Bismuth Confined in Thick Nitrogen-Doped Carbon for Durable Low-Temperature Potassium-Ion Batteries

Bismuth is an alloying-type anode for potassium-ion batteries (PIBs) but faces the challenges of large volume expansion and sluggish potassiation/depotassiation kinetics. Herein, a composite of Bi nanoparticles confined in 10 nm-thick nitrogen-doped carbon layer (Bi@NC) exhibits notable rate capability (333 mAh g–1@30 A g–1) and cycling stability (290 mAh g–1@10 A g–1 after 2000 cycles) in K-storage. The high performance of Bi@NC is mainly ascribed to the encapsulation of Bi with thick N-doped carbon and a partial K+-solvent co-intercalation mechanism in the ether-based electrolyte, which enable the formation of a conductive c-K3Bi discharge product and stable solid electrolyte interphase, ensuring loss-free pulverization while avoiding high energy-consuming desolvation, leading to fast charge transfer kinetics even at low temperature. Accordingly, the PIB assembled with the Bi@NC anode and TiS2 cathode exhibits exceptional rate and cycling performance especially at −40 °C. This study provides an advanced Bi@NC anode for PIBs with exceptional low-temperature performance.