanced Room-Temperature Ionic Conductivity of NaCB11H12 via High-Energy Mechanical Milling.

The body-centered cubic (bcc) polymorph of NaCB11H12 has been stabilized at room temperature by high-energy mechanical milling. Temperature-dependent electrochemical impedance spectroscopy shows an optimum at 45-min milling time, leading to an rt conductivity of 4 mS cm-1. Mechanical milling suppresses an order-disorder phase transition in the investigated temperature range. Nevertheless, two main regimes can be identified, with two clearly distinct activation energies. Powder X-ray diffraction and 23Na solid-state NMR reveal two different Na+ environments, which are partially occupied, in the bcc polymorph. The increased number of available sodium sites w.r.t. ccp polymorph raises the configurational entropy of the bcc phase, contributing to a higher ionic conductivity. Mechanical treatment does not alter the oxidative stability of NaCB11H12. Electrochemical test on a symmetric cell (Na|NaCB11H12|Na) without control of the stack pressure provides a critical current density of 0.12 mA cm-2, able to fully charge/discharge a 120 mA h g-1 specific capacity positive electrode at the rate of C/2.

2021 F. M. Becket Fellowship – Summary Report Measuring Transient Electrochemistry of Lithium Metal Anodes under Varying External Stack Pressures

Lithium metal anodes are challenged by the inherent chemical and electrochemical reactivity of lithium metal, which is further exacerbated by non-uniform high surface area deposition. Recently, lithium difluoro(oxalato)borate (LiDFOB) salt coupled with a fluorinated solvent has been demonstrated to result in densely deposited lithium morphology along with high Coulombic efficiencies due to a stable solidelectrolyte-interphase. Along with other newly discovered electrolyte compositions for stable lithium deposition, these studies typically utilize high stack pressures and elevated temperatures. These developments are promising, and would further benefit from a study that maps out the effects of varying stack pressure and temperature on lithium anode mechanics, chemistry, and electrochemistry.

Mechanical Behavior and Dendrite Resistance of closo‐Hydroborate Solid Electrolyte

AbstractStack pressure and mechanical robustness are two important parameters needed to tackle the interfacial instability of solid‐state batteries. Here, the mechanical behavior of Na4(CB11H12)2(B12H12), as solid electrolyte at the interface with Na anode, is reported. The solid electrolyte is tested as function of stack pressure and different current densities, revealing a critical current density of 0.6 mA cm−2 at room temperature and an optimal stack pressure of 1.5 MPa. These findings are achieved, thanks to the adoption of a multilayer approach, demonstrating the powerfulness of hydroborates to compensate chemical and electrochemical instability, simply employing different complex hydride polyanions that change locally the electrochemical properties while preserving structural and chemical coherence.