A Reduced-Order Electrochemical Model of Lithium-Ion Cells for System Identification of Battery Aging

Lithium-ion batteries continue to garner interest as an energy storage system in stationary and vehicular applications. Considerable research effort is currently devoted to investigating the physical and chemical phenomena leading to aging, namely internal resistance growth and capacity fade. This paper presents a reduced-order model that characterizes the dynamic behavior of a Lithium-ion battery cell. The model is derived from the governing electrochemical principles and is applied to a Li-ion cell based upon a natural graphite negative electrode and iron phosphate positive electrode. The paper describes the modeling approach and equations, followed by a validation with experimental data. A sensitivity analysis is then conducted to investigate the influence of the model parameters on the cell internal resistance and capacity. The results of this study allows one to identify a subset of model parameters that may evolve throughout the battery’s life, providing guidance towards establishing which parameter trajectories must be quantified as batteries age.