Experimental investigation of pressure effect on the PCM performance in Li-ion battery thermal management system

Abstract

To control the maximum temperature in Li-ion batteries, it is inevitable to use a battery thermal management system (BTMS). Compared to the traditional methods, the phase change material (PCM) does not consume energy, so thermal management based on PCM is the best compromise between costs, integration, efficiency, and life cycle. To enhance the performance of PCMs, there are three methods available: 1) improve their thermal conductivity, 2) use other thermal management systems in parallel with them, and 3) enhance their energy storage capacity. The aim of this research is to introduce pressure as a tool to increase the energy storage capability in polyethylene-glycol-1000 (PEG1000) PCM to achieve a more efficient BTMS. The Box-Behnken design was performed by considering the input parameters, including the initial temperature of the cell (30–37 °C), pressure (100–500 kPa), and the discharge rate (1-7C). The effects of input variables are investigated on the maximum temperature, depth of discharge, and discharge energy during the discharge process of a single 18,650 cylindrical cell. The cell temperature of 63 °C was considered as a permissible maximum temperature limit. The results show when the discharge was at 7 C, the cell was able to discharge for almost twice as long when subjected to the pressure of 500 kPa in comparison to when it was under atmospheric pressure. Moreover, increasing the pressure from 100 to 500 kPa almost increased the depth of discharge by nearly 10 % and doubled the extracted energy.