Modulating Lewis Acidity of Covalent Organic Frameworks to Boost Li ⁺ Transport

ABSTRACT

Solid polymer electrolytes offer a promising route to safer lithium metal batteries, but strong Li ⁺ –TFSI ^– coupling and insufficient salt dissociation limit their room‐temperature conductivity. Introducing Lewis acidic sites to competitively bind TFSI ^– can release Li ⁺ , yet the relationship between local Lewis acid–base regulation and ion transport remains unclear. Here, we tune the local Lewis acid–base environment of olefin‐linked pyridinium ionic covalent organic frameworks by exchanging counteranions from Br ^– to BF ₄ ^– , PF ₆ ^– , and TFSI ^– . Comprehensive results show that charge‐delocalized, weakly coordinating counteranions reduce screening of pyridinium cations, enhancing effective Lewis acidity and weakening Li ⁺ –TFSI ^– coupling. Consequently, ICOF‐TFSI@PVDF‐HFP achieves an ionic conductivity of 9.1 × 10 ^{– 4} S·cm ^{– 1} together with a Li ⁺ transference number of 0.81. The electrolyte enables stable Li||Li cycling over 6500 h, retaining 84.3% capacity after 650 cycles at 1 C in Li||LFP cells and 81.7% after 400 cycles at 1 C in Li||NCM90. Molecular dynamics, Raman spectroscopy, and operando characterizations confirm enhanced salt dissociation, regulated interfacial chemistry, dendrite suppression, and mitigated microcracking in high‐Ni cathodes. This study defines local Lewis acid–base regulation as a molecular design strategy for SPEs featuring fast Li ⁺ transport and robust interfacial stability.