Understanding stack pressure effects in sulfide electrolyte-based all-solid-state battery interfaces and components

All-solid-state batteries (ASSBs) are poised to revolutionize energy storage due to their high energy density and enhanced safety. However, the inherent limitations of solid-solid interfaces, particularly poor interfacial contact and mechanical instability, remain critical challenges to practical deployment. Stack pressure has emerged as a powerful tool to improve interfacial contact, reduce impedance, and enable stable cycling performance. This review comprehensively elucidates how stack pressure governs the electrochemical and mechanical behavior of sulfide-based ASSBs. We examine how pressure influences densification and conductivity in sulfide SEs, mitigates void formation during Li plating/stripping, and affects particle contact and microstructure evolution in cathodes. While appropriately applied stack pressure can significantly enhance performance by improving interfacial contact and stability, excessive pressure may instead lead to mechanical degradation, including Li intrusion or active material fracture. We highlight recent experimental and modelling insights that reveal the chemo-mechanical coupling induced by pressure and emphasize the importance of pressure-specific design strategies for different electrode/electrolyte chemistries. Finally, we outline key prospects for enabling high-performance ASSBs through pressure regulation, material design, and advanced cell architectures.