Highly stable aqueous Zn−I2 batteries enabled by the synergistic adsorption/conversion effect via porous graphitic iodine host

Abstract

Aqueous zinc-iodide batteries (AZIBs) are considered to be the promising candidate after lithium-ion batteries due to their low cost and high safety. However, the poor electrical conductivity of iodine and the notorious shuttle effect brought about by resolvable polyiodides have seriously hindered the widespread application prospects of AZIBs. In this work, we develop a sample and effective strategy for synthesizing N-doped hierarchical porous graphitized carbon (CN-Mg-CaCO3) that shows great potential as a host material for iodine confinement. The unique porous structure with graphitic domains and synergistic effects of surface adsorption and efficient conversion contribute to the high performance of AZIBs, with notable specific capacity (185 mA h g−1 at 0.1 mA g−1), impressive rate capability (114 mA h g−1 at 10 A g−1), and excellent long-term cycling stability (85 % retention after 104 cycles at 5 A g−1). The elaborately constructed conductive carbon skeleton enhances iodine utilization, while the redox reaction of I2/I- occurs without the formation of intermediates I3-. Additionally, the presence of surface adsorbed Zn2+ leads to enhanced pseudo-capacitance. This research introduces innovative approaches and broadens new ideas for developing cathode materials for AZIBs.