Simulation Model of a Prismatic Lithium-Ion-Battery for Temperature Propagation in the Cell after a Short Term Thermal Stress

For several years lithium-ion batteries have been commercially used in portable devices such as camcorders, laptop computers and cell phones. Battery lifetime plays only a minor role in such applications due to rapid product innovation and strong competition. However, the increasing demand for lithium-ion batteries for automotive traction applications requires drastic increase in battery life-time and safety.[1] The majority of the existing life-time and performance prognoses are based on accelerated aging tests at elevated temperatures such as 40 °C, since the temperature plays a crucial role on the battery performance, safety and life-time.

However automotive lithium-ion cells must endure multiple production processes during the fabrication of a high-end traction battery system, such as contact welding, where the cells are exposed to elevated temperatures for a short period of time.[2] Up to date there is little information on the temperature propagation within the cell during the short-term thermal stress and also the influence of such short period thermal stress on the cell performance and cyclic ability.

For a better understanding of the temperature propagation in the cell, a simulation model based on the thermal material characteristics of a prismatic Li-NiMnCoO₂ cell was created in COMSOL Multiphysics®. The thermal characteristics of the battery components are experimentally determined using Laser Flash Analysis (LFA) and Differential Scanning Calorimetry (DSC). In order to validate the modeling approach in this work, we built an experimental setup to measure the temperature propagation within a dummy cell. This dummy cell includes a carbonate solution as electrolyte, yet without a lithium salt.

After validating the model is used to describe the temperature propagation after a short-term temperature stress on automotive lithium-ion cells. Furthermore, it’s possible to predict the temperature propagation in the cell with this simulation model, after the short-term stress on different positions on the cell casing surface and at different SOC’s.

[1] J. Vetter, P. Novák, M.R. Wagner, C. Veit, K.-C. Möller, J.O. Besenhard,M. Winter, M. Wohlfahrt-Mehrens, C. Vogler, A. Hammouche; Ageing mechanisms in lithium-ion batteries. J. Power Sources 147 (2005) 269–281

[2] M. Yoshio, R.J. Brodd, A. Kozawa; Lithium-Ion Batteries, Science and Technologies; Springer (2009)