Constructing Non-Confined Fast Lithium-Ion Transport Highway in Metal-Phosphonate-Organic Framework Through Solvent-Free Eutectic Dissociation Strategy

Solvent-free all-solid-state electrolytes offer compelling advantages, yet the simultaneous achievement of efficient salt dissociation and rapid unrestricted conduction remains a challenge. Herein, fast non-confined lithium-ion conduction is constructed in dry-processed metal-phosphonate organic framework (MPOF)-based electrolytes via a eutectic dissociation strategy, which unlocks ion dissociation through dynamic ion-ligand interaction sites. The inherent abundance of phosphonate groups and oxygen vacancies within amorphous MPOF's spatially loose nano-channels drives the dissociation of lithium salt, where Li⁺ ions coordinate with phosphonate groups and TFSI⁻ is immobilized by oxygen vacancies. Impressively, the alternating negatively charged phosphonate groups and positively charged oxygen vacancies establish a continuous ligand channel within the porous matrix, enabling efficient and rapid Li⁺ transport. Thus, the obtained MPOF@Li electrolyte provides an exceptional ionic conductivity (1.1 × 10⁻⁴ S cm⁻¹ at 30 °C) and a high lithium-ion transference number of 0.75. Consequently, with the MPOF@Li electrolyte, the symmetric cell exhibits long cycle life of over 7500 h, and the full cell with LiFePO₄ cathode demonstrates an excellent capacity retention of 95% after 1000 cycles at 0.5 C. Surprisingly, the MPOF@Li electrolyte allows operation at low temperatures (−10 °C), achieving stable cycling in symmetric cells and maintaining ≈70% of room-temperature capacity in full cells.