Balsa‐Wood‐Derived Binder–Free Freestanding Carbon Foam as High‐Performance Potassium Anode

The binder‐free freestanding electrode is assumed as a proven and effective method of increasing the energy density of potassium‐ion batteries (PIBs) because of the addition of binder and conductor. However, an expensive and complex synthesis process hampers its development, Herein, a binder‐free freestanding biomass hard carbon (BHC) foam with balsa wood as the precursor is put forward. The prepared BHC foam maintains a highly hierarchical structure, in which the channels are interconnected and the pipe walls form an extremely stable 3D structure. This 3D porous network is synthesized in one step by a simple, environmentally friendly method, which ensures efficient ion and electrolyte transfer without structure collapse during the electrochemical cycle. When used as PIB anodes, the binder‐free freestanding carbon foam delivers a high reversible capacity of 252.7 mAh g −1 at 100 mA g −1 with a high initial coulombic efficiency of 63.7%, excellent long cycle stability (95.1% capacity retention after 500 cycles, and the average decay rate per cycle is 0.012% over 2500 cycles), and superior rate capability (the capacity of 165 mAh g −1 reserved at 2000 mA g −1 ). This strategy provides a simple and fast way to fabricate a stable and high‐performance anode for PIBs.