Hierarchical NiS2 Modified with Bifunctional Carbon for Enhanced Potassium-Ion Storage

Potassium-ion batteries (PIBs) are currently drawing increased attention as a promising alternative to lithium-ion batteries (LIBs) owing to the abundant resource and low cost of potassium. However, due to the large ionic radius size of K+, electrode material that can stably maintain K+ insertion/deintercalation is still extremely inadequate, especially for anode material with a satisfactory reversible capacity. As an attempt, nitrogen/carbon dual-doped hierarchical NiS2 is introduced as the electrode material in PIBs for the first time. Considering that the introduction of the carbon layer effectively alleviates the volume expansion of the material itself, further improves the electronic conductivity, and finally accelerates the charge transfer of K+, not surprisingly, NiS2 decorated with the bifunctional carbon (NiS2@C@C) material electrode shows excellent potassium storage performances. When utilized as a PIB anode, it delivers a high reversible capacity of 302.7 mAh g(-1) at 50 mA g(-1) after 100 cycles. The first coulombic efficiency is 78.6% and rate performance is 151.2 mAh g(-1) at 1.6 A g(-1) of the NiS2@C@C, which are also notable. Given such remarkable electrochemical properties, this work is expected to provide more possibilities for the reasonable design of advanced electrode materials for metal sulfide potassium ion batteries.