Degradation of Li/S Battery Electrodes On 3D Current Collectors Studied Using X-ray Phase Contrast Tomography

Abstract

Lithium/sulphur batteries are promising candidates for future energy storage systems, mainly due to their high potential capacity. However low sulphur utilization and capacity fading hinder practical realizations. In order to improve understanding of the system, we investigate Li/S electrode morphology changes for different ageing steps, using X-ray phase contrast tomography. Thereby we find a strong decrease of sulphur loading after the first cycle, and a constant loading of about 15% of the initial loading afterwards. While cycling, the mean sulphur particle diameters decrease in a qualitatively similar fashion as the discharge capacity fades. The particles spread, migrate into the current collector and accumulate in the upper part again. Simultaneously sulphur particles lose contact area with the conducting network but regain it after ten cycles because their decreasing size results in higher surface areas. Since the capacity still decreases, this regain could be associated with effects such as surface area passivation and increasing charge transfer resistance.

Combining operando synchrotron X-ray tomographic microscopy and scanning X-ray diffraction to study lithium ion batteries

“…Recently, these X-ray synchrotron techniques have found widespread attention in the lithium ion battery research community123456789101112. While synchrotron X-ray diffraction techniques have been successfully applied to study the phase transformation mechanisms in LiFePO 4 olivine structures8111314 for example, tomographic microscopy was shown to be an excellent tool to track volumetric changes and the resulting crack formation and mechanical degradation mechanisms in alloy anodes upon electrochemical cycling4.…”

Three-Dimensional Visualization of Gas Evolution and Channel Formation inside a Lithium-Ion Battery

“…25 Due to the high fluxes generated by synchrotron sources, synchrotron X-ray imaging has evolved into a powerful characterization tool in the field of materials science. [26][27][28][29][30][31][32][33][34][35][36] Especially synchrotron X-ray tomography has enabled researchers to obtain unprecedented insights into LIBs from the level of individual particles to the scale of entire electrodes. [37][38][39][40] Most recently, Ebner et al, have directly observed and quantified electrochemical and mechanical degradation in a SnO anode.…”

Investigation of non-woven carbon paper as a current collector for sulfur positive electrode—Understanding of the mechanism and potential applications for Li/S batteries

“…Charge capacities of 1027 mAh g -1 and 560 mAh g -1 were obtained for NWC and Al based electrodes respectively, with irreversible capacity loss of ~ 8 % for both cells. In the second cycle, the upper discharge plateau is shifted to higher potential value (2.4 V), which could be explained, as previously reported, 26 by active material reorganization and improved electrode conductivity after first step of sulfur dissolution/formation. In addition, initial cell overpotential may depend on the lithium surface and its resistive passivation layer, which may be improved after first lithium stripping/plating cycle too.…”

“…4b,d, left), therefore confirming the fact that the active material (sulfur or Li 2 S) spreads onto the NWC current collector upon cycling. 26 However, according to our previous report, 26 the largest fraction of sulfur was located on the top of the electrode, where the ink was deposited. This result was in accordance with the higher active surface area of Super P® conductive additive than NWC one.…”