Structure, Electrochemical Properties, and Thermal Stability of New Li[Ni(1/3-z)Co(1/3-z)Mn(1/3-z)Mgz]O2 (z=0, 0.04) materials

Abstract

Many recent reports performed the positive electrode materials that are cheaper, higher capacity, and thermal stability than LiNiO2, LiCoO2. One of the most extensively materials is Li[NixCo1-2xMnx]O2. The family of layered based on Li[NixCo1-2xMnx]O2 has been investigated extensively and this compounds have been reported to improve its thermal and structural instability on cycling. Layered Li[Ni1/3Co1/3Mn1/3]O2 possesses a structure based on the O3 (-NaFeO2) type, which consists of close-packed oxide ion layers stacked in an ABC arrangement. The capacities are close to those of LiCoO2 in a similar operating voltage range. Despite the positive effect of Li[Ni1/3Co1/3Mn1/3]O2 for the thermal stability, Capacity have shown a capacity fading of long-term cycling. Until now, a decrease of the long-term reversible capacity has not been understood. To further improve the electrochemical properties, several cations have been proposed for partially substitution Co/Ni, while S and F have been proposed for O. A cation of particular interest is Mg, used by several authors. The role of this ion prevents occupancy of the Li+ layers by Ni2+ and does not cause local structural collapse and is beneficial for the thermal stability, electrochemical stability. In this paper, In order to achieve understanding of the effect of magnesium on the structure and electrochemical properties, we have studied the effect of a partial substitution of Ni, Co, and Mn with Mg in Li[Ni(1/3-z)Co(1/3-z)Mn(1/3-z)]O2.