A Cobalt-Free Li(Li0.16Ni0.19Fe0.18Mn0.46)O2 Cathode for Lithium-Ion Batteries with Anionic Redox Reactions

Lithium-rich, Mn-based layered oxides Li2MnO3-LiMO2 (M=Ni, Co) have been considered as promising cathode candidates owing to their high capacity. However, the resources shortage and high price of cobalt make it imperious to substitute cobalt with other high-abundance elements. Here, we synthesized a low-cost, cobalt-free, Fe-substituted oxide material, Li(Li0.16Ni0.19Fe0.18Mn0.46)O-2. It exhibited a high reversible capacity of 169.2 mAh g(-1) after 100 cycles and maintained an extraordinarily high discharge potential during cycling. X-ray photoelectron spectroscopy and DFT calculations revealed that super iron Fe-IV exists in the delithiated state, and oxygen participates in the redox reaction in addition to the Ni2+/Ni4+ and Fe3+/Fe4+ redox couples. The anionic oxidation preferentially occurred on oxygen with a Li-O-Li configuration and with oxidized Fe and Ni coordination.