Surface reaction of β-FeOOH film negative electrode for lithium-ion cells

Electrochemical performance of β-FeOOH thin film has been investigated for a low-cost and environmentally friendly negative electrode with a large capacity. The electrode was found out to give an initial large discharge capacity of 864 mAh g−1 and good cycleability with a constant value around 700 mAh g−1 at subsequent cycles. In the first charge process, one electron change reaction proceeded from the initial rest potential of 3.04–1.65 V vs. Li/Li+, resulting in the formation of divalent product FeOOHLi. Further charging caused the surface film formation like solid electrolyte interface (SEI) between 1.65 V and 1.18 V vs. Li/Li+ together with the reduction of Fe compound from divalent to partially zero-valent, followed by its film growth from 1.18 V to 0.07 V vs. Li/Li+.