The effects of Mo doping on 0.3Li[Li0.33Mn0.67]O2·0.7Li[Ni0.5Co0.2Mn0.3]O2 cathode material

Abstract

Mo doped Li excess transition metal oxides formulated as 0.3Li[Li_0.33Mn_0.67]O₂·0.7Li[Ni_0.5-xCo_0.2Mn_0.3-xMo_2x]O₂ were synthesized using the co-precipitation process. The effects of the substitution of Ni and Mn with Mo were investigated for the density of the states, the structure, cycling stability, rate performance and thermal stability by tools such as first principle calculations, synchrotron X-ray diffraction, field-emission SEM, solid state ⁷Li MAS nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), elemental mapping by scanning TEM (STEM), inductively coupled plasma atomic emission spectrometry (ICP-AES) and a differential scanning calorimeter (DSC). It was confirmed that high valence Mo⁶⁺ doping of the Li-excess manganese-nickel-cobalt layered oxide in the transition metal enhanced the structural stability and electrochemical performance. This increase was due to strong Mo–O hybridization inducing weak Ni–O hybridization, which may reduce O₂ evolution, and metallic behavior resulting in a diminishing cell resistance.