A coupled OD electrochemical ageing & electro-thermal Li-ion modeling approach for HEV/PHEV

The technical and commercial success of hybrid-electric vehicles (HEV) and plug-in hybrid-electric vehicles (PHEV) is strongly related to the security, cost and lifetime of the traction battery. Energy and power performances of Li-ion systems are impacted during ageing with a reduction of capacity and an increase of internal impedance. Ageing phenomena occurring in Li-ion batteries are the consequences of combined effect of cycling current, temperature and state-of-charge (SOC). Temperature is one of the most important factors conditioning power performances and ageing of the battery systems. Thermal effects occurring inside cylindrical cells have to be considered in OD battery models for security issues and cycle life optimization through minimization of ageing mechanisms. Most of Li-ion ageing mechanisms have been experimentally identified and described in literature. Ageing models developed in literature generally consider the classical Solid Electrolyte Interphase (SEI)s growth mechanism occurring at the negative carbonaceous electrode. On the one hand, high order pseudo-ID electrochemical models are predictive and reproduce in a good way the evolutions of capacity and power loss during ageing. On the other hand, OD semi-empirical ageing models require lots of experimental data for calibration and are most of the time not predictive with respect to various operating conditions during cycle life of the battery systems. It is then clear that advances in modeling are required to account for physics-based ageing kinetics in zero-dimensional electro-thermal models. In this work, an original OD single electrode electrochemical model taking into account the ageing mechanism of negative electrode surface layer growth via electrolyte diffusion is developed and coupled with a OD impedance-based electro-thermal model. Physics-based first correlations between capacity decrease and impedance increase is proposed. Calibration and validation of the full OD coupled model are performed on experimental data for a commercial cylindrical LiFePO
4
/Carbone 2.3 Ah cell. The ageing model is then used to discuss impact of temperature and State-Of-Charge on PHEV duty cycles.