Research progress and future prospects of battery thermal management system based on heat pipe technology

Abstract

The lithium-ion battery, a key technology for electric vehicles, is an electrochemical power source with complex ion flow and heat transfer processes. Temperature is one of the main parameters affecting the performance of these battery systems, as high temperatures may accelerate the degradation rate of a battery cell and shorten its lifespan. Low temperatures can also reduce the battery efficiency and affect its discharge capacity, and subsequently, its life cycle. In addition, uneven temperature distribution within a battery pack could exacerbate the inconsistency between cells and cause life cycle decay. A suitable working temperature window for the lithium-ion battery is usually between 25°C to 40°C, and the temperature difference among the cells should be maintained below 5°C to ensure the cells performance and durability. Therefore, battery thermal management (BTM) is required to keep the battery temperature within the desirable operating range and maintain temperature uniformity. This paper provides a review of two aspects: The significance of BTM and current BTM strategies, and the research status of heat pipe-based BTM systems. Firstly, the thermal characteristics of the lithium-ion power battery are introduced, and the significance of BTM are expounded. Then, the advantages of heat pipe technology are introduced, and the research status of BTM based on heat pipes is evaluated in detail. In this study, the heat transferred in a heat pipe-based thermal management system was divided into three processes: The heat generation process, which is determined by the operating condition; the heat transfer process of a heat pipe, which is related to its structural design and its arrangement in the system; and the heat dissipation strategy on the condensation section. With respect to heat generation, researchers have studied the effect of operating conditions on the heat generation characteristics of the system. Results show that the temperature is closely related to the dynamic operating conditions. Further research should be combined with the actual vehicle operating conditions to formulate effective real-time control strategies to achieve a high efficiency and low energy consumption BTM system. Researchers have evaluated various factors that affect heat transfer performance. This study concludes that both the internal structure of heat pipe and its arrangement in the battery pack should be considered in the design of the BTM system to achieve optimum heat transfer performance. Future studies should focus on the analysis and optimization of flat plate heat pipes, which have good application prospects in BTM systems. Concerning heat dissipation enhancement, air cooling, direct liquid cooling, and indirect liquid cooling are the most common strategies for heat pipe cooling. However, most designs aim to reduce the temperature rise and temperature difference, and the system parameters are seldom taken into consideration. Further investigation into the heat dissipation enhancement of heat pipes should focus on the multi-objective optimization of the system including, synthesizing the thermal and electrical characteristics, improving energy consumption, and making the system lightweight. In addition, the heat pipe is also a highly efficient heat transfer element for battery heating. Current research has verified its heating rate and heating efficiency. Notably, the heating strategies are now in the pilot testing stage and have not been used in battery pack productions. One of the key elements for future research may involve the heating characteristics of a BTM based on heat pipes in different operating environments. Another aspect could be researching the heating strategy in low temperature environments.