Coupling core–shell Bi@Void@TiO2 heterostructures into carbon nanofibers for achieving fast potassium storage and long cycling stability

Abstract

Bismuth (Bi) has been regarded as a promising anode material for potassium-ion batteries (PIBs) due to its high theoretical capacity (386 mA h g⁻¹). However, the accompanying drastic volume change during charge/discharge processes has seriously hindered its practical application in PIBs. Herein, a multi-core–shell heterostructured Bi@Void@TiO₂ embedded in one-dimensional carbon nanofibers (CNF) is synthesized to solve this problem. Specifically, the chamber between the Bi core and TiO₂ shell can buffer the volume change of Bi, and the TiO₂ shell not only effectively prevents carbon skeleton collapse during carbonization, but also inhibits the agglomeration of Bi during alloying/dealloying. Importantly, theoretical calculations confirm that the heterostructures between the TiO₂ shell and Bi/carbon facilitate the reaction kinetics of K⁺. As a PIB anode, the Bi@Void@TiO₂⊂CNF electrode presents a high capacity of 388.8 mA h g⁻¹ at 0.05 A g⁻¹, and a remarkable capacity of 171.6 mA h g⁻¹ at 2 A g⁻¹ after 3000 cycles with a capacity retention of 85.4%. Moreover, a K-ion full cell based on a Bi@Void@TiO₂⊂CNF anode can afford stable capacity retention over 1500 cycles at 1 A g⁻¹. This work offers a promising strategy to design long-lived PIB anodes that show potential for practical applications.