A low cost Zn 2+ /I − redox active electrolyte for a high energy and long cycle-life zinc hybrid battery–capacitor

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 11; no. 44; pp. 24219 - 24227
• Main Authors: Selvaraj, Balamurugan, Sambandam, Balaji, Kim, Sungjin, Mathew, Vinod, Seo, Sehong, Song, Moonsu, Kim, Jaekook
• Format: Journal Article
• Language: English
• Published: 14.11.2023
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/D3TA03912A

The limited capacities and energy densities in zinc hybrid capacitors are due to the cathode materials and electrolytes that should be further improved to satisfy large-scale applications. To overcome this challenge, in this study, an aqueous zinc hybrid battery–capacitor (AZHBC) using low cost/concentration KI redox additive-added aqueous ZnSO 4 as the electrolyte, Zn metal as the anode, and heteroatom-containing porous carbon (PC) derived from gelatin bio-polymer as the cathode material is developed. The AZHBC configured as Zn//ZnSO 4 + KI//PC exhibited a high capacity of 399 mA h g C −1 and a high energy density of 479.1 W h kg −1 in the voltage range of 0.2–1.8 V, which were higher than those of the high-cost ZnI 2 additive-containing Zn//ZnSO 4 + ZnI 2 //PC AZHBC, respectively. This result can be attributed to the role of the KI additive, which enhances polyiodide redox reactions (3I − /I 3 − , 2I − /I 2 and 2I 3 − /3I 2 ) at the interfacial surface of the PC electrode, and the enhanced faradaic reaction. Additionally, 1 M ZnSO 4 + 0.08 M KI is identified as the optimal electrolyte concentration as it exhibited the best performance (high capacity retention (∼94.5%) after 6000 prolonged cycles). The strategy proposed in this correlation study will provide insight into the exploration of suitable and best redox additives for high-energy low-cost redox active-AZHBCs.