Investigation on Thermal Management of 18650 Lithium-Ion Batteries Using Nano-Enhanced Paraffin Wax: A Combined Numerical and Experimental Study

Abstract

Lithium-ion (Li-ion) battery cells are used as the major power source for every electric vehicle (EV) industry because of their properties like density and voltage. Their optimal operating temperature ranges between 15 and 45 °C. The charge mobility and chemical reaction in Li-ion batteries cause excessive heat generation leading to thermal runaway and ultimately their capacity diminishes over the life cycle. The main idea of the present study is to control the thermal runaway of the Li-ion batteries using nano-enhanced phase change materials (Ne-PCM). Hence, there is a need for the development of a battery thermal management system (BTMS) using either air, liquid, or phase change material (PCM). An 18650 battery cell (normal capacity: 2700 mAh; rated capacity: 2600 mAh; normal voltage: 3.7 V; rated power: 9.62 Wh; anode material: lithiated graphite (LiC₆); cathode material: lithium-nickel-manganese-cobalt-oxide (LiNiMnCoO₂); electrolyte material: lithium hexafluorophosphate (LiPF₆)) along with a complete battery pack (4 cells) is considered in the present study. Transient numerical simulations (using both MATLAB R2022a and ANSYS 2020 R2) are carried out with and without using the paraffin wax. Three different nanoparticles (copper oxide (CuO), aluminum oxide (Al₂O₃), and titanium oxide (TiO₂)) at various concentrations (0%, 3%, 7%, and 10%) are added to the paraffin wax to enhance their thermal conductivity value. However, the experiments are conducted only with and without using the paraffin wax, but not with the nano-enhanced paraffin wax. Hence, this (Ne-PCM case) acts only as a support to the numerical study. For both the numerical and experimental analysis, the temperature and voltage characteristics of the battery packs are measured for a specific time to understand their charging and discharging characteristics. It is found that paraffin wax is a better candidate for maintaining the battery temperature in an optimal range when the battery generates excess heat. Paraffin wax gives a 41% increase in battery life compared to air cooling. The hybrid cooling (combination of paraffin wax and air) technique reduces the battery temperature rise by 4 °C compared to only paraffin wax and by 8 °C compared to only air cooling.