Unraveling the Pseudocapacitive Dual‐Ion Storage Mechanism in Carbon Cathodes with Ultrafast Reaction Kinetics

ABSTRACT Engineering carbonaceous cathodes with fast reaction kinetics is crucial for achieving advanced aqueous zinc‐ion capacitors (ZICs), yet the origin of pseudocapacitance‐induced accelerated kinetics remains elusive. Electrochemical processes are often explained solely through the cation reactions, neglecting the contribution of anions, which hinders a complete understanding of the energy storage mechanisms. Herein, we present a cellulose‐derived N/P co‐doped carbon (CNPC) cathode exhibiting ultrafast reaction kinetics. State‐of‐the‐art electrochemical analyses reveal that the ultrafast kinetics are predominantly governed by pseudocapacitive charge storage, enabling the CNPC‐based ZIC to deliver a high specific capacitance of 308.5 F g −1 , an energy density of 109.7 Wh kg −1 , and excellent durability over 65 000 cycles. Comprehensive DFT calculations and ex situ characterizations confirm that the enhanced pseudocapacitance originates from reversible dual‐ion chemisorption at heteroatom co‐doped active sites. Moreover, the CNPC‐based quasi‐solid‐state ZIC exhibits a low self‐discharge rate of 2.43 mV h −1 , which is attributed to the role of P species in reinforcing structural stability after anion adsorption. This work not only elucidates the mechanism through which co‐doped active sites boost the reversible pseudocapacitive dual‐ion storage but also provides fundamental design principles for developing next‐generation cathodes with ultrafast kinetics.