An in situ solid-electrolyte interphase strategy to inhibit polysulfide shuttles of FeS2-based cathode material

Soluble polysulfide (PS) shuttle severely degrading cyclic performances of high energy–density FeS2-based Li/Na-ion batteries remain unsolved problems. It is established that an ideal solid-electrolyte interphase (SEI) layer generated on the graphite anode of commercial lithium-ion batteries allows fast Li ion transport but completely isolates graphite from electrolyte. Herein, we propose an in situ solid-electrolyte interphase (SEI) engineering strategy from a new viewpoint of isolating the FeS2 cathode from the electrolyte rather than inhibiting the dissolved PS shuttle as suggested by other strategies. A stable SEI layer is designed to be in situ self-generated on hollow-structured FeS2/nitrogen-doped carbon (FeS2/CN) cathode by a few discharge/charge cycles in a low voltage window. The granular SEI layer derived from decompositions of the LiTFSI-based electrolyte consists of LiF, Li2CO3 and organic components, which almost inhibits the LiPS shuttle and endows the Li-FeS2/CN battery with stable 2000 discharge/charge cycles and coulombic efficiencies within (100 ± 0.5)% except a few cycles. Moreover, the SEI layer demonstrates its generality in drastically improving cyclic performance of Na-FeS2/CN battery. This efficient strategy is of convenience and low cost, possessing a great potential to be scaled to industrial level.