All-solid-state-lithium-batteries (ASSLBs) using crystalline solid electrolytes (e.g., garnet-type Li₇La₃Zr₂O₁₂, LLZO) are promising electrochemical energy storage systems. However, Li penetration within the solid-state electrolytes (SSEs) due to large electric field gradient and local electronic conductivity at crystal grain boundary (GB) causes quick cell failures. Here, we design a field-responsive GB with ferroelectric materials for crystalline SSEs to prevent Li nucleation via a weakened local electric field. Additionally, the mixed-conducting interlayer formed at the Li/BaTiO₃-modified LLZO (BTO-LZ) interface is favorable for homogenizing the interfacial Li⁺ flux. As a result, Li penetration through the bulk SSE can be effectively suppressed with an ultra-high critical current density of 6.1 mA cm^-2. ASSLBs with a low interfacial resistance, high capacity and rate performance can be realized using the BTO-LZ electrolyte and thermally soldered LiCoO₂. This study offers a generic strategy against dendrites in various solid-state batteries.