In Situ Alloying Strategy for Exceptional Potassium Ion Batteries

We report an in situ alloying strategy for obtaining homogeneous (Bi,Sb) alloy nanoparticles from (Bi,Sb)(2)S-3 nanotubes for the exceptional anode of potassium ion batteries (KIBs). The operando X-ray diffraction results, along with transmission electron microscopy and energy-dispersive X-ray spectroscopy mappings, successfully reveal the phase evolution of this material, which is (Bi,Sb)(2)S-3 -> (Bi,Sb) -> K(Bi,Sb) -> K-3(Bi,Sb) during the initial discharge and K-3(Bi,Sb) -> K(Bi,Sb) -> (Bi,Sb) in the charging process. The in situ alloying strategy produces a synergistic effect and brings an outstanding electrochemical performance. It achieves ultrahigh discharge capacities of 611 mAh g(-1) at 100 mA g(-1) (0.135C) and 300 mAh g(-1) at 1000 mA g(-1) (1.35C) and retains a capacity as high as 353 mAh g(-1) after 1000 cycles at 500 mA g(-1) (0.675C) with a Coulombic efficiency close to 100%. In addition, the KIBs full cell, which is composed of this anode and a perylenetetracarboxylic dianhydride cathode, reaches an initial discharge capacity as high as 276 mAh g(-1) at 500 mA g(-1) and maintains 207 mAh g(-1) after 100 cycles.