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: hakim iddir
Applicant's institution: ANL
Applicant's division: MSD
Project Name: GAB
Project title: Graphene Applications in Li ion Batteries
Associated funding: EFRC
Other Systems: NERSC
Science: LiMn2O4 (LMO) has emerged as an important battery cathode material owning to its low cost, abundance, and high power capability. However, it experiences voltage fade after few charge/discharge cycles, which has been attributed to manganese dissolution to the electrolyte. The ability to control Mn dissolution is key to extending the lifespan to LMO and making the material attractive for industrial applications. One promising approach is to cover the cathode with a graphene coating, which has been shown to extend the reversibility to hundreds of cycles [1]. Two mechanisms by which graphene controls Mn dissolution have been proposed and investigated theoretically: the creation of an energy barrier for Mn ion migration, and the chemical interaction between graphene and LMO that suppresses the release of Mn ions into the electrolyte [1]. Although the work has provided important insight into the LMO/graphene interaction, the kinetic barriers for Mn ion
migration were calculated with a free standing graphene (without the LMO surface), while the interaction between the two materials was studied with a graphene patch (a flake) chemisorbed perpendicularly on the LMO surface. It is known that the electronic properties of a graphene flake change depending on its geometry, size, and termination type [2].
In this study, we propose to extend the previous research by modeling the LMO (001) surface in the presence of a graphene layer (rather than a patch) physiosorbed like a blanket on LMO, thus bringing the model closer to the experimental setup in [1]. We will explore the mechanisms of how such a graphene coating may prevent Mn dissolution from the bulk. To account for the lattice mismatch between the two materials, we will introduce ripples into our theoretical structure of graphene. Most of the existing models in the literature represent graphene absorption on different substrates as a completely flat layer strained in response to lattice mismatch. This may be convenient to the modeler, but likely does not represent what happens in reality as graphene’s structure is known to be intrinsically rippled [3]. The introduction of corrugations into the theoretical structure of graphene will thus make our model more in line with the experimental observations. Our approach to
creating ripples will be based on previous work where flat graphene was mapped onto a cylindrical surface by linear transformation to create carbon nanotubes [4]. Additionally, we will work with graphene bubbles, which were shown to have large magnetic fields and act as potential catalytic sites [5-6]. With two different models of graphene (rippled graphene and graphene bubbles) on the LMO surface, we will investigate the effect of graphene’s curvature first on the formation energies of divacancies in the graphene’s lattice, and later on their ability to filter Li while hindering Mn migration to the electrolyte. The proposed research is expected to lead to better understanding of the mechanism by which graphene controls Mn dissolution from LMO, and guide the synthesis of the cathode materials with improved stability and electrochemical properties. The work will be performed in collaboration with John Russell (AAAS Science and Technology Policy Fellow) and Weronika Wal
kosz (Loyola University Chicago), and is in line with current EFRC CEES2 project.
References:
[1] “Suppressing Manganese Dissolution from Lithium Manganese Oxide Spinel Cathodes with Single-Layer Graphene” Jaber-Ansari, L. et al., Adv. Energy Mater. 1500646 (2015)
[2] “Modelling the role of size, edge structure and terminations on the electronic properties of graphene nano-flakes” A. Barnard, I. Snook., Model. Simul. Mater. Sci. Eng. 19, 5, (2011).
[3] “Intrinsic ripples in grapheme” A. Fasolino, A. et al., Nature Mater. 6, 858-861 (2007)
[4] “Methane bond activation by Pt and Pd subnanometer clusters supported on graphene and carbon nanotubes” J. Russell, et al., Chem. Phys. Lett. 536, 9-13 (2012)
[5] “Strain-Induced Pseudo–Magnetic Fields Greater Than 300 Tesla in Graphene Nanobubbles” Levy, N. et al., Science 329, 544-547 (2010)
[6] “Transforming moiré blisters into geometric graphene nano-bubbles” J. Lu, A. H. C. Neto, and K. P. Loh, Nature Comm. 3:823, DOI: 10.1038/ncomms1818 (2012)
Project description: As mentioned above, in this work we will investigate the effect of graphene’s curvature on the formation energies of vacancies in the graphene’s lattice and on their ability to filter Li while hindering Mn migration to the electrolyte. All calculations will be performed with Vienna Ab initio Simulation Package (VASP), using plane wave basis sets and PAW potentials. We expect to run 20-25 different calculations involving LMO and rippled graphene with vacancies. For a given vacancy (mono-, di-vacancy), the graphene structures will have 3-4 different curvatures. Similar calculations will be done for LMO and graphene bubbles. Lastly, ~ 20 kinetic barriers will be computed for LMO/rippled graphene and LMO/graphene bubbles systems. We estimate that the minimum cell size to simulate a realistic system is of the order of 200 atoms. Based on our previous work, we expect that each total energy calculation will take about 2000 processor hours, while the ba
rrier calculation will take on average about 20000 processors hours. We are planning to run ~50 total energy calculations and ~ 20 kinetic barrier calculations. Therefore, a total allocation of 490,000 processor hours will be needed to perform the proposed work.
Six members will participate in this project:
Weronika Walkosz
John Russell
Robert Warburton, Jefferey Greeley
Hakim Iddir, Larry Curtiss
Industry partnership:
Project URL:
Requested allocation: 490000
Q1: 130000
Q2: 120000
Q3: 120000
Q4: 120000
Justification:
Storage requirements:
The requester has used undetermined amount hours of their initial startup project.
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