Advanced Functional Materials for Energy Storage

Kappes Branden B, Golden CO

Investigators

Abstract

Since many renewable energy sources are intermittent (e.g., sun, wind) it is necessary to develop reliable and high-density methods for storing energy. Lithium ion batteries (LIBs), with their large energy density and capacity, play a pivotal role in transforming the way energy is stored and used, but their application is hindered by the lack of available electrode materials. This research pursues novel LIB electrodes by using cyberinfrastructure to design materials able to withstand the large volume expansion/contraction that occurs during the battery charge/discharge cycle. Commercially available LIBs are based on the intercalation of lithium within layered electrode materials (graphite, lithium cobalt oxide); however, electrodes based on conversion reactions, or those based on alloying reactions, hold greater promise for improving the energy capacity and density in LIBs. This project involves optimizing the composition and morphology of electrodes during lithium insertion and removal using genetic algorithms, molecular dynamics, and density functional theory (DFT) calculations. At the DFT level, the Nernst potential is calculated from the relative stability of electrode phases. The nudged elastic band and non-equilibrium Green's function methods will provide insight into ionic diffusion pathways and into electrical conductivity, respectively. Molecular dynamics simulations based on reactive force fields interaction models will elucidate the microstructural effects of lithium insertion and removal, with particular focus on deformation and fracture behavior. When combined with the microstructural and compositional optimization capacity of advanced genetic algorithms, these tools allow for a rapid examination of broad compositional and configuration spaces and could provide novel insights into the design of high energy density electrodes that do not significantly degrade when subjected to repeated charge/discharge cycles.