Low-crystalline β-FeOOH and vanadium ferrite for positive active materials of lithium secondary cells

Low-crystalline β-FeOOH and vanadium ferrite were prepared by a simple hydrolysis method. XRD measurement revealed that the former material had a framework of β-FeOOH with somewhat amorphous structure, and that the latter one gave a crystalline structure analogous to that of the hydrated iron orthovanadate. From the electrochemical measurements, it was found that the low-crystalline β-FeOOH positive electrode showed a discharge capacity of 230 mAh/g in the potential range of 4.3 V and 1.6 V versus Li/Li+, and better cycle performance than the high-crystalline one. The vanadium ferrite positive electrode also showed a high discharge capacity over 300 mAh/g and superior cycle performance.