Ball‐Cactus‐Like Bi Embedded in N‐Riched Carbon Nanonetworks Enables the Best Potassium Storage Performance

The potassium‐ion battery (PIB) has emerged as a promising alternative to lithium‐ion batteries. The major challenges confronted by PIB anodes lie in sluggish kinetics and poor cycling stability owing to the inherent large K+ size. Here, a hybrid of ball‐cactus‐like Bi nanospheres embedded in 3D N‐riched carbon nanonetworks (Bi NSs/NCNs) is designed and synthesized by electrospinning. As an anode, Bi NSs/NCNs exhibits an unprecedented rate (489.3 mAh g−1 at 50 A g−1) and long‐cycling performance (457.8 mAh g−1 at 10 A g−1 after 2000 cycles), outperforming all reported PIB anode materials. Such outstanding performance mainly originates from the stable solid‐electrolyte interface formed in the glyme‐based electrolyte and the unique interconnected porous nanostructure, both of which contribute to fast kinetics and high pseudocapacitive contributions upon cycling.