Enhanced Raman Scattering from NCM523 Cathodes Coated with Electrochemically Deposited Gold

Materials with the general composition LiMO2, where M is a mix of nickel, cobalt, and manganese, have been studied extensively as cathodes for lithium-based batteries. Some compositions, like LiNi0.5Co0.2Mn0.3O2 (NCM523), are already being employed in commercial lithium-ion batteries. The study reported here focuses on Raman spectroscopic investigations of NCM523 in the laminate form typically used to fabricate lithium battery cathodes. One of the problems encountered in such studies is that the scattering from LiMO2-type phases gets progressively weaker as the nickel content increases. NCM523 exhibits this behavior due to the fact that half of the transition metal content is nickel. In this study we show that the intensity of the Raman scattering from the NCM523 phonons can be significantly increased by electroplating sub-micron gold clusters on NCM523 laminates. The gold tends to plate preferentially on the NCM523 particles in randomly sized clusters. These clusters stimulate the NCM523 Raman scattering to varying extents approaching 100 times the scattering intensity from uncoated laminates. Intensity enhancement variations created by heterogeneities associated with the multi-phase nature of the NCM523 laminate, the random character of the sub-micron gold deposits, and the induced preferential orientation of NCM523 grains during laminate fabrication are addressed.