High Lithium-Ion Transference Number of Composite Polymer Electrolytes Enabled by Defect-Engineered Metal–Organic Frameworks

Abstract

One of the major challenges of polymer-based solid electrolytes is their relatively low lithium-ion transference number (tLi+), which will induce severe concentration polarization within the electrolytes, thereby compromising the rate capability. Herein, a series of defect-engineered metal organic framework (MOF) was constructed through thermal treatment at different temperatures and then incorporated into a polyacrylonitrile (PAN) electrospun framework to fabricate an in situ polymerized 1,3-dioxolane (DOL) electrolyte. The defect engineering of MOF-303-X (X represents the heat treatment temperature) exposed abundant open metal sites, which effectively promoted lithium-salt dissociation and enhanced the selective transport of Li+, leading to a remarkable increase in the tLi+ up to 0.86. In addition, the porous structure of the MOF, together with the interconnected fibrous network, established continuous ion-transport pathways that facilitated rapid lithium-ion migration, enabling an ionic conductivity of 9.94 × 10–3 mS cm–1 at room temperature. As a result, the Li||Li symmetric cell delivered stable cycling over 1000 h at 0.1 mA cm–2 with a low overpotential of ∼11 mV. Furthermore, the assembled LFP||Li full cell exhibited excellent rate capability and long-term cycling stability, maintaining a discharge capacity of 92.34 mAh g–1 with the capacity retention of 82.4% after 200 cycles at 5C. This work provides an effective strategy for constructing high Li+ transference solid-state electrolytes through defect engineering of MOFs for high-performance lithium metal batteries.