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.