Molecular dynamics simulations of graphite-electrolyte interfaces are perfo
rmed on 3D unit cells with periodic boundary conditions at lithium concentr
ations between 0 and 17% in the carbon phase. The liquid electrolyte consis
ts of a mixture of cyclic carbonates and LiPF6. Staging phenomena, structur
al changes in the modeled graphite systems, charge distribution on the atom
s, and lithium-ion diffusion coefficients are evaluated as a function of li
thium concentration in the solid phase. Transitions between ordered carbon
structures are detected in the model systems. Repulsive lithium-lithium int
erlayer interactions are predominant during the intercalation process. Calc
ulated solid phase diffusion coefficients of lithium ions for a state of ch
arge between 0 and 17% are in the range 10(-8) to 10(-9) cm(2)/s. The maxim
um increase of graphite interlayer 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 electrol
yte phase; the average charge at each side of the solid/liquid interface is
strongly dependent on the composition and electronic properties of the ele
ctrolyte. (C) 2001 The Electrochemical Society.