Covalent organic frameworks (COFs) with their porous structures that are accommodative of Li salts are considered to be potential candidates for solid-state fast Li conductors. However, Li salts simply infiltrated in the pores of solid-state COFs tend to be present in closely associate ion pairs, resulting in slow ionic diffusion dynamics. Here we incorporate cationic skeleton into the COF structure to split the Li salt ion pair through stronger dielectric screening. It is observed that the concentration of free Li ions in the resulting material is drastically increased, leading to a significantly improved Li conductivity in the absence of any solvent (up to 2.09 × 10 S cm at 70 °C).

In recent years solid Li + conductors with competitive ionic conductivity to those of liquid electrolytes have been reported. However, the incorporation of highly conductive solid electrolytes into the lithium-ion batteries is still very challenging mainly due to the high resistance existing at the solid-solid interfaces throughout the battery structure.Here, we demonstrated a universal interfacial modification strategy through coating a curable

COFs with boron-containing frameworks were used to adsorb the free anion in polymer electrolytes. The Li+ transference number of the resulting electrolytes is thus dramatically improved. The optimized COFs or MOFs could be used as functional additives for future all-solid-state batteries.

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