“…Therefore, the fracture of porous electrodes would begin in larger particles. This phenomenon has been verified by many researchers who have studied the fracture of electrodes by numerical simulations or experimental observations …”
Section: Resultsmentioning
confidence: 98%
“…This phenomenonh as been verified by many researchers who have studied the fracture of electrodes by numerical simulations [1-4, 6, 7, 9, 12, 17, 23-26, 31, 44, 45] or experimental observations. [1,20,24,37,42,43,46] Stressesg enerated from the dischargingp rocess were the oppositeo ft hose in the charging process because the effect of stress on diffusion was ignored. Furthermore,t he tensile and compressiveD ISs of electrode particles were of variable amplitude because the concentration of Li ions at agiven position would changed uring charge/discharge cycles.T hat is to say,p re-existing cracksw ould extend upon both discharge and recharge because of the formation of new cracks during dischargea nd recharge.T hesen ew cracks would also appear during subsequent cycles.Z hu et al, [22] who studied DIS and the initial defects in spherical LiMn 2 O 4 particles also found that stress evolution during charge and discharge were different.…”
Section: Fracturemechanisms Of Porouselectrodesmentioning
confidence: 99%
“…Klinsmann et al. developed a coupled model of diffusion mechanics and cracking to study not only the conditions of crack formation during insertion but also the fracturing of storage particles during Li extraction using a phase‐field method. Sun et al .…”
Section: Introductionmentioning
confidence: 99%
“…Many researchers have explored the relationship between particle size and fracturing [16,21] to find that there is ac riticale lectrode particle size that allows fracturing to be avoided.Z hu et al [22] studied the effect of particle size and aspect ratio on the propagation of fractures within LiMn 2 O 4 particles during charge and discharge using the extendedf inite element method. Barai and Mukherjee [23] exploredthe influence of particlesize,concentration-dependent elastic modulus,a nd cycling on fractures within the active particles.K linsmann et al developed ac oupled model of diffusion mechanics and cracking to study not only the conditions of crack formationd uring insertion [24] but also the fracturing of storage particles during Li extraction [25] using ap hase-field method. Sun et al [26] found that crack formation, distribution,a nd density are related to the Li ion concentration and gradient.…”
A multiscale model of porous electrodes based on the Gibbs free energy is developed, in which the Li ion diffusion, diffusion‐induced stress (DIS), and polydispersities of electrode particle sizes are considered. The relationships between the size polydispersities and the concentration profiles and DIS evolution are investigated numerically. Li ion distributions are verified by in situ observation of color changes in a commercial porous graphite electrode. Simulations show small particles exhibit higher charge/discharge degrees and more rapid charge/discharge rates than large particles at the same macroscopic state of charge (SOC)/depth of discharge (DOD). Moreover, DIS is different in different size particles at a specific SOC and DOD, that is, there is a nonuniformly distributed stress field within porous electrodes during the charge/discharge processes. For SOC and DOD, which represent the macroscopic average states of charge and discharge, the influence of the microscopic SOC values and mass fractions of differently sized particles in porous electrodes should, therefore, be considered. Additionally, the fracture of particles in porous electrodes is likely caused by varied amplitude tensile‐compressive DISs during charge/discharge cycles. Reduced sizes and size polydispersities of electrode particles are prone to alleviate these stresses and thus improve battery performance.
“…Therefore, the fracture of porous electrodes would begin in larger particles. This phenomenon has been verified by many researchers who have studied the fracture of electrodes by numerical simulations or experimental observations …”
Section: Resultsmentioning
confidence: 98%
“…This phenomenonh as been verified by many researchers who have studied the fracture of electrodes by numerical simulations [1-4, 6, 7, 9, 12, 17, 23-26, 31, 44, 45] or experimental observations. [1,20,24,37,42,43,46] Stressesg enerated from the dischargingp rocess were the oppositeo ft hose in the charging process because the effect of stress on diffusion was ignored. Furthermore,t he tensile and compressiveD ISs of electrode particles were of variable amplitude because the concentration of Li ions at agiven position would changed uring charge/discharge cycles.T hat is to say,p re-existing cracksw ould extend upon both discharge and recharge because of the formation of new cracks during dischargea nd recharge.T hesen ew cracks would also appear during subsequent cycles.Z hu et al, [22] who studied DIS and the initial defects in spherical LiMn 2 O 4 particles also found that stress evolution during charge and discharge were different.…”
Section: Fracturemechanisms Of Porouselectrodesmentioning
confidence: 99%
“…Klinsmann et al. developed a coupled model of diffusion mechanics and cracking to study not only the conditions of crack formation during insertion but also the fracturing of storage particles during Li extraction using a phase‐field method. Sun et al .…”
Section: Introductionmentioning
confidence: 99%
“…Many researchers have explored the relationship between particle size and fracturing [16,21] to find that there is ac riticale lectrode particle size that allows fracturing to be avoided.Z hu et al [22] studied the effect of particle size and aspect ratio on the propagation of fractures within LiMn 2 O 4 particles during charge and discharge using the extendedf inite element method. Barai and Mukherjee [23] exploredthe influence of particlesize,concentration-dependent elastic modulus,a nd cycling on fractures within the active particles.K linsmann et al developed ac oupled model of diffusion mechanics and cracking to study not only the conditions of crack formationd uring insertion [24] but also the fracturing of storage particles during Li extraction [25] using ap hase-field method. Sun et al [26] found that crack formation, distribution,a nd density are related to the Li ion concentration and gradient.…”
A multiscale model of porous electrodes based on the Gibbs free energy is developed, in which the Li ion diffusion, diffusion‐induced stress (DIS), and polydispersities of electrode particle sizes are considered. The relationships between the size polydispersities and the concentration profiles and DIS evolution are investigated numerically. Li ion distributions are verified by in situ observation of color changes in a commercial porous graphite electrode. Simulations show small particles exhibit higher charge/discharge degrees and more rapid charge/discharge rates than large particles at the same macroscopic state of charge (SOC)/depth of discharge (DOD). Moreover, DIS is different in different size particles at a specific SOC and DOD, that is, there is a nonuniformly distributed stress field within porous electrodes during the charge/discharge processes. For SOC and DOD, which represent the macroscopic average states of charge and discharge, the influence of the microscopic SOC values and mass fractions of differently sized particles in porous electrodes should, therefore, be considered. Additionally, the fracture of particles in porous electrodes is likely caused by varied amplitude tensile‐compressive DISs during charge/discharge cycles. Reduced sizes and size polydispersities of electrode particles are prone to alleviate these stresses and thus improve battery performance.
“…The formation of diffusion‐induced mechanical stresses within the active material is one of the reasons for its mechanical degradation and the associated measurable loss of capacity . In this context, a large number of numerical investigations on single active material particles show that the magnitude of the mechanical stresses depend on the shape and size of the particles and can thereby exceed the tensile strength of the material . This is particularly the case when it comes to phase separation processes …”
Summary
An electrochemical model that is capable to simulate charge and species transport within the three‐dimensional particulate cathode structure of lithium‐ion battery half‐cells is applied to blended electrodes. The electrodes are assumed to consist of physical mixtures of LiMn2O4 (LMO) and Li[Ni1/3Co1/3Mn1/3]O2 (NMC) as cathode active materials. The results of the numerical simulations reveal that there is a significant temporal variation in the distribution of the intercalation current between the active materials on the particulate level. In this context, the LMO component was found to be electrochemically inactive at the beginning and at the end of a simulated discharge process that leads to the identification of a suitable operating window of the half‐cells between 0.2 < DOD < 0.8. It is shown that within this range, a relaxation of the maximum lithium concentration gradients within the NMC component is achievable. As this provides indications of reduced mechanical stresses within the active material particles, an increased cycling stability of this kind of blended electrodes is expectable. Because of the NMC component's higher volumetric capacity compared with LMO, the separator‐near arrangement of NMC allows the magnitude of ionic current density to be reduced by up to 11% compared with a random particle arrangement. As this indicates a reduction of potential temperature‐induced side reactions of the electrolyte, an increased cycle life of the half‐cells, especially for high‐performance applications, is anticipated. Consequently, multiple‐layer coating processes appear particularly attractive for the production of optimized blended positive electrodes for lithium‐ion batteries.
To meet the booming demand of high‐energy‐density battery systems for modern power applications, various prototypes of rechargeable batteries, especially lithium metal batteries with ultrahigh theoretical capacity, have been intensively explored, which are intimated with new chemistries, novel materials and rationally designed configurations. What happens inside the batteries is associated with the interaction of multi‐physical field, rather than the result of the evolution of a single physical field, such as concentration field, electric field, stress field, morphological evolution, etc. In this review, multi‐physical field simulation with a relatively wide length and timescale is focused as formidable tool to deepen the insight of electrodeposition mechanism of Li metal and the electro‐chemo‐mechanical failure of solid‐state electrolytes based on Butler‐Volmer electrochemical kinetics and solid mechanics, which can promote the future development of state‐of‐the‐art Li metal batteries with satisfied energy density as well as lifespan.
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