Publications

A phase field model is presented to capture the formation of a solid electrolyte interface (SEI) layer on the anode surface in lithium ion batteries. In this model, the formation of an SEI layer is treated as a phase transformation process where the electrolyte phase is transformed to the SEI phase due to electrochemical reactions at the SEI/electrolyte interface during SEI growth. Numerical results show that SEI growth exhibits a power-law scaling with respect to time and is limited by the diffusion of electrons across the SEI layer. It is found that during SEI growth, the gradients of both electric potential and concentrations of species are built inside of the SEI layer, and the charge separation at the SEI/electrolyte interface remains with decreasing charge density at the interfacial region. The effects of various factors such as initial conditions, electron diffusivity, SEI formation rate, applied current density and temperature on the SEI growth rate and the distribution of electric potential and concentrations of species are investigated. The capabilities of the present model and its extension are also discussed. © 2013 The Electrochemical Society.

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A phase field model is developed to investigate the formation of a solid electrolyte interface layer on the anode surface in lithium-ion batteries. Numerical results show that the growth of solid electrolyte interface exhibits power-law scaling with respect to time, and the growth rate depends on various factors such as temperature, diffusivity of electrons, and rates of electrochemical reactions. © 2012 Materials Research Society.

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Many of the most important and hardest-to-solve problems related to the synthesis, performance, and aging of materials involve diffusion through the material or along surfaces and interfaces. These diffusion processes are driven by motions at the atomic scale, but traditional atomistic simulation methods such as molecular dynamics are limited to very short timescales on the order of the atomic vibration period (less than a picosecond), while macroscale diffusion takes place over timescales many orders of magnitude larger. We have completed an LDRD project with the goal of developing and implementing new simulation tools to overcome this timescale problem. In particular, we have focused on two main classes of methods: accelerated molecular dynamics methods that seek to extend the timescale attainable in atomistic simulations, and so-called 'equation-free' methods that combine a fine scale atomistic description of a system with a slower, coarse scale description in order to project the system forward over long times.

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