A metal-organic framework derived approach to fabricate in-situ carbon encapsulated Bi/BiO heterostructures as high-performance anodes for potassium ion batteries.

Bismuth-based materials are regarded as promising anode materials for potassium ion batteries (PIBs) due to their high theoretical capacity and low working potential. However, the large volume expansion and sluggish kinetics during cycling are major limitations to their practical application. Herein, a unique Bi/BiO-C heterostructure was designed through a simple Bi-metal-organic framework (MOF) modulation-pyrolysis process. X-ray photoelectron spectroscopy, transmission electron microscopy, and X-ray diffraction revealed that the Bi and BiO can form hetero-particles, which were uniformly embedded in a plate-like carbon skeleton, constructing a Bi/BiO-C heterostructure. The carbon skeleton and the formation of numerous hetero-interfaces between Bi, BiO, and carbon can effectively promote the interfacial charge transfer, shorten the K diffusion pathway, and alleviate the volume expansion of Bi/BiO during potassiation. Consequently, the Bi/BiO-C heterostructure exhibited a high reversible capacity of 426.0 mAh g at 50 mA g, excellent cycle performance of 251.8 mAh g after 350 cycles with a capacity retention of 76.6 %, and superior rate capability of 82.7 mAh g at 1 A g, demonstrating its promising potential for the application of PIBs anode.