Hierarchical porous soft carbon host for the cathode of an aqueous zinc-iodine battery with ultra-long cycle life

Aqueous zinc−iodine battery (AZIB) is a promising energy-storage system due to its high operational safety and the suitable theoretical capacity of 211 mAh g−1 of I2. However, it suffers from poor rate performance and low capacity retention due to the easy loss of active substance and the shuttle effect caused by polyiodide species. Herein, we rationally designed a perylene−3, 4, 9, 10−tetracarboxylic anhydride (PTCDA)−based carbon host at the annealing temperature of 900°C (PTCC900) to alleviate the problems mentioned above. PTCC900 embraces a hierarchical porous structure with the pore width ranging from 1.8 nm to 13 nm, which is beneficial for the confinement of I2 and polyiodide. In addition, the turbostratic graphitic microstructures spread inside PTCC900 also provide fast electronic transmission path to increase the electrical conductivity. Benefitting from the above features, the produced PTCC900@I2 cathode delivers an initial capacity of 240 mAh g−1 and remains a high capacity of 187 mAh g−1 after 600 cycles at the current density of 0.5 A g−1. More importantly, an ultra−long cycle life of over 50000 cycles is also obtained for PTCC900@I2 cathode when the current density increases to 5 A g−1. The improved electrochemical performances corroborate that PTCC900 is expected to be a potentially promising cathode host for zinc-iodine batteries.