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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Due to the complex mesostructure and components of composite active layers in lithium-ion battery (LIB) electrodes, coupled with the concentration-dependent material properties and eigenstrains, efficiently estimating the effective modulus of the active layers remains a great challenge. In this work, the classic Mori–Tanaka method is found to be unable to estimate the modulus of the active layer. By realizing the importance of the mesostructure feature, a rod-rod model is proposed. The resulting modulus is expressed analytically. It is shown that the rod-rod model can accurately estimate the modulus evolution of the active layer if the material properties of the components and the evolution of volume fractions are known in advance. Moreover, a simplified rod-rod model is also developed to reduce the complexity of the proposed method. By knowing the volume fractions at two arbitrary states of charge and subsequently determining two constants, the simplified model can estimate the modulus efficiently. Considering both its accuracy and its simplicity, the simplified rod-rod model is the most suitable for the estimation. Thus, the methods developed in this work provide a new perspective for analyzing the material properties of composite active layers in LIB electrodes. [ABSTRACT FROM AUTHOR]

Prelithiation has been intensively investigated in high-capacity lithium-ion batteries (LIBs). However, the optimization of prelithiation degrees for long service life of LIBs still remains a challenge. The positive efffect 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 approximately 100% with well-designed prelithiation. This work is expected to provide a prelithiation design principle and further improve the mechanical stability of LIB electrodes. [ABSTRACT FROM AUTHOR]

Abstract This article sheds light on advantages of fast charging methods with time-varying current. Analytical solutions of concentration and stress for charging processes with general time-varying currents are derived. A fast charging protocol for a multistage constant current of gradually decreasing value is first evaluated. A properly designed multistage constant-current method is able to simultaneously suppress stress overflow and accelerate charging, but stress undulation induced by sharp switching between stages is inevitable. A charging scheme with a nonlinear exponential current is then investigated. The applied current varies continuously and smoothly with time so stress undulation is avoided. Suggestions for the design of an exponential current method are proposed to achieve the best charging acceleration without sacrificing charging capacity or increasing risk of mechanical failures. A well-designed exponential-current method is superior to a multistage constant-current method in accelerating charging speed. [ABSTRACT FROM AUTHOR]

This article demonstrates the design of charging strategies for lithium ion batteries with considering the balance between diffusion induced stress and total charge time for two- and three-stage charge methods. For the two-stage galvanostatic-potentiostatic charge method the low mechanical stress can be achieved without increasing total charge time by switching the galvanostatic to the potentiostatic at the time moment when the lithium concentration at the surface of particles reaches the limit c ¯ surf = 0 . A three-stage method, which consists of an initial galvanostatic stage of high current, a galvanostatic stage of low current and a potentiostatic ending stage, is suggested. Employing the initial galvanostatic stage of high current is helpful not only in accelerating the charge process, but also in controlling the mechanical stress once the electrical current and time duration of the initial galvanostatic stage are properly designed. [ABSTRACT FROM AUTHOR]

The state of charge (SOC) or the depth of discharge (DOD) to and the time to delamination onset and the critical size for delamination, which are potentially important in lithium ion battery design for preventing the patterned thin film electrodes from delamination, are investigated. A theoretical approach based on the cohesive model is proposed to formulate the time to and the SOC (or DOD) to delamination onset, as well as the critical size for patterned disk-like electrodes. It is found that for negative electrode the delamination initiation is dominated by mode-II during cell charging and by mode-I during cell discharging. For positive electrode both delamination modes are theoretically possible during cell charging. When the electrochemical load factor i ¯ is very high, the mode-I delamination is possible and an optimal size of electrodes exists for a given maximum i ¯ . The SOC to mode-II delamination onset decreases significantly with increasing dimensionless radius, being independent of i ¯ . When the mode-II is the dominated mode the critical size for delamination exists, and a formula for the critical size for delamination has been deduced, which is proportional to interface ductility and inversely proportional to maximum volumetric strain. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, structural configuration of layered Li-ion battery electrode plates is evaluated by analytically formulating the diffusion induced stress. Both symmetric electrode and asymmetric bilayer electrode are discussed. The thickness ratio and the modulus ratio of current collector to active plate are analytically identified to be the important influence parameters on the stress. Applying a material with smaller elastic modulus for current collector could reduce the peak stresses in both current collector and active plate. Increasing the thickness of current collector would reduce the stress in itself while promote the stress in active plate. Therefore, from mechanical viewpoint on designing an electrode, the material for current collector should be as soft and flexible as possible. And the thickness of current collector should be in an appropriate range. Basically, it should be as small as possible on the precondition that the mechanical strength is satisfied. Finally, effects of three charging conditions, i.e. uniform, galvanostatic, and potentiostatic, on the diffusion induced stress is discussed. It is found the maximum stresses for three cases are linear to the total amount of intercalated lithium ions. Based on the stresses, an optimized charging operation, i.e. first galvanostatic followed by potentiostatic, is suggested. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Mechanical properties and lithiation-induced stress are crucial to the performance and durability of lithium-ion batteries. Here, we report the evolution of elastic modulus and stress in a silicon/polyvinylidene fluoride (PVDF) composite electrode coated on a copper foil, along with a model for analyzing the large change in the radius of curvature of the composite electrode/copper foil cantilever. The radius of curvature of the cantilever is captured by a video camera during lithiation/delithiation. The elastic modulus of the composite electrode decreases from about 0.64 GPa to 0.18 GPa during lithiation. It decreases further to about 0.10 GPa after delithiation, which is caused by the fracture of the electrode. The magnitude of the compressive stress increases lineally during lithiation and decreases suddenly to reach a steady state value during delithiation. [ABSTRACT FROM AUTHOR]

In this study, a nanorod-like FeO/graphene nanocomposite is synthesized by a facile template-free hydrothermal method and a following calcination in air at 300 °C for 2 h. The FeO nanorods with diameter of 15-30 nm and length of 120-300 nm are homogenous distributed on both sides of graphene. The morphologies of intermediates at different hydrothermal reaction times are investigated by transmission electron microscopy (TEM) characterization, and a possible growth mechanism of this one-dimensional structure is proposed. It is shown that the α-FeOOH rodlike precursors are formed through a rolling-broken-growth (RBG) model, then the α-FeOOH is transformed into α-FeO nanorods during calcinations, preserving the same rodlike morphology. Electrochemical characterizations demonstrate that the FeO nanorod/graphene composites exhibit a very large reversible capacity of 1063.2 mAh/g at the charge/discharge rate of 0.1 C. [ABSTRACT FROM AUTHOR]