A Cobalt‐Free Li(Li_0.16Ni_0.19Fe_0.18Mn_0.46)O₂ Cathode for Lithium‐Ion Batteries with Anionic Redox Reactions

Abstract

Lithium-rich, Mn-based layered oxides Li₂ MnO₃ -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(Li_0.16 Ni_0.19 Fe_0.18 Mn_0.46 )O₂ . 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.