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

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.