Bismuth Nanoparticles Encapsulated in Mesoporous Carbon Nanofibers for Efficient Potassium-Ion Storage

Bismuth (Bi)-based alloy material is a promising anode material for potassium-ion batteries (PIBs) due to its high theoretical capacity, while serious volume expansion (406%) during the charge/discharge process results in poor cycle stability and inferior rate capacity. Here, Bi nanoparticles encapsulated in mesoporous carbon nanofibers (Bi/PCNFs) were fabricated via simple electrospinning. Benefiting from the carbon coating structure, ultrafine Bi nanoparticles (5 nm), and plentiful vessel-like mesopores, the self-standing three-dimensional (3D) Bi/PCNFs electrodes show an excellent reversible capacity of 163.3 mAh g–1 at 5 A g–1 and ultralong cycle stability of 171 mAh g–1 after 1000 cycles at 1 A g–1. Importantly, the ex situ X-ray diffraction investigation exhibits a reversible alloying/dealloying reaction mechanism of Bi ↔ K3Bi2 ↔ K3Bi for the Bi/PCNFs. In addition, the as-assembled full cell displays a desirable performance, which delivers a fantastic rate capacity (65 mAh g–1 at 1 A g–1) and outstanding long cycle life (69 mAh g–1 after 100 cycles at 1 A g–1). These results manifest that Bi/PCNFs has great potential in the field of potassium-ion battery anodes.