Four-Dimensional Studies of Morphology Evolution in Lithium–Sulfur Batteries

Abstract

Lithium sulfur (Li–S) batteries have great potential as a successor to Li-ion batteries, but their commercialization has been complicated by a multitude of issues stemming from their complex multiphase chemistry. In situ X-ray tomography investigations enable direct observations to be made about a battery, providing unprecedented insight into the microstructural evolution of the sulfur cathode and shedding light on the reaction kinetics of the sulfur phase. Here, for the first time, the morphology of a sulfur cathode was visualized in 3D as a function of state of charge at high temporal and spatial resolution. While elemental sulfur was originally well-dispersed throughout the uncycled cathode, subsequent charging resulted in the formation of sulfur clusters along preferred orthogonal orientations in the cathode. The electrical conductivity of the cathode was found not to be rate-limiting, suggesting the need to optimize the loading of conductive carbon additives. The carbon and binder domain and surrounding bulk pore phase were visualized in the in situ cell, and contrast changes within both phases were successfully extracted. The applications of this technique are not limited to microstructural and morphological characterization, and the volumetric data can serve as a valuable input for true 3D computational modeling of Li–S batteries.

Developments in X-ray tomography characterization for electrochemical devices

“…A key example of the use of three-phase mapping has been demonstrated by Usseglio-Viretta et al [70] who produced a comprehensive study comparing tortuosity-factor estimation methods for graphite and NMC electrodes. However, the applications of three-phase mapping and quantification are not limited to LIBs: Tan et al [71,72] assessed the effective molecular diffusivity of the pore phase and electrical conductivity of the conductive carbon and binder phase via three-phase segmentation in order to conduct simulations of a lithium-sulfur cell.…”

X‐ray Nano‐computed Tomography of Electrochemical Conversion in Lithium‐ion Battery

“…Advanced ex and in situ measurements have promoted fundamental understanding of the structural and morphological modifications along with the effects of metal oxide composition on the conversion reaction features . Among the various investigative approaches, three‐dimensional imaging at the micro‐ and nanoscale may actually shed light on the particle evolution throughout the lithium‐exchange process and reveal crucial morphological parameters for electrode modelling, such as the phase volume fraction and the particle size distribution . In particular, X‐ray nano‐computed tomography (CT) enables a detailed reconstruction of the spatial distribution of the various electrode components and provides useful qualitative compositional information associated with the attenuation of the incident beam .…”

“…[21,27,[30][31][32][33] Among the variousi nvestigative approaches, three-dimensional imaging at the micro-and nanoscale may actually shed light on the particle evolution throughout the lithium-exchange process and reveal crucial morphological parameters for electrode modelling, such as the phase volumef raction and the particle size distribution. [34][35][36] In particular, X-ray nano-computed tomography (CT) enablesadetailed reconstruction of the spatiald istribution of the various electrode components [37] and provides useful qualitative compositional information associated with the attenuation of the incident beam. [38] Insightsi nto the displacementp rocess may pave the way for improved performance by aiming at effective employment of metal oxides as anodes in efficient and stable full-cells, which is considered essential to demonstrate the applicability of this class of materials.…”

4D imaging of lithium-batteries using correlative neutron and X-ray tomography with a virtual unrolling technique

“…I n recent years, the advancement of X-ray computed tomography (CT) capabilities have facilitated a broadening of our understanding of battery materials and devices, with studies spanning multiple length scales, from nanometre to millimetre, and multiple time scales from kilohertz to microhertz 1 . These studies have collectively provided insight into the relationship between electrode microstructure and performance [2][3][4] , battery architecture, safety [5][6][7][8] and new battery materials [9][10][11] . While the majority of these studies have utilised X-ray CT, there is growing interest in the application of neutron imaging for battery applications; the complementarities of X-ray and neutron imaging, which are sensitive to electron and nuclear density, respectively, provide significant opportunities for correlative studies.…”