Slurry Coated Sulfide Separators for Scalable All-Solid-State Battery Manufacturing

The pursuit of safer, higher-energy-density batteries has driven significant research into all-solid-state batteries (ASSBs). Replacing conventional liquid electrolytes with solid-state alternatives promises enhanced safety and the potential for higher energy densities. However, realizing the full potential of ASSBs requires innovative manufacturing techniques that are both scalable and cost-effective for large-scale production. While dry-mixing of solid-state components is under development, slurry-based coating offers a compelling alternative due to its compatibility with established liquid electrolyte battery production infrastructure and its potential for precise material deposition. A significant hurdle in ASSB manufacturing is the fabrication of thin, free-standing sulfide separators, which typically requires temporary carriers like Mylar or Teflon, followed by complex and potentially damaging transfer processes to the electrode surfaces. These processes not only increase manufacturing complexity and cost but also pose challenges to maintaining the integrity of the delicate sulfide separator layer. To address these challenges and unlock the manufacturability of ASSBs, we propose a novel and simplified approach: coating sulfide slurry directly onto the electrode surfaces, followed by lamination to assemble the ASSB cell stack. This method offers a streamlined manufacturing process by eliminating the need for a separate separator film, thereby reducing material handling and processing steps. Furthermore, this approach has the potential to significantly reduce interfacial resistance between the electrodes and electrolyte, a critical factor limiting the performance of ASSBs. By ensuring intimate contact between the solid electrolyte and the electrode materials, we aim to enhance lithium-ion transport and improve overall battery performance. This presentation explores multi-step separator fabrication and integration processes to optimize the interfacial contact and mechanical stability of the ASSB structure. Strategies explored include coating sulfide slurry onto partially calendered electrodes to create a textured surface for improved adhesion, as well as laminating the assembled electrode-electrolyte layers together under controlled pressure and temperature to enhance densification and reduce porosity. We discuss the impact of separator integration methods on cell internal resistance and capacity retention during long-term cycling. Our findings identify the optimal combination of slurry coating, lamination, and densification techniques for achieving high-performance ASSBs with improved manufacturability, reduced interfacial resistance, and enhanced electrochemical stability. This research contributes to the advancement of scalable and cost-effective manufacturing methods for ASSBs, paving the way for their widespread adoption in future energy storage applications.