Low-cost, Resilient, and Non-flammable Rechargeable Fe-ion Batteries with Scalable Fabrication and Long Cycle Life

Abstract

Aqueous Fe-ion batteries are largely unexplored due to their short cycle life despite the extremely low material cost. The working mechanisms are mostly undisclosed with only a few experimental studies. In this study, we demonstrate that our Fe-ion batteries can deliver an impressive specific capacity of 225 mAh/g at a relatively low 5 C rate and exhibited an extremely long cycle life of up to 27,000 cycles with a capacity retention of 82% at 15 C. Furthermore, the anode is simply a carbon steel foil (moderate purity Fe source) along with scalable cathodes and low-cost FeSO4 electrolyte, offering cost-effective solutions. Our theoretical study reveals Fe incorporation processes in the cathode and the corresponding voltage profiles during cycling, attributing mainly to the formation energy of Fe on the emptied N sites of polyaniline and structural deformations with the Fe attachment. Our batteries are shown to be free from fire and failure due to short circuits. With the manufacturing-friendly sandwich-type or 3D cylindrical cathodes eliminating multi-stack electrodes, our batteries have the potential to be cost-effective, long-lasting, and safe for stationary energy storage systems.