Date of Award

10-30-2020

Publication Type

Master Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Automotive pouch cell, Electrochemical-thermal Battery Modelling, High capacity, NMC chemistry, P2D model, Temperature gradient

Supervisor

Ofelia A. Jianu

Rights

info:eu-repo/semantics/embargoedAccess

Abstract

Latest regulatory trends implemented in order to limit emissions combined with research advances in alternative fuels have paved the road toward vehicle electrification. Major original equipment manufacturers (\acrshort{OEM}s) have already marketed electric vehicles in large scale but apart from business strategies and policies, the real engineering problems must be addressed. Lithium-ion batteries are a promising technology for energy storage; however, their low energy density and complex electro-chemical nature, compared to fossil fuels, presents additional challenges. Their complex nature and strong temperature dependence during operation must be studied with additional accuracy, capable to predict their behavior. In this research, a pseudo two dimensional (\acrshort{P2D}) electro-chemical model, coupled with a 3D thermal energy balance for a recent high capacity \acrshort{NMC} pouch cell for automotive applications is developed. The electrochemical model with its temperature dependent parameters is validated at different temperatures and various discharge C-rates to accurately replicate the battery cell operational conditions. The sources of heat are distinguished and characterized via advanced electrochemical-modelling approach, in various battery operations and different thermal boundary conditions. For example, it was determined that the temperature rise during discharge at high C-rates, under natural convection, could result in thermal runaway, if managed incorrectly. Ohmic heat generation of current collectors and cell tabs is investigated and included. Hence, the thermal analysis provides insights on the current and voltage profiles causing the minimum thermal stress on the cell and the location of heat generation spatially and temporally during the battery discharge. Different modelling approximation of the cell are studied starting from the cell fundamental unit. This provides effective design considerations for the battery thermal management system (\acrshort{BTMS}) to enhance performance, cycle life and safety of future electrified vehicle energy storage systems.

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