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 252.7mAhg(-1) at 100mAg(-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 165mAhg(-1) reserved at 2000mAg(-1)). This strategy provides a simple and fast way to fabricate a stable and high-performance anode for PIBs.