From Powder to Sheets: A Comparative Electrolyte Study for Slurry-Based Processed Solid Electrolyte/Binder-Sheets as Separators in All-Solid-State Batteries

Abstract

A key for the market penetration of large-scale and high energy All-Solid-State Batteries (ASSBs) are sheet-type cell components. Herein, we report a slurry-based process to obtain free-standing solid electrolyte (SE)/binder composite sheets as ASSB separators. We investigate three different sulfidic solid electrolyte systems (Li6PS5Cl, Li7P3S11 and Li10SnP2S12) in combination with a hydrogenated nitrile butadiene rubber (HNBR). By means of electrochemical impedance spectroscopy (EIS), the influence of separator composition and processing on the ionic sheet conductivity is evaluated. Independent of the solid electrolyte material, a reduction by a factor of three compared to the pristine powder conductivity at 70 MPa operation pressure and by a factor of eight compared to the maximum powder conductivity is observed. This can be attributed to the addition of the ionically isolating binder, which however is necessary for the production of freestanding sheets. We show the beneficial effect of pre-compressing the sheets to little porosity values on the apparent sheet conductivity. Lastly, we investigate and decouple the influence of fabrication and operating cell pressure on the produced separator sheets.

A Micro-Reference Electrode for Electrode-Resolved Impedance and Potential Measurements in All-Solid-State Battery Pouch Cells and Its Application to the Study of Indium-Lithium Anodes

“…The semi-circles at high frequencies (f apex = 131 kHz, marked by black dots) can be ascribed to the separator resistance. 36 The latter can be more clearly seen in the cell impedance (purple line; see inset), indicating a separator resistance of ∼960 Ω cm 2 ; considering the separator thickness of ∼760 μm (note that a ∼2-fold thicker separator was used for the Li|Li cell compared to that shown in Fig. 1d), leads to a separator conductivity of ∼0.08 mS cm −1 , which is in good agreement with our previous data for a separator porosity of ∼15% and a stack pressure of 3 MPa.…”

“…1d), leads to a separator conductivity of ∼0.08 mS cm −1 , which is in good agreement with our previous data for a separator porosity of ∼15% and a stack pressure of 3 MPa. 36 The resistance contributions of the separator to the Li WE and the Li CE are 464 Ω cm 2 and 492 Ω cm 2 , respectively, indicating that the GWRE is located midway between the two electrodes, which is an important prerequisite for artifact-free impedance measurements using a μμ-RE. 22,39 For the individual electrode impedances, the large semi-circle at mid-frequencies (23 kHz-4 Hz; f apex = 712 Hz, marked by the black triangles) can be assigned to the interface resistance of the separator and the Li metal electrodes, which includes the SEI formed on the lithium metal and the physical contact between lithium and the separator, whereas the low-frequency semi-circles (4 Hz-50 mHz; f apex = 0.5 Hz, marked by black diamonds) represent the chargetransfer resistance.…”

“…Separator and electrode and preparation.-LPSCl/HNBR-composite separator sheets with 5 wt-% HNBR were prepared by a slurry-based process in toluene, as described in our previous work. 36 Pure indium and lithium electrodes were punched using a square punch (Spahn GmbH & Co. KG, Germany) with a side length of 20 mm.…”

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

“…6(a)). 182,183,192,193 The family of rubber binders, including nitrile butadiene rubber (NBR), 194,195 hydrogenated nitrile butadiene rubber (HNBR), 196,197 butadiene rubber (BR), 198 styrene-butadiene rubber (SBR), 199 styrene-butadiene-styrene copolymer (SBS), 200 styrene-ethylene-butylene-styrene copolymer (SEBS) 201 and silicone rubber (SR) 202 is a good example of the case.…”

Impact of fabrication methods on binder distribution and charge transport in composite cathodes of all-solid-state batteries

“…Polymer binders are typically employed in the manufacturing process, which can be categorized as either slurry cast wet or solventfree dry processes [12][13][14]. The dominant electrode manufacturing technology is wet process which involves using organic solvent to create a slurry of active materials, conductive carbon and a soluble polymer binder [15,16]. We previously utilized nitrile butadiene rubber (NBR) in fabricating thin SE membrane [17], leveraging NBR's solubility in nonpolar solvents, which is considered less reactive with sensitive sulfide-based SEs.…”