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

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 BF₄ ^-, PF₆ ^-, 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.