Hotspot to Homogeneous: Amorphous Interfacial Current Redistribution Enables Stable Solid-State Lithium-Metal Batteries.

Interfacial instability in oxide ceramic electrolyte (OCE)-based solid-state lithium metal batteries (SSLMBs) is conventionally attributed to chemical incompatibility or mechanical failure, yet the underlying atomic-scale mechanisms remain elusive. Here, we reveal that grain boundaries (GBs) in polycrystalline OCEs function as bipolar interfacial hotspots, accelerating three degradation pathways: lowering barriers for Li dendrite nucleation and enabling electron-leakage-driven reduction at anode side, while generating localized overpotentials for cathode phase transformation. To deactivate these GB-driven hotspots, we develop a laser-induced amorphization strategy that constructs a GB-free amorphous interlayer capable of homogenizing Li+ flux and blocking electron migration. Applied to a representative sodium superionic conductor-type electrolyte, Li1.3Al0.3Ti1.7(PO4)3, this approach delivers substantially increased critical current density in Li symmetric cells (1.4 to 2.4 mA cm-2) with stable cycling over 2000 h, and achieves an exceptional capacity retention of 101.9 mAh g-1 after 800 cycles in LiCoO2 full cells operated at 4.5 V. The generality of this strategy is further validated on garnet-type and perovskite-type OCEs. This work introduces amorphous interfacial current redistribution as a universal paradigm for engineering stable interfaces, providing a critical atomic-scale interface engineering route to unlock high-voltage, dendrite-free SSLMBs.