Importance of Electronic Conductivity in the Reversibility and Rate Capability of Metal Oxide Lithium Battery Anodes

Tuesday, 3 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
A. Palmieri, B. Ng, A. Oliveira (University of Connecticut), and W. E. Mustain (University of South Carolina)
Lithium ion batteries are the leading technology in the portable electronic market; however, in order to make the transition from laptops and tablets to automobiles and grid storage, materials with higher volumetric and specific energy density are needed. Therefore, new Li battery materials is an area of intensive research focus. At the anode, graphite has served well as the ubiquitous choice for commercial electrodes to date due to the high reversibility of Li intercalation, which resulted in very high stability and cycle life. However, the theoretical capacity of graphite is low, and it is possible that graphite-utilizing lithium batteries may be not be able to meet targets for emerging applications. Therefore, new solutions have to be investigated to increase the energy density of lithium ion batteries, while not sacrificing their stability and cycling performance compared to modern cells.

In recent years, our group has focused on advancing metal oxide-based anode materials toward automotive targets. To reach these targets, it is important to investigate and understand the key parameters that increase reaction reversibility and rate performance. In this poster, we will show how the active material electronic conductivity plays a critical key role in both cycling performance and stability of metal oxide anodes. The electronic conductivity was controlled by adding advanced carbons (i.e. reduced graphene oxide and carbon nanotubes) to increase the inter-particle conductivity, while the intrinsic conductivity of the active material was manipulated by doping. Both of these strategies will be discussed.

More quantitatively, the electronic conductivity was probed by the Van Der Pauw Method and tied directly to the cycle life of lithium cells collected by chronopotentiometric charge/discharge curves. The nanostructural changes of the active materials were investigated by high resolution transmission electron microscopy (TEM), including identical location TEM. Finally, applying the lessons learned from these experiments, highly stable full cells with a metal oxide anode and lithium cobalt oxide cathode were achieved.