Fabricating better metal-organic frameworks separators for Li–S batteries: Pore sizes effects inspired channel modification strategy

More and more researchers have realized the pores within metal-organic frameworks (MOFs) can suppress polysulfides shuttling and improve the performance of Li–S batteries. However, neither the initial “sulfur loss”, nor the related exacerbated voltage polarizations have raised enough attentions. Herein, these issues have been rationally demonstrated by the interactions between polysulfides and metal sites inside MOFs pores, and the sluggish lithium ions transportation pathway which are closely related to metal sites and pore sizes within MOFs. Moreover, as a channel modification strategy, decorating MOF channels with negatively charged sulfonic polymer (NSP) can concurrently turn the charge environment of the MOF channels (by forming sulfurphobic interaction between polysulfides and NSP) and facilitate the transportation of lithium ions, resulting in greatly relieved initial “sulfur loss” and largely reduced voltage polarizations of Li–S batteries. Simultaneously narrow the MOF channels and turn the charge environment of the MOF channels reveled a win-win situation, which we anticipate will provide a rational design strategy for fabricating functional MOFs used as membranes and even solid electrolytes for various energy storage systems.