Scavenging Meets Reinforcement: A Dual‐Functional Electrolyte Additive Approach to Dendrite‐Free Lithium‐Metal All‐Solid‐State Batteries Under Low‐Pressure

Among the challenges facing Li-metal all-solid-state-batteries (ASSBs), achieving stable low-pressure operation remains a formidable task owing to limited interfacial contact and Li-dendrite growth. In this study, a simple yet scalable approach is presented to address these issues via a dual-functional additive strategy. Sulfide-based solid electrolytes (SEs) are reformulated by incorporating mechanically robust and lithium-scavenging Li₄Ti₅O₁₂ (LTO) particles through powder mixing and cold pressing. Careful control of particle size localized smaller LTO particles at grain boundaries and pores without disrupting the bulk Li-ion conduction network. The resulting LTO-incorporated composite solid electrolyte (LTO-CSE) simultaneously offers mechanical reinforcement and electrochemical scavenging/current homogenization via zero-strain lithiation, without imposing mechanical stress within the SE matrix. The LTO-CSE exhibits enhanced stability at high current densities even under low stack pressures, without requiring warm isostatic pressing, not in pouch cells but in custom-built spring-loaded cells. Notably, it raises the critical current density from 4.5 to 7.5 mA cm^-2 at 10 MPa. Furthermore, full cells demonstrate over 900 stable cycles without short-circuiting, delivering a high areal capacity of ≈3.5 mAh cm^-2 under 10 MPa, and stable operation even at pressures as low as 2 MPa. This work establishes a generalizable design framework for next-generation solid-state batteries.