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)₂S₃ 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)₂S₃ → (Bi,Sb) → K(Bi,Sb) → K₃(Bi,Sb) during the initial discharge and K₃(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.