Symmetrical porous graphitized carbon fabric electrodes for ultra-cryogenic and dendrite-free Zn-ion hybrid supercapacitors

Zinc-ion hybrid supercapacitors (ZHSCs) have enormous potential for future applications in electric vehicles, portable/wearable electronic gadgets, etc. However, to accelerate ZHSC technology towards market applications, it is necessary to overcome research challenges such as Zn dendrites, low Zn utilization, and all-climate adaptability, as well as to streamline the device assembly process. In this study, we propose a new strategy for the facile construction of ZHSC via two porous carbon fabrics and a Zn plating solution. The cathode and current collector of the device are both porous graphitized carbon fabric (PGCF) prepared by high-temperature activation of K₂FeO₄, and the Li₂ZnCl₄·9H₂O electrolyte is verified to possess excellent Zn plating/stripping efficiency and inhibition of Zn dendrite growth in a Zn-Zn symmetric cell model. As a result, the assembled ZHSC has the maximum energy density of 2.02 mWh cm⁻² and the highest power density of 11.47 mW cm⁻², and it can operate for 30,000 cycles without capacity degradation. Furthermore, the destruction of the hydrogen bonding network by the high concentration of Cl⁻ at low temperatures endows it with low freezing point properties and excellent ionic activity at low temperatures. The device also operated reliably at –60°C, with a maximum areal capacity of 1.15 mAh cm⁻². This research offers new findings and insights for the development of high-performance ultra-cryogenic ZHSC devices.