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 ClO₄ ^- 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⁺, Zn²⁺, etc.).