High Temperature Cycling Research Articles

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.

MightyLev: An acoustic levitator for high-temperature containerless processing of medium- to high-density materials.

"MightyLev," a new multi-emitter ultrasonic acoustic levitation device capable of extremely stable levitation of materials of density up to at least 11.3g cm-3, is described. The exceptional stability of medium- to high-density samples levitated in MightyLev makes the device highly suitable for chemical and structural analysis using micro-focused spectroscopic and x-ray scattering techniques. In combination with mid-infrared laser heating, MightyLev is capable of levitating metallic and oxide materials during high-temperature cycling and melting above 1500K. Instabilities in particle confinement during heating were investigated by directly visualizing the acoustic field using schlieren imaging. The results reveal jets of hot-air directed along the anti-nodes of the acoustic field. The reaction force on the sample from the jet, coupled with the restoring force of the acoustic trap, generates a parametric lateral oscillation of the sample. This result provides valuable insight for future optimization and wider application of acoustic levitation for high-temperature containerless material processing.

The integrated performance of adaptive temperature control and temperature measurement of PTC materials with high thermal cycle repeatability

Abstract As the temperature increases, the resistance of the positive temperature coefficient (PTC) material becomes larger. Using this material can reduce the complexity of the temperature control system. In this paper, a new PTC material is developed by means of melt blending, which still has operable PTC characteristics after 60 high and low temperature cycles. The data points collected in multiple thermal cycles were fitted to obtain the relationship between the sample’s temperature and resistance. In addition, the integrated performance of adaptive temperature control and temperature measurement of PTC materials is proposed for the first time. Based on the prepared samples, the temperature control characteristics of PTC materials on the controlled object under different environmental conditions are studied experimentally, and the temperature value converted from the resistance value is compared with the temperature value measured by the platinum resistance. The results show that the prepared sample has good temperature control performance, and the material has an operable temperature measurement function in the PTC effect range.

Thermodynamic Comparative Analysis of Cascade Refrigeration System Pairing R744 with R404A, R448A and R449A with Internal Heat Exchanger: Part 2—Exergy Characteristics

The cascade refrigeration systems (CRS) used in hypermarkets and supermarkets, which are used by many people, have been employing R744 for the low-temperature cycle (LTC) and R404A for the high-temperature cycle (HTC) due to environmental and public safety issues. However, the use of R404A is limited due to its high GWP, and therefore research on alternative refrigerants is necessary. Nevertheless, there is no detailed study in the literature that compares and analyzes the three refrigerants for practical design by applying R744 for LTC and R404A, R448A, and R449A for HTC in CRS. Therefore, this study aims to provide data for the practical detailed design of an alternative system to R744/R404A CRS. Under standard conditions, we analyzed how the exergy destruction rate (EDR) and exergy efficiency (EE) of the system and the EDR of each component change when the important factors affecting CRS (degree of superheating (DSH), degree of subcooling (DSC), and internal heat exchanger (IHX) efficiency of HTC, DSH of LTC, condensation temperature (CT), evaporation temperature (ET), cascade evaporation temperature (CET), and temperature difference of CHX) are varied over a wide range. The main conclusions are as follows. (1) Under the given constant conditions, the smallest change in system EDR based on R448A is DSH of HTC (decreased by 0.07–0.1 kW), followed by IHX of HTC (decreased by 0.12–0.3 kW), DSH of LTC (increased by 0.19–0.25 kW), DSC of HTC (decreased by 0.59–0.69 kW), temperature difference of CHX (increased by 1.57–1.83 kW), CET (decreased and then increased by 0.67–4.43 kW), CT (increased by 1.49–3.9 kW), ET (decreased by 2.39–4.61 kW). (2) The highest change rate of system EE based on R448A is CET (increased and then decreased by 1.38–8.28%), followed by temperature difference of CHX (decreased by 2.96–3.16%), ET (increased and then decreased by 0.63–2.75%), DSC of HTC (increased by 1.26–1.34%), CT (increased and then decreased by 0.24–1.12%), IHX of HTC (increased by 0.11–1.02%), DSH of LTC (decreased by 0.35–0.49%), and DSH of HTC (increased by 0.14–0.19%).

Artificially regulated interphase on natural graphite realizes rapid charge and durable high-temperature cycling of Li-ion batteries

Natural graphite (NG) is a strong competitor in the anode market of Li-ion batteries because of its low cost, rich resource, low energy consumption and low carbon dioxide emission during production. The main problems inhibiting its universal application are its high surface area and the attendant unstable solid/electrolyte interphase (SEI), leading to unsatisfactory cycling and rate performance. In this work, a Li+-conductive, thermally and mechanically stable organic polymer layer is successfully constructed on NG surface by virtue of the simultaneous polymerization and crosslinking reactions of chitosan (CS) and acrylic acid (AA). With controllable thickness, the polymer layer denoted as CSAA significantly decreases the specific surface area of NG, works as an inner SEI substrate greatly mitigating the decomposition of electrolyte, and induces the formation of a LiF-rich SEI outer layer. The SEI resistance and activation energy for charge-transfer reactions are considerably reduced. Benefiting from the superior properties of CSAA-derived SEI, the NG@CSAA anodes exhibit a high initial coulombic efficiency of 94.1 %, fast charge/discharge capability and prolonged cycle life at both 25 °C and 45 °C in the LiFePO4 cathodes-based full cells.

Comparative study of multiple statistical damage mechanics models for rock behaviors under high temperature

Under the influence of external factors such as high temperature, chemical corrosion, and loading-unloading cycles, micro-cracks and pores may develop within rock structures. Continuum damage mechanics (CDM) characterizes these micro-defects arising within rocks, investigating the physico-mechanical behaviors of rocks in damaged states. This study, grounded in the theoretical framework of CDM and utilizing the Mohr-Coulomb failure criterion, integrates different probability distributions and damage coupling methods to develop three statistical damage models. The investigation primarily explores the effects of strength criteria, probability functions, and damage coupling mechanisms on the statistical damage models. In addressing the complex interplay between rock micro-defects and external stressors such as high temperatures and chemical corrosion, this study leverages the principles of CDM within the Mohr-Coulomb criterion framework. It advances the field by developing three innovative statistical damage models, enriched by diverse probability distributions and damage coupling methods. The research delineates the substantial impact of strength criteria, probability functions, and damage coupling mechanisms on the behavior of these models. Notably, it achieves a synthesis of theoretical constructs and experimental validation, demonstrating the models' capacity to reflect the nuanced behaviors of damaged rock accurately. Furthermore, this investigation contributes a methodological blueprint for statistical damage model construction, underscoring the critical selection of strength criteria and probability distributions. These efforts fortify the theoretical underpinnings necessary for the enhanced engineering application of statistics-driven damage analysis.

External short circuit of lithium-ion battery after high temperature aging

The microscopic and macroscopic changes of lithium-ion batteries after high temperature cycling and their effect on external short circuit (ESC) are studied in this study. The results indicate that solid electrolyte interphase and cathode electrolyte interphase cover the surface of anode and cathode. Transition metal, Mn is dissolved from the cathode. Capacity and resistance decreases and increases after cycling at high temperature. The safety of batteries after ESC is ranked as: 70 % state of health (SOH) > 100 % SOH > 80 % SOH > 90 % SOH. Thermal runaway only occurs to battery with 90 % SOH after ESC. Increase of resistance after cycling affects heat generation during ESC less. Onset temperature and thermal runaway temperature increases and decreases owing to solid electrolyte interphase growth and Mn dissolution. Compared to fresh battery, safety of battery with 70 % SOH after ESC increases. Fast discharging causes side reactions for aged batteries, which also generate heat. The heat generation effect of fast discharging decreases with the decrease of SOH after 90 % SOH. Local micro internal short circuit causes more heat generation for aged batteries. The results are important for safety control of lithium-ion battery.

An advanced ceramifiable organic-inorganic hybrid polysiloxane coating with superior moisture-resistant property

A ceramifiable organic-inorganic hybrid polysiloxane, prepared via a straightforward solution blending method, was successfully coated on the surface of silicon dioxide ceramic via a scrapping method. A uniform and dense lithium aluminum borosilicon (LABS) vitrified layer in situ formed on the surface of silicon dioxide ceramics was successfully prepared through liquid phase filling method to fulfill the moisture resistance requirements under high temperature cycle conditions. Effects of aluminum content on the microstructure change process and moisture resistance properties of the ceramifiable organic-inorganic hybrid polysiloxane have been systematically researched. With the increase of aluminum content, the ceramic yield of the hybrid polysiloxane and the heat loss capacity of LABS glass-ceramics increase. The crack-free and high temperature fluid vitrified layer endows the LABS glass-ceramic with excellent thermal shock resistance cycle ability, self-healing ability and moisture resistance. Results showed that the LABS vitrified coating with an aluminum-boron ratio of 1:2 presents the most appealing thermal shock cycle resistance and crack self-healing ability after 20 thermal cycles, as well as a water absorption rate of 0.3814 %. By refining the application of modified polysiloxane moisture-resistant coatings in high-temperature circulation environments, this work shed lights on the importance of in situ growth LABS vitrified coating in accelerating surface reconstruction and improving moisture resistance, incenting additional innovative breakthroughs in the LAS-based glass-ceramic materials design and fabrication within the aviation field.

Electrolyte Formulation with Improved Ion Desolvation and Diffusion Kinetics, and Superior Anti-Corrosion Properties for Ultrawide-Temperature Supercapacitors (–70∼100°C)

Electrochemical energy storage (EES) devices operating over a wide temperature range are crucial for extreme applications like near-space exploration (–70 °C) and desert exploitation (80 °C). However, their electrochemical performance is still hindered by the high-energy-barrier desolvation process at low temperature and the parasitic redox corrosion reactions at high temperature. In this work, an ultrawide-operating-temperature-window supercapacitor is proposed by simultaneously regulating ion kinetics of electrolyte and modulating anti-corrosion property of current collector. The optimized kinetics at low temperatures (–70 °C) refer to the enhanced ion dissociation and accelerated desolvation process, which is precisely regulated by the medium dielectric constant and low donor number of both methyl propyl ketone (MPK) and methyl ethyl ketone (MEK) cosolvents. Meanwhile, the remarkable cycling stability at high temperatures (100 °C) is realized by the strengthened corrosion resistance of carbon cloth current collector. The combination of MEK/MPK based electrolyte and carbon cloth current collector enables the supercapacitor to achieve a superior low-temperature capacitance retention (91.13 % @ –60 °C and 75.4 % @ –70 °C), extended high-temperature cycling stability (69.2 % @ 100 °C, 10,000 cycles) and excellent power and energy densities (13,820 W kg–1 @ 20.68 W h kg–1). This research is expected to provide valuable references for the advanced design of EES devices with wide-operating-temperature range in future studies.

Temperature manipulation during incubation: effect on embryo development and incidence of white striping and expression of related genes in broiler chickens from two commercial breeds

ABSTRACT 1. This study evaluated the effects of cyclic eggshell temperature between 10 and 14 d of embryogenesis on traits viz. the expression of MYOZ2, PPARγ and GPx7 in breast muscle, meat quality and incidence of white striping at slaughter age. 2. Eggs were obtained from Cobb and Ross broiler breeders to investigate the response of breeds to eggshell temperature, which regulated air temperature. A total of 784 eggs were incubated at either the control eggshell temperature (37.8°C) from 0 to 18 d or exposed to cyclic high eggshell temperature (CHT) at 38.8°C for 6 h/d between 10 and 14 d of incubation. The temperature was 36.8°C between 18 and 21 d. Hatched chicks were reared under optimum rearing conditions. The birds were sampled at 19 d of incubation, at hatch and at 42 d post-hatch. 3. There was no effect of eggshell temperature on yolk-free body weight and residual yolk sac weight. The CHT chicks had wider breasts on the day of hatching. 4. At hatch and 42d post-hatch, PPARγ expression in Cobb-CHT was upregulated 4.78-fold and downregulated 3.28-fold, respectively, compared to the Cobb-control. At slaughter age, chickens from Ross-CHT had 1.98- and 2.33-fold upregulated PPARγ and GPX7 expressions, respectively, compared to Ross-control. The CHT increased GPx7 expression in the Cobb-CHT day-old chicks compared to the Cobb-control. On ED19, MYOZ2 expression was upregulated in Cobb and downregulated in Ross by CHT. 5. The effects of breed and eggshell temperature on pH15, L*, a*, expressible juice and cooking loss were not significant. The CHT increased the incidence of severe white striping lesions in Ross chickens. 6. It was concluded eggshell temperature modulated embryo development, incidence of white striping and expression of related genes differently in the two commercial breeds.

Insights into the swelling force in commercial LiFePO4 prismatic cell

Lithium-ion batteries undergo reversible and irreversible swelling force during cycling. The mechanical behavior and swelling force of lithium-ion batteries are important in practical applications. In this study, the variation and the aging mechanism of swelling force, and the growth pattern under different cycling conditions have been studied with commercial cells. The findings reveal distinct dynamic stress peaks corresponding to the state of charge (SOC) increase, indicative of notable lattice expansions in both cathode and anode. This expansion intensifies over cycles, with the most significant escalation observed at 30 % SOC, gradually assuming a pivotal role in battery expansion dynamics. Post-mortem analysis, coupled with stress-strain evaluations, attributes this phenomenon primarily to moduli variations across SOC during the aging process. Moreover, the trajectory of swelling force amplification varies across aging paths, with high-temperature cycling demonstrating accelerated growth. This accelerated growth stems from the broadened expansion of battery components beyond solid electrolyte interphase (SEI) formation induced by high-temperature aging.

Effects of yttrium on microstructure and low cycle fatigue properties of superalloy IN713C at high temperature

In order to improve the high temperature and low cycle fatigue performance of the IN713C alloy, trace amounts of yttrium (Y) element were added to such an alloy. The effect of Y on the microstructure and fatigue performance under push-pull loading condition of the IN713C alloy at 650 °C was investigated, and the fracture mechanisms of the IN713C alloy with different Y additions at strain amplitudes of 0.3%, 0.4% and 0.5% were also investigated. The results showed that addition of Y significantly increased the fatigue life of the IN713C alloy under different strain amplitude values. Compared with the traditional IN713C, the fatigue life of the alloy with 300 ppm Y was increased by 44.4%, 213.3%, and 61.4%, and that of the alloy with 500 ppm Y was increased by 184.6%, 66.1%, and 172.1%, respectively, at the strain amplitudes of 0.3%, 0.4%, and 0.5%. Shrinkage pores were found to be the main crack source at low strain amplitude (0.3%), while carbides and other interdendritic precipitates were the source of cracks at high strain amplitude (0.4% and 0.5%). The addition of Y increased the fatigue life of the IN713C alloy by reducing shrinkage and refining carbides and grain size.

Improved Wide Temperature and Rate Performance in Li-Ion Batteries with Fluorinated Electrolyte Solvents

Commercial electrolytes include organic solvents unable to withstand the conditions required for the rapidly growing Li-ion battery industry, such as extreme temperatures and charge rates. The thermal and electrochemical stability limits of these solvents restrict the development of Li-ion batteries needed to sustain automotive electrification and other industrial applications. Further efforts are needed to enable electrolyte formulations suited for the operational demands in the market.Koura has designed a series of fluorinated materials for use in Li-ion electrolytes that demonstrate improved performance and safety over conventional commercial electrolytes. The impact of Koura’s fluorinated solvents on performance in 4.3V Gr/NMC811 was examined, with a particular focus on benefits seen on extreme temperature and rate performance. Testing included cycling and rate performance across a range of temperatures from -20 °C to 45 °C and cycling conditions from C/2 to 4C. It has been found that these materials improve low temperature performance and reduce gassing and increase capacity retention during high-temperature and fast charge cycling. Where appropriate, performance of Koura materials is compared to common commercial solvents.To elucidate the mechanisms responsible for the observed improvements, comprehensive post-test analysis has been conducted, including gas composition analysis and quantification via gas chromatography, bulk electrolyte composition analysis via NMR spectroscopy, and surface layer characterization via XPS and SEM. Bulk transport properties of the materials and electrolytes, including conductivity, viscosity, and Li+ solvation, are correlated to performance benefits.This presentation will show Koura’s efforts to fill a major gap in the demands of the Li-ion battery industry today through the design of fluorinated materials and optimization of advanced electrolyte formulations. Specifically, we will present data highlighting the performance of fluorinated compounds on improving battery performance under strenuous conditions with respect to both temperature and cycling rate. Results from fundamental mechanistic studies will be discussed to highlight the mechanisms underlying the observed performance improvements.

High-Temperature Lithium-Sulfur Batteries with Commercial Paper-Derived Solid-State Electrolyte

Solid-state lithium-sulfur (Li-S) battery technologies could power future electric mobility due to their potential high energy density. However, the current solid-state Li-S batteries face several challenges, such as high internal impedance at the electrode/electrolyte interfaces, shuttling of lithium polysulfides, and Li dendrite formation. Herein, we introduced a novel Li-rich cellulose-based solid-state electrolyte in combination with sulfurized polyacrylonitrile (SPAN, 36.5 wt.% S) cathode, leading to durable Li-S batteries for high-temperature applications. We utilized SPAN due to its reasonable conductivity, high reversible capacity, and stable cycling performance. The solid-state electrolyte in this study was prepared by infusing Li ions (Li+) into a copper-coordinated cellulosic paper. The infusion of Li+ was carried out by soaking the copper-treated paper in a 1 M LiTFSI in EC0.5DME0.25DOL0.25 solution (where subscripts indicate the volume fraction), followed by complete evaporation of the solvents. Three types of cellulosic paper were explored, from which the commercial copy paper resulted in the highest area-normalized conductance of 24.4 mS cm-2 and Li-ion transference number of 0.76 at 50 °C. At this temperature, the Li-SPAN cells with paper-based electrolyte delivered an initial reversible capacity of 1536 mAh gs -1 at 168 mA gs -1 (0.1C). After high-temperature cycling for 150 cycles at 0.5C, the Li-SPAN cells exhibited an exceptional capacity retention of 82.2% (from 982 to 807 mAh gs -1). The conformability of the paper-based electrolyte ensures good interfacial contact with the SPAN and Li electrodes. As a result, when this solid-state Li-S battery was subjected to fast charging/discharging (1C) at 50 °C, it delivered a reversible capacity of 670 mAh gs -1. In this talk, we will outline the results from our electron microscopy, X-ray diffraction measurements, electrochemical impedance spectroscopy, and cyclic voltammetry studies on Li-S cells to unravel the superior performance of paper-based Li-S batteries at high temperatures. Figure 1

Mechanical and failure characteristics of flawed granite after high-temperature cycling: An experimental study using biaxial compression

Unveiling the mechanical and failure characteristics of flawed granite subjected to high-temperature (HT) cycles is essential for assessing the stability of underground engineering. There is limited advanced knowledge of the rock performance under HT cycles even today. To that end, biaxial compression experiments with the simultaneous acoustic emission (AE)-digital image correlation (DIC) monitoring are conducted on flawed granite containing the flaw pairs, with the emphasis on the influences of HT cycles on the mechanical and failure characteristics of flawed granite. Experimental results suggest that the rock strength is increased at 400 °C, regardless of the cycle number, while it is weakened at 600 °C, especially under the thermal cycles. By the coupling analysis of acoustic-optical-mechanical data, the levels of cracking in flawed granite are revealed as the process zone nucleation and quasi-static growth, along with the macrocrack initiation, propagation, and coalescence until the eventual failure, dictated by the stress shielding effect and stress amplification effect. The splitting crack, hook crack, and far-field network crack are reported for the first time. Moreover, the flawed granite at different temperatures transitions from tensile-dominated cracks to mixed tensile-shear (T-S) cracks. Besides, thermal cycling causes rock fatigue damage, and the alternating thermal stress generated by HT cycling promotes the initiation and propagation of microcracks, leading to the development and further intensification of thermally induced fracture.