Synthesis, structural characterization, electrochemical properties, and thermal stability of Al-substituted LiMn1.5Ni0.5O4

Abstract

One of the interesting lithium-ion battery cathode materials which have been developed over the last 20 years is the lithium manganese nickel oxide (LMNO). However, problems with lifetime remain. Increasing the lifetime of LMNO is crucial to its commercial adoption, and one of the promising techniques to do this is substituting different elements of the structure. In this thesis, the structure, electrochemistry, and thermal stability of LMNO have been investigated with different amounts of aluminum substitution attempted to replace either manganese, nickel, or both elements evenly. The findings suggest that substituting manganese is not easily done, as impurities form. However, by replacing mainly nickel, aluminum is successfully incorporated into the structure at a stoichiometric amount of 0.2. This type of substitution was also found to change the electrochemical voltage plateau of the material, in addition to prolonging its cycle life. The aluminum substituted material also exhibited better thermal stability above 100℃.