Three-Dimensional Thermal Simulations of 18650 Lithium-Ion Batteries Cooled by Different Schemes under High Rate Discharging and External Shorting Conditions

Yang Li,Liang Hao,Xuanyu Liu,Zhifu Zhou,Yongchen Song,Yubai Li,Jian Zhao,Yulong Li,Minli Bai

doi:10.3390/en14216986

Abstract

In this work, three-dimensional thermal simulations of single 18650 lithium-ion battery cell and 75 V lithium-ion battery pack composed of 21 18650 battery cells are performed based on a multi-scale multi-domain (MSMD) battery modeling approach. Different cooling approaches’ effects on 18650 lithium-ion battery and battery pack thermal management under fast discharging and external shorting conditions are investigated and compared. It is found that for the natural convection, forced air cooling, and/or mini-channel liquid cooling approaches, the temperature of battery cell easily exceeds 40 °C under 3C rate discharging condition. While under external shorting condition, the temperature of cell rises sharply and reaches the 80 °C in a short period of time, which can trigger thermal runaway and may even lead to catastrophic battery fire. On the other hand, when the cooling method is single-phase direct cooling with FC-72 as coolant or two-phase immersed cooling by HFE-7000, the cell temperature is effectively limited to a tolerable level under both high C rate discharging and external shorting conditions. In addition, two-phase immersed cooling scheme is found to lead to better temperature uniformity according to the 75 V battery pack simulations.

Highlights

Lithium-ion batteries are regarded as one of the most promising power sources in the worldwide trend of vehicle electrification
Compared with natural convection, forced air cooling and mini-channel liquid cooling, when the battery adopts single-phase direct cooling by FC-72 or two-phase immersed cooling by HFE-7000, the temperature cooling schemes such as forced air cooling or mini-channel liquid cooling, the temper fluctuation of the cell is small, and the maximum temperature of the battery does no ceed 24 °C during the entire discharge process
A multi-scale multi-domain (MSMD) model was used to perform three-dimensional thermal simulations for a lithium-ion battery and lithium-ion battery pack cooled by different methods

Summary

Introduction

Lithium-ion batteries are regarded as one of the most promising power sources in the worldwide trend of vehicle electrification. While, cooling is an important aspect of the lithium-ion battery thermal management due to two major reasons. Under normal operating conditions, the lithium-ion battery generates heat. The heat needs to be dissipated to keep the battery temperature lower than a certain level (about 40 ◦ C) to prevent capacity loss of the lithium-ion battery cell [4]. If cell temperature reaches 80–100 ◦ C, there is risk that the thermal runaway process will be triggered and catastrophic battery fire may even happen [4]. The thermal runaway can be caused due to various reasons [6], while internal shorting [7] and external shorting [8] are possible triggers for the thermal runaway. Ceasing the thermal runaway under internal shorting condition via cooling approach is hard [9]

Methods

Results

Conclusion