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 per-formance is limited by their intrinsic poor conductivity and large volume fluctuation during the insertion/ex-traction of large potassium ion.Herein,the battery per-formance of iron sulfide anode is significantly en-hanced 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.