Mechanistic Insights into the Cycling Behavior of Sulfur Dry‐Film Cathodes

Abstract

All‐solid‐state lithium–sulfur batteries (ASSB‐LiS batteries) are considered among advanced candidates for next‐generation energy storage systems, as they break with restrictions and limitations that liquid electrolytes impose on lithium‐ion batteries and lithium‐sulfur batteries (LiS‐batteries), meaning enhanced safety and higher energy densities. However, investigations under realistic conditions on pouch cell level are challenging, as it is necessary to implement a scalable preparation method for sheet‐type cathodes with high sulfur utilization and loading. In this study, a solvent‐free process to prepare free‐standing cathode sheets with low binder content down to 0.1 wt% PTFE is demonstrated. The contribution of binder and electrolyte on the conversion reaction of sulfur is discussed. Sheet‐type cathodes reach nearly theoretical sulfur utilization of 1672 mAh gS−1 and outstanding reversible capacity retention with 72% of initial discharge capacity after 400 cycles by adapting cut‐off voltages to the stability window of the electrolyte. Furthermore, an all‐solid‐state pouch cell is demonstrated using the dry‐film cathode, which is successfully tested for 50 cycles at different C‐rates. Thickness monitoring of the cell stack gives fundamental insights into the volume change and breathing behavior of both cathode and anode.

A review of polymers in sulfide-based hybrid solid-state electrolytes for all-solid-state lithium batteries

“…Compared with wetcoating techniques, dry-film techniques demonstrate other advantages of environmental friendliness by removing volatile organic compounds (VOCs) originating from organic solvents, cost reduction in processing, and maintaining sulfide SSEs' intrinsic properties (e.g., ionic conductivity) with the elimination of a side reaction with solvents. [211][212][213] Thus, it provides promising prospects for the battery industry.…”

Co, Ni-Free Ultrathick Free-Standing Dry Electrodes for Sustainable Lithium-Ion Batteries

“…Dry electrode fabrication is an exciting pathway toward sustainable electrode manufacturing that avoids the use of conventional toxic solvents, although the use of polytetrafluoroethylene (PTFE) comes with other challenges. In general, dry electrode fabrication can be classified into three techniques: electrostatic spray dried (ESD) electrodes, , soft template (holey graphene) assisted electrodes, , and fibrillation of the binder. ,− The ESD method involves an additional high-voltage source, and the scalability of the method is debatable. , The holey graphene-assisted electrode has limitations associated with the additional inactive component and requires high pressure for the electrode roll-to-roll fabrication . The third method is currently the most affordable on a manufacturing scale and requires only slight adjustments in the current manufacturing lines. , By using a fibrillation polymer (e.g., PTFE), the electrode thickness can be tuned without the binder-carbon migration phenomenon which on its own is the main advantage .…”

“…LMO dry electrodes with various conductive agents and PTFE were fabricated based on previous reports. , All the components were mixed in a hot mortar and pestle for several minutes, followed by passing the mixture through a hot roll press at 80 °C to prepare thick, free-standing electrodes (see Supporting Information for details). During the mortar and pestle mixing process, the three-dimensional molecular chains in PTFE transform into a less ordered structure with shear force.…”

“…10 Moreover, thick dry electrodes can sufficiently reduce the pack size and increase the overall energy density of the pack, favoring practical applications. 20,27 In this study, a solvent-free method for creating Co-and Nifree LiMn 2 O 4 (LMO) dry electrodes using a fibrillation polymer has been successfully developed for Li-ion batteries. To ensure a sustainable approach, Co-and Ni-free electrodes, LMO, and Li 4 Ti 5 O 12 (LTO) were carefully selected as the cathode and anode materials, respectively, in the current study.…”

“…The third method is currently the most affordable on a manufacturing scale and requires only slight adjustments in the current manufacturing lines. , By using a fibrillation polymer (e.g., PTFE), the electrode thickness can be tuned without the binder-carbon migration phenomenon which on its own is the main advantage . Moreover, thick dry electrodes can sufficiently reduce the pack size and increase the overall energy density of the pack, favoring practical applications. , …”