Bismuth Nanoparticles Confined in Carbonaceous Nanospheres as Anodes for High-Performance Potassium-Ion Batteries.

Bismuth (Bi) has been considered as a promising alloying-type anode for potassium-ion batteries (PIBs), owing to its high theoretical capacity and suitable working voltage plateaus. However, Bi suffers from dramatic volume fluctuation and significant pulverization during the discharge/charge processes, resulting in fast capacity decay. Herein, we synthesize Bi nanoparticles confined in carbonaceous nanospheres (denoted as Bi@C) for PIBs by first utilizing BiOCl nanoflakes as a hard template and a Bi precursor. The construction of the loose structure buffers the mechanical stresses resulting from the volume expansion of Bi during the alloying reaction and avoids the fracture of the electrode structure, thus improving the cycling performance. Moreover, the carbonaceous layers increase the electronic conductivity and disperse the Bi nanoparticles, enhancing the charge transportation and ionic diffusion, which further promotes the rate capability of Bi@C. It exhibits a superior capacity (389 mAh g at 100 mA g after 100 cycles), excellent cycling stability (206 mAh g at 500 mA g over 1000 cycles), and an improved rate capability (182 mAh g at 2.0 A g). This work provides a new structuring strategy in alloying materials for boosting reversible and stable potassium-ion storage.