Boosting pseudocapacitive sodium storage while restraining the shuttle effect of polysulfides in holey nickel disulfide nanoplatelets by a polypyrrole-coating strategy

[Display omitted] •A polypyrrole coating strategy is proposed to mitigate the “under-voltage failure” and enhance the rate capability of sulfide-based electrodes for SIBs.•The holey structure of NiS2 and the conductive polypyrrole coating boost fast interfacial pseudocapacitive charge storage.•The intermediate polysulfides are efficiently adsorbed by nitrogen atoms on the polypyrrole framework.•NiS2@PPy delivers high capacities of 393 and 373 mAh/g at 2.0 and 5.0 A/g over 1700 cycles. The application of transition metal sulfide-based anodes in sodium-ion batteries (SIBs) is held back by the poor rate capability and the knotty shuttle effect of polysulfides. Herein, a facile and scalable polypyrrole coating strategy is proposed to address the aforementioned issues. In-situ polymerization of pyrrole on porous NiS2 nanoplatelets produces a polypyrrole-coated NiS2 composite (NiS2@PPy). The holey structure of NiS2 enhances ion transport while increasing contact area with polypyrrole shells. When used as the anode for SIBs, the conductive polypyrrole coating of NiS2@PPy can significantly accelerate the electrode kinetics by boosting fast interfacial pseudocapacitive charge storage, which accounts for ∼90 % of total capacity even at a low sweep rate of 0.1 mV s−1. Meanwhile, the conformal coating can accommodate the volume expansion of NiS2 during cycling, enhancing the long-term durability of NiS2@PPy. More importantly, the intermediate polysulfides are efficiently adsorbed by the nitrogen atoms on the polypyrrole framework, thereby alleviating the under-voltage failure caused by the shuttle effect. Consequently, the as-prepared NiS2@PPy achieves high capacities of 393 and 373 mAh/g at 2.0 and 5.0 A/g over 1700 cycles. Motivated by the encouraging results in SIBs, we also explored the potentiality of NiS2@PPy for the potassium-ion batteries.