Boosting Stable and Fast Potassium Storage of Iron Sulfide through Rational Yolk-Shell Design and Ni Doping

Metal sulfides have been regarded as promising anodes for potassium-ion batteries (PIBs) due to their high theoretical capacities, while the performance is limited by their intrinsic poor conductivity and large volume fluctuation during the insertion/extraction of large potassium ion. Herein, the battery performance of iron sulfide anode is significantly enhanced through yolk-shell (Y-S) structure design and nickel doping, aiming to realize good structure stability and superior electron/ion transportation. For potassium storage, as-prepared Y-S Ni-FeS2@C shows excellent cyclic performance and sustains high capacities of 328 mA h g(-1) after 100 cycles at 0.2 A g(-1) and 226 mA h g(-1) after 1000 cycles at 1 A g(-1). Especially, it displays a superior rate capacity of 200 mA h g(-1) at 20 A g(-1), higher than that of Y-S FeS2@C and most as-reported metal sulfide anodes for PIBs. The experimental analysis and theoretical calculation illuminate the effect of Ni-doping on decreasing the particle size of iron sulfide and enhancing the ion/electron transport ability, thus accounting for the exceptional rate capability of Y-S Ni-FeS2@C composite.