Fabrication of binder-free iron nanosheet arrays by an electrodeposition method for flexible Fe//I2 batteries anodes

Aqueous iron-iodine batteries (Fe//I2) are considered as a promising for portable and wearable electronics by virtue of the high theoretical specific capacity (~960 mA h g-1) and rich natural abundance of Fe. However, the low actives utilization ratio of Fe foil and poor flexibility limit their practical usage. Here, we fabricate binder-free Fe nanosheet arrays electrode (Fe-CC) as anode by a simple and controllable electrochemical technique for flexible Fe//I2 batteries, which dramatically improve actives utilization ratio, avoid electrode damage/fracture caused by chemical corrosion and enhance the reaction kinetics. As a result, the assembled aqueous Fe-CC//I2@AC/CNT battery exbibits a stable cycling of 400 cycles, superior to that of Fe foil and anode-free Fe//I2 batteries. With the use of polyacrylamide-FeSO4 hydrogel electrolyte, a flexible quasi-solid-state Fe-CC//I2@AC/CNT battery is further designed. It has a high specific capacity of ~195.4 mAh g-1 at a high rate of 3 A g-1, better than previous zinc ion batteries and Fe//I2 batteries. We also demonstrate the good ambient stability in terms of temperature and pressure and excellent flexibility of the quasi-solid-state Fe-CC//I2@AC/CNT battery. This work promotes the development of low-cost and high safety flexible iron-ion batteries on portable and wearable electronics.