  Experiments, numerical simulations, and analytical calculations are used to
calibrate a diffuse-interface Cahn-Hilliard model of Li-Sn thin film electrodes
that experience a transformation from Sn to Li2Sn5. It is shown that a
concentration-gradient dependent mobility can be used in the Cahn-Hilliard
equation to give the interface a finite mobility and capture its nonequilibrium
behavior. Comparing experiments and simulations, the free-energy of Li-Sn,
diffusivity of Li in Sn and Li2Sn5, the exchange current density for the
surface reaction, and the mobility of the Sn/Li2Sn5 interface are extracted.
The implications of finite interface mobility for practical battery electrodes
are discussed.
