High Temperature Cycling Research Articles

Influence of Cooling Rate on Crack Growth and Stress Distribution in Die Steel under Thermal Cycles

Die casting molds are prone to thermal fatigue under high-temperature and high-pressure cycles, which significantly affects their service life. In this study, a three-dimensional numerical simulation method is employed to analyze the temperature field, stress field, and crack development process of the mold under different cooling cycles. The results show that shorter cooling cycles (15s, 30s) lead to larger temperature gradients and stress concentrations within the mold, thereby accelerating crack initiation and propagation. In contrast, longer cooling cycles (70s) help to reduce the temperature gradient and stress fluctuations, which in turn slows down crack propagation and effectively extends the mold's service life.

Research on the performance of ultra-low temperature cascade refrigeration system based on low GWP refrigerants

The EU Security Council and Parliament have tentatively agreed to ban fluorinated gases with a global warming potential (GWP) higher than 150 in split air conditioners and heat pumps from 2027. This will further motivate the refrigeration industry to accelerate the search for refrigerants with low GWP and zero ozone depletion potential (ODP). At present, research into low GWP refrigerants for cascade systems is limited, focusing mainly on single refrigerant substitutes without comprehensive comparisons and lax GWP restrictions. In this study, the cascade refrigeration cycle (CRS) system is established to meet the demand of −100 to −50 °C. The GWP of the refrigerants is strictly controlled below 150, and a comprehensive screening of the four generations of refrigerants is carried out to identify refrigerant pairs that meet environmental and refrigeration requirements. The relationship between the high-temperature cycle (HTC) evaporation temperature and the optimal coefficient of performance (COP) is determined, and the effects of the low-temperature cycle (LTC) evaporation temperature Te concerning with mass flow rate, discharge temperature of compressor, compressor power consumption, exergy destruction, and exergy efficiency are analyzed in detail. The thermodynamically superior refrigerant pairs are identified by comparison with several conventional refrigerant pairs. The results show that when Te > −67 °C, R170/R600a is preferred, and when Te ≤ −67 °C, R170/R1270 is preferred. In the temperature range of −100 ∼ −50 °C, R170/R1270 is the better refrigerant pair, which can improve the performance by 6.39–13.11 % than traditional refrigerant pairs. Finally, the exergy destruction analysis of CRS components is carried out, which provides a reference for refrigerant selection and system optimization of CRS in the field of ULT.

High-temperature (800 °C) performance of spodumene slag-based ternary sulphate composite phase change materials with improved mechanical property

The large deployment of electric vehicles leads to decarbonised road transport. However, the mining and smelting of lithium resources will continue to increase, which generates lithium slag and urgently needs to be recycled. The integration of spodumene slag with ternary sulphate presents a green and promising approach to achieve resource recycling and high-performance composite phase change material (CPCM). Herein, toughened and strengthened CPCMs are prepared by the hybrid sintering method with mechanical properties better than reinterned glass, even after high-temperature thermal cycling. After the cold compression and hot sintering process, the production of colloidal sodium silicate bonds the ternary sulphate with the spodumene slag skeleton, which greatly enhances the strength of the CPCM for efficient and durable thermal energy storage (TES). The Hydroxyl polar group of sodium silicate interacts with the skeleton and leads to a record-breaking compressive strength of 155.23 MPa, and the CPCM can support its stacking of 23.6 m and 15 kg loading test at 700 °C. A negligible mass loss of 0.26 wt% was observed after 50 thermal cycles at 800 °C. Moreover, the CPCMs exhibit a high TES density of up to 873.0 J/g in the temperature range of 100–800 °C. High charging and round-trip efficiency in the heat recovery process from spodumene roasting is also achieved, as it is 5 % and 19 % higher than the common magnesium bricks, respectively. The CPCM achieves high thermal efficiency TES, and it is the effective resource recycling of lithium slag with simple material preparation, which, from two angles at once, attacks the carbon emission from the life cycle of the lithium-ion battery.

Comparative analysis of a modified cascade refrigeration cycle including an auto-cascade refrigeration cycle using different zeotropic refrigerant mixtures for reducing the environmental impact

The two primary challenges in auto-cascade refrigeration (ACR) cycles are high compressor discharge temperatures and low efficiency at ultra-low temperatures. This study proposes a modified cascade refrigeration cycle (MCR) combined with an ACR cycle for cooling to –60 ℃. The innovative aspect of this work is to improve the ACR performance with simpler designs without increasing the system complexity, contrary to the common trend. For the high-temperature cycle (HTC), a dual evaporator refrigeration cycle with R1234yf is used while an ACR cycle is used for the low-temperature cycle (LTC). Environmentally friendly refrigerant mixtures, such as R170/R290, R170/R600a, and R170/R600, were analyzed using energy, exergy, and exergoeconomic methods. The results show that compared to R23/R134a, the R170/R600 significantly improves the performance of the MCR by increasing the COP and exergy efficiency by 24.0 %, and reducing the exergy destruction by 26 %, unit cooling cost by 11.2 %, and total investment cost by 9.7 %. Moreover, when compared with theoretical studies COP improvements range from 38.7 % to 94.1 %, demonstrating the importance and superiority of the system proposed in this study.

Mechanical properties and damage characterization of cracked granite after cyclic temperature action

Due to the unique geographical environment of the plateau, large-scale damage and destruction of fractured surrounding rock often occur during geotechnical engineering construction as a result of high-temperature cycles. Therefore, this study aims to investigate the mechanical properties and damage characteristics of fractured granite under the influence of cyclic temperature, uniaxial compression tests were conducted on granite specimens with pre-existing fractures at cyclic temperatures of 30 °C, 50 °C, 70 °C, 100 °C, and 130 °C. The study integrated analyses of characteristic stress, acoustic emission parameters, damage variables, fractal dimensions, and SEM to explore the mechanical properties and damage features of granite. The results indicated that at a 45° fracture inclination and a temperature of 70 °C, granite exhibited a distinct turning point in mechanical properties and damage characteristics. At the same cyclic temperature, granite with a 45° pre-existing fracture showed significant decreases in peak stress, elastic modulus, and σci/σm ratios, with the AE b-value drop point noticeably earlier, and both cumulative AE ring count and total energy reduced. The damage variable quickly reached its maximum, and the development of internal microcracks in the specimen is highly orderly. At the same fracture inclination, peak stress, elastic modulus, and σci/σm slightly increased at 70 °C, while AE ring counts and total energy were lower, indicating the degree of internal thermal damage in the specimen has significantly decreased, and the development of internal microcracks in the specimen has shown a marked reduction in orderliness. These findings provide theoretical insight into the meso-damage and failure mechanisms of granite influenced by different cyclic temperatures and fracture inclinations.

Evaluation of B-Site Doped Barium Niobate Perovskite Anodes for the Electrochemical Oxidative Coupling of Methane

More efficient usage of shale gas reserves and natural gas resources will allow for higher olefin yields and lower greenhouse gas emissions. The oxidative coupling of methane (OCM) is a direct pathway for converting methane to ethylene at temperatures >700 °C. OCM catalysts preferably avoid COx products and limit coke formation on the catalyst. Often, catalysts are analyzed via computationally expensive DFT computations in combination with experimental results leading to long lead times for catalyst development. Perovskite oxide catalysts are useful for OCM due to their flexible bond networks and varied properties (conductivity, selectivity, surface area) based on synthesis/doping. This work aims to illustrate the utility of the bond-valence bond-length model (ionic model)1 ,2 in conjunction with gas reduction experiments for rapid structure evaluation of the co-doped perovskite BaMg0.33Nb0.67-xFexO3-δ (BMNF, x=0.17,0.25,0.33). This perovskite catalyst has previously been adopted as a CO2 sensing material3 and an active/stable anode for the electrochemical oxidative coupling of methane4 (E-OCM). Further evaluation of this perovskite by our group illustrated the unique stability of ionic Fe into the BMNF while performing the oxidative coupling of methane5. This work delves into the crystal structure of the BMNF material as well as its chemical stability validated using a much more facile computational methodology featuring the bond-valence bond-length method. XPS, XRD, and reduction/oxidation high temperature cycling are utilized in conjunction to illustrate the stabilizing mechanisms for cations within the BMNF perovskite when exposed to highly reducing environments. References (1) Pauling, L. "The principles determining the structure of complex ionic crystals."J. Am. Chem. Soc. 1929, 51 1010-1026.(2) Lufaso, M. W.; Woodward, P. M. Prediction of the Crystal Structures of Perovskites Using the Software Program SPuDS. Acta Crystallogr. B 2001, 57 (6), 725–738. https://doi.org/10.1107/S0108768101015282.(3) Kannan, R.; Mulmi, S.; Thangadurai, V. Synthesis and Characterization of Perovskite-Type BaMg0.33Nb0.67−xFexO3−δ for Potential High Temperature CO2 Sensors Application. J. Mater. Chem. A 2013, 1 (23), 6874–6879. https://doi.org/10.1039/C3TA10572E.(4) Denoyer, L. H.; Benavidez, A.; Garzon, F. H.; Ramaiyan, K. P. Highly Stable Doped Barium Niobate Based Electrocatalysts for Effective Electrochemical Coupling of Methane to Ethylene. Adv. Mater. Interfaces 2022, 9 (27), 2200796. https://doi.org/10.1002/admi.202200796.(5) Denoyer, L. H.; Benavidez, A.; Garzon, F. H.; Electrochemical oxidative coupling of methane: deciphering the exceptional properties of BaMg0.33Nb0.67-xFexO3-δ for enhanced electrocatalysis and durable operation. Accepted by Energy & Fuels Feb. 2024

Transition Metal Dissolution: Impacts on Cell Performance and Mitigation by Electrolyte Formulation

Layered lithium transition metal oxides with nickel, cobalt, and/or manganese are nearly ubiquitous as cathodes in lithium-ion batteries for high energy density applications. As the cells age through cycling or exposure to high temperatures, degradation mechanisms within the battery can lead to release of transition metals from the cathode lattice. The dissolution of transition metals from the cathode and deposition on the anode have been linked to increased capacity fade and poor coulombic efficiency, attributed to constant degradation of electrolyte at the anode interface and lithium inventory loss.1 Orbia’s Battery Materials Innovation Center (formerly known as Silatronix) specializes in the design, synthesis, formulation, and optimization of electrolyte components for specific applications, as well as electrolyte performance cell testing and cell post-mortem analyses. In this study, we explored modification of the electrolyte composition as a method to reduce transition metal dissolution in Gr/NMC811 multi-layer pouch cells. Battery tests under a variety of aging conditions such as high temperature cycling, low temperature cycling, calendar life, and high-rate tests were studied to understand the conditions that lead to transition metal dissolution, which was quantified by ICP-OES. The relationships between transition metal dissolution and cell performance were investigated, including correlations between capacity fade, cell impedance, voltage hysteresis, and lithium plating. Next, a wide range of electrolyte formulations were tested under the above aging conditions and the effects of electrolyte composition were assessed, including the selection and concentration of solvents, additives, and salts, on transition metal dissolution and performance impacts. Electrolyte components that consistently reduce manganese dissolution and improve cell performance under a wide range of conditions were identified and are discussed in this presentation. These results provide insights into the practical design of electrolytes for reducing transition metal dissolution in a manner that is specifically correlated with performance improvements.

Decoupling the Capacity Fading in Ni-Rich Layered Materials during High-Temperature Cycling in the Full-Cell System

The performance of commercial lithium-ion batteries (LIBs) tends to degrade over time owing to the deterioration of key components, including cathode, anode, and electrolyte. To enhance performance, it is crucial to gain insights into the actual deterioration state of each element. Here, the high-temperature deterioration of a Ni-rich layered cathode is investigated, which is widely used in electric vehicles. In the refresh process after a prolonged cycle, a significant recovery of the lattice structure predominantly occurs in the discharge region. This pseudo-deterioration of the Ni-rich cathode within the full-cell system is mainly due to the consumption of the Li-ion forming the solid electrolyte interphase layer at the graphite anode during the cycle. Moreover, irreversible deteriorations that are not restored through the refresh process are observed in both charge and discharge regions. Structure analyses reveal that the long-term cycling at the high temperature leads to a mixed fading of charge and discharge via various deterioration such as the formation of NiO-like rock salt phase on the cathode surface and increased cation disorder in the bulk. These findings deepen the understanding of the deterioration behavior of Ni-rich cathodes in full-cell systems, providing insights for enhancing the performance of high-temperature cycling. Figure 1

SOC Imbalance of the Electrodes in All-Solid-State LTO/LCO Batteries Examined by Three-Electrode Cell

All-solid-state lithium-ion batteries (LIBs), which have overwhelmingly higher thermal stability and longer calendar life compared to liquid-based LiBs, are suitable for environments where conventional liquid-based LIBs cannot be used, leading to dramatically expand their applications. In all-solid-state LIBs, sulfide-type solid electrolytes have been most extensively examined owing to their excellent conductivity and flexibility. Although applying the solid electrolytes enables to stable operation of the batteries even at 100oC, capacity moderately decreases during cycling under such severe conditions.This study examines high-temperature long-term cycle tests of all-solid-state Li[Li1/3Ti5/3]O4/LiCoO2 (LTO/LCO) batteries in order to clarify the origin of capacity fading at high temperature. For cycle tests, a three-electrode cell (MX-3E-5T-CWS, Tomcell, Japan) were used to monitor state-of-charges (SOCs) of LCO positive and LTO negative electrodes during cycling, because the imbalance of SOCs of the electrodes causes capacity fading even without material deterioration. All-solid LIBs used in this study were consisted of LTO negative and LCO positive electrodes, and argyrodite-type solid electrolyte (Li7-xPS6-xClx). The LTO and LCO electrodes were consisted of LTO:SE = 65:35 wt% and LCO:SE:AB = 73:26:1 wt%, respectively. The size of the electrodes was the same (9 mm diameter and 0.85 mm 9 thickness) and electrode weight was 0.10 g for LTO and 0.15 g for LCO electrodes. Li metal placed on the solid electrolyte was used as the reference electrode.Fig. (a) shows charge-discharge curves of the LTO/LCO cell before and after the cycle test. After cycling, the charge-discharge curves of both the LCO and LTO electrodes shifted to the right (higher capacity side), and the capacity decreased by the difference in the amount of shift between the two electrodes. This means that the capacity fading of the all-solid-state battery is caused by the imbalance of SOCs between LCO positive and LTO negative electrode, which is essentially the same capacity fading mechanism as that of liquid-based LIBs.To quantitatively analyze the SOC imbalance, side reaction current at both electrodes were estimated from a cumulative capacity plot (Fig. b). In the figure, the derivative of cumulative capacity at the end of charge and discharge corresponds to the side reaction current at LTO negative and LCO positive electrodes, respectively. As can be seen in Fig. (b), larger side reaction current at LCO than LTO electrodes indicates SE decomposition at LCO is faster than that at LTO. The capacity fading mechanism due to side reactions in all-solid-state LTO/LCO batteries is schematically illustrated in Fig. (c). Because of the formation of a local cell at each electrode consisting of Li insertion and side reactions, the current due to the Li insertion reaction, namely current efficiency differs between the electrodes. The difference in current efficiency between LTO and LCO electrodes induces the deviation of the SOC balance between the electrodes, resulting in a capacity fading of the battery without deterioration of active materials.From the above results, we will discuss the quantitative prediction of the lifetime for all-solid-state batteries based on the mass balance in the cell. Figure 1

Solubility of Beryllium Metal in Molten 2LiF-BeF2

Fluoride salt-cooled High-temperature Reactors (FHRs) are a subtype of molten salt reactors (MSRs) in which a molten salt fills the role of a low pressure coolant to coated particle fuel. Another use for molten salt is in fusion reactors as a fusion blanket/coolant. The use of a molten salt as the coolant or blanket offers several safety advantages when compared to the current water-based designs due to the low vapor pressure of molten salts and their boiling point being far above the maximum coolant temperature. It also allows to integrate passive safety systems and to use a high-temperature power cycle. Careful control over the chemistry of the molten salt coolant must be kept in FHRs to reduce the corrosion of structural materials. The primary coolant candidate for FHRs is FLiBe (66.7%LiF-33.3%BeF2), which is not corrosive in its pure form, but impurities in the salt (commonly oxygen or water) and tritium fluoride generated from neutron irradiation of the salt can create an oxidizing environment.1 This in turn leads to structural corrosion, which degrades the system and and further modifies the properties of the salt. Because of this, redox control of the coolant salt is a key issue in FHRs.2 One of the methods for redox control is to introduce excess Be as a redox control agent to the salt, which reacts with tritium fluoride and decreases the redox potential. However, it has been found that when Be metal is contacted with FLiBe containing HF, it does not simply react with the HF, but is also dissolved in the salt. Another method is to add LiH to the FLiBe mixture as a hydrogen donor, which will induce the formation of dissolved metallic Be. This dissolution is not well understood, but could prove to be an elegant way for introducing a reducing agent to the system as the salt could be left in contact with Be metal in one part of the reactor to saturate the salt everywhere or be periodically saturated using LiH. The solubility of Be plays an important role here as it sets the limits for this saturation. Phases with visually different colours at different contents of Be in FLiBe have been reported in the literature, but no comprehensive analysis has been conducted to understand the solubility of metallic Be in FLiBe.3 In this study, we present data on these different phases of dissolved Be in FLiBe using LiH additions to understand the solubility of metallic Be. The crystal structure of different phases will be characterized using powder X-ray diffraction, the elemental composition via inductively coupled plasma mass spectrometry and melting points and latent heats via differential scanning calorimetry. Cyclic voltammetry will be used to determine activity coefficient of BeF2 in with different amounts of Be dissolved in it and electrical conductivities of different phases of the melt will be measured via electrochemical impedance spectroscopy. Additionally, neutron diffraction PDF data of Li2BeF4 with and without 1 mol% of metallic Be dissolved inside will be shown. A better understanding of the characteristics and speciation of dissolved Be in FLiBe will allow for closer redox control of the coolant melt and a longer lifetime for structural elements in FHR coolant loops. References (1) Vergari, L.; Scarlat, R. O.; Hayes, R. D.; Fratoni, M. The Corrosion Effects of Neutron Activation of 2LiF-BeF2 (FLiBe). Nuclear Materials and Energy 2023, 34, 101289. https://doi.org/10.1016/j.nme.2022.101289.(2) Zhang, J.; Forsberg, C. W.; Simpson, M. F.; Guo, S.; Lam, S. T.; Scarlat, R. O.; Carotti, F.; Chan, K. J.; Singh, P. M.; Doniger, W.; Sridharan, K.; Keiser, J. R. Redox Potential Control in Molten Salt Systems for Corrosion Mitigation. Corrosion Science 2018, 144, 44–53. https://doi.org/10.1016/j.corsci.2018.08.035.(3) Hara, M.; Hatano, Y.; Simpson, M. F.; Smolik, G. R.; Sharp, J. P.; Oya, Y.; Okuno, K.; Nishikawa, M.; Terai, T.; Tanaka, S.; Anderl, R. A.; Petti, D. A.; Sze, D.-K. Interactions between Molten Flibe and Metallic Be. Fusion Engineering and Design 2006, 81 (1), 561–566. https://doi.org/10.1016/j.fusengdes.2005.06.372.

Surface-Enhanced Ni-Rich Cathodes for Reversible Li Intercalation

Energy-dense nickel (Ni)-rich layered oxide cathodes can enable lithium (Li)-ion batteries to power electric vehicles (EVs) for long distance. Employing Ni-rich cathodes, however, faces challenges in stabilizing cathode-electrolyte interfaces, leading to substantial degradation of the layered structure at the cathode surface during cycling process. In particular, high-voltage operation for the layered oxide cathodes leads to substantial volume change and structure collapsing, and thereby chemo-mechanical degradation. Cation doping, surface engineering, and/or composition gradient designs are common approaches to stabilizing charged structures at high voltage. They have proven effective in suppressing surface degradation of the layered oxide particles by promoting phase stability or providing extrinsic protection.In this presentation, we propose a reactive coating method to obtain active cathode particles with protective passivation via transition metal doping, which could primarily address parasitic side reactions occurring at the cathode-electrolyte interface. Our designed Mo (or Ti)-doped layered oxide cathodes contain more than 90% Ni and demonstrate high-voltage stability and good capacity retention under high temperature cycling environment. This results from an electrochemically stable, 10 nm-thick surface phase that was formed in situ during one step calcination process. Electron microscopy combined with elemental analysis indicates that the surface is Mo (or Ti)-rich phase. An electron diffraction pattern from the high-resolution transmission electron microscopy (TEM) reveals that the surface has rocksalt-like structure, while the bulk maintains the layered structure.This surface-enhanced cathode delivers 216 mAh/g at the second discharge (0.2C, room temperature) with excellent capacity retention of 89% over 50 cycles (1C, 45oC). This outperforms the pristine Ni-rich cathode without doping, in which the retention rate is 78%. Since the capacity fading of these Ni-rich layered cathodes largely originates from the cyclic internal stress caused by the repetitive H2-H3 phase transitions. Here, the differential capacity-voltage analysis and ex situ X-ray diffraction suggest that the surface coating can delay and suppress the unfavorable H2-H3 phase transition at high state of charge for the Ni-rich cathode, extending cycle life. Consequently, the Mo (or Ti) surface disordered rocksalt phase alleviated the structural stress associated with the repetitive phase transition by reducing the abrupt lattice collapse/expansion. The effects of the reduced lattice distortion, Ti/Mo-rich surface phase were reflected by the enhanced cycling stability of the coated cathodes in rate capability analysis. We consider that our work demonstrates how doping can stabilize the particle surface of Ni-rich cathodes to promote Li intercalation reversibility and energy density. And we expect that this dual modification design represents future research direction towards high-performance cathodes and will inspire waves of efforts to develop multifunctional materials for next-generation batteries.

Development of Localized High-Concentration Electrolytes Containing DME Solvent for Long-Life and High-Power Lithium-Ion Batteries

1.IntroductionWe are promoting electrification towards carbon neutrality, since the evolution of batteries is indispensable, we are developing high energy, high power and long-life lithium-ion batteries.While Ni-rich layered cathodes such as NCM811 have high capacity, the cycle life using NCM811 at high temperatures decrease. To overcome poor cycle performance, reported localized high concentration electrolytes (LHCE) which contains DMC solvent [1] was adapted to our chemical system and evaluated. Although better cycle performance at high temperature was observed, the resistance of cells using the LHCE should be lowered toward practical application.In this study, the types and concentrations of solvents were investigated for long-life and high-power battery. 2.ExperimentalThe LiFSI salt concentration was set to 1.7 mol/L, and mixtures was prepared using 1,2-Dimethoxyethane (DME) and Ethylene carbonate (EC) as solvents, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) as a diluent as shown in Figure 1 by weight ratio of solvents.350mAh-class laminate cells were fabricated with NCM811 as the positive electrode active material and a mixture of silicon oxide and graphite as the negative electrode active material. The electrolyte amount was set to 11g/Ah. Resistance measurements were performed at 25°C with a SOC of 50%, applying a 10-second pulse from 0.2 to 2.5C for six points. Cycle tests were carried out at 60°C, charging at 0.3 C rate discharging at 0.8 C rate with cut-off voltage of 3.0-4.15 V.３. Results and DiscussionThe area specific DCR (ASD) and the absolute value of the slope of the capacity retention against the cumulative discharge energy were illustrated on the ternary diagram shown in Figure 2. The weight of EC to 15-20wt.% reduced ASD, and favorable cycle performances were obtained with a weight of TTE at 55wt.% or higher. By optimizing the electrolyte composition using DME, high-temperature cycle performance was improved by 3% and ASD resistance was reduced by 15% compared with reported LHCE using DMC which was shown as “ref” in Figure 2.The effects of electrolyte compositions and the mechanisms for improving performance will be discussed based on data such as initial charging curves, energy levels of Li-FSI state by DFT calculation, coordination number of Li-FSI by molecular dynamics simulation.*Since there was the potential risk of the corrosion on an aluminum current collector with our LHCE, investigations were conducted, and results were reported by our colleague.

The snowball effect in electrochemical degradation and safety evolution of lithium-ion batteries during long-term cycling

Lifespan and safety are the most critical issues for the application of lithium-ion batteries (LIBs). During long-term service, the degradation mechanisms and safety evolution of LIBs remain unclear, posing significant obstacles to battery design and management. This study analyzes the electrochemical degradation mechanisms of LIBs under normal temperature cycling (NTC) and high-temperature cycling (HTC) conditions, linking these mechanisms to the evolution of battery safety. The findings reveal that during NTC, there is a “snowball effect” in performance degradation and safety evolution, leading to sudden death of battery and posing serious safety risks. The degradation pattern of LIBs during NTC and HTC is consistently dominated by the increase of internal resistance and the loss of lithium inventory (LLI). In the aging process, electrolyte consumption and the growth of the solid electrolyte interface (SEI) cause localized lithium plating on the anode, resulting in accelerated capacity decay. However, in batteries subjected to NTC, rapid accumulation of localized lithium plating can trigger a snowball effect, causing electrode deformation, internal short-circuit (ISC) and separator melting. These interacting catastrophic events form a vicious cycle, ultimately leading to battery sudden death and pose significant safety hazards. Additionally, thermal safety analysis reveals the correlation between thermal safety parameters and state of health (SOH), quantifying the thermal safety degradation caused by sudden death. Sudden death directly alters the evolution pattern of battery safety, leading to a severe decline in battery safety. These findings offer new insights into potential safety hazards associated with long-term use of LIBs.

Experimental investigation of La0.6Sr0.4FeO3 -δ pellets as oxygen carriers for chemical-looping applications

Lanthanum Strontium Ferrite (LSF), as an oxygen carrier, is used for chemical looping H2 production and CO2 utilization. In this work, the first attempt to upscale and understand the heat and mass transfer using 400 g of LSF pellets in a dynamically operated packed bed reactor is carried out.Experiments were conducted at 650–820 °C and 1–5 barg, evaluating the pellets' reactor heat management, phase stability, and mechanical integrity over 70 h for the high-temperature redox cycling in chemical looping water-gas shift (CL-WGS) and chemical looping reverse water-gas shift (CL-RWGS) reactions.Key results at the reactor scale indicate a maximum cyclic average H2O-to-H2 conversion of 31%, with a peak oxygen carrier capacity for CL-WGS of 0.38 mmol/gLSF. In the case of CL-RWGS, a peak CO2-to-CO conversion of 99.8% was achieved, with an oxygen carrier capacity of 0.57 mmol/gLSF.Reactor heat management for exothermic and endothermic redox reactions showed the ability to maintain a high temperature profile where the heat front lagged the reaction front over a 15 cm reactive bed length. A maximum ΔT of 45 °C and 35 °C were observed during the oxidation of the LSF bed with H2O and CO2, respectively. In the case of air oxidation, a maximum ΔT of 120 °C indicates that the reaction is more exothermic and can be used to raise the temperature of the bed especially if heat is required to sustain the process.No evidence of material performance degradation was recorded over 70 h of testing, maintaining the pellets' operational cyclability, phase stability, and mechanical integrity. The results demonstrate the robustness of the material, and they are encouraging versus the scalability of LSF for chemical looping applications, into H2 production and CO2 utilization processes.

Layered/Olivine Composite Structure-Induced Stable Gradient Interfacial Chemistry toward High-Temperature Lithium-Ion Batteries.

The state-of-the-art layered oxide as the cathode material for lithium-ion batteries has attracted wide attention; however, harsh operations of high-energy and high-safety energy-storage technology at high temperature is challenging owing to the aggravated structural instability and parasitic reactions at the cathodes. Herein, the layered/olivine composite structure architecture is designed at the grain surface to govern constant electrochemistry in a harsh environment, and a gradient LiF interlayer is developed onto the cathodes to suppress the interfacial degradation. By a combination of interfacial-sensitive characterizations and theoretical analysis at the cathode/interface, the formation mechanism of this special interphase induced by the composite structure cathode is revealed. The composite structure cathode could deliver an excellent high-temperature cycling stability with 90.8% retention for 300 cycles in the half cell and 95.6% retention for 1000 cycles in the pouch cell and simultaneously enhances ∼51% of the thermal stability, which broadens the approaches for developing high-stable cathodes that work in extreme environments.

Physiological and transcriptomic characterization of cold acclimation in endodormant grapevine under different temperature regimes.

It is essential for the survival of grapevines in cool climate viticultural regions where vines properly acclimate in late fall and early winter and develop freezing tolerance. Climate change-associated abnormities in temperature during the dormant season, including oscillations between prolonged warmth in late fall and extreme cold in midwinter, impact cold acclimation and threaten the sustainability of the grape and wine industry. We conducted two experiments in controlled environment to investigate the impacts of different temperature regimes on cold acclimation ability in endodormant grapevine buds through a combination of freezing tolerance-based physiological and RNA-seq-based transcriptomic monitoring. Results show that exposure to a constant temperature, whether warm (22 and 11°C), moderate (7°C), or cool (4 and 2°C) was insufficient for triggering cold acclimation and increasing freezing tolerance in dormant buds. However, when the same buds were exposed to temperature cycling (7±5°C), acclimation occurred, and freezing tolerance was increased by 5°C. We characterized the transcriptomic response of endodormant buds to high and low temperatures and temperature cycling and identified new potential roles for the ethylene pathway, starch and sugar metabolism, phenylpropanoid regulation, and protein metabolism in the genetic control of endodormancy maintenance. Despite clear evidence of temperature-responsive transcription in endodormant buds, our current understanding of the genetic control of cold acclimation remains a challenge when generalizing across grapevine tissues and phenological stages.

Failure analysis of ternary lithium-ion batteries throughout the entire life cycling at high temperature

The operation life is a key factor affecting the cost and application of lithium-ion batteries. This article investigates the changes in discharge capacity, median voltage, and full charge DC internal resistance of the 25Ah ternary (LiNi0.5Mn0.3Co0.2O2/graphite) lithium-ion battery during full life cycles at 45 °C and 2000 cycles at 25 °C for comparison. The batteries before and after cycling were disassembled, and the structure, morphology, interface characteristics, element content of the cathode and anode plates of the battery were characterized. By analyzing the failure factors of the performance of the ternary batteries during the 45 °C cycling, a reaction mechanism for the rapid decline of high-temperature cycling performance of ternary batteries has been proposed. The results show that the performance degradation of the ternary lithium-ion batteries in the whole life operated at high temperature is characterized by slow decline in the initial stage and rapid drop in the latter stage. Further analysis of physical and chemical performance revealed irreversible damage to both the cathode and anode. The dissolution of transition metal ions from the cathode and their deposition on the anode surface catalyze the decomposition of electrolyte solvents to produce a large amount of gas. Gassing, accompanied by the deposition of Li2CO3 and the thickening of SEI, leads to an increase in the internal resistance of the battery. The coupling between gassing and increased internal resistance is responsible for the rapid drop in the performance of the ternary batteries during high-temperature cycling.

Enhancing Thermochemical Energy Storage Performance of Perovskite with Sodium Ion Incorporation

Perovskite materials are promising for thermochemical energy storage due to their ability to undergo redox cycling over a wide temperature range. Although BaCoO3 exhibits excellent air cycling properties, its heat storage capacity in air remains suboptimal. This study introduces Na into the lattice structure to enhance oxygen vacancy formation and mobility. DFT+U simulations of the surface structure of Na-doped BaCoO3−δ indicate that incorporating Na improves surface stability and facilitates the formation of surface oxygen vacancies. NaxBa1−xCoO3−δ compounds were synthesized using a modified sol–gel method, and their properties were investigated. The experimental results demonstrate that Na doping significantly enhances the redox activity of the material. The heat storage capacity increased by above 50%, with the Na0.0625Ba0.9375CoO3−δ solid solution achieving a heat storage density of up to 341.7 kJ/kg. XPS analysis reveals that Na doping increases the concentration of surface defect oxygen, leading to more active oxygen release sites at high temperatures. This enhancement in redox activity aligns with DFT predictions. During high-temperature cycling, the distribution of Na within the material becomes more uniform, and no performance degradation is observed after 300 cycles. Even after 450 cycles, Na0.0625Ba0.9375CoO3−δ retains over 96% of its initial redox activity, significantly outperforming fresh BaCoO3−δ. These findings elucidate the mechanism by which Na doping enhances the thermochemical heat storage performance of BaCoO3−δ and provide new insights for the design of perovskite-based materials.

Analysis of High and Low Temperature Performance of Titanium Zirconium Molybdenum Alloy and High Temperature Alloy Brazed Joint

Abstract Using niobium as the intermediate layer and gold nickel (Au82-Ni) filler metal, TZM alloy and high-temperature alloy GH3128 were brazed. The brazed specimens were subjected to 400 cycles of high and low temperature cycling tests at temperatures ranging from 650 °C ∼ 680 °C (high temperature) to -196 °C (low temperature) for 10 minutes seperately. Then the microstructure variation before and after the experiment were observed and the shear strength of the specimens were tested at room temperature for 50 cycles of 400 high and low temperature testing.. The results show that the microstructure of the transition zone at the brazing interface after brazing is uniform and dense, with good wettability with the substrate and no defects such as cracks. The solder and substrate undergo diffusion reactions, and the molybdenum alloy, niobium, and niobium, high-temperature alloy had each form diffusion layers, formed intermetallic compounds on the brazing surface. After high and low temperature cycling, cracks exist in the braze seam between molybdenum alloy and niobium alloy. The cracking mode should be thermal fatigue based on the fracture morphology and phase analysis. The reasons of interface cracking are that due to different thermal expansion coefficients, low mutual solid solubility, and the formation of a large number of different types of intermetallic compounds, Mo and Nb materials have poor brazing compatibility and lower interface strength. Under cold and hot cycling conditions, brittle intermetallic compounds are prone to form crack source areas. As the number of cycles increases, the cracks gradually expand, ultimately leading to product leakage. In addition, the shear strength of brazed joints shows a decreasing trend with the increase of high and low temperature cycles in 400 high and low temperature tests.

Optimizing cascade refrigeration systems with low GWP refrigerants for Low-Temperature Applications: A thermodynamic analysis

This study offers a comprehensive thermodynamic analysis of a cascade refrigeration system conducted for low-temperature applications, focusing on the use of low-GWP and zero-ODP refrigerants to improve efficiency and sustainability. The target of this study is to explore the performance of the system using a combination of refrigerants: low-temperature cycle refrigerants such as R744, while high-temperature cycle refrigerants such as R717, R1234yf, R1234ze(E), R1336mzz(E), and R1336mzz(Z), respectively. The ECS model incorporating in REFPROP 10.0a tool was utilized to extract the data through coding for analysis. The assessment of this system involves the examination of various parameters such as its coefficient of performance, total compressor workload, total exergy, and exergy efficiency across various operational conditions. The results are compared with and without superheated and subcooled conditions to understand the impact of these parameters on the system performance. The system with R744 in the low-temperature cycle and R717, R1234yf, R1234ze(E), R1336mzz(E), and R1336mzz(Z) in the high-temperature cycle provides a higher COP and lower total compressor work compared to the conventional cascade refrigeration system. In optimal CRS, the R744-R717 pair attains the highest COP of 2.05 at the lowest possible compressor work from 9.53 to 4.87 kW than other refrigerants pair while evaporator temperature shifting from −55 °C to −20 °C. The exergy efficiency of R744/R717 is found at 26.47 % at an evaporator temperature of −55 °C, but it extends to a peak of 51.73 % at −20 °C. The study also shows that the superheating and sub-cooling of the refrigerants have a significant impact on the performance of the cascade refrigeration system. Superheating and sub-cooling at 10 °C, improves the COP of the system by reducing the compressor work and increasing the heat transfer efficiency. The research offers valuable insights into the system’s thermodynamic performance when employing low GWP refrigerants in low-temperature applications. These findings have the potential to guide the design and optimization of cascade refrigeration systems over the range of low-temperature applications.