Analysis of thermal management and anti-mechanical abuse of multi-functional battery modules based on magneto-sensitive shear thickening fluid

Electric vehicles(EVs)have garnered significant attention as a vital driver of economic growth and environmental sustainability.Nevertheless,ensuring the safety of high-energy batteries is now a top priority that cannot be overlooked during large-scale applications.This paper proposes an innovative active protection and cooling integrated battery module using smart materials,magneto-sensitive shear thickening fluid(MSTF),which is specifically designed to address safety threats posed by lithium-ion batteries(LIBs)exposed to harsh mechanical and environmental conditions.The theoretical framework introduces a novel approach for harnessing the smoothed-particle hydrodynamics(SPH)methodology that incorporates the intricate interplay of non-Newtonian fluid behavior,capturing the fluid-structure coupling inherent to the MSTF.This approach is further advanced by adopting an enhanced Herschel-Bulkley(H-B)model to encapsulate the intricate rheology of the MSTF under the influence of the magnetorheological effect(MRE)and shear thickening(ST)behavior.Numerical simulation results show that in the case of cooling,the MSTF is an effective cooling medium for rapidly reducing the temperature.In terms of mechanical abuse,the MSTF solidifies through actively applying the magnetic field during mechanical compression and impact within the battery module,resulting in 66%and 61.7%reductions in the maximum stress within the battery jellyroll,and 31.1%and 23%reductions in the reaction force,respectively.This mechanism effectively lowers the risk of short-circuit failure.The groundbreaking concepts unveiled in this paper for active protection battery modules are anticipated to be a valuable technological breakthrough in the areas of EV safety and lightweight/integrated design.

A pre-strain strategy of current collectors for suppressing electrode debonding in lithium-ion batteries

The interfacial debonding between the active layer and the current collector has been recognized as a critical mechanism for battery fading,and thus has attracted great efforts focused on the related analyses.However,much still remains to be studied regarding practical methods for suppressing electrode debonding,especially from the perspective of mechanics.In this paper,a pre-strain strategy of current collectors to alleviate electrode debonding is proposed.An analytical model for a symmetric electrode with a deformable and limited-thickness current collector is developed to analyze the debonding behavior involving both a pre-strain of the current collector and an eigen-strain of the active layers.The results reveal that the well-designed pre-strain can significantly delay the debonding onset(by up to 100%)and considerably reduce the debonding size.The critical values of the pre-strain are identified,and the pre-strain design principles are also provided.Based on these findings,this work sheds light on the mechanical design to suppress electrode degradation.

Effects of stress dependent electrochemical reaction on voltage hysteresis of lithium ion batteries

Intercalation of lithium ions into the electrodes of lithium ion batteries is affected by the stress of active materials, leading to energy dissipation and stress dependent voltage hysteresis. A reaction-diffusion-stress coupling model is established to investigate the stress effects under galvanostatic and potentiostatic operations. It is found from simulations that the stress hysteresis contributes to the voltage hysteresis and leads to the energy dissipation. In addition, the stress induced voltage hysteresis is small in low rate galvanostatic operations but extraordinarily significant in high rate cases. In potentiostatic operations, the stresses and stress induced overpotentials increase to a peak value very soon after the operation commences and decays all the left time. Therefore,a combined charge-discharge operation is suggested, i.e., first the galvanostatic one and then the potentiostatic one. This combined operation can not only avoid the extreme stress during operations so as to prevent electrodes from failure but also reduce the voltage hysteresis and energy dissipation due to stress effects.

Two-way coupled analysis of lithium diffusion and diffusion induced finite elastoplastic bending of bilayer electrodes in lithium-ion batteries

A fully coupling model for the diffusion induced finite elastoplastic bending of bilayer electrodes in lithium-ion batteries is proposed. The effect of the mechanical stress on the lithium diffusion is accounted for by the mechanical part of the chemical potential derived from the Gibbs free energy along with the logarithmic stress and strain. Eight dimensionless parameters, governing the stress-assisted diffusion and the diffusion induced elastoplastic bending, are identified. It is found that the finite plasticity starting from the interface of the bilayer increases the chemical potential gradient and thereby facilitates the lithium diffusion. The full plastic flow makes the abnormal lithium concentration distribution possible, i.e., the concentration at the lithium inlet can be lower than the concentration at the interface(downstream). The increase in the thickness of the active layer during charging is much larger than the eigen-stretch due to lithiation, and this excess thickening is found to be caused by the lithiation induced plastic yield.

Review on electrode-level fracture in lithium-ion batteries

Fracture occurred in electrodes of the lithium-ion battery compromises the integrity of the electrode structure and would exert bad influence on the cell performance and cell safety.Mechanisms of the electrode-level fracture and how this fracture would affect the electrochemical performance of the battery are of great importance for comprehending and preventing its occurrence.Fracture occurring at the electrode level is complex,since it may involve fractures in or between different components of the electrode.In this review,three typical types of electrode-level fractures are discussed:the fracture of the active layer,the interfacial delamination,and the fracture of metallic foils(including the current collector and the lithium metal electrode).The crack in the active layer can serve as an effective indicator of degradation of the electrochemical performance.Interfacial delamination usually follows the fracture of the active layer and is detrimental to the cell capacity.Fracture of the current collector impacts cell safety directly.Experimental methods and modeling results of these three types of fractures are concluded.Reasonable explanations on how these electrode-level fractures affect the electrochemical performance are sorted out.Challenges and unsettled issues of investigating these fracture problems are brought up.It is noted that the state-of-the-art studies included in this review mainly focus on experimental observations and theoretical modeling of the typical mechanical damages.However,quantitative investigations on the relationship between the electrochemical performance and the electrode-level fracture are insufficient.To further understand fractures in a multiscale and multi-physical way,advancing development of the cross discipline between mechanics and electrochemistry is badly needed.

Analysis of diffusion induced elastoplastic bending of bilayer lithium-ion battery electrodes

Bilayer electrode, composed of a current collector layer and an active material layer, has great potential in applications of in-situ electrochemical experiments due to the bending upon lithiation. This paper establishes an elastoplastic theory for the lithiation induced deformation of bilayer electrode with consideration of the plastic yield of current collector. It is found that the plastic yield of current collector reduces the restriction of current collector to an active layer, and therefore, enhances in-plane stretching while lowers down the rate of electrode bending. Key parameters that influence the elastoplastic deformation are identified. It is found that the smaller thickness ratio and lower elastic modulus ratio of current collector to an active layer would lead to an earlier plastic yield of the current collector, the larger in-plane strain, and the smaller bending curvature, due to balance between the current collector and the active layer. The smaller yield stress and plastic modulus of current collector have similar impacts on the electrode deformation.

Prelithiation design for suppressing delamination in lithium-ion battery electrodes

Prelithiation has been intensively investigated in high-capacity lithiumion batteries(LIBs).However,the optimization of prelithiation degrees for long service life of LIBs still remains a challenge.The positive effect of prelithiation on suppressing degradation of LIBs,besides directly pursuing the high first Coulomb efficiency which has been widely reported in the literature,is revealed and discussed based on an analytical model focusing on the interfacial delamination in electrodes.For full charge-discharge cycling,well-designed prelithiation can effectively suppress the delamination and reduce the debonding size by approximately 25%,compared with the case without prelithiation.For the strategy combining partial charge-discharge cycling and prelithiation,the largest reversible capacity without debonding can be significantly improved by approximately100%with well-designed prelithiation.This work is expected to provide a prelithiation design principle and further improve the mechanical stability of LIB electrodes.

西江流域大型底栖无脊椎动物物种多样性及维持机制

作为我国第三大河流珠江的主支,西江孕育了丰富且独特的生物多样性。受多重人为压力影响,流域内生物多样性日渐降低。然而,人们对西江底栖动物物种多样性格局及维持机制的认识明显不足。本研究基于历史文献调研和2021–2023年现场调查,系统评估了西江主要水体底栖动物物种多样性,厘定和编撰物种名录,甄别驱动群落结构变化的关键因子及受胁因素,并提出保护对策。结合历史文献和实地调查,共记录大型底栖无脊椎动物5门10纲33目150科437属704种(历史记录506种,2021–2023年调查记录352种),中国特有种占比高达26%。现场调查结果显示,全流域底栖动物的平均密度和平均生物量分别为437.53 ind./m^(2)和38.65 g/m^(2)。全流域的优势种为长足摇蚊属一种(Tanypus sp.)、雕翅摇蚊属一种(Glyptotendipes sp.)、纹沼螺(Parafossarulus striatulus)和河蚬(Corbicula fluminea)。支流、干流和湖泊的底栖动物群落结构差异显著,支流的物种丰富度、Simpson优势度指数和Shannon-Wiener多样性指数均高于干流和湖泊。典范对应分析显示,海拔、电导率、高锰酸盐指数等环境因子和空间因子是影响群落结构的重要因素。方差分解表明,支流和湖泊的群落主要受环境过滤驱动,而干流的群落主要受空间过程(质量效应)的影响。流域内的多重人类活动(航运业、大型水利设施、挖沙业、水体污染、土地无序开发利用和外来种入侵等)严重威胁底栖动物多样性。建议采取相应对策,包括打击过度捕捞、管控挖沙业、恢复湖滨带以维持水文自然节律、控制污染物排放以及科学防控外来入侵种等。

Effects of calendering state on coupled electrochemical-mechanical performance of silicon based composite electrodes

The super volume changes and severe mechanical degradation have been a hindrance in the wide application of silicon based composite electrodes in commercial lithium-ion batteries(LIBs).Calendering,one procedure in producing LIBs'electrodes,is indispensable to ensure low porosity and energy density.However,the repercussions of the calendering process on the physical characteristics related to the behavior of silicon(Si)based electrodes during the electrochemical reaction have not been well understood.Thus,on account of the deformation characteristic of cantilever electrodes,an in-situ technique is employed to analyze the repercussions of calendering status on the coupled electro-chemo-mechanical performances.During the electrochemical cycling,Young's modulus and diffusion-induced stress in composite electrodes are quantified.The results show that the swelling strain,the stress and the modulus of the Si-based electrode and the calendering degree are positively correlated.Meanwhile,the stress induced by diffusion in the active layer tends to increase in the stage of lithiation and reverses during the delithiation process.Accompany with the SEM analysis,we conclude that the calendering process can induce larger stress,driving the formation of cracks in electrodes.These findings can help understand how the calendering process could affect the capacity dissipating and lifetime of Si based electrodes.

长江上游支流赤水河流域底栖动物物种多样性与保护对策

作为长江上游唯一未在干流建坝的一级支流和长江上游珍稀特有鱼类国家级自然保护区的核心区,赤水河流域孕育和保护了极为丰富的底栖动物多样性。然而对赤水河底栖动物的了解仍不充分,缺乏涵盖整个流域的连续性、季节性的底栖动物调查。本研究于2019–2021年按季度开展4次调查,系统评估了赤水河水系底栖动物物种多样性,更新了物种名录,甄别出其驱动机制及受胁因素,并提出相应的保护对策。本次调查共记录底栖动物5门9纲22目86科186属209种。全流域优势种均为昆虫类,如蜉蝣属一种(Ephemera sp.)、扁蜉属一种(Heptagenia sp.)、河花蜉属一种(Polamanthus sp.)、四节蜉属一种(Baetis sp.)、潜水蝽科一种(Naucoridae sp.)和多足摇蚊属一种(Polypedilum sp.)。春季底栖动物的物种丰富度、Shannon-Wiener多样性指数、Simpson优势度指数、Pielou均匀度指数均高于其他季节。上游的密度、物种丰富度、Shannon-Wiener多样性指数和Simpson优势度指数均明显高于中下游。主坐标分析显示,不同季节和不同河段间底栖动物群落结构差异显著。冗余分析结果显示,底栖动物的分布主要受底质、海拔、流速、溶解氧、NH4+-N和大尺度空间因子PCNM1、PCNM2、PCNM3、PCNM6的驱动。方差分解结果表明,环境过滤对群落结构的影响大于空间因子(随机效应)。流域内的多重人类活动(如支流的梯级电站、采矿业、土地开发利用、酿酒业、旅游业等)严重影响底栖动物多样性。建议采取退耕还林、维持水文的自然节律、管控采矿业和酿酒业、优化防治外来入侵种等一系列对策,建立有效的预测和风险评估机制。

雅鲁藏布江中下游底栖动物物种多样性及其影响因素

雅鲁藏布江流域维系着丰富而独特的生物资源,是全球生物多样性研究的热点区域。然而,该流域底栖动物多样性的调查却极不充分。本文于2015年10月和2016年3月对雅鲁藏布江干流(朗县至墨脱段)和主要支流的底栖动物进行了调查,并采用单因素方差分析(one-way ANOVA)和典范对应分析(canonical correspondence analysis)等对群落多样性格局进行解析。共采集到底栖动物270种,隶属于5门8纲20目92科,包括昆虫纲246种,寡毛纲14种,腹足纲4种,其他动物6种。春季和秋季分别采集到底栖动物184种和214种,优势种均以喜清洁和冷水的水生昆虫为主,包括四节蜉属一种(Baetissp.)、花翅蜉属一种(Baetiella sp.)、蚋属一种(Simulium sp.)、小突摇蚊属一种(Micropsetra sp.)和短石蛾属一种(Brachycentrus sp.)等。全流域平均密度为939.1 ind./m^(2),平均生物量为5.44 g/m2。底栖动物的物种组成、密度和多样性在季节和区域之间存在一定差异,支流的多样性显著高于干流。典范对应分析显示,海拔、流速、河宽和底质类型等环境因子是影响雅鲁藏布江流域底栖动物群落结构的关键环境因素,而大峡谷地区多变的气候类型和地理阻隔是造成群落变化的根本原因。本研究可为雅鲁藏布江流域底栖动物多样性评估和环境监测提供重要的基础和参考。

南洞庭湖区软体动物物种多样性评估及保护对策

洞庭湖孕育和维持了较高和独特的软体动物多样性。尽管有关该湖软体动物的调查较多,但多分散于各文献中。本文结合文献调研和现场调查(2013–2018年),系统评估了南洞庭湖区软体动物物种多样性,解析驱动群落格局演变的关键因子,并提出合理的保护对策。共记录2纲5目14科33属87种(腹足纲41种,双壳纲46种),其中本调查记录54种,隶属于2纲5目12科31属,包括腹足纲22种,双壳纲32种。评估结果显示处于近危和受威胁等级物种21种,包括腹足纲4种和双壳纲17种。调查区域软体动物平均密度和生物量分别为173.1 ind./m2和279.3 g/m2。优势种为河蚬(Corbicula fluminea)、大沼螺(Parafossarulus eximius)、铜锈环棱螺(Bellamya aeruginosa)、卵河螺(Rivularia ovum)。基于距离的冗余分析(distance-based redundancy analysis, dbRDA)结果显示,局域环境因子(底质类型、水深、pH、总溶解固体和总磷)制约软体动物的群落变异。另外,区域内的人类活动(如商业采砂、建坝和沿岸土地利用、过度捕捞和非法电捕等)亦深刻影响软体动物的生存。这些人类干扰已导致软体动物物种多样性显著下降,可能造成一些特有物种的局域性灭绝。为了恢复和保护软体动物物种多样性和资源,应采取一系列对策,包括管控合法的挖沙业和取缔非法挖沙业、禁止过度捕捞和非法电捕、维持水文的自然节律、恢复沿岸自然湖滨带和控制点源和面源污染物排入等。我们呼吁尽快在南洞庭湖区建立软体动物国家级自然保护区,以保护该湖区(可能是整个洞庭湖)残存的软体动物物种多样性和特有性。

Agricultural Risk Factors Influence Microbial Ecology in Honghu Lake

Agricultural activities, including stock-farming, planting industry, and fish aquaculture,can affect the physicochemical and biological characters of freshwater lakes. However, the effects of pollution producing by agricultural activities on microbial ecosystem of lakes remain unclear.Hence, in this work, we selected Honghu Lake as a typical lake that is influenced by agriculture activities. We collected water and sediment samples from 18 sites, which span a wide range of areas from impacted and less-impacted areas. We performed a geospatial analysis on the composition of microbial communities associated with physicochemical properties and antibiotic pollution of samples. The co-occurrence networks of water and sediment were also built and analyzed. Our results showed that the microbial communities of impacted and less-impacted samples of water were largely driven by the concentrations of TN, TP, NO_3^--N, and NO_2^--N, while those of sediment were affected by the concentrations of Sed-OM and Sed-TN. Antibiotics have also played important roles in shaping these microbial communities: the concentrations of oxytetracycline and tetracycline clearly reflected the variance in taxonomic diversity and predicted functional diversity between impacted and less-impacted sites in water and sediment samples, respectively. Furthermore, for samples from both water and sediment, large differences of network topology structures between impacted and less-impacted were also observed. Our results provide compelling evidence that the microbial community can be used as a sentinel of eutrophication and antibiotics pollution risk associated with agricultural activity; and that proper monitoring of this environment is vital to maintain a sustainable environment in Honghu Lake.

PREDICTIVE APPROACH TO FAILURE OF COMPOSITE LAMINATES WITH EQUIVALENT CONSTRAINT MODEL

This work established a new analytical model based upon the equivalent constraint model （ECM） to constitute an available predictive approach for analyzing the ultimate strength and simulating the stress/strain response of general symmetric laminates subjected to combined loading, by taking into account the effect of matrix cracking. The ECM was adopted to mainly predict the in-plane stiffness reduction of the damaged laminate. Basic consideration that progressive matrix cracking provokes a re-distribution of the stress fields on each lamina within laminates, which greatly deteriorates the stress distributed in the primary load-bearing lamina and leads to the final failure of the laminates, is introduced for the construction of the failure criterion. The effects of lamina properties, lay-up configurations and loading conditions on the behaviors of the laminates were examined in this paper. A comparison of numerical results obtained from the established model and other existed models and published experimental data was presented for different material systems. The theory predictions demonstrated great match with the experimental observations investigated in this study.

A modified pulse charging method for lithium-ion batteries by considering stress evolution,charging time and capacity utilization

The stress evolution, total charging time and capacity utilization of pulse charging (PC) method are investigated in this pape匚 It is found that compared to the conventional constant current (CC) charging method, the PC method can accelerate the charging process but will inevitably cause an increase in stress and a decrease in capacity. The charging speed for PC method can be estimated by the mean current. By introducing stress control, a modified PC method called the PCCC method, which starts with a PC operation followed by a CC operation, is proposed. The PCCC method not only can accelerate charging process but also can avoid the stress raising and capacity loss occurring in the PC method. Furthermore, the optimal pulsed current density and switch time in the PCCC method is also discussed.

Stress-Induced Uphill Diffusion with Interfacial Contact Loss in Solid-State Electrodes

We simulate the mechanical-chemical coupling during delithiation and relaxation of a cathode in a solid-state lithium-ion battery.Contact loss at the interface between the active particle and the solid electrolyte is considered.Uphill diffusion is observed during delithiation and relaxation.This phenomenon is explained by analyzing the total chemical potential and its two components.Contact loss at the interface greatly influences the stress and stress gradient in the active particle.As delithiation continues,the stress and stress gradient grow considerably,and the mechanical part of the total chemical potential becomes dominant over the chemical part of it.In the latter stage of delithiation,the influence of the incomplete interfacial constraint on the stress becomes dominant,while the effect of the concentration gradient becomes negligible.After relaxation,the concentration and stress gradients increase in a particle with contact loss.The influence of the degree of contact loss on the mechanical-chemical coupling is investigated.The overall tensile stress in the active particle increases with decreasing contact loss,causing a sharp decrease in local concentration.We also check the effect of the elastic modulus of the solid electrolyte on the coupling of the active material.A rigid solid electrolyte with a higher elastic modulus more strongly restricts the active particle,leading to a higher tensile stress,a larger stress gradient,and a greater concentration gradient.

Understanding Modulus Variation of the Active Layers of Silicon Composite Electrodes

The variation of the effective modulus of silicon composite electrodes,which is a fundamental feature to analyze the coupled mechanical–electrochemical behavior of Si-based electrodes in high-capacity lithium-ion batteries,remains qualitatively controversial.To clarify the contradictory experimental results,numerical modeling of a representative volume element with silicon particles,carbon-binder domains(CBDs),and pores has been performed for the lithiation process.The key parameters for modulus variation were identified and evaluated.A mesostructure change is proposed to be a crucial mechanism that affects the modulus variation,and silicon softening is another key mechanism.Silicon softening and the decreasing CBD volume fraction collectively result in a decrease in the effective modulus of the composite,whereas an increase in the silicon volume fraction along with a decrease in porosity has the opposite effect.The findings of this work provide an in-depth and fundamental understanding of the mechanical properties of silicon composite electrodes.

Lithium Diffusion and Stress in a Polycrystalline Film Electrode

In the present work, the two-dimensional analytical solution for Li diffusion in grains and grain boundaries of a polycrystalline film electrode is established with consideration of Li-segregation at the grain boundary. The stress field induced by the inhomogeneity of Li con- centration, called chemical stress here for brevity, is analyzed via the finite element simulation. The effects of the grain boundary including its size, its diffusion coefficient as well as the segrega- tion phenomenon on the solute concentration and the chemical stress are examined. It shows that grain boundaries can assist fast diffusion and significantly affect the stress profile in the whole film. It proves that tailoring the grain boundary size or other grain boundary-related parameters may provide an alternative strategy for improving the overall diffusivity and mechanical stability of battery electrodes.