Sustainable Manufacturing of Carbon Nanomaterials for Energy Storage Applications

Abstract

In order to preserve long-term human sustainability on Earth, many researchers have focused significant efforts towards developing technologies that 1) decrease greenhouse gas emissions, and 2) utilize atmospheric carbon dioxide as a feedstock gas for the production of materials, chemicals, and fuels. While Li-ion batteries have emerged as an ideal technology to reduce emissions through electric vehicles and the storage of renewably-generated energy for electricity, the current cost of Li-ion batteries today limits widespread integration. This cost is fueled mainly by the low earth abundance and high processing cost of Li-ion materials. In this dissertation, I focus on the use of low-cost and earth abundant materials for both Li- and Na- ion battery applications. A platform for the capture and conversion of atmospheric CO2 into solid carbon structures is developed, with an emphasis on the catalytic growth of carbon nanotubes (CNTs) through electrochemical routes. Small diameter CNTs are synthesized through the development of an inert anode capable of activating catalytic particles present at the cathode-electrolyte interface, and careful study of dynamic catalytic processes leads to the first mechanistic understandings of electrochemical CNT growth from CO2. Phenomena such as catalyst size dictating the structure of CNTs synthesized and Ostwald ripening of catalysts over time are studied, and electrochemical “pinning” of catalytic particles through the use of high current pulses is demonstrated to drive the formation of small-diameter CNTs with the first observation of single-walled CNTs from CO2 characterized by Raman spectroscopy. Lastly, these CO2-derived CNTs are integrated into Li-ion batteries at both the anode (as the active material) and the cathode (as the conductive additive with Fe-based active materials) and demonstrate a full-cell with a 68% reduction in CO2 emissions associated with Li-ion materials.