Hello, A new project on the LCRC cluster has been requested. Please forward the information on to the LCRC Allocation sub-committee. Applicant's name: Maria Chan Applicant's institution: ANL Applicant's division: CNM Project Name: LiAirLDRD-TMOxides Project title: Investigations of transition-metal oxides as electrocatalysts for Li-air batteries Associated funding: Argonne LDRD Other Systems: CNM Carbon Science: Argonne has recently funded a Grand Challenge LDRD project in the development of Li-air batteries [1]. Li-air batteries offer significantly higher capacities than their Li-ion counterparts, but there are significant technological challenges before widespread applications are feasible. Among the challenges are large polarizations between charge and discharge and limited cycleability. Recently, our experimental collaborators at Argonne, Lynn Trahey and Mike Thackeray, have found [2] that the use of Li-Fe/Mn-oxides as electrocatalysts useful both in reducing polarization and improving cycleability, when compared with carbon. The mechanism of this significant improvement remains unknown, and first principles computation is important in unraveling this mystery. The electrocatalysts considered are Fe and Mn oxides that incorporate or can accomodate Li2O in their structures. The goal of our project is to investigate the thermodynamics and mechanism of removal and insertion of Li and Li-O_x species from and into these transition metal (TM) oxides, in order to understand their underlying role of in the Li-O2 reaction and suggest improvements. The calculation of total energies of these TM oxides at various stages of Li/Li-O_x removal and insertion will allow us to associate the thermodynamic phases with a equilibrium voltage, which will be compared with the voltages of Li2O and Li2O2 formation. Additional information from atomic radial distribution functions and XANES spectra will corroborate the calculated configurations and electronic structures with experimental characterization carried out at the APS. Calculations involving Li-O_x species on the surfaces of these TM-oxides will allow the deduction of thermodynamic barriers and overp otentials for Li-O2 reactions. Finally the kinetics of Li and Li-O_x transport in these structures are investigated to delineate where transport may be limited. [1] http://www.anl.gov/Media_Center/News/2009/batteries090915.html [2] L. Trahey, C. S. Johnson, J. T. Vaughey, S.-H. Kang, L. J. Hardwick, S. A. Freunberger, P. G. Bruce,b, and M. M. Thackeray, "Activated Lithium-Metal-Oxides as Catalytic Electrodes for Li–O2 Cells" Electrochemical and Solid-State Letters, 14 (5) A64-A66 (2011). Project description: We will use density functional theory (DFT) with the Hubbard U (+U) correction and hybrid functionals which have been demonstrated to produce accurate energetics and reasonably accurate electronic structures in correlated systems such as TM oxides. We will perform DFT+U total-energy calculations involving Li-O_x insertion and removal from Fe/Mn oxides, which involves significant configurational sampling. An estimated 500 such calculations requiring 100-500 core-hours each are needed. Where feasible, accurate energetics and electronic structures will be obtained from optimal structures using hybrid functionals, which are more computationally expensive than DFT/+U. Approximately 50 such calculations requiring 1000-3000 core-hours each are needed. Ab initio molecular dynamics calculations will be used to extract the radial distribution functions and diffusion coefficients. Approximately 100 such calculations requiring 500-1000 core-hours each are needed . Using the projector-augmented wave method, only valence electrons will be included which reduces computational costs. We will use well-established DFT codes VASP and GPAW, which use a plane wave basis set and real space grids respectively. For large systems such as nanostructures, VASP has been tested on Fusion for computation involving systems with up to 7000 electrons. For routine calculations, hard scaling efficiency of 70%-80% has been demonstrated for 64 to 128 cores compared to 8 cores, thus enabling efficient calculations of large numbers of configurations. Project URL: Requested allocation: 325000 Justification: The requester has used 1366 hours of their initial startup project. In addition to approving an initial amount, please specify a Category and Subcategory for this project. For a list of the current selection of approved categories, please see: https://wiki.lcrc.anl.gov/wiki/Processes/Categories Once the Allocation committee has approved the project, please go to the Project Management page to create it: https://accounts.lcrc.anl.gov/projects.php Thank You, The LCRC Accounts System