Three‐dimensional simulation of transport processes within blended electrodes on the particle scale

Abstract

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.

Ternary Cathode Blend Electrodes for Environmentally Friendly Lithium‐Ion Batteries

“…[14] Supported by simulation studies, the different working potentials result in significantly higher stress of one material at a given potential and the performance of the blend is negatively affected. [15] In contrast to these studies, blend electrodes are generally reported to show advantageous electrochemical performance. As frequently reported, particle-particle interactions of different active materials lead to synergistic effects within the electrode.…”

“…used a model system without intermixed particles to show that the currents applied during charge and discharge are inhomogenously distributed among the different electroactive materials [14] . Supported by simulation studies, the different working potentials result in significantly higher stress of one material at a given potential and the performance of the blend is negatively affected [15] . In contrast to these studies, blend electrodes are generally reported to show advantageous electrochemical performance.…”

Simultaneous effect of particle size and location on stress development in the electrodes of lithium‐ion batteries

“…11 Dai et al reported that the stress level in LiMn 2 O 4 (LMO) particles can be reduced by blending in LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) particles. 12 However, since the single and P2D models are limited in capturing the complex microstructural characteristics of electrodes, electrochemical models that combine with the two-dimensional (2D) 13 or three-dimensional (3D) electrode model 14 have been proposed. For example, Xu et al developed a three-dimensional electrode particle model to explain the relationship between mechanical failure and impedance increase.…”

Spatially resolved lithium‐ion battery simulations of the influence of lithium‐nickel‐manganese‐cobalt‐oxide particle roughness on the electrochemical performance

“…In this publication, the electrochemical model published by Kespe et al [17][18][19] is used. It consists of two nonoverlapping domains and considers the charge and mass transport in a spatially resolved positive electrode.…”

“…The focus was mainly on mechanical degradation. Kespe et al [17][18][19] developed a 3D model taking into account periodic electrode structures consisting of smooth and spherical particles, whereby different particle sizes, the electrode structure, the carbon black distribution and blended cathodes were used to derive recommendations for optimized manufacturing processes. Mistry et al 20 investigated the complex interaction of the electrochemically coupled transport processes using spherical AM particles and the effect of the carbon black morphology and electrode porosity on battery performance.…”