The search for a clean and green locomotive propulsion system is gaining importance due to the increased cost of imported oil and the requirement to meet the higher EPA standards for reduced emission of greenhouse gases and pollutants. A hybrid diesel engine and battery locomotive with regenerative braking system is one such potential electric propulsion system that has been under consideration by railroad industries around the world. Lithium ion batteries are considered as one of the leading types as compared to the other batteries for the battery systems to be employed in electric vehicles (EVs) or hybrid electric vehicles (HEVs). Some of the major challenges with the full-scale commercial use of batteries for electric or hybrid vehicles are the requirement of high energy density, compatibility with high charge and discharge rates for different load cycles while maintaining high performance, and prevention of any thermal runaway conditions.
The objective of this research is to develop a computer simulation model for coupled electrochemical and thermal analysis and characterization of a lithium ion battery performance subject to a range of charge and discharge loading, and thermal environmental conditions. The electrochemical model includes species and charge transport through the liquid and solid phases of electrode and electrolyte layers along with electrode kinetics. The thermal model includes a number of heat generation components such as reversible, irreversible and ohmic heating, and heat dissipation by conduction through layers of battery cell and convection from the surface. Simulation results show sensitivity of charge and discharge rates on the electrochemical performance and thermal conditions of the battery. Variation in the voltage loss due to reaction and ohmic irreversibilities are observed when the battery is subjected to different discharge and charge rates, and thermal conditions. The cell temperature distributions for different load cycles and boundary conditions indicate the need for cooling the cell in order to avoid thermal run-away. The model developed helps in gaining a good insight of the complex processes and can form a platform for identifying materials for enhanced battery performance and thermal management system for EVs and HEVs.