Systematic Optimization of Slurry-Cast All-Solid-State Battery Cathodes and Their Characterization

Due to their superior ionic conductivity and mechanical ductility, sulfide-based solid electrolytes (SEs), such as Li₆PS₅Cl (LPSCl), have been extensively studied and are commonly used for testing all-solid-state batteries (ASSBs). However, compared to state-of-the-art lithium-ion batteries (LIBs) in large-scale formats, the practical implementation of ASSBs still requires significant improvements and optimization in various aspects of their components and processing parameters. While most ASSB components are in powder form, which allows for relatively simple preparation and processing at the laboratory scale, up-scaling for industrial production demands a shift. In particular, the sheet-type electrodes (especially for cathodes) traditionally used in liquid electrolyte systems should be adapted for ASSB application.
Moreover, the electro-chemo-mechanical effect within the cathode composite presents significant challenges to the practical implementation of ASSBs. As a result, systematic optimization of ASSB cells is necessary, focusing on key components, including layered Ni-rich oxide cathode active material [CAM; here LiNi_0.85Co_0.10Mn_0.05O₂, referred to as NCM85], superionic SE, and anode material.
Recently, we have optimized the slurry casting of ASSB cathodes. To reduce (electro-)chemical degradation at the CAM|SE interface, we applied sol-gel and advanced nanoparticle coatings to mitigate side reactions, particularly at high cut-off potentials. Additionally, we introduced a strategy to minimize mechanical degradation due to electrode breathing by balancing anode and cathode. Our findings highlight the trade-off between achievable capacity and capacity retention in sulfide-based ASSBs, as we aim to match the energy density of LIBs. Furthermore, we have developed a reliable three-electrode (3E) setup for ASSBs to gain better understanding of the kinetics and limitations of commonly used cathode and anode materials.