Dendrite-free anodes enabled by MOF-808 and ZIF-8 modified glass microfiber separator for ultralong-life zinc-ion hybrid capacitors

Abstract

Zinc-ion hybrid capacitors (ZIHCs) have been attracted attention for aqueous electrochemical energy storage systems owing to their high safety, low cost, abundant natural resource of zinc, convenient assembly (in an air atmosphere), robust stability with aqueous electrolytes, and the unique electrochemical characteristics of metallic zinc (Zn) as an anode electrode. Nevertheless, the growth of dendrite is the main challenge of zinc electrode in an aqueous electrolyte, leading to short circuit failure. Herein, metal-organic frameworks (MOFs) have been employed to decorate the separator. The porous nature of MOFs has been identified as beneficial for directing uniform zinc deposition. This study focuses on the operational efficiency and lifecycle of ZIHCs utilizing MOFs, specifically MOF-808 and ZIF-8, to modify glass microfiber separators. The results demonstrated that the symmetrical cell using MOF modified separators exhibited high performance, maintaining stable voltage over 1000 h. attributed to the enhanced uniformity of Zn ion flux during striping/plating processes. Additionally, at the current density of 1.0 A g−1, ZICs with MOFs modified separators exhibited higher specific capacities compared to those using the pristine separator and prolonged the cycle life over 20,000 cycles with capacity retention of 56.73 and 63.89 %, respectively. Because the MOFs modified separators can inhibit non-uniform dendritic zinc growth on a zinc anode surface according to the scanning electron micrographs.