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• Design for hybrid battery pack with high energy density and high safety. • Thermal Management Optimization Layout Design for Hybrid Battery Packs. • The P2D model is used to study electrochemical properties of single battery. • Multiphysics coupling analysis of electro-thermal behavior. • The SOC estimation method for hybrid battery pack. As traditional battery systems, lithium iron phosphate (LFP) batteries have better safety but lower energy density and nickel manganese cobalt oxide (NMC) batteries have higher energy density but poorer safety. In this work, we design a hybrid battery pack that has both higher energy density and higher battery safety. By analyzing the thermal properties of battery packs with aligned, staggered, and staggered arrangements, it can be concluded that the aligned arrangement has superior cooling efficiency and space-efficient optimization compared to the other arrangements, which have shorter flow paths to minimize air energy loss and reduce pressure drop. Notably, we design the optimal arrangement to avoid placing the NMC cells near the air outlet, to avoid NMC concentration, and to decentralize the LFP cells to reduce the relatively high maximum temperature and temperature difference. This hybrid battery pack is expected to give a boost to lithium-ion battery applications. [ABSTRACT FROM AUTHOR]

The era of electric mobility has started, and petrol/diesel vehicles are being replaced by electric vehicles (EVs). The phase change material (PCM) is a trending field of research in its application of energy storage and thermal management. PCM-based thermal management method is found to be quite simple and effective for battery packs. However, its commercialization is difficult due to its low thermal conductivity and extra weight addition to the battery pack. Hence, the present research focuses on the battery performance with PCM. The experimental setup for a 48V, 25Ah battery pack is developed, and its performance is explored with and without PCM. The numerical model for same sized battery pack is developed, and validated with experimental results. The major objective of the present research is to find the optimal gap between two battery cells so that a sufficient amount of PCM can be filled inside the battery pack. Initially, inline and staggered cell arrangements are examined, and no significant difference in thermal performance is found. Further, cell spacing of 5 mm, 3 mm, and 1 mm are examined, and maximum temperature and temperature difference are compared along with the weight and volume of the battery pack. For a single charging process, 1 mm cell spacing is found sufficient, considering the weight of the battery pack and thermal performance. However, with 1 mm cell spacing, temperature increases significantly after each charging and discharging. At the same time, 3 mm and 5 mm are found as feasible solutions considering single and double charging-discharging cycles, respectively. 3 mm cell spacing is better option when weight is a critical issue, while 5 mm cell spacing is better when thermal performance is a critical issue. The current study offers guidance in the advancement of battery packs, particularly in cases where space constraints are a concern. • The research focuses on utilization of optimal amount of PCM. • The battery charging experiments are carried out on 48V, 25Ah battery pack. • PCM OM42 reduced battery temperature by 18 %. • The inline and staggered arrangements are found equally effective. • 3 mm cell spacing is found sufficient with limited weight increment. [ABSTRACT FROM AUTHOR]

A powerful thermal management scheme is the key to realizing the extremely fast charging of battery electric vehicles. In this scheme, a water-cooled plate is set at the bottom of the battery modules, which has a remarkable heat dissipation ability but increases the temperature difference between the top and bottom of the battery. This temperature difference problem is more obvious during the high-rate charge/discharge process; in particular, in the area of battery tabs, which are usually located far from the cooling plate, heat accumulates, risking thermal runaway. To address this problem, a thermal management method based on an ultrathin vapour chamber (UTVC) is proposed in this paper to improve temperature uniformity and reduce the highest temperature of batteries. According to the number of applied UTVCs, a unilateral UTVC (U-UTVC) and a bilateral UTVC (B-UTVC) cooling approach were presented, the effectiveness of which was verified by a set of thermal performance experiments. The test data show that the temperature differences in the batteries under the U-UTVC and B-UTVC schemes are 39.77% and 73.54% lower than those under the traditional method at a 25 °C ambient temperature and a 1.39C charge rate, respectively. The temperature difference on the battery surface with the B-UTVC scheme is approximately 3 °C at 25 °C and 40 °C ambient temperature. • An ultra-thin vapour chamber-based power battery thermal management is proposed to improve the temperature uniformity. • The methods have limited effect on battery volumetric specific energy, and the volumetric specific energy of battery is only reduced by 1.2% which is far less than reported investigations. • Temperature difference and maximum temperature of battery module of the presented scheme are reduced by 15.49% and 73.54%, respectively. [ABSTRACT FROM AUTHOR]

• A computationally efficient model for large-scale battery packs is developed. • Parameters are devised to evaluate the structural designs for the battery pack. • Pros and cons of the alternative structural designs are analyzed. • Interspersed battery pack design is suggested to enhance the thermal performance. In this paper, a comparative study for structural design of battery thermal management system is presented for electric vehicles. A thermal model for the pouch battery pack with liquid cooling is developed for thermal analysis of various pack designs. Typical battery pack with fin-cooling structure is set as a reference design, and thermal behavior of the battery pack is examined in the aspect of cooling performance and temperature uniformity. Numerical results indicate that poor heat conductivity from the bottom of the cell stack to the cooling plate is one of the major barriers to the efficient heat dissipation and asymmetric design of fin-cell arrangement have negative effect on the temperature uniformity of the battery pack. To improve the performance of the thermal management system, various structural designs are suggested and evaluated based on plural criteria. A new structural design for the large-scale battery pack is suggested to enhance the cooling performance and temperature uniformity of the battery pack minimizing the increase in system volume, weight, and pressure drop. [ABSTRACT FROM AUTHOR]

• The quantity of heat generation that induce TR in lithium-ion batteries is lower than in other overheating strategies. • The trigger time of thermal runaway decreases with the increasing current density. • The series tab connection will accelerate the thermal runaway of the adjacent battery. • The parallel tab connection will induce thermal runaway propagation to all parallel-connected batteries. Thermal runaway (TR) of lithium-ion batteries is the main safety obstacle to the further development of electric vehicles (EVs) and electric energy storage systems (EESSs). Understanding the mechanism of TR propagation is one of the primary ways to improve the thermal safety of the lithium-ion battery. In this paper, an electro-thermal model coupled with the lumped thermal runaway model is applied to investigate the TR behaviors induced by tab overheating and the TR propagation in a battery module with different tab connection methods. The electro-thermal model is used to calculate the heat generation at tabs and the cell body during the normal charge/discharge process, and the lumped thermal runaway model is applied to calculate the TR behavior and TR propagation in the battery module. The results exhibit that the TR behavior and TR propagation are influenced by different aspects (C-rates, insulator, and tab connection modes) in the battery module. The largest quantity of heat generation is at 3C-rate, about 0.98 kJ, because of the heat accumulation in the battery. Besides, the quantity of heat generation that induce TR in lithium-ion batteries in this paper is lower than that from the reference, which means that tab overheating is more dangerous than other heating strategies for triggering the thermal runaway of batteries. The trigger time of TR decreases with the increasing C-rate and the tab connection modes mitigate the TR propagation in the battery module at a low C-rate because of the increasing heat dissipation rate, while the TR propagation is accelerated in the battery module at a high C-rate. At low C-rate conditions, the parallel tab connection exhibits a more significant effect on mitigating the TR behavior, and the effect of mitigation decreases with the increasing C-rate. At high C-rate conditions, the series tab connection accelerates the TR propagation to the adjacent battery, while the parallel tab connection speeds up the TR propagation of all the connected batteries. This work is important for understanding the TR propagation mechanism and improving the thermal safety of pouch-type lithium-ion batteries in EVs. [ABSTRACT FROM AUTHOR]

Battery thermal barriers are reviewed with regards to extreme fast charging. Present-day thermal management systems for battery electric vehicles are inadequate in limiting the maximum temperature rise of the battery during extreme fast charging. If the battery thermal management system is not designed correctly, the temperature of the cells could reach abuse temperatures and potentially send the cells into thermal runaway. Furthermore, the cell and battery interconnect design needs to be improved to meet the lifetime expectations of the consumer. Each of these aspects is explored and addressed as well as outlining where the heat is generated in a cell, the efficiencies of power and energy cells, and what type of battery thermal management solutions are available in today's market. Thermal management is not a limiting condition with regard to extreme fast charging, but many factors need to be addressed especially for future high specific energy density cells to meet U.S. Department of Energy cost and volume goals. [ABSTRACT FROM AUTHOR]

• A comprehensive model based on battery aging effect is developed for MHP-BTMS. • A framework combing deep learning and multi-objective genetic algorithm. • BTMS shows poor cooling capacity due to SEI formation inside the aged battery. • Two optimization strategies are proposed for multi-objective optimization. • The trade-off between battery temperature and performance is achieved. Battery thermal management and electrochemical performance are critical for efficient and safe operation of battery pack. In this research, a multi-physics model considering the battery aging effect is developed for micro heat pipe battery thermal management system (MHP-BTMS). A novel multi-variables global optimization framework combining multi-physics modeling, deep learning and multi-objective optimization algorithms is established for optimizing the structural parameters of MHP-BTMS to improve battery thermal management and electrochemical performance simultaneously. It is found that MHP-BTMS fails to control the temperature of aged battery pack due to the higher heat generation caused by solid electrolyte interphase formation. After 1000 cycles, the maximum temperature and maximum temperature difference were increased by 3.32 K, 2.49 K, 2.04 K and 1.78 K, 1.46 K, 1.26 K, respectively. It is also found that the battery electrochemical performance during the cycling is highly related to battery thermal behaviors. MHP-BTMS with 0.004/s inlet velocity achieved the best performance in preventing SEI formation and battery aging effect, which was lower by 7.01 nm (SEI) and 1.65% (aging), 2.31 nm and 0.58% as compared to 0.002 and 0.003 m/s cases. Besides, MHP-BTMS with optimized inlet velocity, MHP arrangement and cold plate can improve cooling performance and electrochemical performance. Multi-variables global optimization can provide the optimal structure parameters of MHP-BTMS under the different combinations of weighted coefficients and optimization strategies to achieve the trade-off between battery thermal issues and electrochemical performance. In addition, it is demonstrated that the weighted coefficients and optimization strategies in this novel framework can be changed according to the actual needs in engineering applications. [ABSTRACT FROM AUTHOR]

Phase change material as the core of latent heat energy storage technology, suffers from the "solid-liquid phase change" problem. In this study, "solid-solid" composite phase change materials (CPCMs) have been developed using olefin block copolymers (OBC) and decanoic acid. With ≥30 wt% OBC, the physical shapes of the developed CPCMs nearly remain unchanged after 100 times of thermal cycling, without significant changes in the phase change properties. The addition of graphite powder leads to a significant enhancement in thermal conductivity of up to 18 times, which leads to excellent control of battery maximum temperature and temperature uniformity. In the battery thermal management test, the developed CPCM achieves a maximum of 3 °C and 10.5 °C reductions in maximum temperature difference and peak temperature, respectively. The CPCMs also prolong the thermal preservation time by 3 times. In the pack level test, the use of CPCM plates leads to a maximum temperature reduction of 15 °C on the commercial battery pack under 55 °C extreme working temperature. • CPCMs retain their shape and properties after 100 times of thermal cycling. • The thermal conductivity of the CPCMs were improved by up to 8 times. • 10.5 °C of peak temperature reduction was achieved with the CPCM. • The developed CPCMs prolonged the thermal preservation time by ∼3 times. [ABSTRACT FROM AUTHOR]

• Composite PCM is designed by in-situ constructing phase changeable framework in PEG. • The novel composite PCM possesses dual phase change temperature regions (PCTRs). • The two PCTRs are precisely tailored at 31.7–42.1 ℃ and 42.1–51.2 ℃, respectively. • The lower PCTR ensures suitable working temperature for battery at normal operation. • The higher PCTR prevents thermal hazards of battery under high ambient temperature. The phase change material (PCM)-based battery thermal management technology still remains a contradiction of guaranteeing a suitable operating temperature (20–40 ℃) of the batteries under regular working conditions, while avoiding the malfunction of the PCM under high ambient temperature (>40 ℃). Therefore, a novel composite PCM (CPCM) possessing dual phase change temperature regions (PCTRs) is designed herein by in-situ constructing a phase-changeable polymer (PCP) framework in the polyethylene glycol (PEG)/expanded graphite (EG) slurry. As prepared, the lower PCTR at 31.7–42.1 ℃ from the PCP framework provides a latent heat of 35.0 J g−1, while the higher PCTR at 42.1–51.2 ℃ from the PEG offers a latent heat of 68.3 J g−1. Additionally, the nanoscaled PCP framework strongly adsorbs the PEG, preventing the leakage phenomenon (mass loss < 1%), and the uniformly dispersed EG endows the CPCM with a high thermal conductivity of 1.98 W m−1 K−1. In consequence, under the normal ambient temperature of 25 ℃, the lower PCTR effectively keeps the battery module operating within the suitable temperature range of 25.9–34.9 ℃ and with a low temperature difference (ΔT) of 2.4 ℃ at the discharge rate of 1C. For comparison, the battery module adopting classical CPCM with a single PCTR at 40.9–55.1 ℃ demonstrates a much higher temperature range and maximum ΔT at 28.0–40.9 ℃ and 4.8 ℃, respectively. Under the high ambient temperature of 40 ℃, the higher PCTR starts to work like the single PCTR of traditional CPCMs, and controls the T max and ΔT of the module below 49.2 and 2.2 ℃ at the discharge rate of 1C, respectively, preventing thermal hazards. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) are extremely sensitive to their temperature and therefore, require a battery thermal management system (BTMS). BTMS is commonly employed to prevent thermal runaway of the LIB pack by controlling their operating temperature. This review paper provides various cooling strategies, including active and passive approaches, utilized in BTMSs. Air-cooled, liquid-based, and PCM-cooled techniques are first reviewed. This article presents an assessment of the application of nanofluids and nano-phase change materials (nano-PCMs) in BTMSs to improve heat dissipation from the LIB pack. This work emphasizes the utilization of these materials to intensify their thermal conductivity and suggests further investigations on their application in BTMSs. • Lithium-ion batteries are extremely sensitive to their temperature. • BTMS is employed to prevent battery thermal runaway by controlling its temperature. • Providing various cooling strategies for BTMS: active and passive approaches. • Presenting an assessment of the application of nanofluids and nano-PCMs) in BTMSs. [ABSTRACT FROM AUTHOR]

• A numerical analysis is performed for direct liquid cooling of lithium-ion batteries using different dielectric fluids. • Study and compared the thermal performance of three different dielectric fluids including mineral oil, deionised water, and one engineered fluid. • The temperature rise is limited to below 3 °C for 1c- discharge by using deionised water at all mass flow rates, where oil-based fluids are delivering better performance only at higher mass flow rates of 0.05 kg/s. • The mineral oil and engineered fluids deliver almost an equal thermal performance, however, the latter consumed 76.43% less power at a mass flow rate of 0.05 kg/s. Lithium-ion battery (LIB) cells are responsible for powering most electric vehicles. LIB is still a superior battery available in the market because of its high energy density, specific power, and long cycle life. However, LIB comes with the challenges like thermal management as it is highly sensitive to temperature. Amongst different cooling methods, direct liquid cooling, also known as immersion cooling, can deliver a high cooling rate mainly because of its complete contact with the heat source. The single-phase liquid immersion with dielectric fluids (DELC) offers safety and cooling performance with lower parasitic power consumption and space requirements. This research involves studying and comparing different DELC's for the direct cooling of lithium-ion batteries. A numerical analysis of the 4S1P arrangement of LIB cells with direct cooling is conducted with three different DELC's including deionised water, mineral oil, and an engineered fluid. The transient behaviour of the battery module for various mass flow rates of DELC and at 1C,2C,3C-discharge rates are examined. All DELC maintains an excellent temperature homogeneity within the individual cells and LIB cells. The DELC with higher specific heat and thermal conductivity is suitable for cooling the LIB cells during high discharge conditions. However, all the dielectric fluids studied here effectively limit the temperature rise below 5 °C at 2-C discharging operation when the mass flow rate is increased to 0.05 kg/s. This improvement in thermal performance comes at the expense of extra power consumption. Even though both DELC-2 and DELC -3 delivered almost similar temperature rise values of 6.1, 5.2 °C, respectively during 2C discharging operation, the latter consumed 76.43% less power at a mass flow rate of 0.05 kg/s. For this reason, engineered fluids with lower viscosity values can be preferred over mineral oils. The deionised water is more effective for limiting the temperature rise below 2.2 °C for 3C discharging with the least parasitic power consumption of 0.52 mW at a mass flow rate of 0.05 kg/s. A variable cyclic load matching HWFET-driving cycle has been applied to the battery pack with all three DELCs, and all three fluids limited temperature rise below 1 °C. [ABSTRACT FROM AUTHOR]

• TPC-et skeleton is introduced to realize the room-temperature-flexibility of FCPCM. • TPC-FCPCM shows great applicability to various kinds of cells and battery modules. • TPC-FCPCM shows outstanding cooling performance compared to classical rigid CPCM. • TPC-FCPCM is favorable to alleviating the compressive stress in actual application. Flexible composite phase change materials (CPCMs) can minimize the thermal contact resistance in battery thermal management. However, these "thermally-induced" flexible CPCMs only present well-flexibility above the phase change temperature, which is unfavorable to the flexible assembly of the cells and battery modules with variable specifications. Herein, a kind of flexible CPCM with well-retained flexibility in a wide temperature range is prepared by carefully selecting a copolyester thermoplastic elastomer with polyether soft segment (TPC-et) to replace the conventional olefin block copolymer (OBC) skeleton. The internal rotation resistance of the ether bond in TPC-et is much lower than that of the C–C bond in OBC, thus giving rise to a better flexibility in room and low temperatures from 20 to −5 ℃. Combining the room-temperature-flexibility with the high thermal conductivity of 1.64 W m−1 K−1, enough latent heat of 102 J g−1 and suitable phase change region of 40–50 ℃, the obtained TPC-et based flexible CPCM shows outstanding applicability and cooling performance to various cells and battery modules through facile installations. The maximum temperature of the cylindrical, prismatic and pouch battery modules with TPC-et based CPCM is 51.5, 42.1 and 50.0 ℃, respectively, 4.0, 3.9 and 5.4 ℃ lower than the modules using rigid CPCM, respectively. [ABSTRACT FROM AUTHOR]