Influence of carbon binder domain on the performance of lithium‐ion batteries: Impact of size and fractal dimension

Abstract

A lithium-ion battery (LIB) cathode comprises three major components: active material, electrical conductivity additive, and binder. The combination of binder and electrical conductivity additive leads to the formation of composite clusters known as the carbon binder domain (CBD) clusters. Preparation of a LIB cathode strongly influences the dispersion of the above-mentioned constituents leading to the formation of distinct pore and electrical conduction networks. The resulting structure thus governs the performance of LIBs. The presence of CBD is essential for the structural integrity and sufficient electrical conductivity of the LIB cathode. However, CBD abundance in LIB cathodes leads to unfavorable gravimetrical and volumetrical consequences owing to its electrochemical inertness. Increasing CBD content adds to the weight of the LIBs, thus negatively impacting the energy density. Furthermore, increased electrical conductivity is won at a cost of ionic conductivity as CBD clusters breach the pore networks in the cathode microstructure. The following study establishes a link between the various possibilities of CBD cluster size and fractal dimension that may eventualize during the mixing process of slurry preparation to the resulting microstructural properties and hence to the performance of LIBs by means of idealized cathode geometries. Since the performance determining processes occur at the microstructural scale, which are often very tedious to study via experimental research, the study makes use of spatially resolving microstructural, numerical, simulations. The results demonstrate that the CBD cluster size has a strong influence on the cathode microstructure. The CBD cluster fractal dimension on the other hand displayed a minor influence on the structural properties of the cathode, and the size of the cluster primary particles was shown to be the dominant factor. Finally, performance evaluation simulations confirmed the trends seen in structural properties with changing cluster size and fractal dimension.

Application of Poly-L-Lysine for Tailoring Graphene Oxide Mediated Contact Formation between Lithium Titanium Oxide LTO Surfaces for Batteries

“…The microscopic findings indicate that a layer-wise assembly was implemented and that similar findings for their topography and thickness are expected for the layers formed on LTO as for the layers formed on TiO 2 when using the PLL approach described in previous sections. Thin-layer and well-dispersed rGO is desirable to decrease the amount of carbon that does not contribute to the contact area with the LTO surface, because it is the constituent that helps to enhance the electrical conductivity but decreases ionic conductivity and also increases the volume and weight of the electrode [ 60 ]. However, obtaining a completely wrapped particle without proving ion conduction paths might not allow for sufficient ion transport and therefore would be unfavorable [ 61 ].…”

Numerical Investigation of Conductivity Additive Dispersion in High‐Power and High‐Energy NMC‐Based Lithium‐Ion Battery Cathodes: Application‐Based Guidelines

“…To transform the particulate assemblies resulting from the previously elaborated DEM simulations into half‐cell computational domain, at first these were extended periodically. [ 19 ] Subsequently, to prepare the particulate assemblies for meshing in Simcenter STAR–CCM+, [ 24 ] the point contacts between the particle were treated by means of the surface wrapper utility. [ 25 ] Herein, points on the surfaces of particles closer than a predefined size were bridged together to form a sort of wrap over the entire assembly.…”

“…However, with rising tip speeds, the peak of the agglomerates diminishes and the population of the aggregates and smaller fragments rises. To the realize the change in microstructure that would result from such deagglomeration during mixing the measured size distributions were incorporated into idealized cathode geometries [ 19 ] intended for numerical investigations. The idealized geometries generated for the purpose of this work are composed of the active component, lithium nickel manganese cobalt oxide (NMC), and the passive component, comprising the conductivity additive and the binder modeled as smooth spheres.…”

Insights into Influencing Electrode Calendering on the Battery Performance

“…From work in electrochemical impedance spectroscopy (EIS) and modeling it has been seen that a variety of parameters, including the intrinsic properties of the CAM, the structure of the oxide particles and the interface between the oxide particle and the carbon network all have a significant influence on the performance. [61,65,70,75,[146][147][148][149] For this reason, it is important to better understand the properties of different CAMs and how the calendering processes of cathodes based on these CAMs impact the electrode morphology, material properties, and electrochemical performance.…”