Fabrication and Characterization of Nanostructured Cathodes for Li-Ion Batteries

Li-ion batteries have emerged as a leading energy storage technology for several applications including portable electronics devices and electric vehicles. Rigorous efforts are made to develop these batteries with higher energy density, higher power density, and better cycling stability while reducing cost and environmental impact. To better understand how electrode microstructure contributes to the electrode performance, the spinel LiMn2O4 (LMO) cathode material was prepared using a template-assisted sol-gel synthesis method. This method involves soaking of polycarbonate template membranes in the precursor solution followed by drying, to remove the solvent. The dried templates containing precursor materials were etched in an oxygen plasma to remove the template, and the nanostructured electrode formed was then calcined to convert these nanostructures to spinel LiMn2O4. Simultaneously, powdered LMO was prepared using the same synthesis procedure, but without the aid of a template to control electrode morphology. A series of tests were performed to study the effect of processing conditions on the structure and morphology of the nanostructured electrodes. The resulting electrodes were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM) in support of efforts to understand the effects of process parameters on the electrochemical performance of the electrode. The template assisted synthesis approach yielded an electrode of well-defined nanotubules. Extending the template soaking time was found to provide better definition of individual tubule structures. Increasing calcination temperature was found to create a better defined spinel structure for the LMO. These observations provide insight into process parameters relevant to electrode preparation and substrate selection when producing nanostructured electrodes using template-assisted methods.