Cationic Porous Aromatic Frameworks for Enhanced Lithium-Ion Dissociation and Transport in Solid Polymer Electrolytes

It poses a challenge to promote the dissociation of strong ion pairs of lithium salts and the rapid transport of Li+ in solid-state polymer electrolytes. In this study, the cationic porous aromatic frameworks (iPAF-7) containing imidazolium groups were prepared by constructing an anion-receptor strategy. The cationic imidazolium groups were used to limit anions via electrostatic interactions and reduce the dissociation energy barrier of Li+, thus promoting the dissociation and transport of Li+. Density functional theory (DFT) calculations further confirmed that the constraining effect of iPAF-7 on TFSI– promoted the effective dissociation of Li+, significantly reduced concentration polarization, and ultimately inhibited lithium dendrites. iPAF-7-QSPE showed stable lithium plating/stripping behavior; it maintained a uniform polarization for over 4500 h at a current density of 0.2 mA cm–2. The discharge specific capacity of Li//iPAF-7-QSPE//LFP reached as high as 167 mAh g–1 at 0.2 C. After 600 cycles, it maintained an acceptable capacity retention of 89%.