Lithiation of covalent organic framework nanosheets facilitating lithium-ion transport in lithium-sulfur batteries

Abstract

The effective strategy of depositing modified layer on separator is widely utilized to suppress polysulfides shuttle in lithium-sulfur batteries, in which the modified layer partly sacrifices the transport of lithium-ion. Thus far, to simultaneously achieve fast lithium-ion transport and polysulfides-blocking remains a hot yet challenging issue. Herein, we developed a two-dimensional lithiated covalent organic framework nanosheets (Li-CON) layer that possess ordered lithiated-sites in the intrinsic nanopores of Li-CON. Those lithiated-sites can significantly facilitate the lithium-ion transport owing to low diffusion barrier. Besides, the Li-CON promotes Li-S bond breaking of relatively low reactivation energy due to the synergy effect of triazole units and lithiated-sites resulting in fast polysulfides conversion kinetics. Thus, Li-CON modified separator exhibits high lithium-ion conductivity and transference number, meanwhile, suppresses polysulfides shuttle and reduces the charging overpotential contributing to superior long cycle and high rate performance.