Natural MOFs enable hydrogen bonded ion highways for solid state batteries

Abstract

Solid-state batteries hold great promise for energy storage but remain constrained by the inherent trade-off between high ionic conductivity and interfacial stability in polymer electrolytes. Here, we introduce a natural, biocompatible β-cyclodextrin-based MOF (β-CD-MOF) as a multifunctional filler in a poly(ethylene oxide)/polyacrylonitrile composite. The inherent hydroxyl groups of the β-CD-MOF create a pervasive hydrogen-bonding network that actively bridges the polymer phases, constructing continuous three-dimensional ion transport highways. This bio-derived framework simultaneously disrupts polymer crystallinity, anchors anions, and regulates the lithium-ion coordination environment. The resulting solid electrolyte exhibits a high ionic conductivity of 3.97 × 10⁻⁴ S cm⁻¹ at 30 °C and an elevated Li⁺ transference number of 0.54. This synergistic mechanism enables exceptional interfacial stability, allowing a Li∥Li symmetric cell to cycle steadily for over 1000 hours and a LiFePO₄∥Li full cell to retain 87.2% of its capacity after 1000 cycles at 1C. Our work demonstrates that natural MOFs can be engineered to create sophisticated ion-conducting networks, moving beyond the conventional role of passive fillers. This approach establishes a new strategy for sustainable material design in next-generation energy storage, unifying performance with environmental considerations.