Lithium manganese oxides (LMOs) have drawn significant interest as cathode materials for lithium (Li)-ion batteries due to their high thermal stability, high energy density, and a longer cycle life at a lower cost than lithium cobalt oxides. A significant amount of research has been conducted to prepare cathode materials for Li-ion batteries ex-situ and then to integrate them into electrodes after forming a slurry with the binder and deposition onto the current collector. An alternative pathway to achieve active LMO cathodes is to directly synthesize them on the current collector via electrodeposition (ED). Using ED not only could improve active material utilization and electrode mechanical properties, but it may also reduce the cost of electrode fabrication as well as provide a pathway for facile recycling of spent manganese from a number of applications (e.g. alkaline batteries).

To date, a few studies have reported the synthesis of LMOs by electrodeposition [1,2]. When doing this, the first step of the process is to deposit manganese oxide (s), Mn_xO_y. Then, the oxide is lithiated to form the LMOs (i.e. LiMn_xO_y). Despite the fact that this process has been demonstrated, and active materials with reasonable capacity have been shown, it is presently unknown what LiMn_xO_y phase or phases are active. It is also not definitively known which Mn_xO_y phase(s) is(are) involved in the transformation. To move the application of direct deposition of manganese oxide active phases closer to reality, a critical understanding of the solid-state chemistry for its conversion and energy storage is needed.

In this study, Mn oxides were electrochemically prepared by potentiostatic deposition on multiple substrates and treated by lithium hydroxide. After that, the heat treatment of the lithiated deposits gave a mixture of LMOs as the cathode materials on the substrate. This talk will discuss the likely reactions for the formation of LMOs as well as their chemistry during charge/discharge. The morphology and the elemental composition of LMOs will be shown by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The composition and presence of crystalline Mn oxides and LMOs will be clarified by X-ray diffraction. Lastly, results will be shown regarding the cycle performance of the electrochemically prepared LMOs as well as the crystalline phases present after charge-discharge.

References:

1. Quan, S. Ohguchi, M. Kawase, H. Tanimura, and N. Sonoyama, J. Power Sources, 244, 375 (2013).
2. Rana, M. Stan, R. Kloepsch, J. Li, G. Schumacher, E. Welter, I. Zizak, J. Banhart, and M. Winter, Adv. Energy Mater., 4, 1300998 (2014).