Zinc-ion hybrid supercapacitors with ultrahigh areal and gravimetric energy densities and long cycling life

Zinc ion hybrid supercapacitor (ZIHSC) with promising energy and power densities is an excellent answer to the ever-growing demand for energy storage devices. The restricted lifespan due to the dendrite formation on metallic zinc (Zn) is one of the main roadblocks. Herein, we investigate the electrochemical capability of oxygen-enriched porous carbon nanofibers (A-CNF) and nitrogen, oxygen-enriched porous carbon nanofibers (N-CNF) cathode materials for structural ZIHSCs. To this end, a series of samples with different chemical compositions (N and O contents) are prepared to present deep insight into the electrochemical mechanism between N/O doping and Zn-ion storage. The as-prepared ZIHSC in the presence of N-CNF cathode and ZnCl2 electrolyte offers a battery-level gravimetric energy density of 143.2 Wh kg−1 at a power density of 367.1 W kg−1. The free-standing N-CNF electrodes in ZIHSCs enjoy delivering an outstanding areal energy density of 110.4 µWh cm−2 at 0.24 mW cm−2, excellent rate capability, and noticeable cycling stability over 10,000 cycles at 10 A g−1 with less than 7% decay. It was also concluded that active pyrrolic N dopants might deliver and facilitate more pseudocapacitance in ZIHSCs than other N configurations,resulting in higher adsorption/ desorption and insertion/extraction process of ZnCl+. Taking advantage of the beneficial properties of a free-standing continuous cathode, this novel generation of structural cathode material offers high areal and gravimetric energy densities and mechanical properties in a single zinc-ion-based package.