Hierarchically porous copper-based metal–organic framework for high-performance PEO-based solid-state electrolytes

The inherent low ionic conductivity and lithium dendrite growth challenges of poly(ethylene oxide) (PEO)-based solid-state electrolytes pose significant barriers to their utilization in safe, high-energy-density lithium metal batteries. To overcome these challenges, this study designed a novel composite solid electrolyte by introducing a HKUST-1 metal-organic framework (HP-Cu-MOF) with a hierarchical microporous/mesoporous structure into a PEO matrix. The unique dual-pore structure of HP-Cu-MOF enables synergistic regulation: its micropores effectively confine TFSI − anions, significantly increasing the Li + transference number t Li + to 0.40 at 60 °C (vs. 0.11 for pure PEO), while the interconnected mesopores construct continuous ion transport channels, achieving a high ionic conductivity of 7.83 × 10 −4  S cm −1 at 60 °C. Simultaneously, the regular octahedral rigid framework of HP-Cu-MOF enhances the mechanical strength of the electrolyte, with Young's modulus increasing to 2.17 GPa (vs. 1.09 GPa for pure PEO). This enables a high critical current density of 1.7 mA cm −2 and excellent cycling stability, with Li symmetric cells stably operating for over 1800 h at 0.2 mA cm −2 . Furthermore, the electrolyte exhibits a broad electrochemical stability window of 5.1 V, enabling compatibility with high-voltage cathodes. The assembled LFP full cell delivers an initial discharge specific capacity of 151.2 mAh g −1 at 0.5C with excellent capacity retention. This work demonstrates that hierarchically porous MOFs offer an efficient electrolyte design strategy for developing next-generation lithium metal batteries integrating high energy density, long cycle life, and enhanced safety.