Thin nanostructured LiMn₂O₄ films by flame spray deposition and in situ annealing method

A new approach has been developed to rapidly synthesize nanostructured LiMn₂O₄ thin films by flame spray deposition (FSD) and in situ annealing. A precursor solution of lithium acetylacetonate and manganese acetylacetonate in an organic solution was supplied through a flame spray pyrolysis (FSP) reactor. The liquid solution spray was ignited and stabilized by a premixed methane/oxygen flame ring surrounding the FSP nozzle. Thus, LiMn₂O₄ nanoparticles were formed by combustion and deposited onto a current collector followed by in situ annealing. Two different types of current collectors, i.e. stainless steel and aluminum coated with carbon-based primer were tested. The prepared thin films were characterized by X-ray diffraction and field-emission scanning electron microscopy. The electrochemical properties of the thin films were evaluated by cyclic voltammetry and galvanostatic cycling. The LiMn₂O₄ films exhibited good cyclability. Films that underwent sintering and crystal growth during in situ annealing developed more robust film structures on the current collector surface and exhibited better electrochemical performance than poorly adhered films.