Oriented nanoporous MOFs to mitigate polysulfides migration in lithium-sulfur batteries

Abstract

Abstract Metal-organic frameworks (MOFs) have several attractive features for energy applications including tunable pore sizes, highly-ordered structures and versatile chemical reactivity. Here, we show the antiferroelectric perovskite dimethylammonium zinc formate (DMAZF) MOF [(CH3)2NH2] Zn (HCO2)3 as an effective molecular sieve to mitigate polysulfide (PS) migration in lithium-sulfur batteries (LSBs) when combined with conductive carbon nanotubes (CNTs). The DMAZF was selected due to both its nanopore structure and the presence of the Zn-metal site. The nanopores facilitate PS physical separation, whereas the Zn-site acts as a Lewis-acid site to attract the PS and also as a catalytic site to encourage electrochemical redox reactions. The hybrid DMAZF/CNTs/sulfur electrode, with 5 mg cm−2 sulfur loading, delivers an initial high specific capacity of 1260 mAh g−1 at 0.05C and 1007 mAh g−1 at 0.1C with the degradation of only 0.07% after 120 cycles. Even at 7 mg cm−2 sulfur loading, the electrode performance decreases only 0.12% per cycle even after 500 cycles at 0.5C.