LiMn2O4 cathodes for 3D thin film all solid state Li-ion batteries: towards conformal deposition on high aspect ratio substrates

Abstract

Li-ion batteries are known as promising candidates to overcome the energy storage problem due to their high working voltages, energy density and long life. However, contemporary Li-ion batteries could be improved significantly by increasing the surface area of the electrodes, yielding a 3D battery, which will provide high Li ion conductivity, high capacity (compared to the planar system) and high power, due to the increased surface area and short diffusion lengths1. LiMn2O4 (LMO) is an excellent candidate as cathode due to its high voltage plateau, non-toxicity and good recyclability. In this study, spray-coating route is being explored for the LMO thin films deposition on TiN and Pt coated Si planar substrates and 3D micropillars. Through an elaborated study of aqueous and organic precursors chemistry, deposition and processing parameters (such as deposition and annealing temperature, atmosphere, time), specific conditions are derived for the successful formation of crystalline and electrochemically active LMO. The film features depend mainly of the precursors and spray-coating parameters. The stoichiometry, crystallinity, morphology, thickness and electrochemical properties are studied via Raman, XRD, (cross-sectional)SEM and Cyclic Voltammetry, respectively. The study yields interesting insights in the LMO synthesis, deposition and electrochemical activity both in 2D and 3D systems, bringing a 3D all-solid state battery one step closer.