Electrodeposition of Adherent Submicron to Micron Thick Manganese Dioxide Films with Optimized Current Collector Interface for 3D Li-Ion Electrodes

Three-dimensional (3D) configuration of high-performance energy storage devices has been the subject of ongoing investigations targeting their integration in autonomous microelectronic systems. In this study we demonstrate a route toward the realization of high capacity cathode material for 3D thin-film lithium-ion (Li-ion) batteries. Electrolytic manganese dioxide (EMD) film can be applied as a Li-ion intercalation electrode upon its conversion to lithium manganese dioxide (LiMn2O4 or LMO) by solid-state reaction. The main challenges of depositing thicker EMD film directly on the current collector often lay in achieving a good film adhesion and preventing oxidation of non-noble current collectors such as TiN, Ni. To improve the adhesion of the EMD films we modify the surface of the current collector by means of thin-film or seed layer coatings, which also prevent the oxidation of the underlying current collector substrate during the anodic deposition process. As a result submicron to micron thick EMD films with good adhesion were deposited on various current collectors. The acidity of the electrolyte solutions was varied depending on the type of the surface coating or current collector used. The mechanism of the EMD film growth and morphology on different substrates was examined. Compatibility of the proposed current collector interface modification for the electrodeposition of conformal thick EMD films on high-aspect ratio microstructures was demonstrated. A method of EMD film conversion to LMO at low-temperature on different substrates was shown as the path toward their application in 3D Li-ion batteries.