Metal‐Organic Framework Electrolytes for Sub‐ –60°C Solid‐State Lithium Batteries

ABSTRACT Solid‐state lithium battery (SSLB) operating at ultralow temperatures (< −60°C) poses a formidable challenge for conventional solid‐state electrolytes (SSEs), including polymeric and inorganic materials. Herein, we report the design and fabrication of electron‐cloud‐homodistributed metal‐organic framework (ECH–MOF) with weakly temperature‐dependent Li + transport as SSE materials for SSLB operation at ultralow temperatures. To be specific, the metal nodes anchor electron‐rich ClO 4 − anions as Li + conducting sites, and organic ligands with strong electron‐withdrawing groups contribute to electron cloud homodistribution along Li + transport path, affording a spatially uniform, ultralow‐energy‐barrier landscape for ultralow‐temperature Li + transport. We reveal that Li + in ECH–MOF SSE migrates via a quantum‐tunneling‐like slipping manner, rather than the classical thermally activated hopping manner. The ECH‐MOF SSE yields the ultralow E a of 0.045 eV and single Li + conductivity of 1.2 × 10 −5 S cm −1 at −60°C—a temperature where most SSEs are essentially insulators. The assembled high‐voltage NCM 811||Li half‐cell delivers high discharge capacity of 109.2 mAh g −1 with high‐capacity retention of 62% after 1000 cycles at −60°C and 1C, extending the operational envelope of SSLBs into the ultralow‐temperature regime. The electron‐cloud homogenization strategy presents a universal platform for developing next‐generation low‐temperature ionic conductors (H + , Li + , Na + , Zn 2+ , etc.).