MOF 801(Ce)-modified polypropylene separator as efficient barrier for lithium–organosulfide batteries

Abstract

Phenyl tetrasulfide (PTS) is a high-capacity cathode material for lithium batteries. However, it also suffers the shuttle effect of polysulfides to the lithium anode in the charge because some lithium polysulfides are still formed due to the middle sulfur atoms in the structure of PTS. The separator modification is considered as a convenient and effective strategy to reduce the shuttle effect. In this report, metal-organic framework (MOF)-801(Ce) is synthesized and coated on a polypropylene separator (MOF-801(Ce)−PP) as a polysulfide barrier. MOF-801(Ce) has a pore size of 6 Å, which is smaller than the sizes of lithium thiophenolate and lithium polysulfides. Therefore, the MOF-801(Ce)−PP can effectively inhibit the migration of active species to the lithium metal anode without affecting the passage of lithium ions. Consequently, the Li/PTS cell with the MOF-801(Ce)−PP exhibits a discharge capacity of 340.8 mAh g−1 at 0.5 C after 250 cycles, which is better than the control cell. Even when the PTS areal mass loading is 5.4 mg cm−2, the cell with the MOF-801(Ce)−PP can still deliver a high specific capacity of 430 mAh g−1 at 0.5 C rate. This study proves a feasible strategy to overcome the polysulfide shuttle issue of organosulfide cathode materials.