Application of ZIF-67/ZIF-8 derived Co3O4/ZnO heterojunction in lithium-sulfur battery separators

Abstract

Lithium-sulfur batteries (LSBs) have attracted widespread attention because of their advantages such as high discharge capacity and high energy density. Although LSBs have good development potential, there are still many obstacles, such as poor conductivity, volume expansion etc., especially shuttle effect which seriously limit the application of LSBs. To restrain the shuttle effect, we proposed a novel Co3O4/ZnO dodecahedral heterojunction as a separator blocking layer which was derived form ZIF-67/ZIF-8 bimetallic MOF. Since the bimetallic oxide heterojunction contains more abundant oxygen vacancies, it has better adsorption and catalytic performances than monometallic oxides. Co3O4/ZnO coated on the PE separator can effectively block the lithium polysulfides (LiPSs) shuttle due to its good adsorption ability, furthermore, the catalytic effect will accelerate the reaction of LiPSs and improve the electrochemical performances. Consequently, the initial discharge specific capacity of the Co3O4/ZnO modified separator battery at 0.5 C rate reaches up to 875.5 mAh g−1 when the cathode sulfur areal density is 3 mg cm−2, and still keep 500.9 mAh g−1 after 400 long cycles. Even when the cathode sulfur areal density is 5 mg cm−2, it still shows good cycle stability.