Compact aqueous zinc–carbon capacitors with high capacity and ultra-long lifespan

Abstract

Aqueous zinc–carbon capacitors possess great potential for bridging the gap between conventional batteries and supercapacitors by offering abundant high-power energy. However, their practical utility in applications such as public transport has been impeded by their limited volumetric capacity and cycle life. In this study, we present a comprehensive approach to address these limitations, aiming to achieve a high volumetric capacity and long cycle life for the carbon cathode. To accomplish this, we employed a low-temperature carbonization process to synthesize nitrogen-rich porous carbon from a covalent triazine framework with a dense two-dimensional structure and intrinsic honeycomb micropores. The resulting carbon electrode exhibited a density of 1.1 g cm⁻³ (with a mass loading of 12.0 mg cm⁻²), surpassing the porous carbon electrodes used in commercial supercapacitors (typically < 0.6 g cm⁻³), and exhibits a high volumetric capacity of 176 mA h cm⁻³ at 0.11 A cm⁻³ (0.1 A g⁻¹). Notably, the electrode demonstrated exceptional durability, retaining over 90% of its initial capacity even after 100 000 cycles. The unprecedented capabilities demonstrated by our proposed strategy pave the way for the accelerated adoption of aqueous zinc–carbon capacitors in diverse energy applications.