Polyimide@Ketjenblack Composite: A Porous Organic Cathode for Fast Rechargeable Potassium-Ion Batteries

Potassium‐ion batteries (PIBs) configurated by organic electrodes have been identified as a promising alternative to lithium‐ion batteries. Here, a porous organic Polyimide@Ketjenblack is demonstrated in PIBs as a cathode, which exhibits excellent performance with a large reversible capacity (143 mAh g^{-1} at 100 mA g^{-1}), high rate capability (125 and 105 mAh g^{-1} at 1000 and 5000 mA g^{-1}), and long cycling stability (76% capacity retention at 2000 mA g^{-1} over 1000 cycles). The domination of fast capacitive‐like reaction kinetics is verified, which benefits from the porous structure synthesized using in situ polymerization. Moreover, a renewable and low‐cost full cell is demonstrated with superior rate behavior (106 mAh g^{-1} at 3200 mA g^{-1}). This work proposes a strategy to design polymer electrodes for high‐performance organic PIBs