Developing novel electrode materials in energy storage devices for hybrid electric vehicles

This thesis is aimed at the study and development of environmentally-friendly, safe, and inexpensive electrodes for lithium-ion batteries and the study of an environmentally-friendly novel carbonaceous material as a possible hydrogen storage material for fuel cells for future use in HEVs, which will reduce the vehicle emissions to the atmosphere. With those goals in mind, the reaction mechanism of a cathodic material, for lithium-ion batteries was studied. LiNi 0.8Co0.15Al0.05O2, was chosen because it substitutes part of the most dangerous metal used in commercial batteries for others that are less environmentally hazardous in its structure. The study included thermal stability by differential scanning calorimeter (DSC), thermal gravimetric analysis (TGA), and accelerating rate calorimeter (ARC) as well as characterization by X-ray diffraction (XRD) at different states of charge (SOC) of the material. The suggested mechanism consists of three steps. The first step involves the loss of oxygen from LiNi0.8Co0.15 Al0.05O2, producing a deformation in the structure. The second step entails the reaction of this oxygen with the electrolyte. The third step consists of the decomposition of the active material.; A pure carbon-based material with applications in electrochemical processes was synthesized using different fractions of sepiolite clay. The preparation method requires lower temperatures than commercial anodes. The produced carbon was initially characterized to determine its purity and physical properties. The electrochemical properties for using the synthesized carbon as an electrode in Li-ion batteries in half cells and full cells (using LiNi0.8Co 0.15Al0.05O2 as the positive electrode) were evaluated using conventional electrochemical testing methods such as charge/discharge, area specific impedance (ASI) and electrochemical impedance spectroscopy (EIS). The results indicated that the electrochemical performance of the sepiolite-derived carbon as lithium cell anodes is related to their surface chemical rather than their BET surface area.; The same carbon-based material was characterized to determine its surface properties including transmission electron microscopy (TEM), surface area, pore volume, and pore diameter. High-resolution transmission electron spectroscopy (HRTEM) showed nanofibers in the carbon structures. The hydrogen storage capability was explored in a hydrogen storage setup built in our laboratory at room temperature and 10 MPa obtaining a gravimetric storage capacity close to 2.2% w/w. The results indicated that there is a correlation of the hydrogen storage ability and the surface properties of the carbonaceous material.