Influence of Microstructure on Impedance Response in Intercalation Electrodes

Abstract

The active particle morphology and microstructure affect the impedance behavior of intercalation electrodes due to the underlying charge transport, active material/electrolyte interfacial surface area, and solid-phase diffusion in lithium-ion batteries (LIB). In order to capture the impact of the electrode microstructural variability on the impedance response, an integrated electrochemical impedance predictive analysis is presented. In the analysis, stochastically reconstructed 3-D microstructures of representative LIB electrodes are considered with variations in the active material morphology and particle size distribution. With the properties evaluated from the virtual 3-D microstructures, the corresponding impedance response is predicted. The concept of electrochemical Sauter mean diameter (ESMD) has been introduced to investigate the effect of active particle morphology, such as particle agglomeration. This integrated analysis is envisioned to offer a virtual impedance response probing framework to elucidate the influence of electrode microstructural variability and underlying electrochemical and transport interactions. Lithium-ion batteries (LIBs), due to their favorable energy density and power capability, are considered as the candidate of choice for vehicle electrification. [1][2][3][4] To further improve the cell performance, different efforts have been undertaken to study the microstructural characteristics, including electrode thickness, 5 porosity, 6 particle size, 7 conductive additives 8 and composition. 9 Particularly, the influence of electrode microstructure on charge (i.e. electron and ion) transport, and solid-phase diffusion is critical, which ultimately affects the cell performance.One of the powerful methods for analyzing the electrochemical and transport behavior in porous electrodes is the electrochemical impedance spectroscopy (EIS), which measures the response of a small perturbation of potential or current.10-17 By investigating the impedance response, the charge transport resistance, including electron transport in the solid phase, ionic transport in the electrolyte, solid-state diffusion in the active material, and the intercalation process, can be quantified.14,18-26 Meyers et al. proposed a mathematical model to capture the impedance behavior of a spherical active particle dependent on the physical properties related to the faradaic and nonfaradaic impedance.14 The model also included the effect of particle size distribution on the impedance response.The impedance response of intercalation electrodes, which is sensitive to the interfacial processes, the surface morphology, and the charge transport, has been described mathematically by the fundamental physical approach for various electrochemical systems.14,27-39The effect of various properties, such as electrical and ionic conductivity, and layer thickness, have been investigated by Levi and Aurbach. 28 Besides the electrode properties (e.g. electrical conductivity, ionic conductivity, and layer thickness), the electrode microst...

Towards Next Generation Lithium-Sulfur Batteries: Non-Conventional Carbon Compartments/Sulfur Electrodes and Multi-Scale Analysis

“…36 The carbon framework substrate, the porous structure that stores solid sulfur and provides pathways for ionic transport, was artificially generated by using a stochastic method. [37][38][39][40] During the reconstruction process, the spherical pores were randomly distributed within the carbon substrate, with the actual pore size distribution assigned in accordance with our experimentally fabricated carbon framework. Here, the spherical pores were permitted to overlap with one another.…”

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