Electrochemical-thermal coupled investigation of lithium iron phosphate cell performances under air-cooled conditions

Abstract

The power battery performance is of great importance for electric vehicles (EVs) and hybrid electric vehicles (HEVs). Lithium Iron Phosphate (LFP) battery is a promising choice for the power of EVs, because of its high cell capacity and good economics in long term usage. The discharge process of a lithium-ion battery is affected by its operating conditions. In this paper, an electrochemical-thermal coupling numerical model is developed for a cylindrical LFP battery. The effects of discharge rate, ambient temperature, and convective heat transfer coefficient on the discharge characteristics and heat generation performance are discussed. The results show that the cell discharge voltage and the depth of discharge decrease with the increase of discharge rate. The cell temperature rise increases almost linearly at the same discharge rate. When the ambient temperature is increased, both the cell discharge voltage and the depth of discharge increase. The cell temperature rise decreases approximately linearly with the increase of the ambient temperature. In the low temperature environment, both the cell discharge voltage and the depth of discharge (DOD) decrease with the increase of the heat transfer coefficient. However, when the convective heat transfer coefficient is changed in the high temperature environment, the cell discharge voltage and the DOD unchanged. Both in the low temperature environment and high temperature environment, the cell temperature rise decreases with the increase of the heat transfer coefficient.