In-situ coupling construction of interface bridge to enhance electrochemical stability of all solid-state lithium metal batteries

Polymer-based composite electrolytes composed of three-dimensional Li_6.4La₃Zr₂Al_0.2O₁₂ (3D-LLZAO) have attracted increasing attention due to their continuous ion conduction and satisfactory mechanical properties. However, the organic/inorganic interface is incompatible, resulting in slow lithium-ion transport at the interface. Therefore, the compatibility of organic/inorganic interface is an urgent problem to be solved. Inspired by the concept of “gecko eaves”, polymer-based composite solid electrolytes with dense interface structures were designed. The bridging of organic/inorganic interfaces was established by introducing silane coupling agent (3-chloropropyl)trimethoxysilane (CTMS) into the PEO-3D-LLZAO (PL) electrolyte. The in-situ coupling reaction improves the interface affinity, strengthens the organic/inorganic interaction, reduces the interface resistance, and thus achieves an efficient interface ion transport network. The prepared PEO-3D-LLZAO-CTMS (PLC) electrolyte exhibits enhanced ionic conductivity of 6.04 × 10⁻⁴ S cm⁻¹ and high ion migration number (0.61) at 60 °C and broadens the electrochemical window (5.1 V). At the same time, the PLC electrolyte has good thermal stability and high mechanical properties. Moreover, the LiFePO₄|PLC|Li battery has excellent rate performance and cycling stability with a capacity decay rate of 2.2% after 100 cycles at 60 °C and 0.1 C. These advantages of PLC membranes indicate that this design approach is indeed practical, and the in-situ coupling method provides a new approach to address interface compatibility issues.