Increasing Energy Densities of Sulfur Cathodes using Dispersing and Calendering Processes for Lithium–Sulfur Batteries

Abstract

Lithium–sulfur batteries are nearly ready to be commercialized. However, each material composition has specific challenges regarding its adaption to state of the art production lines of lithium‐ion batteries. The influence of the dispersing and calendering process on the battery performance is investigated with an easy‐to‐implement material approach and a solvent‐based process. The slurry is treated by different dispersing intensities using an extruder and a triple roller mill, which leads to increased energy densities. The coating is calendered to increase the energy density by maintaining the specific capacity. The reactions within the sulfur cathodes are investigated by evaluating the potentials of the upper and lower voltage plateaus. It was determined that the variation of the process parameters leads to a changed reactivity of the polysulfide reactions but not to a shift of the sulfur utilization within the sulfur cathodes. The process parameters influence the pore structure of the cathode, resulting in different sensitivities for higher C‐rates.

The Importance of Swelling Effects on Cathode Density and Electrochemical Performance of Lithium−Sulfur Battery Cathodes Produced via Dry Processing

“…These results conflict not only with the ones made by the group of Xiao [24] but also with the ones of Gröbmeyer et al [23] However, these results agree with the studies of Kim et al, [26] as well as with the Kwade group. [25] Both used cathodes with comparable electrode densities (0.6-1.1 g cm À3 ) and showed that the compaction of the cathode has a negligible influence on its performance and capacity at moderate C-rates. Kim et al demonstrated an increase in cycling stability by heavily compacting their cathodes (1.7 g cm À3 ) at elevated temperatures.…”

“…This in accordance to the results of Titscher et al, who demonstrated that macropores are eliminated by calendering. [25] In the SEM images with the highest magnification (Figure 1c,f ), the single carbon nanoparticles and the multi-walled carbon nanotubes (MWCNTs) can be observed.…”

“…In the literature, it is demonstrated by mercury intrusion studies that the calendering of S/C slurrybased cathodes has no influence on the inner porosity of the KB/S agglomerates, whereas it decreases the porosity created by the interparticular distances. [25] The compaction of the dry-film cathodes by calendering leads to severe reduction of the overall cathode porosity. The initial porosity of the noncalendared cathode (active material coating) is 56%, whereas the porosity invoked by pores smaller than 5 μm is 47%.…”

“…Furthermore, they demonstrated that slight densification of the cathode yields a higher initial discharge capacity, yet reduces cycling stability and the batteries' lifetime. [24] In contrast, the groups of Kwade and Zaghib reported that the compaction of the cathode does not influence the performance of the cell at C rates <1 C. [25,26] These studies are hardly comparable through as different electrolyte/sulfur (E/S) ratios, cell types, testing, carbon host materials, sulfur loadings, and electrolytes were applied.…”

Sustainability Assessment and Engineering of Emerging Aircraft Technologies—Challenges, Methods and Tools

“…Foreground data models refer to the processes related to the system under consideration concerning its whole life cycle (i.e., repositories of experimental results from measurements, simulations, calculations, or reports regarding materials, components or processes, industry-specific data, or company internal data). Looking into batteries, considering the different processes for the production lines (e.g., processing electrodes: dispersing, formulation, coating, drying, and calendaring), the process strategies and parameters can strongly influence the energy density of the cathode and the performance of the battery, as investigated for the case of sulfur batteries [15]. In this way, in order to model the foreground processes related to the battery technology involved, understanding the interactions between battery cell production technologies, material and process parameters, and product properties are necessary.…”