PRIMARY AND SECONDARY BATTERIES
Our work focuses on increasing the energy density and reliability for batteries that power our increasingly mobile lives as well as defense applications. We leverage our expertise in materials development, electrochemistry and electrochemical engineering to bring new solutions to our funders and collaborators.
HIGH CAPACITY METAL OXIDE ANODES FOR LI-ION BATTERIES
Graphite materials have exclusively been used at the Li-ion battery anode since their commercialization in the 1990s. Until now, graphite materials have been sufficient since the energy density of these batteries has been more than sufficient. However, the power demand of mobile devices is rapidly increasing as the public’s demand for enhanced functionality shows no sign of stopping. The automotive industry is also putting considerable pressure on traditional materials as increased energy storage is needed to enable an acceptable vehicle range. Both these applications demand lightweight, small footprint solutions that can only be accomplished by transitioning from graphite to higher capacity materials. Transition metal oxides are a promising class of materials because they allow for multiple electron transfer steps per mol of active material. Unfortunately, most metal oxides undergo alloying or chemical conversion reactions that change the bonding of active materials, and sometimes even forming electrochemically inactive materials, limiting both cycle retention and rate capability. Our primary work in this area has revolved around understanding the roles of structure and conductivity in the reaction reversibility during charge and discharge of metal oxides, with NiO being our primary probing compound, though we have done a lot of work with Co, Mn and Sn oxides as well. To date, We have been able to achieve anodes with > 700 mAh/g capacity over several 100 cycles.
PRIMARY ALKALINE BATTERIES
In alkaline batteries, one of the main issues remains the evolution of hydrogen gas during cell life. Hydrogen gassing occurs both on the shelf and during cell rest - from thermodynamically driven corrosion of the anode material. Hydrogen gassing also occurs in rechargeable alkaline cells - significantly reducing the faradaic efficiency below the desired levels. Hydrogen gassing is even worse on so-called "next generation" materials like aluminum because the driving force is greater in Al-anode alkaline batteries than commercial Zn-anode batteries. Our work in this area focuses on understanding the material structures that are responsible for corrosion and developing new approaches to mitigate it - not only to make existing batteries safer and more reliable, but also to enable the use of higher energy density materials to be used and rechargeable ultra-low cost alkaline battery platforms to be realized.
NEW METHODS DEVELOPMENT
The behavior of materials in operating devices is very complex. During charge and discharge, cells are cycling between (at least) two completely distinct chemical phases, which impacts electronic conductivity, ion diffusion, etc. In our group, we work to create new methods to study the operation of materials and cells in-situ and operando. We have developed several tools in our lab that fall into this category. For batteries, we have recently created new techniques that allow for multiphase diffusion decoupling, identical location TEM imaging and direct observation of the active materials during the discharge of operating alkaline AA cells.
Professor William E. Mustain
Department of Chemical Engineering
Swearingen Engineering Center
University of South Carolina
301 Main St.
Columbia, SC 29208