Effect of Slurry Properties on the Cathode Wet Process in Sulfide-based All-Solid-State Batteries

Abstract

To improve the energy density and establish a mass production system for sulfide-based all-solid- state batteries (ASSBs) with fire safety and high energy density, wet process and thick electrodes are required. These enable the use of conventional lithium-ion battery (LIB) technology and facilitate mass production. However, problems such as electrode material non-uniformity arise due to sedimentation, migration by evaporation flux, and agglomeration. This study investigates the electrode material non- uniformity and its impact on electrode resistance, depending on the properties of sulfide-based ASSBs cathode slurry. Electrode material non-uniformity varies with the solid concentration and the material ratio of the slurry, acting as a factor that increases resistance and deteriorates cell performance. At low solid concentration, vertical non-uniformity caused by sedimentation and migration leads to high ionic resistance. Conversely, at high solid content, partial non-uniformity due to agglomeration results in high electronic resistance. Additionally, higher active material (AM) ratios were found to increase internal resistance, and the non-uniformity of electrode materials was more significantly affected by changes in solid concentration. The optimal points were identified at 76.7 wt% AM with a slurry solid concentration of 29.8 vol% and at 80 wt% AM with a solid concentration of 31.6 vol%, where the electrodes had the best electrical properties. This study proposes strategies to reduce electrode material non-uniformity and lower resistance in wet processes for sulfide-based ASSBs, offering a pathway to improve performance and accelerate the commercialization of ASSBs.