In‐situ Nano‐Crystallization and Solvation Modulation to Promote Highly Stable Anode Involving Alloy/De‐alloy for Potassium Ion Batteries

For advanced anode materials involving alloy/de‐alloy chemistry for potassium ion batteries (PIBs), two‐dimensional (2D) bismuth subcarbonate (BCO) nanosheets that possess high theoretical capacity of 631 mAh g −1 are proposed. The large lattice spacing of 0.683 nm along b axis facilitate insertion of K + ion to boost high‐capacity delivery of ca. 610 mAh g −1 , and the in situ nano‐crystallization well ease volume changes of the integrated particle and shorten ion diffusion path during potassiation/depotassiation. After coupling with a concentrated KFSI‐G2 electrolyte, the robust and efficient SEI built from enhanced participation of FSI − synergistically endow structural stability of the flower‐like BCO, and enable a prolonged cycling performance with capacity of ca. 300 mAh g −1 at 0.2 A g −1 for 1500 cycles, achieving an ultralow decay rate of 0.007 %. Mechanistic investigations probe the electrochemistry involving alloy/de‐alloy and phase transition of the electrode.