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.