A Molecular Dynamics Study of Interfacial Structure and Ion Transport of Mixed Carbonate/LiPF6 Electrolytes Near Graphite Electrode Surfaces

Tuesday, 30 May 2017
Grand Ballroom (Hilton New Orleans Riverside)
M. J. Boyer and G. S. Hwang (University of Texas at Austin)
Electrolyte and electrode materials utilized within lithium ion batteries have been extensively studied as separate segments, however the structural and dynamical properties of the electrode/electrolyte interface remain relatively undefined their immense role in dictating cell performance. By utilizing molecular dynamics simulations, we examine the structural reorganization of solvent molecules (cyclic ethylene carbonate: linear dimethyl carbonate 1:1 and 1:3 molar ratio doped with 1M LiPF6) upon the immersion of a graphite anode at various charge states. The interfacial structure was found to be sensitive to the molecular geometry and polarity of each solvent molecule as well as the surface structure and charge distribution of the negative electrode. An in depth analysis of the rearrangement of molecules at the anode/electrolyte interface elucidates structural influence on ion transport of both Li+ and fully or partially decomposed solvent molecules in order to better understand transient electrochemical processes which occur at this interface during the early stages of the SEI formation. The coupling of enhanced sampling techniques, such as metadynamics, with equilibrium structural data provides a computational framework for studying these processes at their onse,t which may further assist in efforts to engineer the anode/electrolyte interface leading to an optimal SEI layer.