Metal-organic frameworks Derived frustrated Lewis acid-base pairs accelerate ion dynamics to dendrite-free solid-state lithium batteries

Abstract

The Poly(ethylene oxide) (PEO)-based polymer electrolytes exhibit the drawbacks of high crystallinity and low ionic conductivity (<10−5 S m−1), which significantly restrict their application in solid-state lithium metal batteries. This study presents the bismuth metal-organic frameworks (MOFs) as a PEO-based electrolyte filler, incorporating frustrated Lewis acid-base pairs, which is formed in-situ through the coordination of ellagic acid (EA) and bismuth ions (Bi3+). The simultaneous presence of Lewis acids (unsaturated Bi3+) and bases (free nitrate, NO3−) in the MOFs, which effectively transfers and transports the lithium ions through the synergistic interaction based on the polymer matrix and the lithium salts, resulting in the high durable solid-state lithium batteries. Meanwhile, NO3− can further promote the dissociation of lithium ion (Li+) and the formation of inorganic solid electrolyte interfaces (SEIs) with lithium metal, which is conducive to the dynamic repair of SEIs. Characterizations and calculations show that Bi-MOFs promote the increase of composite ionic conductivity (6.4 × 10−4 S cm−1, 60 °C) and lithium transference number (0.52, 60 °C). At a current density of 0.4 mA cm−2, the assembled Li–Li symmetric battery can be continuously cycled for more than 500 h. This strategy opens a new window for improvement of solid-state electrolyte performance.