• Energy Research

Abstract This paper presents the concept of a hybrid thermal management system (TMS), including air cooling and heat pipe for electric vehicles (EVs). Mathematical and thermal models are described to predict the thermal behavior of a battery module consisting of 24 cylindrical cells. Details of various thermal management techniques, especially natural air cooling and forced-air cooling TMS are discussed and compared. Moreover, several optimizations comprising the effect of cell spacing, air velocity, different ambient temperatures, and adding a heat pipe with copper sheets (HPCS) are proposed. The mathematical models are solved by COMSOL Multiphysics®, the commercial computational fluid dynamics (CFD) software. The simulation results are validated against experimental data indicating that the proposed cooling method is robust to optimize the TMS with HPCS, which provides guidelines for further design optimization for similar systems. Results indicate that the maximum module temperature for the cooling strategy using forced-air cooling, heat pipe, and HPCS reaches 42.4 °C, 37.5 °C, and 37.1 °C which can reduce the module temperature compared with natural air cooling by up to 34.5%, 42.1%, and 42.7% respectively. Furthermore, there is 39.2%, 66.5%, and 73.4% improvement in the temperature uniformity of the battery module for forced-air cooling, heat pipe, and HPCS respectively.

Abstract Thermal management of lithium-ion (Li-ion) batteries in Electrical Vehicles (EVs) is important due to extreme heat generation during fast charging/discharging. In the current study, a sandwiched configuration of the heat pipes cooling system (SHCS) is suggested for the high current discharging of lithium-titanate (LTO) battery cell. The temperature of the LTO cell is experimentally evaluated in the 8C discharging rate by different cooling strategies. Results indicate that the maximum cell temperature in natural convection reaches 56.8 °C. In addition, maximum cell temperature embedded with SCHS for the cooling strategy using natural convection, forced convection for SHCS, and forced convection for cell and SHCS reach 49 °C, 38.8 °C, and 37.8 °C which can reduce the cell temperature by up to 13.7%, 31.6%, and 33.4% respectively. A computational fluid dynamic (CFD) model using COMSOL Multiphysics® is developed and comprehensively validated with experimental results. This model is then employed to investigate the thermal performance of the SHCS under different transient boundary conditions.

Abstract Nowadays, the most used thermal management system (TMS) is air-cooling, but due to weight and volume limitations, more promising cooling methods such as PCMs with high latent heat seems to be attractive. However, their disadvantages, like low thermal conductivity, should be managed to have an efficient TMS. Hence, aluminum-foil (PCM-Al) is added to the PCM in this work to enhance the PCM conductivity, and accurate experiments are accomplished to verify the simulation results. In this paper, a phase change material (PCM) with aluminum mesh grid foil is proposed to enhance cooling and temperature uniformity of a high-power dual-cell lithium capacitor (LiC) module. The optimization objective is keeping the temperature of the system below the safe range while maximizing the uniformity and minimizing the cost of the system. The effect of forced-convection (zero-PCM strategy), pure PCM, PCM-Al, PCM thickness, and influence of dual PCMs by different phase change temperatures on the thermal behavior of the module are studied numerically. The results indicate that the PCM-Al technique shows better thermal performance while reducing the maximum module temperature by 20%, and 13% in comparison with forced-convection and pure PCM, respectively. Moreover, 7 mm thickness is quite optimal, considering the cost, weight, and volume.

The solid–electrolyte interphase (SEI), the passivation layer formed on anode particles during the initial cycles, affects the performance of lithium-ion batteries (LIBs) in terms of capacity, power output, and cycle life. SEI features are dependent on the electrolyte content, as this complex layer originates from electrolyte decomposition products. Despite a variety of studies devoted to understanding SEI formation, the complexity of this process has caused uncertainty in its chemistry. In order to clarify the role of the substituted functional groups of the SEI-forming compounds in their efficiency and the features of the resulting interphase, the performance of six different carbonyl-based molecules has been investigated by computational modeling and electrochemical experiments with a comparative approach. The performance of the electrolytes and stability of the generated SEI are evaluated in both half-cell and full-cell configurations. Added to the room-temperature studies, the cyclability of the NMC/graphite cells is assessed at elevated temperatures as an intensified aging condition. The results show that structural adjustments within the SEI-forming molecule can ameliorate the cyclability of the electrolyte, leading to a higher capacity retention of the LIB cell, where cinnamoyl chloride is introduced as a novel and more sustainable SEI forming agent with the potential of improving the LIB capacity retention.

Abstract The parasitic power consumption of the battery thermal management systems is a crucial factor that affects the specific energy of the battery pack. In this paper, a comparative analysis is conducted between air type and liquid type thermal management systems for a high-energy lithium-ion battery module. The parasitic power consumption and cooling performance of both thermal management systems are studied using computational fluid dynamics (CFD) simulations. The 48 V module investigated in this study is comprised of 12 prismatic-shape NMC batteries. An experimental test bench is built up to test the module without any cooling system under the natural convection at room temperature, and the numerical model of the module is validated with experimental results. Two different cooling systems for the module are then designed and investigated including a U-type parallel air cooling and a new indirect liquid cooling with a U-shape cooling plate. The influence of coolant flow rate and coolant temperature on the thermal behavior of the module is investigated for a 2C discharge process. It was found that for a certain amount of power consumption, the liquid type BTMS results in a lower module temperature and better temperature uniformity. As an example, for the power consumption of around 0.5 W, the average temperature of the hottest battery cell in the liquid-cooled module is around 3 °C lower than the air-cooled module. The results of this research represent a further step towards the development of energy-efficient battery thermal management systems.

Nowadays, the use of electric vehicles (EVs) equipped with lithium-ion (Li-ion) batteries, has been growing every day. Li-ion batteries' performance, effectiveness, and safety importantly depend on thermal management systems (TMSs). In this paper, a novel and advanced hybrid TMS for cooling the battery module, using phase change material (PCM) and liquid cooling, has been experimentally studied. Passive PCM heat buffer plate and liquid cooling plates are connected from down and lateral sides, respectively. Cooling with natural convection could not preserve the module temperature in the desired operational temperature at fast charging. The average module temperature for the charging and discharging process reaches 41.4 °C and 43 °C respectively. The results display the module temperature equipped with a PCM heat buffer plate at the end of the charging and discharging process reaches 35.8 °C and 36.2 °C which experience a 13.3% and 15.8% temperature reduction, respectively. Using the hybrid cooling system, the module temperature at the end of the charging and discharging process reaches 31.2 °C and 31.8 °C which experience a 24.6% and 26% temperature reduction compared with natural convection. Moreover, using the hybrid cooling system the temperature uniformity has been improved by 56% and 34.8% for the charging and discharging process, respectively.

Thermal management is the most vital element of electric vehicles (EV) to control the maximum temperature of module/pack for safety reasons. This paper presents a novel passive thermal management system (TMS) composed of a heat sink (HS) and phase change materials (PCM) for lithium-ion capacitor (LiC) technology under the premise that the cell is cycled with a continuous 150 A fast charge/discharge current rate. The experiments are validated against numerical analysis through a computational fluid dynamics (CFD) model. For this purpose, a comprehensive electro-thermal model based on an equivalent circuit model (ECM) is designed. The designed electro-thermal model combines the ECM model with the thermal model since the performance of the LiC cell highly depends on the temperature. Then, the robustness of the model is evaluated using a precise second-order ECM. The extracted parameters of the electro-thermal model are verified by the experimental results in which the voltage and temperature errors are less than ±5% and ±4%, respectively. Finally, the thermal performance of the HS-assisted PCM TMS is studied under the fast charge/discharge current rate. The 3D CFD results exhibit that the temperature of the LiC when using the PCM-HS as the cooling system was reduced by 38.3% (34.1 °C) compared to the natural convection case study (55.3 °C).

AbstractLithium‐ion technologies have become the most attractive and selected choice for battery electric vehicles. However, the understanding of battery aging is still a complex and nonlinear experience which is critical to the modeling methodologies. In this work, a comprehensive lifetime modeling twin framework following semi‐empirical methodology has been developed to predict the crucial degradation outputs accurately in terms of capacity fade and resistance increase. The constructed model considers all the relevant aging influential factors for commercial nickel manganese cobalt (NMC) Li‐ion cells based on long‐term laboratory‐level investigation and combines both the cycle life and the calendar life aspects. To demonstrate robustness, the model is validated with a real‐life worldwide harmonized light‐duty test cycle (WLTC). The model can precisely predict the capacity fade and the internal resistance growth with a root‐mean‐squared error (RMSE) of 1.31% and 0.56%, respectively. The developed model can be used as an advanced online tool forecasting the lifetime based on dynamic profiles.