An LLTO-containing heterogeneous composite electrolyte with a stable interface for solid-state lithium metal batteries

The interaction between Li_0.33La_0.56TiO₃ (LLTO) and metallic lithium leads to severe interfacial instability of LLTO-containing solid-state electrolytes with a lithium metal anode. To improve the interfacial stability, a heterogeneous composite electrolyte PVDF-HFP@LLTO/PEO (PLTP) is designed and fabricated with a PEO electrolyte layer adhered to the PVDF-HFP@LLTO (PLT) electrolyte membrane. The PLTP heterogeneous composite electrolyte exhibits a superior ionic conductivity of 3.23 × 10⁻⁴ S cm⁻¹ at 60 °C and a highly stable electrochemical window of up to 4.7 V (vs. Li/Li⁺). Remarkably, taking advantage of the effective protection of the PEO electrolyte layer, the chemical stability at the electrolyte/lithium metal anode interface is significantly enhanced. As a result, solid-state Li||LiFePO₄ and Li||LiNi_0.6Co_0.2Mn_0.2O₂ batteries with the heterogeneous electrolyte exhibit an impressive electrochemical performance with high Coulombic efficiency and stable cycling capability. The strengthened interfacial stability enables the heterogeneous electrolyte to be a promising alternative for the further development of solid-state lithium metal batteries.