Cylindrical Lithium-ion Battery Cells Research Articles

Experimental measurement and modeling of the internal pressure in cylindrical lithium-ion battery cells under abuse conditions

The internal pressure evolution of cylindrical lithium-ion battery cells under abuse tests is evaluated in this work. The pressure evolution is recorded through a cavity at the center of the inner structure of the cylindrical cell. Understanding pressure buildup due to exothermic reactions aids in designing safety features, such as improved venting mechanisms. The pressure activation for the safety mechanism depends on both the venting cap design and the different abuse test conditions. This study focuses on two important parameters: the state of charge (SOC) and the overheating ramp. The SOC significantly influences the venting pressure activation at the overheating abuse tests. The 18650 cell exhibits a similar venting behavior as the 21700 cell, with pressure safety mechanisms activating sooner for the 18650 cell. The geometric structure of the battery and safety mechanisms significantly influence vent-activation thresholds. After the Current Interruptor Device (CID) breakdown, pressure rises exponentially until venting occurs, due to gas generation from the decomposition of internal components and electrolyte vaporization. With the experimental data for the overheating abuse test, a model that predicts the evolution of the pressure has been developed. For the overcharging abuse test, the pressure evolution has been measured with different current rates (C-rates) to simulate overcharge with standard charging current and fast charging current. However, the internal pressure inside the cell activates the current interrupt device, which avoids overcharging the cell, thus preventing the thermal runaway (TR) from occurring.

Influence of pin fins and channel geometry on the hydrothermal performance of hexagonal mini-channel heat sink for cooling cylindrical batteries

This study numerically and experimentally examined the effects of pin fin configuration and channel geometry on the performance of a hexagonal mini-channel heat sink (HMCHS) to cool cylindrical lithium-ion battery cells. Various configurations of HMCHS with circular pin fins are studied, including circular fins centrally positioned within flat channels, circular fins positioned within grooved channels, circular fins situated within hybrid channels transitioning between wavy and straight channels and circular fins placed within hybrid channels that incorporate secondary flow channels between the primary flow channels. This numerical study utilized the finite volume method to investigate the laminar water flow at Reynolds numbers below 800. Findings showed that the HMCHS exhibited superior thermal performance compared with the conventional cylindrical mini-channel heat sink design. Moreover, the incorporation of pin fins into the HMCHS design was more effective in enhancing the Nusselt number than simply increasing the Reynolds number across various configurations. Meanwhile, the hybrid channel design with secondary channels, combined with the addition of pin fins, achieved the optimal overall performance of the HMCHS, resulting in the highest performance index of 1.88.

Parametric study of battery module cooling: Configuration optimization using response curve method

Recently, cylindrical lithium-ion battery cells have been widely used in electric vehicles due to efficient automated production and cheap kilowatt-hour capacity. For optimal operation of a cell, the internal temperature of the cell should be maintained within the range of 15–35 °C by employing suitable cooling mechanism. This study comprehensively compares multiple air-cooling configurations specifically designed for lithium-ion battery three-series and three-parallel (3S3P) modules using. The methodology involves an experimental phase to measure the parameters of Bernardi's equation, essential for calculating heat generation with consideration of both Joule's heat and entropic heat. Subsequently, a numerical simulation using Ansys Fluent examines battery heat generation within the 3S3P modules, employing diverse air-cooling configurations. Each configuration undergoes simulation with the aid of design of experiments and parametric analysis, allowing the observation of cooling behavior across various input parameters. To ensure reliability of simulation, the cooling of the unit cell module is simulated under similar conditions. The comparison between these simulated results and experimental values is conducted to validate the accuracy of the overall analysis methodology. The heat measurements indicated a unit cell heat output of 0.9028 W at an average rate of 0.85C. Among the investigated air-cooling configurations, the SIDO (Single Input Double Output) arrangement stood out as the most effective in maintaining a consistently lower average cell temperature, as determined through the application of the response curve method. This study emphasizes the importance of air-cooling design for improving the performance and safety of lithium-ion battery modules used in electric vehicles.

Degradation behavior of 21700 cylindrical lithium-ion battery cells during overdischarge cycling at low temperatures

Lithium-ion battery (LIB) cells are prone to overdischarge or overcharge when connected in series or parallel as a module or pack for large-format applications, such as electric vehicles (EVs) because of variations in battery capacities and difficulty in maintaining similar state-of-charge (SOC) of every single battery. However, the thermo-electrochemical behavior of LIBs during overdischarge has not been investigated at low temperatures. This study unveils the thermo-electrochemical behavior of overdischarged 21700 cylindrical LIB cells at −20 °C and 25 °C. Also, a thermo-electrochemical model was built to explain the heat generation within the cells and correlate them with the observed electrochemical characteristics. It was found that contrary to the severe cell degradation observed in the overdischarged cell compared to the standard cell at 25 °C, both cells show similar degradation behavior under low temperature cycling conditions. Thus, at low temperatures, overdischarge does not adversely affect cell degradation as observed at room temperature. This was attributed to the significant increase in the internal temperature, which results in improved electrochemical characteristics of the cell.

Thermal performance assessment for an array of cylindrical Lithium-Ion battery cells using an Air-Cooling system

Modern society depends on energy storage systems like Lithium-ion (Li-ion) batteries. Li-ion battery cells are delicate to changes in temperature. Extreme environmental conditions affect their life cycle and performance. Therefore, effective cell temperature management is a must for secure and dependable battery operation. Additionally, the high production costs of electric cars must be countered by the adaptability of the battery pack design for modern electric vehicles. As the chemical reactions generate more heat and raise the battery's temperature, it may cause the battery to explode and cause fires in the workplace. To address this issue, the present work attempts to numerically study a novel design of an efficient air-cooling system for improving the performance of lithium-ion batteries by reducing the operational temperatures under a different coolant flow rate. The main output of the presented study is the analysis of a novel design of an efficient air-cooling system for lithium-ion batteries. The study aims to reduce the operational temperatures of the batteries under different coolant flow rates to improve their performance and service life. The numerical simulations are carried out using a finite volume-based computing tool with the K-epsilon (k-ε) turbulence model. The analysis is performed for various pertinent parametric ranges, including the spacing between the batteries, Reynolds numbers, and average Nusselt numbers. The results indicate that increasing air inlet velocity (Re) substantially reduces the average air temperature of the cooling pack and temperature difference (ΔT) of the battery cells, and the cooling pack's average heat transfer rate (Nu) increases monotonically as the Re increases.

Passive thermal management system of lithium-ion batteries employing metal foam/ pcm composite for the development of electric vehicles

ABSTRACT Electric vehicles with a pack of lithium-ion batteries (LIBs) are taking a significant place in the field of transportation. Since lithium-ion battery efficiency relies on battery pack temperature, the temperature of the battery pack must be maintained within the safe limits for proper working of the system. This paper proposes a novel experimental method to dissipate and maintain the thermal energy emitted by LIBs based on a nickel foam/paraffin composite and a composite of copper foam/paraffin for thermal management of Panasonic NCR 18650B cylindrical lithium-ion battery cells. The results indicate that the surface temperature of the battery is reduced by 30.95% by comparing with ambient air convection and 24% temperature reduction by comparing with PCM by the application of nickel foam at a 2C discharge rate. By using copper foam/paraffin composite 34% and 25% temperature reduction by comparing with ambient air convection and PCM (paraffin) accordingly was achieved at a 2C discharge rate. Additionally, the result of temperature uniformity on the thermal management of the battery pack was also studied.

Heat generation rates and anisotropic thermophysical properties of cylindrical lithium-ion battery cells with different terminal mounting configurations

This paper investigates the variation in the heat generation rates and anisotropic thermophysical properties of cylindrical 18,650 and 21,700 lithium-nickel-manganese-cobalt-oxide (NMC) battery cells when the negative terminal is mounted at different points on the cell surface. We developed a methodology that combines experimental data with a numerical inverse heat transfer (IHT) model to quantify the differences in these properties under two strategies for connecting the negative terminal to the cell surface. In the first, the negative terminal is connected at the top rim of the cell, adjacent to the positive terminal; in the second, the negative terminal is connected at the bottom of the cell, adjacent to the negative current collector. Applying this methodology, we found that the total heat generation over 1000 s for 18,650 and 21,700 cells with the negative terminal at the top rim is higher than that for batteries with the negative terminal at the bottom by up to 4.6 % and 10.7 %, respectively. The additional heat was concentrated in the cell canisters, resulting in non-uniform heat generation across the cell volume. Without considering this non-uniformity in the numerical IHT model, the characterization process yielded 15–22 % discrepancies in the predicted thermal conductivities. By considering the canister and jelly roll of the cell as separate heat generation domains, the discrepancies were reduced below 6 % and 7 % for 18,650 and 21,700 cells, respectively. This work developed an improved battery cell characterization methodology taking into account localized heat generation and extrinsic terminal mounting effects. The results underline the importance of high-fidelity cell characterization in the battery cell design process.

Influence of Breathing and Swelling on the Jelly-Roll Case Gap of Cylindrical Lithium-Ion Battery Cells

Cylindrical 18650 and 21700 lithium-ion batteries are produced with small gaps between the jelly roll and the case. The size of these gaps and the mechanical attachment of the jelly roll to the case can have a significant impact on the thermal and mechanical properties of cells. To investigate the influence of the state of charge (SOC) and state of health (SOH) on the size of the gap, computed tomography (CT) and gray-value analysis was conducted with various cell types at 0% and 100% SOC and after cycling. The results show a significant influence of the SOC on the gap for new cells and a substantial reduction in the gap during the first cycles.

RETRACTED: Study of pressure drop and heat transfer in cooling of lithium-ion battery with rhombic arrangement with two different outlets and different inlet dimensions

This article models a two-dimensional battery pack (BAP) containing 45 battery cells. The cylindrical lithium-ion battery cells are arranged in a rhombic pattern in the pack. The pack has one inlet and two outlets so that laminar airflow exchanges heat with the battery cells. The temperature of the battery cells (TBC), the pressure drop (PD) in the BAP, the changes in the air velocity (Vair) in the BAP with the outlet air temperature (OAT) for each outlet separately are evaluated by changing the dimensions of the air inlet and two outlets, at four velocities of 0.005, 0.01, 0.015, and 0.02 m/s. The BAP is simulated using the COMSOL software. According to the findings of this research, an increase in Vair increases the pressure decrease in the BAP. Increasing Vair, on the other hand, lowers the maximum temperature (TMA) and the average TBC. An enhancement in the dimensions of inlet and outlets reduces the average and TMAs of the battery. As the Vair is intensified, the amount of OAT is reduced. Model D = 0.6 has the maximum OAT and model D = 1 has the minimum OAT at two outlets.

Combining an active method and a passive method in cooling lithium-ion batteries and using the generated heat in heating a residential unit

In this paper, a gentle air flow is simulated among cylindrical lithium-ion battery (LIIB) cells using COMSOL software. A circular PCM compartment is placed around the battery cells. The hot air from cooling the battery is used to heat the house. By changing the battery position in three modes in PCM in the air speed range of 1 × 10−3 to 5 × 10−3m/s, the volume fraction of solid PCM, the average PCM temperature (TAve−PCM), the maximum battery temperature (Tmax−b) and the exhaust air temperature at different times from 0 to 1000 seconds are analyzed. The percentage of time energy provided by this system of the total energy required for this residential house has also been examined. The results of this study show that over time at high speeds, the Tmax−b of the LIIB first increases and then decreases. The passage of time also reduces the amount of TOutlet. If the LIIB is placed on the air inlet side of the PCM instead of the air outlet side, the Tmax−b is reduced by 1.53 degrees at high speeds. Placing the LIIB on the left side of the PCM causes the output temperature (TOutlet) to be higher and also increases the amount of solid PCM by up to 5% in 1000 seconds compared to placing the LIIB on the right side. Using 50 cells of LIIB and air flow of 0.005 m/s in this system can provide up to 22% of the required energy for heating the building in a winter day.

Numerical study on the air-cooled thermal management of Lithium-ion battery pack for electrical vehicles

A Lithium-ion battery is one of the most common batteries being widely used as the power source in Electric Vehicle (EV) due to its high energy density, power density, long life span and environment friendly. Due to the high power requirement of EV, thousands of cylindrical Lithium-ion battery cells are typically connected in parallel and/or series forming a battery pack. This significantly generates enormous heat through the internal resistance effect and exothermic reactions inside the battery during the charge or discharge process. If the fetal heat cannot be dissipated sufficiently, the battery cells may encounter capacity fade, thermal runaway and instability issues. Thus, efficient thermal management of the Lithium-ion battery pack is essential to restrain high temperature and non-uniformity of temperature in the battery pack. This issue remains a challenge, although much research has been conducted on this topic. In this work, the air cooling thermal management system is numerically investigated due to lower manufacturing cost, simple layout requirements and higher reliability of the system. A transient three-dimensional heat transfer model of the cylindrical Lithium-ion battery pack is developed to study the effect of the inlet velocity, discharge rate and cell arrangement structure on the cooling performance. The proposed system is designed to minimize the maximum cell temperature and the cell temperature uniformity. The simulated results can be further applied as a reference in designing the structures of the battery pack and planning the cooling strategies.

Application of Nonlinear Krylov Solvers for Conjugate Heat Transfer Simulations of Electrical Battery Packs

Abstract Krylov-based methods are an attractive alternative to traditional fixed-point iterative schemes, being much more robust and accurate when solving elliptic equations (e.g., the energy equation in the solid domain). This study assesses the performance of a Krylov-based accelerator, when used for conjugate heat transfer (CHT) simulations of an electrical battery pack. The nonlinear nature of CHT simulations (due to spatial and temporal changes in boundary conditions) necessitates the use of the non-inear form of the Krylov-based accelerator (termed NKA), which utilizes the generalized minimized residual (GMRES) method, and works by accelerating an existing fixed-point iteration scheme. NKA is used while performing steady-state CHT simulations of an air-cooled lithium-ion battery pack, specifically to help accelerate the solution of the solid domain energy equation. The effect of using either isotropic or anisotropic thermal conductivity within the cylindrical lithium-ion battery cells is also evaluated. Results obtained using the NKA accelerator are compared, in terms of accuracy and speed, with those obtained from a traditional nonlinear fixed-point iterative scheme based on successive over-relaxation (SOR). The NKA accelerator is found to perform quite well for the problem at hand, providing results with the specified accuracy, while also being between 5 and 20 times faster than SOR (while solving the solid energy equation). The robust nature of NKA also leads to better global heat balance within the battery pack at all times during the simulation. These observations hold for both the isotropic and anisotropic thermal conductivity conditions. Overall, computational cost reductions of 30–40% are observed when using NKA for the battery pack simulations. Although the performance of NKA is demonstrated for a battery cooling application, NKA performs quite well in other applications also.

Quasi steady state method to measure thermophysical parameters of cylindrical lithium ion batteries

The thermophysical parameters such as thermal conductivity and specific heat play a vital part in the thermal design of the power battery pack composed of cylindrical lithium ion battery cells. This work proposes a quasi steady state method with considering heat loss to measure the thermophysical parameters of two classes of 21700 and 18650 cylindrical cells, respectively. To this end, the theoretical model and the corresponding measurement method were developed in consideration of the heat loss, and the two cells' thermophysical parameters were experimentally determined over a wide operating temperature range of −20–60 °C. The results show that both of the thermal conductivity and the specific heat of the cells increase linearly with the increase of the operating temperature. In comparison, the cell temperature has a greater influence on the specific heat than that of the thermal conductivity. The experimental verification reveals that the measurement error is behind 5.1%. Having a short measurement time within 930s, the present work provides a fast and convenient solution on determining the thermophysical parameters of the cylindrical cells without resorting to the costly instruments.

Temperature estimation from current and voltage measurements in lithium-ion battery systems

Performance and safety of lithium-ion batteries depend on the ability to efficiently estimate their temperature during charge/discharge operations. We propose a novel algorithm to infer temperature in cylindrical lithium-ion battery cells from measurements of current and terminal voltage. Our approach employs a dual ensemble Kalman filter, which incorporates the enhanced single-particle dynamics to relate terminal voltage to battery temperature and Li-ion concentration. The numerical results and experimental validation from LGChem LiNiMnCoO2 battery (INR21700 M50) cell data demonstrate the method’s ability to estimate temperature at various charge/discharge C-rates.

An Investigation on the Electrical Energy Capacity of Cylindrical Lithium-Ion and Lithium Iron Phosphate Battery Cells for Hybrid Aircraft

An Investigation on the Electrical Energy Capacity of Cylindrical Lithium-Ion and Lithium Iron Phosphate Battery Cells for Hybrid Aircraft

Study on the thermal interaction and heat dissipation of cylindrical Lithium-Ion Battery cells

Cylindrical Lithium-Ion Batteries have been widely used as power source for electric and hybrid vehicles because of their compact size and high power density. The battery pack is commonly consisted by hundreds of cylindrical Lithium-Ion battery cells in several strings. Because the distance among battery cells is only a few millimeters, the thermal status of battery would directly influent the current efficiency and battery life. In order to maintain proper function of the battery pack, the heat dissipation around battery cells should be deeply investigated and well controlled. This question is undeniably important and which has gained increasing attentions. Researchers have developed some models of the transient temperature distribution in Lithium-Ion battery during the discharge cycle and the thermal management on various kinds of battery packs has been studied. However, because of the compacted and complicated structure inside battery pack, the full thermal status and detail distributions are difficult to be revealed in the same time. In this work, three-dimensional simulation methods have been used to solve the above questions on the combination of several cylindrical Lithium-Ion battery cells. Existing heat generation models in Lithium-Ion battery is defined as the thermal boundary conditions. The flow and convection on the spacing has been studied. The transient thermal interactions and convections among adjacent battery cells have been investigated to explore the influences by spacing and transient heat release rules. The achieved results can be used as critical reference for designing the structures of battery pack and planning the cooling strategies.

State-of-Charge and Deformation-Rate Dependent Mechanical Behavior of Electrochemical Cells

The state-of-charge and deformation-rate dependent mechanical behavior of cylindrical lithium-ion battery cells was investigated. The research revealed that both state of charge and deformation rates affected the stiffness of the battery cells. Battery mechanical failure load was only weakly dependent on the state of charge. For the deformation-rate dependency on the mechanical integrity of battery cells, the battery mechanical failure load was either decreased significantly at high state of charge or decreased slightly at low state of charge as deformation rate increased. For the correlation between mechanical integrity and electrical failure, the displacement at the battery mechanical failure load coincided with a voltage drop. However, at high state of charge, premature and incomplete voltage drops were observed before the definite final voltage drop. No such premature voltage drop was observed in low state-of-charge specimens. The results of this research may be used as a reference for the design of impact and damage tolerant electric vehicle battery systems.

A new approach to the internal thermal management of cylindrical battery cells for automotive applications

Conventional cooling approaches that target either a singular tab or outer surface of common format cylindrical lithium-ion battery cells suffer from a high cell thermal resistance. Under an aggressive duty cycle, this resistance can result in the formation of large in-cell temperature gradients and high hot spot temperatures, which are known to accelerate ageing and further reduce performance. In this paper, a novel approach to internal thermal management of cylindrical battery cells to lower the thermal resistance for heat transport through the inside of the cell is investigated. The effectiveness of the proposed method is analysed for two common cylindrical formats when subject to highly aggressive electrical loading conditions representative of a high performance electric vehicle (EV) and hybrid electric vehicle (HEV). A mathematical model that captures the dominant thermal properties of the cylindrical cell is created and validated using experimental data. Results from the extensive simulation study indicate that the internal cooling strategy can reduce the cell thermal resistance by up to 67.8 ± 1.4% relative to single tab cooling, and can emulate the performance of a more complex pack-level double tab cooling approach whilst targeting cooling at a single tab.

Clay-like mechanical properties for the jellyroll of cylindrical Lithium-ion cells

In this investigation, several quasi-static mechanical tests on cylindrical Lithium-ion battery cells are performed to reveal the essential mechanical properties of the jellyroll. Utilizing the plastic flow rule, it was found that the homogenized mechanical properties of the jellyroll are similar to the clay (clay-like). According to the mechanical characteristics of clay, a linear equation was proposed to describe the nonlinear constitutive behavior of the jellyroll. An explicit finite element model for the jellyroll that could accurately predict its mechanical response during deformation using crushable foam constitutive behavior was established in HyperWorks/LS-DYNA to validate the proposed approach. The simulation results of various loading cases are in good agreement with the corresponding experimental results. By proposing a micro stress area, the stress-strain relations for components of the jellyroll were calculated individually. A finite element model was developed to compare the mechanical properties of the jellyroll by changing the thickness of different components, including the metal foils and the active particles. The simulation results indicate that the change of the thickness of the coating active particles will influence the mechanical properties of the jellyroll.

Impact modeling of cylindrical lithium-ion battery cells: a heterogeneous approach

In this study, a heterogeneous finite element model was developed in LS-DYNA to investigate lateral impact on 6P cylindrical lithium-ion battery cells manufactured by Johnson Controls Inc. The results were compared to those from a homogenized model previously reported by the authors and also experimental data and showed a good agreement. In order to find the stress-strain curves needed for the finite element simulations, compression tests were conducted on stacks of jellyroll's individual layers, i.e. coated aluminum, coated copper and separator. It was found that the load carrying capacity of the jellyroll comes primarily from the coated aluminum layers. SEM images of the separator layers showed their trilayer structure and how they collapse under excessive compressive loads. Compression experiments were also performed on flattened jellyroll samples after being soaked in electrolyte for 24 h. The measured stress-strain relations showed a very good agreement with the results from a similar set of experiments on dry jellyrolls. This suggested that characterizing dry cells could predict how live cells would react under compression/crash tests without dealing with all the safety provisions needed for those experiments.