Modeling the formation of passive films on metal surfaces

Anodic passivation is a critically important phenomenon in lithium ion battery systems. The formation of the SEI (Solid Electrolyte Interphase) layer on the anode during the first few cycles of charging and discharging has a profound effect on battery performance. Formation of the passive layer protects the anode from unwanted side reactions with the electrolyte. However, incomplete or uncontrolled passivation leads to excessive consumption of lithium and this reduces specific capacity.; Mathematical models are developed to study the formation of passive films on metal surfaces. The Point defect model is developed to study the formation of passive films on metal surfaces. Vacancy diffusion and migration are considered to be key parameters in studying passive film growth. The variation of the electric field strength is studied across passive film layer. The Point defect Model is compared with the High field model and the results are applied to different metal systems.; The formation of anodic passive films on iron metal is studied. Modeling results are compared with experimental data from literature. Though we have studied metal passivation thus far, the applicability of the model lies in the model being able to simulate passive film growth on carbon anodes for lithium ion battery systems. Future battery model studying capacity fading for lithium ion battery systems will be able to use this model to study the impact of passive film on battery behavior.