Precursor Inhomogeneities Influence the Properties of Multimetal Oxides as Shown for LiNi0.5Mn1.5O4 Derived from Hydrothermally Synthesized Precursors

Co-precipitation is an attractive means for synthesizing mixed metal oxides, a material class with a wide range of application prospects. Often soluble metal salts are precipitated as metal hydroxides or -carbonates, which subsequently are converted to the corresponding oxide(s) upon thermal treatment. The thermal treatment step is used to induce compositional homogeneity on the atomic level. In order to shed some more light on this effect, detailed analyses of a mixed Li-Ni-Mn-oxide with the target composition LiNi_0.5Mn_1.5O₄ (LNMO), which is a promising cathode material for rechargeable Li-ion batteries are performed. The first synthesis step is the precipitation of a Ni-Mn-carbonate, which is subsequently thermally lithiated and transformed into an oxide. A combination of X-Ray diffraction (XRD), Raman microscopy, scanning electron microscopy coupled with energy dispersive X-Ray spectroscopy (EDX) in combination with elemental analysis, as well as electrochemical characterization, revealed that chemical inhomogeneities present already in the precursor particles have a direct influence on the electrochemical performance of the final product. The broader implications of these results in relation to co-precipitation-based syntheses of functional materials are discussed, with special focus on the importance of the particle size distribution of the secondary particles.