High Discharge Rates Research Articles

Is the impact of groundwater on lake greenhouse gas dynamics underestimated? A comparative analysis of subsurface and ecological factors

Lakes are recognized as important sources of greenhouse gases (GHGs) emissions to the atmosphere, influenced by various ecological processes. Groundwater discharge into lakes, despite its small volume, has high concentrations of dissolved carbon and nitrogen that significantly affect the production and emission of GHGs from lakes. Therefore, a comprehensive investigation of the mechanisms behind lake GHGs emissions under the influence of groundwater discharge and ecological processes, holds substantial scientific importance. However, due to uncertainties and quantification challenges associated with groundwater discharge, related research is currently limited. Here, we conducted year-round field observations on Honghu Lake, a large shallow eutrophic lake in Hubei Province, China. We analyzed the seasonal variation of GHGs emissions and quantified the groundwater discharge flux using radon (222Rn). The fluxes of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) at the water–air interface were estimated to be 31.1 ± 4.88 mg m−2 d−1, 386 ± 90.7 mg m−2 d−1, and 0.327 ± 0.072 mg m−2 d−1, respectively. CH4 is the primary greenhouse gas in Honghu Lake, contributing to 82.2 % and 62.2 % of the lake’s total emissions over 20-year and 100-year frames. The average rate of groundwater discharge was 8.19 ± 0.471 mm d−1, with the highest discharge rate in winter and the lowest in spring. The daily groundwater discharge volume accounts for 0.649 % of the lake’s total water volume. The daily contributions of groundwater discharge to the lake’s total emissions of CH4, CO2, and N2O were 0.318 %, 12.1 %, and 2.59 %, respectively. The facilitative role of groundwater discharge in CO2 emissions primarily manifests through the transport of dissolved organic carbon (DOC) and high concentrations of CO2 into the lake. Meanwhile, CH4 emissions depend on the activity of methanogenic bacteria, substrate availability, and anaerobic conditions, whereas N2O emissions are influenced by temperature and nutrient levels. Our study reveals that in the short term, the effect of groundwater on lakes is relatively minimal. Yet, its long-term role as a steady supplier of carbon and nutrients to lakes should not be overlooked. This study reveals the ways in which groundwater discharge and internal lake dynamics collectively fuel GHGs emissions. Our findings offer a new perspective and critical theoretical support for the assessment of lake greenhouse gas emissions.

Experimental investigation on battery thermal management using phase change materials with different arrangement schemes

Thermal management is imperative for regulating battery temperature during operation. In this paper, lithium iron phosphate batteries were taken to experimentally investigate the battery thermal management system module utilizing phase change materials. Various phase change material (PCM) plates with uniform and gradient phase change material arrangements were produced by pressing phase change material powder to closely adhere to the battery. The experimental results illustrated that the phase change material plate had a good temperature uniformity effect on the battery, and this effect became more noticeable under high-rate battery discharge. Over 80% of the experimental group’s the maximum temperature difference could be maintained within 3 °C. In addition, there was an optimal range for phase change material plate thickness, the effect of reducing the battery maximum temperature weakened and the efficiency of phase change material utilization decreased when the phase change material plate thickness exceeded a critical value. Specially, a gradient arrangement of the phase change material with different phase change temperatures had better cooling effect on the battery. Compared with uniform arrangement of PCM, the temperature difference with gradient arrangement of PCM was decreased by 55.6%, 70.8%, and 77.4% at 2C, 2.5C, and 3C discharge rates, respectively. To guarantee that the battery’s high heat-generating areas can always be cooled by phase change material through latent heat absorption in the middle and later stages of discharge, phase change material with higher phase-change temperatures should be placed in these areas, which can coordinate the non-uniform heat generation of battery and prevent severe temperature rise as well as further reduce the maximum temperature difference. The findings presented in this study provide new insights for designing a battery thermal management system utilizing phase change material.

Multi-U-Style micro-channel in liquid cooling plate for thermal management of power batteries

In order to cope with the problem of the shortening of automotive power battery life and the reduction of occupant safety due to the large amount of heat generated by automotive power batteries of high-energy–density at high discharge rates, this paper proposes a Multi-U-Style micro-channel in the liquid-cooled plate (Multi-U), based on the heat generation characteristics and temperature distribution of automotive power batteries. The impact of different Multi-U arrangements on the cooling performance of the batteries is explored, and the results indicate that the cooling performance is better with the side face arrangement. Compared to main face 1, the maximum temperature (Tmax) and maximum temperature difference (ΔTmax) of the batteries decrease by 2.40 K and 2.50 K, respectively. In addition, through a comparative analysis with typical serpentine micro-channel chilled plate (SMCP) and parallel micro-channel chilled plate (PMCP), Multi-U exhibits superior overall performance. Furthermore, the influence of equally incremental and decreasing channel width of Multi-U from the center to the periphery on cooling performance of the batteries is explored. It turns out that when the channel width is equally decreasing 1 mm Multi-U (D 1 mm), the heat dissipation is most effective. Finally, the critical parameters of the Multi-U are optimized to improve the power density of batteries. The impact of critical parameters of the Multi-U on the cooling performance of the batteries is studied through orthogonal experiments. The optimal parameter combination is found to be a channel width (W) = 12 mm, channel thickness (H) = 6 mm, inlet mass flow rate (F) = 0.02 kg∙s−1, and inlet coolant temperature (T) = 292.15 K. Compared to the original Multi-U, the Tmax and ΔTmax of batteries decrease by 5.83 K and 0.06 K, respectively, while the pressure drops decrease by 89 %.

Differential training benefits and motor unit remodeling in wrist force precision tasks following high and low load blood flow restriction exercises under volume-matched conditions

BackgroundBlood flow restriction (BFR) resistance training has demonstrated efficacy in promoting strength gains beneficial for rehabilitation. Yet, the distinct functional advantages of BFR strength training using high-load and low-load protocols remain unclear. This study explored the behavioral and neurophysiological mechanisms that explain the differing effects after volume-matched high-load and low-load BFR training.MethodsTwenty-eight healthy participants were randomly assigned to the high-load blood flow restriction (BFR-HL, n = 14) and low-load blood flow restriction (BFR-LL, n = 14) groups. They underwent 3 weeks of BFR training for isometric wrist extension at intensities of 25% or 75% of maximal voluntary contraction (MVC) with matched training volume. Pre- and post-tests included MVC and trapezoidal force-tracking tests (0–75%–0% MVC) with multi-channel surface electromyography (EMG) from the extensor digitorum.ResultsThe BFR-HL group exhibited a greater strength gain than that of the BFR-LL group after training (BFR_HL: 26.96 ± 16.33% vs. BFR_LL: 11.16 ± 15.34%)(p = 0.020). However, only the BFR-LL group showed improvement in force steadiness for tracking performance in the post-test (p = 0.004), indicated by a smaller normalized change in force fluctuations compared to the BFR-HL group (p = 0.048). After training, the BFR-HL group activated motor units (MUs) with higher recruitment thresholds (p < 0.001) and longer inter-spike intervals (p = 0.002), contrary to the BFR-LL group, who activated MUs with lower recruitment thresholds (p < 0.001) and shorter inter-spike intervals (p < 0.001) during force-tracking. The discharge variability (p < 0.003) and common drive index (p < 0.002) of MUs were consistently reduced with training for the two groups.ConclusionsBFR-HL training led to greater strength gains, while BFR-LL training better improved force precision control due to activation of MUs with lower recruitment thresholds and higher discharge rates.

CFD investigation of pouchtype lithium-ion battery

PurposeIn the dynamic realm of energy storage, lithium-ion batteries stand out as a frontrunner, powering a myriad of devices from smartphones to electric vehicles. However, efficient heat management is crucial for ensuring the longevity and safety of these batteries. This paper aims to delve into the process of lithium-ion battery heat management systems, exploring how cutting-edge technologies are used to regulate temperature and optimize performance. In addition, computational fluid dynamics (CFD) studies take center stage, offering insights into the intricate thermal dynamics within these powerhouses.Design/methodology/approachIn this study, thermal behavior of pouch type lithium-ion battery cell has been investigated by using CFD method. Result of different discharge rates have been evaluated by using multi-scale multi-dimensional (MSMD) battery model. By using MSMD Model 0.5C, 1C, 2C, 3C and 5C discharge rates are compared in equivalent circuit model (ECM) and NTGK empirical models by monitoring averaged surface temperature on battery body wall. In addition, on NTGK model, air cooling effect has been studied with the 0.1 m/s, 0.2 m/s and 0.5 m/s air, velocities.FindingsResults shows that higher discharge rate causes higher temperature on battery zones and air cooling is effective to obtain the lower zone temperatures. Also, ECM model gives higher temperature than NTGK model on battery zone.Originality/valueWhen the literature is evaluated, comparison of the models used in battery cooling (ECM and NTGK) has never been done before. Within the scope of this study, model comparison was made. At the same time, the time step has always been ignored in the literature. In this study, both time step and forced convection conditions were considered when comparing the models.

Numerical Modeling of a Low-Cobalt All-Solid-State Cell with Ceramic Electrolyte Using a Deformable Geometry

All-solid-state batteries with a lithium negative electrode and a ceramic electrolyte are key toward high energy density. To ensure a safe, fast, accurate, and cost-effective development of this technology, the experimental methodology must be supported by the numerical modeling approach. This work proposes and describes an electrochemical model of a Li7La3Zr2O12 (LLZO) and Ni-rich NMC-based lithium cell with a deformable lithium negative electrode. Simulations were computed using the finite element method at different operating conditions to demonstrate the scope of the modeling work. Discharge rate tests, deformation tracking, geometric defect investigation, and polarization decomposition are described. Theoretical validation of the mass balance, the stripping rate, the ohmic polarization, and the mesh deformation demonstrated the consistency of the volumetric deformation strategy. We demonstrated in this study a deformable modeling strategy, which was found to be useful for the electrostripping analysis of anodic geometry defects during discharge. Non-uniformity in the lithium stripping rate was found along the anodic interface with defects, and this non-uniformity was accentuated with a higher discharge rate. The cell’s discharge potential was decomposed by considering the equilibrium potential and the polarizations of the main components of the cell. This post-processing was found to be useful for the understanding of the cell’s behavior.

Single-phase static immersion-cooled battery thermal management system with finned heat pipes

Effective thermal management is of critical importance to the performance and safety of lithium-ion batteries. However, research on small and medium-sized battery packs remains scarce. This paper proposes a new immersion cooling method. It combines finned heat pipes with a single-phase static immersion fluid, achieving optimal battery pack homogeneity in existing studies while outperforming the performance of conventional immersion cooling. The method is particularly suitable for energy storage batteries and small and medium-sized battery pack cooling applications. This paper presents a verification of the cooling performance of the cooling method through a combination of simulation analysis and experimental validation. The results demonstrate that the cooling method can enable small and medium-sized battery packs to meet the heat dissipation requirements of 3C or even higher discharge rate under natural convection conditions. In the active cooling scenario, when the battery pack is discharged at a 3C multiplier, the cooling scheme of 9 finned heat pipes can reduce the maximum temperature of the flow-submerged cooled battery pack by 6.4 °C and the maximum temperature difference between cells by 5.3 °C. Even when the battery is discharged at an extreme multiplication rate of 6C, the maximum temperature of the battery pack can be maintained at approximately 60 °C, with a maximum temperature difference between cells of around 15 °C. Based on the aforementioned simulation and experimental results, this paper also validates and analyses the main factors affecting the cooling effect of the method, namely the type of submerged liquid and the number of finned heat pipes.

Simulations on hybrid thermal management of mini-channel cold plate and PCM for lithium-ion batteries under discharging and thermal runaway conditions

In this study, we compared the performance of different structures of mini-channel cold plate (MCP) - phase change material (PCM) hybrid thermal management on discharge and thermal runaway. The heat transfer structures for them can be categorized into three types: (a) uncoupled, (b) semi-coupled, and (c) fully coupled. Among these, the semi-coupled design B exhibits the best performance. Specifically, in the high rate discharge condition, the structure can control the battery temperature at 44.37 °C at low coolant mass flow rate, and the temperature at 36.47 °C at high mass flow rate, while the temperature difference (TD) of a single cell does not exceed 2.01 °C. In a low-multiplier discharge zero-energy system, the pack temperature rise can be limited to no more than 10 °C in 35 °C environment. Under external short-circuit conditions, a lower coolant mass flow rate is sufficient to keep the pack temperature at 43.22 °C. Under internal short-circuit thermal runaway (TR), lower coolant mass flow rate can prolong the TR of the adjacent cell up to 521 s, and higher mass flow rate can completely inhibit the occurrence of TR. The objective of this study is to offer valuable references for the design and implementation of hybrid MCP-PCM cooling systems.

Geospatial analysis of volcano-tectonic interactions: implications for spatiotemporal variations in water quality and quantity at Lake Beseka, East Africa, Ethiopia

ABSTRACT Water quality deterioration in the Main Ethiopian Rift Lakes is a problem affecting the area’s public health and socioeconomic development. The present study aimed to assess the water level rise in Lake Beseka using Landsat images from 1975 to 2023 and dilution trends at the pumping site from 2004 to 2022. In addition, the spatial water quality parameters, including pH, EC, TDS, and water surface temperature, for the years 2007, 2018, 2021, and 2023 were determined. The water level increased dramatically from 3 km2 in the 1960s to 27.5 km2 in 1980 following the construction of the Koka dam and the beginning of irrigation activity (sugarcane plantation) for the Metehara sugar estate factory. The water level reached a maximum (50 km2 in the dry season) in the mid of 1910s and become decreased and fluctuated after 2015. The observed pH, EC, and TDS were higher in the central portion of the lake, grouped under brackish water, and lower in the southwest, south, and northeast shores. The EC and TDS were higher in 2007, decreased in 2018, and fluctuated. The geothermal anomaly of the area varies from 23.1 to 47.9°C with the highest anomaly occurring at the northern side of the lake at a recent volcanic area that interlinked with geological structures. However, the observed and estimated water temperatures of the lake decreased from west to east due to hot spring discharge from the southwest shore of the lake. The series of hot springs in the southwest and west shores of the lake with high discharge rates indicate the presence of structural connectivity that leads to the emission of heat from a deep-seated source and heated groundwater of the area recharged from irrigation activity. Overall, spatiotemporal lake water quality variations were due to anthropogenic and geogenic factors, including hot springs and groundwater discharge to the lake, water level rise and bathymetric depth variation, evaporation, and irrigation activity. This study is significant in continuously estimating water level fluctuations and providing early warnings and preparedness to maintain the region's socioeconomic development.

Regulation of Interfacial Chemistry Enabling High-Power Dual-Ion Batteries at Low Temperatures.

Interfacial chemistry plays a crucial role in determining the electrochemical properties of low-temperature rechargeable batteries. Although existing interface engineering has significantly improved the capacity of rechargeable batteries operating at low temperatures, challenges such as sharp voltage drops and poor high-rate discharge capabilities continue to limit their applications in extreme environments. In this study, an energy-level-adaptive design strategy for electrolytes to regulate interfacial chemistry in low-temperature Li||graphite dual-ion batteries (DIBs) is proposed. This strategy enables the construction of robust interphases with superior ion-transfer kinetics. On the graphite cathode, the design endues the cathode interface with solvent/anion-coupled interfacial chemistry, which yields an nitrogen/phosphor/sulfur/fluorin (N/P/S/F)-containing organic-rich interphase to boost anion-transfer kinetics and maintains excellent interfacial stability. On the Li metal anode, the anion-derived interfacial chemistry promotes the formation of an inorganic-dominant LiF-rich interphase, which effectively suppresses Li dendrite growth and improves the Li plating/stripping kinetics at low temperatures. Consequently, the DIBs can operate within a wide temperature range, spanning from -40 to 45°C. At -40°C, the DIB exhibits exceptional performance, delivering 97.4% of its room-temperature capacity at 1C and displaying an extraordinarily high-rate discharge capability with 62.3% capacity retention at 10C. This study demonstrates a feasible strategy for the development of high-power and low-temperature rechargeable batteries.

Phase structure and electrochemical properties of A5B19 La0.8-xPrxMg0.2Ni3.8 (x = 0–0.3) hydrogen storage alloy anode material

The La0.8-xPrxMg0.2Ni3.8 (x = 0, 0.05, 0.1, 0.2, 0.3) alloy were synthesized useing the induction melting method. X-ray diffraction, scanning electron microscope, electron probe micro analyzer, and electrochemical tests were used to analyze the structure and electrochemical performance of the La0.8-xPrxMg0.2Ni3.8 (x = 0–0.3) alloy. It was studied how the Pr element affected the electrochemical characteristics and microstructure of the A5B19 La-Mg-Ni based hydrogen storage alloy. The results show that the alloy consists of the CaCu5-LaNi5 phase, 2 H-Pr5Co19 phase, and 3R-Ce5Co19 phase. The abundance of the A5B19 phase increase with the increase of Pr content, while the abundance of the LaNi5 phase decrease, and the addition of Pr promotes the formation of the 2 H-Pr5Co19 phase. According to the results of the electrochemical test, every sample has good activation qualities, and the activation can be completed in 3–4 times. The activation properties are not significantly altered by the addition of Pr. The maximum discharge capacity increases at first, then decreases, reaching the highest 371.15 mAh g−1 at x = 0.2. The cyclic stability gradually improves with increasing content of Pr, and the maximum capacity retention rate reaches 85.80 % after 100 cycles. The primary factor influencing the alloy's high rate discharge ability is the exchange current density. With the increase of the exchange current density, the high rate discharge performance is gradually enhanced.

Performance of a combined battery thermal management system with dual-layer phase change materials and air cooling technologies

Lithium-ion batteries are increasingly applied in electric vehicles, energy storage and more. In order to ensure its stable operation under different ambient temperature, an innovative battery thermal management system (BTMS) based on phase change material (PCM) has the dual-layer PCMs arrangement is proposed in this research. To prove the effectiveness of this structure, the temperature variation of lithium-ion battery 18,650 with single PCM and dual-layer PCMs arrangement is calculated and compared by numerical simulation. The findings reveal that the dual-layer PCMs arrangement proposed in this paper has better environmental adaptability at different ambient temperatures (Tamb). When the Tamb is 20 °C and the discharge rate increases from 1C to 5C, the maximum temperature (Tmax) of the battery under the dual-layer PCMs arrangement is 25.33 °C, 30.80 °C, 33.58 °C, 35.80 °C, 39.07 °C, respectively. And in response to the high ambient temperature and high discharge rate, the dual-layer PCMs layout is combined with air cooling to form a hybrid BTMS. The results show that Tmax of the hybrid BTMS is reduced by 21.5 % compared with the PCM-based BTMS when the Tamb is 40 °C and the discharge rate is 3C. The proposed hybrid BTMS with dual-layer PCMs structure controls the Tmax of the battery pack well and the temperature uniformity is also maintained within acceptable level, which has great application potential in battery thermal management.

Mechanical vibration's effect on thermal management module of Li-ion battery module based on phase change material (PCM) in a high-temperature environment

PCM-based systems play a crucial role in managing the thermal conditions of electric vehicle (EV) battery modules, a critical aspect in ensuring their optimal performance. However, an often overlooked facet in current research is the impact of mechanical vibration on EV battery modules during real-world driving scenarios. Addressing this gap, the current article takes a pioneering approach, drawing inspiration from the groundbreaking study by Du and Chen in 2023. This study delves into the effects of mechanical vibration on a PCM-based Battery Thermal Management System (BTMS) specifically adapted for battery modules operating in high-temperature environments. The results, shedding light on a previously underestimated factor, unveil the remarkable ability of mechanical vibration to ameliorate the surge in temperature within the battery module, particularly under high discharge rates. An unprecedented revelation surfaces as mechanical vibration emerges as a factor influencing the thickness of the encapsulated PCM, offering a unique avenue for augmenting the energy density of the powertrain. In this challenging thermal environment, mechanical vibration fosters temperature uniformity among batteries and curtails heat accumulation within the battery module. Remarkably, when the vibration amplitude surpasses a critical threshold, the impact of amplitude variations becomes negligible. Moreover, the intricate relationship between vibration frequency and temperature change complicates the scenario, with medium to high frequencies demonstrating a propensity to enhance the management system's overall thermal performance. These groundbreaking findings transcend the theoretical realm, offering tangible insights with immense implications for practical design and application. By recognizing and harnessing the potential benefits of mechanical vibration, engineers and designers can optimize BTMS, paving the way for more efficient and resilient EV battery modules.

Ramie Degumming Waste‐Derived Biomass Carbon for High‐Performance Lithium–Sulfur Batteries

The application of lithium–sulfur batteries (LSBs) is still hampered by the shuttle effect of soluble lithium polysulfides (LiPSs) intermediates and slow redox kinetics. Therefore, in this work, a novel Mo,N co‐doped porous carbon (Mo,N‐C) was successfully synthesized by simply calcining a mixture of ramie degumming waste with cost‐effective molybdenum salt, and then employed as the LiPSs anchor. Due to the conductive carbon matrix, abundant porous structures as well as the doping Mo and N heteroatoms, the sluggish redox kinetic of the cathode has been significantly improved and the shuttle phenomenon of LiPSs has been effectively inhibited, consequently, the synthesized Mo,N‐C/S‐0.4 composite cathode could demonstrate a good initial capacity of 1379.2 mAh g‐1 at 0.2 C, and the reversible capacity could remain at 997.5 mAh g‐1 after 100 cycles. Even at a high discharge rate of 1.0 C, the capacity could remain at 700.2 mAh g‐1 after 400 cycles. This work provides a new avenue for utilizing the waste biomass on clean energy storage.

Performance analysis of a battery thermal management system combining thermoelectric, composite phase change material, and liquid cooling under extreme operating conditions

To maintain optimal operating temperatures for lithium-ion batteries under extreme operating conditions, a battery thermal management system (BTMS) integrating the thermoelectric cooler (TEC), liquid cooling, and composite phase change material (CPCM) is developed. Moreover, a transient numerical model has been established, considering thermal, electrical, and fluid multiphysics fields, to precise evaluation the system's performance. The outcomes indicate a decrease in both the maximum battery temperature and CPCM liquid fraction as the expanded graphite (EG) mass fraction, TEC cooling input current, and coolant flow speed increase. Furthermore, the temperature difference among batteries exhibits a decrease as the EG mass fraction increases, but experiences an elevation with an increase in both current and coolant flow speed. The BTMS features the lowest power consumption and optimal cooling performance at the EG mass fraction of 12 %, the TEC cooling input current of 3 A, and the coolant flow speed of 0.05 m/s. In preheating situations, the battery pack can achieve a temperature of 293.15 K starting from 263.15 K with the assistance of TEC preheating input currents of 4 A and 5 A, taking 5600 s and 2240 s, respectively, to complete the entire preheating procedure. This study will offer new insights into the advancement of the BTMS, allowing for the control of battery temperatures in high-temperature and high-discharge rate conditions, coupled with preheating at low-temperature.

Water/N,N-Dimethylacetamide-Based Hybrid Electrolyte and Its Application to Enhanced Voltage Electrochemical Capacitors

The growing interest in hybrid (aqueous–organic) electrolytes for electrochemical energy storage is due to their wide stability window, improved safety, and ease of assembly that does not require a moisture-free atmosphere. When it comes to applications in electrochemical capacitors, hybrid electrolytes are expected to fill the gap between high-voltage organic systems and their high discharge rate aqueous counterparts. This article discusses the potential applicability of aqueous–organic electrolytes utilizing water/N,N-dimethylacetamide (DMAc) solvent mixture, and sodium perchlorate as a source of charge carriers. The hydrogen bond formation between H2O and DMAc (mole fraction xDMAc = 0.16) is shown to regulate the original water and cation solvation structure, thus reducing the electrochemical activity of the primary aqueous solution both in the hydrogen (HER) and oxygen (OER) evolution reactions region. As a result, an electrochemical stability window of 3.0 V can be achieved on titanium electrodes while providing reasonable ionic conductivity of 39 mS cm−1 along with the electrolyte’s flame retardant and anti-freezing properties. Based on the diagnostic electrochemical studies, the operation conditions for carbon/carbon capacitors have been carefully optimized to adjust the potential ranges of the individual electrodes to the electrochemical stability region. The system with the appropriate electrode mass ratio (m+/m− = 1.51) was characterized by a wide operating voltage of 2.0 V, gravimetric energy of 13.2 Wh kg−1, and practically a 100% capacitance retention after 10,000 charge–discharge cycles. This translates to a significant rise in the maximum energy of 76% when compared to the aqueous counterpart. Additionally, reasonable charge–discharge rates and anti-freeze properties of the developed electrolyte enable application in a broad temperature range down to −20 °C, which is demonstrated as well.

Regulating sodium deposition by specific surface area composite ratio for anode-free Na metal batteries

Anode-free sodium metal batteries (AFSMBs) have greater potential to be one of the electrochemical storage technology choices for high energy density. However, the anode-free current collector is more likely to grow dendrites than the metal anode. Here we report a transformative structural combination strategy to build an anode-free current collector with an ultraconformal structure between the conducting network and metallic sodium deposition space in anode-free metal batteries. The reversibility of the sodium plating/stripping process is significantly enhanced using this strategy, achieving stable operation for more than 2100 cycles at current density (1 mA cm−2) with 1 mA h cm−2 while maintaining an average coulombic efficiency of 99.5 %. The Na-diffused ZnIn2S4 current collector delivers an excellent maximum current density of 10 mA cm−2. In addition, optimization of the structure in the ZnIn2S4||Na3V2(PO4)3 full cell system leads to the successful realization of high-energy-density anode-free sodium cells. These cells exhibit excellent cycling stability under high-rate discharge conditions (5 C), with a capacity retention rate of 91 % after more than 500 cycles. The study presents a promising strategy for constructing an ultraconformal structural framework for high-performance AFSMBs.

Characterising sex-related differences in lower- and higher-threshold motor unit behaviour through high-density surface electromyography.

Emerging questions in neuromuscular physiology revolve around whether males and females share similar neural control in diverse tasks across a broad range of intensities. In order to explore these features, high-density electromyography was used to record the myoelectrical activity of biceps brachii during trapezoidal isometric contractions at 35% and 70% of maximal voluntary force (MVF) on 11 male and 13 female participants. Identified motor units were then classified as lower-threshold (recruited at ≤30%MVF) and higher-threshold (recruited at>30%MVF). The discharge rate, interspike interval variability, recruitment and derecruitment thresholds, and estimates of neural drive to motor neurons were assessed. Female lower-threshold motor units showed higher neural drive (P<0.001), accompanied by higher discharge rate at recruitment (P=0.006), plateau (P=0.001) and derecruitment (P=0.001). On the other hand, male higher-threshold motor units showed greater neural drive (P=0.04), accompanied by higher discharge rate at recruitment (P=0.005), plateau (P=0.04) and derecruitment (P=0.01). Motor unit discharge rate normalised by the recruitment threshold was significantly higher in female lower-threshold motor units (P<0.001), while no differences were observed in higher-threshold motor units. Recruitment and derecruitment thresholds are higher in males across all intensities (P<0.01). However, males and females have similar activation and deactivation strategies, as evidenced by similar recruitment-to-derecruitment ratios (P>0.05). This study encompasses a broad intensity range to analyse motor unit sex-related differences, highlighting higher neural drive and discharge rates in female lower-threshold motor units, elevated recruitment and derecruitment thresholds in males, and convergences in activation and deactivation strategies. HIGHLIGHTS: What is the central question of the study? Do male and female motor units behave similarly in low- and high-intensity contractions? What is the main finding and its importance? Female motor units show higher discharge rates in low-intensity tasks and lower discharge rates in high-intensity tasks, with no differences in recruitment behaviour. A broader inter-spike interval variability was also observed in females. These findings underline that there are sex-specific differences concern the firing strategies based on task intensity.

Effect of low temperature and high-rate cyclic aging on thermal characteristics and safety of lithium-ion batteries

With the popularity of electric vehicles and climate change, it has become a typical scene to charge lithium-ion batteries (LIBs) at low temperatures at a high rate. Low temperature and high-rate charge and discharge would change the performance and then affect temperature rises, heat production and thermal runaway (TR) characteristics. This study tests the temperature rises of aging 18650 LIBs at various ambient temperatures and charge and discharge rates. The entropy and enthalpy changes of the batteries are computed based on the entropy coefficients, and subsequently, the heat productions of the batteries are computed. The TR test is carried out to explore the influence of rapid aging at low temperature environment on the thermal safety of LIBs. In this work, the heat generation mechanism and thermal runaway characteristics of lithium-ion batteries after low-temperature and high-rate cyclic aging are introduced in detail, aiming to provide a reference for the process safe design and application of lithium-ion batteries at low-temperature and fast charging scenarios.

VO2/VS4 heterostructures structure–modified 3D reduced graphene oxide aerogel as an advanced host for lithium–sulfur batteries

Lithium–sulfur batteries face challenges including volume expansion, slow reaction kinetics, and shuttle effects. To overcome these limitations, we utilized a combination of vanadium–based heterostructures and conductive porous reduced graphene oxide aerogels to improve charge transfer kinetics. The researchers synthesised vanadium–based reduced graphene oxide aerogels (VO2/VS4@RGO) via tube furnace calcination and a one–step hydrothermal method. Vanadium–based heterostructures were electrostatically adsorbed onto the surface of three–dimensional reduced graphene oxide aerogels. The fibrous structure of VO2/VS4 promoted charge transfer, while the high conductivity of VS bonds lowered the surface reaction barrier. The VO2/VS4@RGO–3/S cathode exhibited outstanding cycling stability at a high discharge rate of 2C, demonstrating an initial discharge specific capacity of 771.94 mAh g−1 and an average decay rate of 0.071 % after 700 cycles. It also maintained excellent electrochemical performance under high sulfur loading.