Covalent Organic Framework Quantum Dots for Near‐Frictionless Ion Transport Battery Electrolyte

Optimization of electrolyte with enhanced energy density and durability in battery system is highly demanded yet challenging owing to the high ion transport resistance and complex by-reactions in electrolyte. In this work, we tailored the solid-liquid phase transport interface by adding covalent organic frameworks quantum dots (COFs QDs) into electrolyte. COFs QDs with abundant lipophilic ether-oxygen groups and ∼12 nm nano-size can serve as myriad ion-transport nano-engines for constantly replenishing the interface with Li+ to achieve near-frictionless ion transport (tLi + = 0.98) and exceptional stability (>400 days). Lithium-sulfur battery based on COFs QDs shows high discharge specific capacity of 1063.7 mAh g-1 after 100 cycles at 0.2 C and maintains a low overpotential (∼16 mV) over 4000 h at 1 mA cm-2 with 1 mAh cm-2 in Li//Li symmetric battery. A Li-S pouch battery has also been successfully assembled to validate the practicality. Our results may promote the development of COFs QDs in energy storage field.