A hierarchical sandwich Li6.4Ga0.2La3Zr2O12/ZIF-8@SiO2/PVDF-HFP heterostructure with high ionic conductivity for dendrite-free solid-state lithium batteries

Poor interfacial stability and dendrite penetration at the lithium metal anode interface are critical bottlenecks hindering the practical application of garnet-type solid electrolytes, despite their high intrinsic ionic conductivity. Herein, we resolve this long-standing trade-off by designing a hierarchical sandwich heterostructure. This architecture comprises a dense Li 6.4 Ga 0.2 La 3 Zr 2 O 12 (C-LGLZO) ceramic scaffold sandwiched between two ZIF-8@SiO 2 /PVDF-HFP (ZSPH) composite interfacial layers. The resulting composite solid electrolyte (CSE) C-LGLZO/ZSPH exhibits exceptional electrochemical properties: a high Li + transference number (t Li+  = 0.77) and an outstanding ionic conductivity of 1.31 × 10 −3  S cm −1 at 30 °C. Mechanistically, while the robust central C-LGLZO scaffold provides a continuous Li + pathway and physically blocks dendrites, the honeycomb-like porous ZSPH interfacial layers homogenize the interfacial electric field and promote a stable solid electrolyte interphase (SEI). This synergistic design endows the CSE with a wide electrochemical stability window (4.8 V vs. Li/Li + ) and enables stable Li plating/stripping for over 1000 h. Furthermore, cells using a LiFePO 4 cathode retain 76.3 % of their capacity after 500 cycles at 0.5C, demonstrating exceptional high-rate cycling stability. This work offers a versatile architectural strategy for engineering robust solid-state batteries (SSBs).