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 surround...
Highlights
Lithium sulfur (Li−S) batteries have the potential to supersede conventional Li-ion technology, in applications that require high gravimetric energy densities, offering a factor of ca. 6 higher theoretical gravimetric energy density (2567 Wh kg−1 of sulfur) compared to Li-ion technology[1] (387 Wh kg−1 of LiCoO2)
Morphological parameters of the sulfur phase were extracted from volumetric image data at different states of charge through the first cycle, and where elemental sulfur was not present, contrast evolution of the carbon binder domain and surrounding electrolyte percolated bulk pore phase was analyzed
Electrochemical performance was equivalent to larger 1/2′′ Swagelok-type cells made from the same electrode material and electrolyte, demonstrating that the miniaturized cell design was sufficiently representative and that X-ray exposure had a negligible effect on the sample.[24]
Summary
Lithium sulfur (Li−S) batteries have the potential to supersede conventional Li-ion technology, in applications that require high gravimetric energy densities, offering a factor of ca. 6 higher theoretical gravimetric energy density (2567 Wh kg−1 of sulfur) compared to Li-ion technology[1] (387 Wh kg−1 of LiCoO2). Lithium sulfur (Li−S) batteries have the potential to supersede conventional Li-ion technology, in applications that require high gravimetric energy densities, offering a factor of ca. In addition to active material loss to the electrolyte phase, polysulfide solubility invariably results in a phenomenon known as the polysulfide shuttle effect, where mobile charged polysulfide species shuttle between the sulfur electrode and lithium metal electrode, driven by a potential difference and exacerbated at low C-rate. In addition to parasitic losses during charge, gas evolution results from degradation of the lithium metal anode because of side reactions with commonly used ether-based electrolytes.[3] a significant volumetric penalty on energy density arises from the need for a substantial amount of conductive carbon additives within the sulfur electrode because of the electrically insulating nature of S8 and Li2S
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