(636c) Kinetic Monte Carlo Simulation of Surface Heterogeneity for Lithium-Ion Batteries: Passive Layer Formation and Simulation of Capacity Fade

Rechargeable lithium-ion batteries have been extensively used in mobile communication and portable instruments due to its high volumetric and gravimetric energy density and low self-discharge rate. The lithium-ion battery is also promising for electric (plug-in and hybrid) vehicles and stationary energy storage applications, which has motivated many scientists and engineers to work towards developing lithium-ion batteries with improved performance and longer life.

In the operation, battery undergoes many charging and discharging cycles, an active solid-electrolyte-interface (SEI) layer forms mainly in the first cycle of charging. This SEI layer should be thin, porous, and stable to provide the barrier between the electrolyte and the electrode and low resistance lithium ion passages. In some cycles during the life of the battery, the battery may get subjected to overcharging and leads to the formation of unwanted byproducts. These byproducts plate the pores of the SEI layer and increase the thickness of the SEI layer called the passive SEI layer, which result in increasing the resistance to the intercalation/deintercalation of lithium ions and in turn result in reducing the capacity of the battery. This phenomenon produces high temperature and can result in the battery entering into thermal runaway [1-3]. The properties and chemical composition of the SEI layer (active and passive) has been a subject of intense research due to its importance in the safety, capacity fade, and cycle life of Li-ion secondary batteries [4-10].

In this talk, Kinetic Monte Carlo (KMC) simulation is applied to explore the formation and growth of passive SEI layer in the tangential direction of the lithium-ion intercalation in a graphite anode (see Figure 1). The effects of operating parameters such as the exchange current density and temperature on the formation of the SEI layer are investigated on the active as well as passive layer. The potential for coupling the KMC model with porous electrode theory-continuum models will be discussed, to arrive at a multi-scale model for understanding, analyzing, and minimizing capacity fade.

Figure 1: Mechanism for formation of a passive SEI layer on the tangential direction of the graphite electrode

Acknowledgements

The authors acknowledge financial support by the National Science Foundation under grant numbers CBET-0828002, CBET-0828123, and CBET-1008692, United States Government and I-CARES (WUSTL).

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