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

Abstract 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 Li ₄ Ti ₅ O ₁₂ (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.