Unleashing the high energy potential of zinc–iodide batteries: high-loaded thick electrodes designed with zinc iodide as the cathode

Abstract

The realization of high energy is of great importance to unlock the practical potential of zinc–iodine batteries. However, significant challenges, such as low iodine loading (mostly less than 50 wt%), restricted iodine reutilization, and severe structural pulverization during cycling, compromise its intrinsic features. This study introduces an optimized, fully zincified zinc iodide loaded onto a hierarchical carbon scaffold with high active component loading and content (82 wt%) to prepare a thick cathode for enabling high-energy Zn–I₂ batteries. The synergistic interactions between nitrogen heteroatoms and cobalt nanocrystals within the porous matrix not only provide forceful chemisorption to lock polyiodide intermediates but also invoke the electrocatalytic effects to manipulate efficient iodine conversion. The ZnI₂ cathode could effectively alleviate continuous volumetric expansion and maximize the utilization of active species. The electrochemical examinations confirm the thickness-independent battery performance of assembled Zn–I₂ cells due to the ensemble effect of composite electrodes. Accordingly, with a thickness of 300 μm and ZnI₂ loading of up to 20.5 mg cm⁻², the cathode delivers a specific capacity of 92 mA h g_cathode⁻¹ after 2000 cycles at 1C. Moreover, the Zn–I₂ pouch cell with ZnI₂ cathode has an energy density of 145 W h kg_cathode⁻¹ as well as a stable long cycle life.