1 Introduction
1.1 Energy and environmental demand drive
The global energy crisis and environmental pollution have prompted a shift towards safer, cleaner, and more efficient renewable energy sources, while transportation relies on fossil fuels, leading to excessive energy consumption and greenhouse gas emissions, thus requiring cleaner and more sustainable modes of transportation. Lithium ion battery driven electric vehicles are a promising solution for reducing dependence on fossil fuels and lowering greenhouse gas emissions.
The key role of battery thermal management: The operating temperature and internal heat generation of lithium-ion batteries have a significant impact on their performance, lifespan, and safety. Battery thermal management systems (BTMS) are crucial for protecting batteries from the negative effects of temperature rise and internal heat generation. The internal heat generated by batteries during charge and discharge cycles can lead to uneven temperature distribution, affecting battery life and efficiency. Hot spots often form near the electrodes.
1.2 Importance of BTMS
Maintaining battery performance and lifespan: BTMS is crucial for maintaining the optimal performance and longevity of lithium-ion battery packs (composed of multiple batteries in different configurations). Battery efficiency is highly dependent on temperature, and effective thermal management can solve the problem of temperature imbalance and improve battery performance in electric and hybrid vehicles.
1.3 Recent progress and analysis of BTMS
Improvement of air cooling technology: The air cooling method is constantly evolving, and various improvements such as honeycomb structure and multi inlet/outlet system are used to enhance performance, improve cooling efficiency, and temperature uniformity.
Advantages of liquid cooling systems: Liquid cooling systems (especially advanced cold plate and cooling channel designs) have excellent thermal management capabilities, and research on biomimetic spiral fins and liquid cooling plates has demonstrated significant enhancements in heat dissipation and temperature control.
PCM cooling characteristics: PCM is used in BTMS to provide passive thermal management, effectively absorbing heat during phase change. The hybrid PCM system (combined with air cooling or liquid cooling) improves thermal performance and energy efficiency.
Progress in thermoelectric cooling: Recent advances in thermoelectric cooling (TEC) have focused on integrating with other cooling methods to achieve precise temperature control and improve efficiency, enabling the battery temperature to be maintained within the optimal range under high heat loads.
1.4 Research Motivation
Innovative achievements emerge: In 2023-2024, researchers will propose more innovative BTMS ideas, and simulation software and methods will rapidly develop.
Comprehensive Innovation Analysis: This study focuses on innovation during this period, not only categorizing traditional cooling methods, but also emphasizing hybrid systems. By analyzing the role of novel design improvements (such as biomimetic structures, advanced materials, optimized geometric configurations) in improving performance and comparing technical and economic aspects, insights are provided for future research and development, promoting the development of lithium-ion batteries in electric vehicles and renewable energy storage systems, highlighting the important value of this research for battery technology progress.
2 Recent progress in BTMS research
2.1 Overview of Research Methods
Numerous studies have extensively explored various forms of battery thermal management systems (BTMS) through experiments and numerical analysis. Scientists conduct experiments at multiple levels, including batteries, modules, and battery packs, to study the temperature operation of batteries under different conditions. Many researchers also use computational fluid dynamics (CFD) for mathematical modeling. Experimental research is crucial for determining variable relationships and understanding the impact of parameters, which helps to effectively control the thermal performance of lithium-ion batteries in different categories.
2.2. Air cooled BTMS
Characteristics and limitations of air cooling method: Air cooling is a natural cooling method for BTMS, which is divided into natural convection and forced convection. It has the advantages of simplicity, low cost, no leakage concerns, and easy maintenance. However, its responsiveness to battery pack cooling requirements in high temperature environments is limited, especially natural air cooling.
Improvement measures and effects
Air duct improvement: Scientists have extensively studied air cooling methods that change airflow patterns, such as the X-type double inlet double outlet symmetrical air cooling BTMS, which significantly reduces the maximum temperature, temperature difference, and power consumption of battery packs compared to symmetrical air cooling systems; The honeycomb cylindrical battery pack is equipped with an air distribution plate and a biomimetic heat sink, which reduces the maximum temperature and temperature difference inside the battery pack; A multi inlet/outlet cooling framework based on thermal fluid coupling topology optimization design improves cooling efficiency and temperature uniformity, suitable for electric and hybrid vehicles.
Improvement of battery arrangement: Non vertical Z-type air-cooled BTMS reduces the maximum temperature and temperature difference of the battery, improves cooling performance and temperature uniformity; The staggered arrangement of BTMS optimized by physical simulation and evolutionary algorithm has improved the thermal management of lithium-ion battery packs.
Adding fin structure: Experimental and computational analysis was conducted on lithium-ion battery air-cooled BTMS using radial fins, and it was found that radial fins can significantly improve cooling efficiency; The direct current cooling BTMS with flow guide plate and lipid organic liquid coolant achieves lower average surface temperature and temperature difference, providing an innovative solution for efficient battery thermal management.
2.3 Liquid cooled BTMS
Classification and characteristics of liquid cooling systems: Liquid cooling systems are divided into liquid indirect cooling (LIDC-BTMS) and liquid direct cooling (LDC-BTMS, i.e. immersion cooling system). LIDC-BTMS utilizes liquid cooled plates to absorb and dissipate the heat generated by battery charging and discharging, with high heat transfer efficiency, but is limited by the thermal resistance of the cooling plate in contact with the battery; LDC-BTMS enables direct interaction between the coolant and the battery, reducing thermal resistance, effectively maintaining the ideal temperature of the battery, extending battery life, and reducing thermal runaway. However, the design needs to accurately address the issues of coolant containment and system sealing.
Optimization design and results
Cold plate optimization: Optimizing the cold plate is crucial for improving the thermal efficiency of liquid cooling systems, such as introducing a hybrid BTMS with integrated phase change materials and spider mesh liquid cooling channels, which can maintain the temperature of battery modules below 40 ° C at high discharge rates; diamond channel cold plates improve the efficiency of liquid cooled BTMS.
Cooling channel improvement: Changing the shape of the cooling channel can enhance heat dissipation, ensure uniform temperature, reduce energy consumption, and optimize system performance. The liquid cooling design of cylindrical lithium-ion batteries has found that the mini channel cylinder (MCC) has good cooling performance but large temperature changes and complex manufacturing, while the channel cooling radiator (CCHS) has a more uniform temperature distribution; The BTMS, which integrates biomimetic spiral fins and embedded integrated cold plates, has optimized its structural design through numerical experiments, improving cooling and preheating efficiency; The parallel sandwich cooling structure reduces the average temperature, maximum temperature, and temperature difference of the battery pack compared to the series cooling system.