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• Study the battery thermal runaway induced by non-metallic nail penetration. • Explore the effects of nail diameter and SOC on nail-penetration induced thermal runaway. • A high-SOC cell penetrated by a metal nail reaches a higher peak temperature due to larger Joule heating. • A low-SOC cell penetrated by a non-metallic nail reaches a higher peak temperature due to weaker cooling. The nail penetration test is widely adopted to evaluate the safety of lithium-ion batteries by triggering the internal short circuit. This work compares the phenomena, temperature rise rate, surface temperature, and mass loss under the penetration test for different nail materials, nail diameters, and cell SOCs. The thermal runaway behaviour and characteristics of these test cells are studied in depth. The results show that the maximum temperature and temperature rise rate of the cell increase with the increase of SOC. The maximum temperature and the temperature rise rate of the cell decrease with the increase of the nail diameter. Under high SOC conditions (greater than 75 % SOC), the more conductive nail increases the release of Joule heat generation inside the battery, which leads to a more intense thermal runaway behaviour. At low SOC (less than 50 % SOC), the more conductive nail promote cooling, which reduces the intensity of thermal runaway. However, non-conductive nails show the exact opposite effect. This dual effect of different nail materials was elucidated by a simplified heat transfer analysis. By calculating the heat production and heat dissipation during the thermal runaway process, the effects of the nail material and the cell SOCs on the thermal runaway behaviour of the battery can be summarized. This work deepens the understanding of the safety of batteries under external shocks and provides new scientific insights into battery design and its safety testing. [ABSTRACT FROM AUTHOR]

• The dynamics of the thermal runaway front in large-scale Li-ion batteries are deduced theoretically. • The velocity of the front yields a 1/2 power relationship between the thermal conductivity and reaction rate. • Freezing thermal runaway front is possible in theory and validated by experiments. • Heat dissipation enlarged by heat transfer time delay is critical for the freeze. Large-scale lithium-ion batteries are favored in electric vehicles and energy storage stations; for instance, BYD blade batteries and CATL Kirin batteries are popular. A tiny defect will trigger thermal runaway from a local point towards the other parts of the battery, and the boundary between the failure region and the intact region is called the "thermal runaway front," of which the dynamics are still unclear. Herein, this paper deduces two formulas for the moving speed (v TR) of the thermal runaway front by applying the principles of energy conservation (Formula I) and flame front (Formula II); formulas for the thermal runaway front velocity (v TR) are derived. The velocity v TR conforms to the 1/2 power of the heat conductivity and reaction rate in both formulas. Data regression for the experimental data demonstrated that the overall estimation error was 10 % using Formula I and 25 % using Formula II. As the zero velocity value indicates the termination of thermal runaway propagation, further derivations reveal that forced cooling can suppress thermal runaway as long as the heat dissipation power is higher than the heat generation power. Sufficient heat dissipation time is achieved by the time delay of heat transfer in the long run of thermal runaway propagation. The formula for the dynamics of thermal runaway propagation universally applies to various large-scale lithium-ion batteries, assisting the safe design of high-energy batteries and providing new insights into suppressing battery thermal runaway by the heat transfer delay effect. [ABSTRACT FROM AUTHOR]

• Stimulus strategy with auxiliary heat load is valid for start-up promotion and heat transfer enhancement of PHP. • High interference temperature, weak auxiliary heat load and long period are optimal for stimulus strategy. • Phase-change mechanism and hysteresis of working medium in PHP is the main reason for validity of stimuls. Stimulus strategy is proposed to enhance the heat dissipation performance of Pulsating Heat Pipe (PHP) at low heat load for local hot spot regression in Battery Thermal Management (BTM). An auxiliary heat load is applied to stimulate the start-up of PHP. The performances of PHP with and without stimulus are compared and the properties of PHP after stimulus are discussed. It is concluded that the application of auxiliary heat load is able to stimulate the start-up of PHP in experiments. The strategy is mainly based on the phase-change mechanism as well as the hysteresis of working medium. Thermal resistance and the evaporator temperature are significantly reduced, if PHP starts operation after stimulus. Long period of stimulus and strong auxiliary heat load are favored for the reduction of thermal resistance and the shortening of period for start-up. The thermal resistance may be reduced by 29.1 ∼ 69.6 % and the temperature may be regressed by around 8 °C. However, PHP may suffer from temperature uplift and overshot to the maximum evaporator temperature. Therefore, high interference temperature coupled with weak auxiliary heat load and long period of stimulus are suggested as the optimal strategy. The verified strategy offers a new method for local hot spot regression and a possible way to mitigate the risk of thermal runaway, since the heat dissipation is enhanced at the initial stage of damage or destruction. [ABSTRACT FROM AUTHOR]

Highlights • A plug-in OHP with flat-plate evaporator and tube condenser was developed. • Excellent heat transfer performance of plug-in OHP was achieved using ethanol-water mixtures. • EV battery temperature could be well-controlled below 46.5 °C based on the plug-in OHP. Abstract The development of highly-efficient, cost-effective, and reliable cooling schemes of electric vehicle (EV) battery is still a big challenge for massive commercialization of EVs. In this work, a proof-of-concept plug-in oscillating heat pipe (OHP) with flat-plate evaporator and tube condenser has been developed and experimentally tested for the potential applications in EV battery thermal management. Pure water, ethanol, and binary-fluid mixtures of them at different mixing ratios (MRs) ranging from 1:1 to 4:1 were used at volumetric filling ratios (FRs) of 30%, 40% and 50%. Owing to the zeotropic properties in phase transition and the complex molecular interactions between the ethanol component and water component, the OHP charged with ethanol-water mixtures exhibited better start-up and heat transfer performance. The average battery pack temperature could be controlled below 46.5 °C under the power input of 56 W. Besides, well-satisfied temperature uniformity was achieved on the battery module and the maximum temperature differences were mostly in the range of 1–2 °C. The complementary features for ethanol-water mixture thermo-physical properties and temperature/concentration gradients induced mass transport account for the OHP performance improvement. The novel plug-in OHP associated with desirable heat transfer performance provides a promising candidate for battery thermal management system. [ABSTRACT FROM AUTHOR]

• The predicted results agree with the experimental results an average error of 1.28%. • Coolant-improved flow direction and thermophysical properties significantly affect the decreasing maximum operating temperature and temperature gradient across a cell. • The highest temperatures of the battery module are 30.06 °C, 30.00 °C, 29.91 °C, 29.89 °C, and 29.49 °C for models II, IV, III, I, and V. • The maximum temperature gradient across a cell, models I, II, and III give the highest value [0.42 °C], and consequently, models [0.40 °C] and model v [0.15 °C]. The operating battery temperature significantly affects electric vehicle performance, reliability, and safety. Therefore, batteries need to keep within the operating temperature design. The 3D Eulerian model is applied to determine battery thermal behavior with five different flow directions of coolant throughout the battery pack jacket. The computational domain consists of sixty cylindrical Li-ion cells inserted into the cooling module socket with constant power input conditions. The predicted results are consistent with the experimental results, with an average error of 1.28%. Coolant-improved flow direction and thermophysical properties significantly affect the decreasing maximum operating temperature and temperature gradient across a cell. The highest temperatures of the battery module are 30.06 °C, 30.00 °C, 29.91 °C, 29.89 °C, and 29.49 °C for models II, IV, III, I, and V, respectively. In addition, for the maximum temperature gradient across a cell, models I, II, and III yield the highest value [0.42 °C], followed by models IV [0.40 °C] and model V [0.15 °C], respectively. The proposed battery nanofluid cooling pack can therefore optimize the thermal management system of the EV pack. [ABSTRACT FROM AUTHOR]

• Thermal performance of refrigerant-based battery thermal management system for a real HEV battery pack is analyzed. • Effect of battery discharging C-rate, refrigerant mass flow rate, inlet temperature, vapor quality, and heating power on thermal performance of battery pack is studied. • Thermal performance of battery pack at real driving cycle operational conditions for refrigerant cooling is discussed. • Heat flow distribution on the battery pack at different discharging C-rates is analyzed. The thermal performance of refrigerant-based battery thermal management system (BTMS) for a real HEV battery pack in both the cooling and heating conditions is numerically and experimentally investigated in this paper. The heat generation model of battery cells and the numerical methodology for predicting the cooling performance of refrigerant-based cooling system are validated by experiments and the predicted results are consistent with experimental data. The effects of discharging C-rate, mass flow rate, initial temperature and vapor quality of refrigerant on thermal performance of battery pack are analyzed in detail. The thermal performance of refrigerant-based BTMS at a real driving cycle is also examined. The results indicate that the discharging C-rate has a significant impact on thermal performance of battery pack due to the distinctive heat transfer behaviors of battery pack at different discharging C-rates. Increasing mass flow rate of refrigerant is contributed to descend the maximum temperature and improve temperature uniformity of battery pack. Decreasing initial temperature of refrigerant is beneficial to reducing the maximum temperature of battery pack but is disadvantageous to temperature uniformity. The effect of vapor quality on thermal performance of battery pack is limited. The cooling performance of refrigerant satisfies the requirement of BTMS at the real driving cycle. The optimum heating power of the battery pack at heating condition ranges from 400 W to 460 W. [ABSTRACT FROM AUTHOR]

• Diverging channel design cooling plate with oblique fins is newly proposed. • Thermal unbalance of the battery module is improved using the proposed design. • Cell-to-cell temperature difference in the pack cooling is decreased by 19.07%. • The pumping power to satisfy the temperature conditions is decreased by 67.8%. In this study, the thermal and hydraulic performances of a battery thermal management system are investigated in terms of the design of the cooling plate. A diverging channel with oblique fins (DCOF) cooling plate is newly proposed to overcome the limitations of the conventional straight channel cooling plate. The diverging design is applied to control the coolant velocity and heat transfer area, with oblique fins inserted to enhance the heat transfer efficiency. A simulation model of the battery and cooling system is developed and experimentally validated. When the DCOF design is applied to the battery module, the temperature uniformity is improved in terms of the temperature difference and standard deviation. As the investigation is extended from the module to the battery pack, the temperature difference and temperature standard deviation in the battery module are improved by 19.07% and 27.14%, respectively. Considering the power consumption of the cooling system, as the thermal performance of the DCOF design and baseline design is maintained, the power consumption of the coolant pump of the DCOF design is significantly reduced by 67.8%. [ABSTRACT FROM AUTHOR]

• A manifold immersion cooling scheme for LIB thermal management is developed. • Influence of structural parameters are numerically studied for cooling optimization. • Manifold system can adapt its cooling ability for lateral surfaces of batteries. • This scheme achieves high cooling performance with extremely low pressure drop. Thermal management is very important because lithium-ion batteries generate a lot of heat under high rate charging and discharging. Inspired by the manifold microchannel (MMC) structure for chip cooling, this paper proposes a new manifold immersion (MI) cooling structure used for battery thermal management. The optimization analysis is performed in numerical simulation models. The local convective heat transfer coefficients of the lateral and baffle surfaces are analyzed separately. The results show that unlike the MMC for chip cooling, MI cooling structure's demands high heat transfer in the lateral surface of batteries but not the bottom or baffle surface. Subsequently, the influence of the design parameters on the cooling capacity is analyzed. The results show that the manifold channel length L ch,m and the battery spacing channel width W ch greatly influence the MI cooling performance. Stable wall jet flows are beneficial for MI cooling. It can be formed when L ch,m or W ch is large enough. MI cooling structure requires smaller vortex regions leading to better thermal load and temperature uniformities. The optimized MI cooling structure achieves the maximum temperature of 35.06 °C for a lithium ion battery pack at 5 C discharging, with the bulk temperature non-uniformity θ bulk of 6.66 °C, and the surface temperature non-uniformity θ sur of 3.52 °C. [ABSTRACT FROM AUTHOR]

• The evap. and cond. HTCs of 9 AMFHPs with 3 fluids at FR100% were tested. • Higher q e causes the rise of evap. HTCs and the fall of cond. HT of most samples. • Higher v air results in the fall of evap. HTCs as well as cond. HT of most samples. • Cooper correlation predicts the evap. HTCs of AMFHPs at high FR excellently. • Rohsenow correlation predicts cond. HTCs of R134a at FR100% well. An experimental investigation was conducted to evaluate the evaporation as well as condensation heat transfer of air-cooled multi-port flat heat pipes (AMFHPs), designed for extreme working conditions of power battery thermal management in electric vehicles. The experimentally obtained evaporation as well as condensation heat transfer coefficients (HTCs) under various working conditions were compared and analyzed. It was found that, both the orders of the intensity of heat transfer mode in the liquid pool and the condensation Nu c were R134a > ammonia > acetone. The orders of the evaporation HTCs referring to ammonia and R134a AMFHPs with different filling ratios (FRs) were 50 > 30 > 100 > 70 and 30 > 50 > 70 > 100%, while those of Nu c were 50 > 30 > 70 > 100 and 30–50–70 > 100%, respectively. In most cases, evaporation HTC increased with the rise of heating power as well as the decrease of cooling air velocity, while the condensation Nu c decreased with the increasing in the heating power as well as the air velocity slightly. The measured evaporation HTCs were compared with some predictive correlations of pool boiling and pool boiling-thin film evaporation expressions for the evaporator section at different FRs, and the condensation HTCs were also evaluated by several available filmwise condensation models. Results showed that Cooper correlation for pool boiling revealed quite a good agreement with measured results for the AMFHPs of 100% R134a, 70% ammonia and 100% ammonia, and Rohsenow correlation predicted the condensation HTCs of R134a AMFHPs with FR<100% accurately. However, for ammonia, the prediction of the evaporation HTCs in the case of FR < 70% was difficult, and Nusselt theory significantly overestimated the condensation HTCs of all the ammonia samples. [ABSTRACT FROM AUTHOR]

l The critical thermal issues of lithium-ion batteries are introduced. l The design principles for batteries thermal management are presented. l The latest advances on battery thermal management systems are summarized. l Emerging technologies for next-generation power batteries are discussed. Replacing conventional gasoline-powered cars with electric vehicles (EVs) can reduce not only pollution emissions but also the dependence on fossil fuels. As the most widely used power source to propel EVs, lithium-ion batteries are highly sensitive to the operating temperatures, rendering battery thermal management indispensable to ensure their high performance, long cycle life and safe operation. In this review, we summarize the recent advances in thermal management for lithium-ion batteries. The critical thermal issues caused by high temperature, low temperature and temperature non-uniformity are firstly discussed. The design principles and the existing thermal management systems are then presented and elaborated extensively. Emerging technologies such as thermoelectric devices and internal heating methods for future battery thermal management are analyzed. We highlight that the combination of passive and active cooling/heating methods is promising to meet the stringent thermal requirements, particularly under dynamic conditions with drastic power fluctuations. Finally, the remaining challenges and perspectives of thermal management systems with high efficiency and durability are provided. This review offers comprehensive guidance on the design of advanced thermal management system for next-generation power batteries. [ABSTRACT FROM AUTHOR]

• Phase change material (PCM) based thermal battery is developed. • Additive manufacturing enabled grid heat exchanger design for thermal energy storage. • Such thermal batteries offer rapid energy charging-discharging for waste heat recovery. • The grid structure enables a more uniform temperature stabilization during melting. • These experimental results advocate large-scale PCM storage systems. [Display omitted] The low thermal conductivity of organic phase change materials (PCMs) hinders their usage for energy storage purposes. We demonstrate a compact PCM-based thermal battery that employs three-dimensional (3D) printed metal surfaces for a robust thermal energy storage and recovery. The thermal battery could be utilized to store excess heat from various sources. The concept includes organic paraffin and fatty acid PCMs embedded within aluminum silicon alloy grid heat exchangers (GHE) produced via additive manufacturing. The heat exchangers consist of two parts: (i) a planar part with embedded water channels and (ii) a surface extrusion grid outside the planar part embedded in the PCM storage system. Three different grid designs are investigated and compared with a simple planar heat exchanger (PHE) without grid extension. The charging and discharging processes of the thermal battery were analyzed experimentally. The laboratory scale experiments reveal that the 3D printed grid surfaces of GHE significantly reduce the charging and discharging time from more than 240 min to less than 20 min. In contrast to PHE, the GHE may increase thermal power by a factor of ∼ 20 from 35 W to 670 W. Furthermore, the grid structure positively restrains the natural convection flow of the PCM melt, increasing conduction in the highly conductive grid structure and resulting in high charging-discharging power of the thermal battery. The swift charging and discharging with high power and energy density make the compact grid thermal battery a promising solution for thermal energy management. [ABSTRACT FROM AUTHOR]

• Flow boiling of R1233zd(E) in a parallel channel heat sink was studied. • Transition of heat transfer pattern was verified with flow boiling visualization. • Local heat transfer data were compared with present correlations. • Simple modification was conducted to improve the prediction accuracy. Aiming for the application of refrigerant two-phase cooling on battery thermal management, this study presented an experimental investigation on the flow boiling characteristics of R1233zd(E) in a parallel mini-channel heat sink, which consisted of 21 channels with the length of 140 mm and the cross section of 1.5 × 1.5 mm2. Under the saturation pressure of 125 kPa, the boiling curve of R1233zd(E) and the heat transfer coefficient were analyzed under different heat fluxes (5-100 kW/m2), mass fluxes (150-600 kg/m2 s) and inlet subcoolings (2.5-8 K). In addition, the flow pattern was captured using high-speed camera. The results showed that the onset of nucleate boiling was delayed with the increase of refrigerant mass flux and inlet subcooling, while the transition of heat transfer was verified by flow pattern visualization. The measured wall superheat was compared with present correlations, showing that the predicted value was always smaller than the experimental results. Flow boiling on local points showed that the nucleate boiling was triggered later at the channel located at the center axis of the heat sink, meanwhile the approach of critical heat flux was more obvious at channel outlet. Due to the graduate transition of flow boiling mechanism, refrigerant mass flux had limited influence on the local heat transfer coefficient when the heat flux was lower than 30 kW/m2, while enhancement on heat transfer could be observed with larger mass flux when the heat flux exceeded 30 kW/m2. The local experimental data of heat transfer coefficient were compared with 6 correlations from the literatures. It was found that the best prediction was presented by Liu and Winterton model with a MAE of 23.4%, while Kim and Mudawar model showed best agreement under different mass fluxes. A simple modification was conducted on Kim and Mudawar model, and the calibrated model presented a better prediction accuracy with the MAE of 17.6% and 83.2% of total data within the error of ±30%. [ABSTRACT FROM AUTHOR]

• Pulsating heat pipe with TiO 2 nanofluids for EV power battery thermal management was proposed. • Thermal performance of pulsating heat pipe with TiO 2 nanofluids for EV power battery under various thermal management strategies was investigated. • Series of thermal management tests were carried out on power battery under low temperatures. • Thermal management system had excellent heating performance and highly improved the low temperature usability performance of power battery. For effective solutions to performance problems, such as discharge capacity attenuation of the pure electric vehicle (EVs) power battery under low temperatures, the heating module of the pulsating heat pipe (TiO 2 CLPHP) for the power battery was constructed with TiO 2 nanofluid as working medium. Moreover, heating performance experiments under different heating strategies were carried out through consideration of the higher efficient bidirectional thermal transfer and thermal conductivity characteristics of the pulsating heat pipe, along with thermal management technology. The results demonstrated that the optimal heat transfer performance of TiO 2 CLPHP could be achieved with working medium concentration of 2% and heat pipe filling ratio of 50%. In addition, TiO 2 CLPHP was utilized for the preheating and heat preservation of power batteries, which could highly reduce the fluctuation of voltage during discharge, as well as improve the low-temperature discharge capacity of power batteries, followed by the effective surface temperature uniformity improvement of the battery (maximum temperature difference on power battery surface did not exceed 2.6°C). Furthermore, when TiO 2 CLPHP was utilized for the power battery heating under continuous heat preservation, the discharge capacity of the power battery reached 58.69Ah, while the capacity enhancement ratio reached up to 56.6%. Therefore, on the basis of the current research, through comprehensive consideration of preheating, heat preservation (preheating time, discharge voltage and discharge capacity) and energy consumption, it proved that the preheating coupled continuous heat preservation was an ideal heating strategy. Through this strategy, rapid heating along with discharge voltage and discharge capacity increase to the maximum extent, the performance of the EVs power battery under low-temperatures was improved. [ABSTRACT FROM AUTHOR]

• 3D-printed polymer-based battery thermal management system is proposed • Coolant flow architecture reduces the effect of polymer low thermal conductivity • Low coolant temperature raise leads to lower BTMS energy consumption The thermal performance of a novel battery thermal management system produced by additive manufacturing is investigated through simulations. The performance of 3D-printed polymer-based battery thermal management systems is investigated for heat-managing high power density Li-ion batteries for electric vehicles and stationary applications. The manufacturing of the battery packs through 3D-printing allows for greater complexity and novelty in the design of the coolant flow domains, in order to achieve a high heat transfer coefficient by the coolant. Having a high heat transfer coefficient at the coolant side allows the use of lower conductive materials in the body of the battery pack. The proposed system takes advantage of 3D-printing technology to embedded heat fins in the cooling channel. The simulations consider various discharging rates from 2C to a high of 3C to take the battery from a 100% to 20% state of charge in the discharging process. For the charging rates 2C and 3C, the maximum battery temperature within the pack reached 22.8°C and 24.5°C, respectively. However, the maximum temperature difference across a six-battery pack reached no more than 1.5°C and 4.5°C, respectively. A maximum temperature difference achieved by the proposed system shows the ability of the 3D-printed polymer-based system to achieve the required performance and demonstrates the potential of such systems that are equipped with the advantage of additive manufacturing. [ABSTRACT FROM AUTHOR]