Electron Percolating Shielded Interlayer Enabling Ultrastable All-Solid-State Lithium Metal Batteries

The electron percolation of grain boundaries in Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) induces internal lithium deposition and penetration, causing short circuits of all-solid-state batteries, which has become a significant obstacle hindering the practical application of LLZTO. In this work, an electron-percolating shielded interface constructing strategy is proposed between LLZTO and lithium metal (Li) to simultaneously suppress the Li dendrite growth at both the interface and within the LLZTO electrolyte. A Poly[bis(4-phenyl)(2,4,6-triMethylphenyl)aMine] (PTAA)/SnO₂ (PS) bilayer is therefore designed between LLZTO and Li metal (LLZTO-PS|Li), where the hole-rich PTAA and electron-rich SnO₂ generate a reverse electric field that effectively blocks the electron leakage, thereby reducing the electronic conductivity of LLZTO and preventing its internal dendrite formation. Furthermore, the smooth and compact PTAA/SnO₂ coating significantly enhances interfacial contact and equalizes the interfacial potential to promote a uniform Li plating. As a result, the Li|LLZTO-PS|Li symmetric battery achieves stable cycling for over 5000 h at 0.1 mA cm^-2 and 2500 h at 0.5 mA cm^-2. The Li|LLZTO-PS|LiFePO₄ full battery demonstrates 86.2% capacity after 2000 cycles at 1 C. This study presents a novel interfacial engineering strategy for enhancing the performance and durability of garnet-based all-solid-state lithium-metal batteries.