A High‐Performance Dual‐Carbon Na‐Ion Capacitor Fabricated from a Single Biowaste Precursor

Abstract

A major limitation of sodium‐ion capacitors (NIC) lies in their dissimilar charge storage mechanism of ion adsorption cathodes with fast reaction kinetics, versus battery‐like anodes, having slow kinetics. It is possible to address this concern by designing NIC architecture with effective electrode strategies. In this study, a dual carbon NIC is constructed from a single bio‐waste precursor (pistachio shell) by employing a facile approach to achieve a graphene sheet‐like activated carbon cathode and disordered hard carbon anode as respective positive and negative electrodes. Detailed textural analysis of the activated carbon material indicates a highly ordered sp2 carbon composition and a sheet‐like morphology. The dual carbon NIC delivers a specific capacity of 71 mAh g−1 and yields an excellent energy density of 141 Wh kg−1 at 198 W kg−1 (based on total active material mass) whereas the activated carbon‐based supercapacitor exhibits an energy density of 24 Wh kg−1 at 675 W kg−1. Hence, the pistachios shell derived carbon sheets with large effective surface area possess sufficient porosity for facile ion transfer kinetics resulting in high adsorption capacity, while hard carbon anode with disordered structure facilitates Na‐ion intercalation, thus balancing the electrode kinetics of both the electrode materials in NIC device.