************ The 2nd Lab Seminar ***************************************

Title : Molecular Dynamics Study of Graphite/Electrolyte Interfaces
Andres Marquez and Perla B. Balbuena,
Journal of The Electrochemical Society 148, A624 (2001). 

Speaker : Monno Yohei

Date : Thu. June. 6th, 1:30 pm

Abstract :
Molecular dynamics simulations of graphite-electrolyte interfaces are 
performed on 3D unit cells with periodic boundary conditions at lithium 
concentrations between 0 and 17% in the carbon phase. The liquid electro-
lyte consists of a mixture of cyclic carbonates and LiPF6. Staging 
phenomena, structural changes in the modeled graphite systems, charge 
distribution on the atoms, and lithium-ion diffusion coefficients are 
evaluated as a function of lithium concentration in the solid phase. 
Transitions between ordered carbon structures are detected in the model 
systems. Repulsive lithium-lithium interlayer interactions are predominant 
during the intercalation process. Calculated solid phase diffusion 
coefficients of lithium ions for a state of charge between 0 and 17% are 
in the range 10^28 to 10^29 cm^2/s. The maximum increase of graphite inter-
layer spacing found when the lithium ions are intercalated varies from 6 
to 10% depending on the degree of intercalation. An electrostatic double 
layer is formed between the solid and the electrolyte phase; the average 
charge at each side of the solid/liquid interface is strongly dependent 
on the composition and electronic properties of the electrolyte.


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