Prismatic Battery Research Articles

Effect of safety valve types on the gas venting behavior and thermal runaway hazard severity of large-format prismatic lithium iron phosphate batteries

The safety valve is an important component to ensure the safe operation of lithium-ion batteries (LIBs). However, the effect of safety valve type on the thermal runaway (TR) and gas venting behavior of LIBs, as well as the TR hazard severity of LIBs, are not known. In this paper, the TR and gas venting behavior of three 100 A h lithium iron phosphate (LFP) batteries with different safety valves are investigated under overheating. Compared to previous studies, the main contribution of this work is in studying and evaluating the effect of gas venting behavior and TR hazard severity of LFP batteries with three safety valve types. Two significant results are obtained: (I) the safety valve type dominates over gas venting pressure of battery during safety venting, the maximum gas venting pressure of LFP batteries with a round safety valve is 3320 Pa, which is one order of magnitude higher than other batteries with oval or cavity safety valve; (II) the LFP battery with oval safety valve has the lowest TR hazard as shown by the TR hazard assessment model based on gray-fuzzy analytic hierarchy process. This study reveals the effect of safety valve type on TR and gas venting, providing a clear direction for the safety valve design.

Cell teardown and characterization of an automotive prismatic LFP battery

A key challenge in lithium-ion battery research is the need for more transparency regarding the cell design and production processes of battery as well as vehicle manufacturers. This study comprehensively benchmarks a prismatic hardcase LFP cell that was dismounted from a state-of-the-art Tesla Model 3 (Standard Range). The process steps and manufacturing peculiarities were traced by disassembling the cell and analyzing the characteristics on the material level. A butterfly-design with two jelly rolls was found for the cell design in order to minimize the void volume (6.4%). Cross-sections and microscopy analyses from the cell cap revealed the application of multiple laser-welding processes that are needed to provide a high stability and tightness. The coatings of the approximately 22m long electrodes showed a high homogeneity with thickness fluctuations less than 2µm. Scanning electron microscopy images revealed a pure graphite anode and a bimodal particle distribution within the lithium iron phosphate cathode, whereby the edges of the cathode were covered in a 27µm thick aluminum oxide (Al2O3) insulation layer. Electrochemical analyses were performed showing the improved performance of the inherent electrolyte over a common LP572 electrolyte. A gravimetric energy density of 163Wh/kg and a volumetric energy density of 366Wh/l was determined based on a nominal cell capacity of 161.5Ah. Overall, the purpose of this work is to demonstrate which design decisions and manufacturing challenges are addressed in industrial cell production, so that the focus of academic research can align with the state-of-the-art.

Optimization of liquid cooling for prismatic battery with novel cold plate based on butterfly-shaped channel

For maintenance of the batteries working at appropriate temperature, an effective thermal management system is required to handle the heat production during the operating process. In this work, a novel butterfly-shaped channel structure is designed and integrated into the liquid cooling system for the 50 Ah ternary prismatic battery module. First, a comparison of the cooling performance between the butterfly-shaped design and other traditional designs was investigated regarding the maximum temperature, temperature difference, and pressure drop. The calculation results of the desirability function revealed the optimal overall performance of the butterfly-shaped channel. Secondly, the inlet width, outlet width, and the height were set to be 8, 12, and 2 mm respectively while the channel width was adjusted to be 9 mm between the positive and negative terminals upon optimizing structural parameters. Accordingly, the maximum temperature was reduced to 32.72 °C while pressure was dropped to 25.7 Pa as well, demonstrating a 29.1 % decrease compared to the previous configuration. Finally, the effect of the mass flow on the thermal performance of the battery module was carried out. As the coolant mass rate of flow increased, the maximum temperature and temperature difference of the battery module decreased accordingly while the descent rate gradually slowed. In addition, when the mass rate of flow was controlled at 5 g·s−1, the maximum temperature was 30.86 °C, with a 4.96 °C temperature difference where the pressure loss of each cold plate was 338.57 Pa.

An Electrothermal Model of an NMC Lithium-Ion Prismatic Battery Cell for Temperature Distribution Assessment

Charge time has become one of the primary issues restricting the development of electric vehicles. To counter this problem, an adapted thermal management system needs to be designed in order to reduce the internal thermal gradient, by predicting the surface and internal temperature responses of the battery. In this work, a pseudo 3D model is developed to simulate battery cell performance and its internal states under various operational scenarios such as temperature and convection conditions as well as the applied current during charge and discharge. An original mesh of the JR is proposed where heat exchanges in the three directions (radial, orthoradial and axial) are considered. The model represents one of the solutions that enable increasing the lifespan of batteries while decreasing charging time. It offers the opportunity to optimize operating parameters to extend battery life. In this paper, attention was paid not only to the core and non-core components, but also to the experiments required to parametrize the thermal and electrochemical models (heat generation). Unlike existing approaches documented in the literature, the model developed in this work achieves an impressive balance between computational efficiency and result accuracy, making it a groundbreaking contribution in the field of electric vehicle technology.

Active and passive safety enhancement for batteries from force perspective

Thermal runaway (TR) has become a critical issue for Li-ion battery applications in electric vehicles and energy storage stations. To address this issue, early warning and thermal runaway propagation (TRP) mitigation are significant for the active and passive safety of the battery system, respectively. This study proposes the expansion force as a reliable warning signal, which is proven to provide more interval (>500 s) for escape and rescue compared with voltage and temperature signals. Besides, the TR expansion force changing mechanism due to thermal expansion, gas generation/accumulation, and venting is investigated. Furthermore, the TRP expansion force and deformation changing mechanism is explained from the perspective of expansion, squeeze, and venting. The TRP debris deformation trend is verified through mechanical modeling. The maximum TR expansion force increment (ΔFmax)-capacity (Q) equalization and ΔFmax-cell index equations are proposed based on the TR/TRP tests of three types of prismatic batteries. Moreover, a TRP mitigation structure is proposed to amplify the TR expansion force, which is validated to effectively amplify the force, causing the mechanical destruction of the in-line module holder. A TRP mitigation test proves that the first TR cell capsizes the module holder to hinder the heat transfer between the front/back surfaces of the prismatic batteries when the TR expansion force exceeds the preload. Without enough heat transfer, the TR of the following battery cells cannot be triggered even under jet fire impact. This study guides the active and passive safety design for the prismatic battery system.

Optimization design of the forced air-cooled battery thermal management system with a stepped divergence plenum

In order to improve heat dissipation performance of battery pack with air-cooled structure, a novel stepped divergence plenum in Z-type air-cooled structure is proposed in a prismatic battery pack. Then the accuracy and effectiveness of computational fluid dynamics (CFD) model are verified by comparison with experimental results. Subsequently, the effects of the total height of all steps and the height of every step on the maximum temperature, temperature difference and temperature standard deviation of battery pack with air-cooled structure are explored, respectively. Finally, the stepped divergence plenum at different inlet airflow velocity is further optimized to achieve better cooling performance. Numerical results indicate that 1) For the larger total height of the steps, the stepped divergence plenum is suitable for Z-type air-cooled structure, and the stepped divergence plenum is better than the slanted one in the aspect of cooling efficiency while the latter is superior to the former for the smaller total height of the steps 2) Compared with the slanted divergence plenum, a stepped divergence plenum improves the heat dissipation performance of the battery for Z-type air-cooled structure. 3) The height of every step and inlet airflow velocity plays an important role in the cooling performance of the battery. The optimization results are h = 0.125 (i.e, Hopt = [1.39, 2.51, 2.51, 2.02, 2.02, 1.89, 1.76, 1.39, 1.51]) and 3 m/s, and the corresponding maximum temperature, temperature difference and temperature standard deviation of the battery pack are respectively reduced about 34.65 %, 77.51 % and 99.04 % in comparison with those for Z-type model. The optimization scheme proposed in this work provides a design guideline to improve the cooling performance of the air-cooled structure.

Comparative study of flow-channel layout schemes in liquid cooling plates of a prismatic battery module

Liquid cooling is an important method for battery thermal management (BTM) of electric vehicles (EVs), and improving its heat transfer capacity has always been a research focus. In this paper, the performances of the cooling plates with various channel shapes for a prismatic battery module at high discharge rate are numerically investigated. The factor j/f considering the flow resistance and the heat transfer capacity is introduced to evaluate the cooling plates. The mechanism of heat transfer enhancement by using different flow-channel layout schemes in the cooling plate is analyzed based on the distributions of pressure and velocity. The results show that flow recirculation occurs in the circular slots on the flow-guiding walls in the cooling plate. The recirculating flows damage the boundary layer, thereby the heat transfer is enhanced. In order to further study the factors affecting the performances of the cooling plates, evaluation is carried out for the cooling plates with circular slots of different diameter (Dslot) and depth (d2). The maximum improvement of the factor j/f is 41.79%. In addition, the maximum temperature of the battery is also lower. Therefore, the cooling plate with the circular slots is more suitable for the BTM system under fast discharging.

Performance analysis of liquid cooling battery thermal management system in different cooling cases

An efficient battery thermal management system can control the temperature of the battery module to improve overall performance. In this paper, different kinds of liquid cooling thermal management systems were designed for a battery module consisting of 12 prismatic LiFePO4 batteries. This paper used the computational fluid dynamics simulation as the main research tool and proposed a parameter to evaluate the performance of the cold plate in terms of both heat transfer and flow resistance, then the effect of cooling surface, number of inlets, and direction of coolant flow on the cooling effect were studied. It was found that the maximum temperature of the battery module could be controlled at 303.6 K and the maximum temperature difference between the batteries at 2.3 K when the cooling surface was Face A which was between the batteries, the number of coolant inlets was 3, and the coolant flow direction was arranged alternately. Finally, the study was conducted for different mass flow rates of a single inlet and different charging rates. It was found that the overall performance is optimal when the mass flow rate of a single inlet is 1.2 g/s and the designed thermal management system can meet the temperature requirement (the maximum temperature of the battery module is 313 K and the maximum temperature difference between the batteries is 5 K) of the battery module with charging rate below 3C.

Experimental study of thermal runaway process of 256Ah prismatic nickel-rich battery

Lithium-ion batteries (LIBs) are plagued by risks of combustion and explosion during thermal runaway (TR), which hinder their broader applications. Currently, there is limited research on thermal runaway experiments for batteries with a capacity exceeding 200 Ah. In this study, a non-commercial 256 Ah prismatic battery was utilized, featuring Li (Ni0.8Mn0.1Co0.1)O2 as the cathode material and silicon-doped graphite as the anode material. The investigation focused on the thermal runaway characteristics of the battery under 100% state of charge (SOC) conditions. Three repetitive thermal runaway experiments were conducted within a 1000L lithium battery constant volume test chamber (AEC) under a nitrogen environment. Temperatures at various points within the battery were recorded during the experiments, and high-speed cameras were employed to capture moments of thermal runaway. The research findings are as follows: 1) The ejection velocity of smoke at the instant of safety valve opening was measured at approximately 140 m/s, while the velocity of the ejected flame was approximately 55 m/s. 2) Within an extremely short time range after safety valve opening, the temperature at the safety valve nozzle reached a peak value of 701.8°C ± 42 C. 3) The average duration of ultra-high-speed ejections was measured at 5.0 ± 1.6 s, high-speed ejections lasted for 11.9 ± 2.7 s, and slow-speed ejections exhibited an average duration of 21.6 ± 3.7 s, resulting in a total ejection duration of 36.2 ± 4.7 s. This study provides valuable insights into the original state of the jetting process during thermal runaway in high-capacity LIBs and offers certain guidance for BTMS design.

Simulating the Electrochemical-Thermal Behavior of a Prismatic Lithium-Ion Battery on the Market under Various Discharge Cycles

In this paper, a computational fluid dynamics (CFD) model to predict the transient temperature distributions of a prismatic lithium-ion polymer battery (LiPo) cooled by natural convection at various discharge cycles is developed. The thermal behavior of a lithium-ion (Li-ion) battery cell is important for its safety, performance and degradation, and it requires both measurement and modeling. However, most existing thermal models for Li-ion battery cells only account for steady-state temperature fields, while the exercise of a Li-ion battery cell is usually transitory. The Newman’s pseudo-2D approach was used to perform an electrochemical CFD analysis. This approach treats the porous electrode as a collection of equal-sized, isotropic, homogeneous spherical particles. This simplifies the electrode microstructure and assumes a smooth and uniform lithium insertion/extraction in the electrode. The model has been validated through variable discharge rate experimental tests in a controlled chamber. Additionally, infrared images of the battery cell during discharging are taken and the experimental numerical gradient temperature was compared. We have validated the CFD simulations by comparing the temperature, state of charge and voltage curves with experimental data. The model predictions match the experimental data very well. The difficulty in CFD battery simulations with an electrochemical approach lies in the setting of many physical parameters that are difficult to find. In this work, the parameters’ characteristics of the simulated battery are assumed and validated; these can be useful for modeling batteries of the same type. Consequently, the model developed in this work can be applied to predict the temperature distribution of the LiPo prismatic battery and can be used by the battery designers and by the designers of all systems that include batteries.

Mechanical strain signal based early warning for failure of different prismatic lithium-ion batteries

Thermal runaway propagation (TRP) is the most challenging safety issue of lithium-ion battery systems. An early warning signal is promising for providing time to mitigate or prevent TRP and further disasters timely. This study investigates the strain characteristics of different format prismatic batteries during the TR/TRP processes, dividing the strain-changing trend into three stages according to the complex chemical composition interactions and TR features. Experimental results prove that the signal provides more than a 500s interval for a timely solution from the battery management system. Besides, the maximum strain increment (Δεmax)/capacity(Q)-Q equalization is quantitively analyzed. Moreover, Δεmax-Q and RI-Q equalizations are proposed to reveal the TR mechanical feature and guide the TR warning threshold definition of battery management systems (BMSs). Furthermore, the strain-changing trend and warning effect is also proved in TRP tests. TRP strain mechanism is unlocked from the mechanical deformation perspective. Battery deformation is opposite to the TRP direction, which guides accident analysis. This study proposes a cheap and reliable warning signal for an in-line configuration battery system, with only one strain gauge attached to the surface center of the first/last battery casing, which has more potential to guarantee the active safety of battery systems.

Numerical modeling of the behavior of a lithium battery after a collision

This study is carried out to verify numerically the deformation and Von Misses stresses of a lithium-Ion battery (Li6PF 43 ah, 3.7v) after impact against a solid sphere, using the specialized program in Dynamic Simulation. and Ls-Dyna Finite Elements. With the aim of advancing in the studies to validate the safety of batteries in electric cars this study creates a model of the analyzed prismatic battery.

A numerical investigation of hydrogen impingement-effusion array jet for a heat sink cooling using solid/porous fins: A thermo-hydrodynamic analysis

Increasing the aim of hydrogen use as fuel in vehicles motivates applying it to other critical requirements, such as cooling, owing to its thermal properties. Therefore, the effect of applying hydrogen impingement jets for cooling a hot surface of electrical devices, such as a prismatic battery, is investigated in this numerical study. The dependent variables are the volumetric flow rate, the jet distance from the target to the jet diameter, the coolant type, and the fins configuration, called in-line and staggered, and types, as solid or porous. The convective heat transfer coefficient, thermal resistance, pressure drop, and temperature and velocity distribution for the studied cases are considered. The simulation is conducted using the SST k-ω turbulence model, SIMPLE algorithm, and second-order method for discretization differential equations. Applying hydrogen as the coolant decreases the maximum temperature up to 2% and increases heat transfer by about 10%, while it mitigates the pressure drop by a factor of 1/12 if compared to air coolant. Further, inserting porous fins improves heat transfer by about 10% and 17%, respectively for air and hydrogen coolant in comparison with the case without fins. The fin decreases the temperature on the root and makes the recirculation zones.

Enhancing the performance of liquid-based battery thermal management system by porous substrate minichannel

Using lithium-ion batteries in electric vehicles is a suitable replacement for fossil fuels but it has some challenges such as temperature increasing that reduced the efficiency of the system and make the possibility of fires and explosions. Porous media have high surface-to-volume ratios and therefore have a very effective role in the improvement of convection heat transfer. In this study, the effects of the porous material in cold plate minichannels for a prismatic battery thermal management system have been investigated by numerical simulation. In general, increasing the inlet velocity in a fully porous minichannel improves the cooling performance more than in a conventional (non-porous) channel. For inlet velocity of 0.05 m/s with a parallel flow arrangement, using the fully porous channel maintains the maximum temperature of the battery module at 38.1 °C, while the temperature difference is 12.7 °C. In a parallel-flow arrangement, the hydrothermal performance factor for fully porous minichannels at the inlet velocities of 0.05 m/s and 0.075 m/s are 52 % and 193 % more than conventional channels, respectively. The use of counter-flow arrangement in conventional channels makes the temperature more uniform, but in fully porous minichannels, it greatly reduces the uniformity of temperature distribution compared to the parallel-flow arrangement. Therefore, the application of the fully porous channels with the parallel-flow arrangement is proposed as an effective way of enhancing the thermal management of liquid-based batteries.

Multiobjective Optimization of a Parallel Liquid Cooling Thermal Management System for Prismatic Batteries

Adhering to the thermal management requirements of prismatic battery modules, an improved lightweight parallel liquid cooling structure with slender tubes and a thin heat-conducting plate is proposed. The multiobjective optimization of the structure, operating parameters of the thermal management system, and thermal characteristics of a battery module are carried out. The effects of the equivalent diameter of the square tubes and the inner diameter of the circular tubes on the maximum temperature, maximum temperature difference of the batteries, and coolant pressure drop of liquid cooling battery thermal management system (BTMS) are investigated. The more significant factors, selected as the design variables, are the equivalent diameter of the square tubes, the inner diameter of the circular tube, and the coolant inlet velocity. Combining the computational fluid dynamics (CFD) method with multiobjective optimization, the different conditions of heat management parameters obtained by Latin hypercube sampling are numerically calculated, and the optimization of these parameters is carried out by the second-generation Elitist Nondominated Sorting Genetic Algorithm (NSGA-II). Compared with the thermal characteristics of the battery module before optimization, the maximum temperature of the module after optimization is reduced by 9.3%, the maximum temperature difference is reduced by 20.7%, and the coolant pressure drop from inlet to outlet is reduced by 49.1%.

Testing and impact modeling of lithium-ion prismatic battery under quasi-static and dynamic mechanical abuse

Understanding the failure behavior of lithium-ion batteries under mechanical abuse is essential for the safety design of electric vehicles (EV). Here, the failure behavior and mechanical properties of the lithium-ion prismatic batteries (LPB) under quasi-static and dynamic loads are investigated experimentally through universal test machine (2 mm/min) and drop tower (1 m/s and 5 m/s), respectively. The results show that load velocity has a significant effect on the failure behaviors and mechanical properties of LPB. The main failure behavior of LPB under cylindrical impactor in the X directions is the fracture of enclosure as well as the bulking of jellyrolls, while that in the Y direction is the wrinkle of enclosure as well as the delamination and fold of jellyrolls. When the battery under ball impactor in the Z direction, its main failure behavior is the fracture of jellyrolls. Furthermore, the homogenous models of LPB are developed to make the crash simulation of full EV feasible. Under the impact in the Y and Z directions, the homogenous model possesses higher prediction accuracy on mechanical properties than detailed model. More importantly, its efficiency is approximately 8.8 times higher than detailed model according to the solving time. Then, the damage tolerance of LPB is explored to indicate the short-circuit of battery. This investigation is anticipated to provide some fundamental data for EV safety design.

Thermal management of a prismatic lithium battery pack with organic phase change material

BackgroundThis article examines a T-shaped lithium-ion battery pack (BPC) consisting of six prismatic cells using the finite element method (FEM). An optimal model is introduced for batteries’ thermal management (THMT) by changing the position of the inlets and outlets. MethodsThe outlet is where the fully developed airflow leaves, and the walls use the no-slip boundary condition. The batteries are placed in an enclosure filled with phase change material (PCM) to create temperature uniformity on the batteries. The hydrodynamic and thermal modeling of airflow and the melting and freezing of PCM are performed in this study using the COMSOL program. Significant findingsThe results demonstrate that the batteries’ maximum temperature (TMX) changes by changing the location of the inlets. Changing the position of inlets also affects the melting and freezing of the PCM, and better temperature uniformity on the batteries may be achieved using some models. The M4 model, in which the inlet and outlet are on the left and right sides, and an outlet is in the center, is the most appropriate model for industrial applications.

A candidate strategy for low-temperature preheating of lithium-ion batteries based on supercooling salt hydrates

Preheating is necessary for lithium-ion batteries to avoid severe performance degradation and potential safety hazards at temperatures below 283.15 K. Supercooling salt hydrates as latent heat storage materials provide a promising candidate to preheat batteries in an extremely low-temperature environment. This paper selects Na2S2O3⋅5H2O (STP) and CH3COONa⋅3H2O (SAT) with deep supercooling properties and a prismatic LiFeO4 battery as the study objects. A parametric study is carried out to obtain an optimal design. The target preheating temperature of the battery is 293.15 K. After weighting the preheating time, effective utilization, specific energy, and specific power, the configuration that all the sides of the battery are covered with a salt hydrate thickness of 8.0 mm is considered to be the optimal design at 253.15 K. Heating rates are 0.236 K/s and 0.205 K/s for SAT and STP, respectively. However, when the ambient temperature increases to 273.15 K, the effective utilization of SAT and STP decreases by 30.46 % and 34.41 %, respectively. When the discharge rate increases from 1C to 5C, the state of charge (SOC) relative to the cut-off time of SAT and STP reduces from 85.45 % to 56.69 % and from 82.95 % to 57.46 %, respectively. This means a higher effective utilization is provided for a high discharge rate. Due to a higher melting point and higher fusion of heat, SAT shows a faster-preheating rate and higher effective utilization relative to STP, while the difference in average battery temperatures is slight.

Investigation on the thermal management performance of a non-contact flow boiling cooling system for prismatic batteries

It is a great challenge to control the temperature of high energy-density lithium-ion batteries within an appropriate working range during rapid charging and discharging with a battery thermal management system (BTMS). As a hot topic in current BTMS research, boiling cooling technology with high heat transfer efficiency is a reliable way to solve these thermal management problems. In this study, a novel thermal management system for prismatic batteries based on cooling by non-contact flow boiling is proposed, and various cold-plate structures are considered with different numbers and locations of coolant inlets and outlets inside the cold plate cavity, and with different numbers and arrangements of ribs and fins. A three-dimensional transient model was conducted to investigate the effect on the cooling performance of the boiling BTMS of several variables — notably inner-channel design schemes, the number of ribs or fins in the cold plate, coolant inlet temperatures, and inlet Reynolds numbers. The results indicate that among the six design schemes that were considered, the best comprehensive heat transfer performance is achieved with two pairs of inlets and outlets, a vertical fin arrangement, and fin height equal to 3/4 of the inner channel dimension. With an increase in the number of fins, the maximum temperature and maximum temperature difference of the structures that were considered decrease by no <0.8 °C and 0.2 °C, respectively. Also, the temperature uniformity of the battery pack can be improved by appropriately increasing the coolant inlet temperatures and reducing the inlet coolant flow rate. When the number of fins is 19, the inlet temperature is 29 °C, and the inlet Reynolds number is 893, the preferred BTMS is always able to maintain its maximum temperature below 35.67 °Cand the maximum temperature difference to below 4.47 °C, at 3C high discharge rate.

Development of a Detailed 3D Finite Element Model for a Lithium-Ion Battery Subject to Abuse Loading

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Lithium-ion batteries (LIBs) have been used as the main power source for Electric vehicles (EVs) in recent years. The mechanical behavior of LIBs subject to crush loading is crucial in assessing and improving the impact safety of battery systems and EVs. In this work, a detailed 3D finite element model for a commercial vehicle battery was built, in order to better understand battery failure behavior under various loading conditions. The model included the major components of a prismatic battery jellyroll, i.e., cathodes, anodes, and separators. The models for these components were validated against the corresponding material coupon tests (e.g., tension and compression). Then the components were integrated into the cell level model for simulation of jellyroll loading and damage behavior under three types of compressive indenter loading: (1) Flat-end punch, (2) Hemispherical punch and (3) Round-edge wedge. The comparisons showed reasonable agreement between modeling and experiments. With the validated numerical model, parametric studies were further performed to analyze the effect of separator anisotropy, to highlight its important role in the overall structural response of LIBs.&lt;/div&gt;&lt;/div&gt;