Cylindrical Lithium-ion Battery Research Articles

Experimental study on the characteristics of thermal runaway propagation process of cylindrical lithium-ion batteries

ABSTRACT This study examines the risks of thermal runaway in Lithium-ion batteries, especially under abusive conditions, which can lead to high temperatures, combustion, and explosions, posing safety threats. It focuses on thermal runaway propagation, temperature changes, propagation time, mass alterations, gas composition, and concentration shifts. Experiments were conducted on various Lithium-ion batteries with different SOCs. The results show inevitable thermal runaway in one-dimensionally arranged cylindrical Li-ion batteries. Higher SOC batteries have increased combustion risks, faster transfer rates, longer gas release, and produce irritating gases like NH3, HCl, and HF. Trigger temperatures and times vary with SOC: 100% SOC batteries trigger at 97°C in 185 s, while 25% SOC batteries trigger at 232°C in 299 s. The propagation time between adjacent batteries decreases from 273 s to 74 s as SOC increases from 25% to 100%. A predictive model is introduced to calculate peak temperatures and analyze propagation paths, enhancing understanding and safety considerations of thermal runaway in batteries.

Mechanical Behavior and Failure Prediction of Cylindrical Lithium-Ion Batteries Under Mechanical Abuse Using Data-Driven Machine Learning

Abstract Mechanical failure prediction of lithium-ion batteries (LIBs) can provide important maintenance information and decision-making reference in battery safety management. However, the complexity of the internal structure of batteries poses challenges to the generalizability and prediction accuracy of traditional mechanical models. In view of these challenges, emerging data-driven methods provide new ideas for the failure prediction of LIBs. This study is based on an experimental data-driven application of machine learning (ML) models to rapidly predict the mechanical behavior and failure of cylindrical cells under different loading conditions. Mechanical abuse experiments including local indentation, flat compression, and three-point bending experiments were conducted on cylindrical LIB samples, and mechanical failure datasets for cylindrical cells were generated, including displacements, voltages, temperatures, and mechanical forces. Six ML models were used to predict the mechanical behavior of cylindrical batteries, four metrics were used to evaluate the prediction performance, the coefficients of determination of eXtreme Gradient Boosting (XGBoost) regression and random forest were 0.999, and the root-mean-square errors (RMSE) were lower than 0.015. It is shown that the integrated tree models tested in this study are suitable for the failure prediction of LIBs under the conditions of mechanical abuse. Also, the random forest prediction model outperforms other ML prediction models with the smallest RMSE values of 0.005, 0.0149, and 0.007 for local indentation, flat compression, and three-point bending, respectively. This work highlights the capability of ML algorithms for LIB safety prediction.

Elucidating effects of form factors on thermal and aging behavior of cylindrical lithium-ion batteries

Cylindrical lithium-ion cells are commercially available in different form factors, e.g., 18650, 21700, 26650, 32700 and 4680. The larger 4680 cells are gaining popularity, especially after the patent filing by Tesla. This paper aims to perform a comparative analysis of the thermal and aging behavior of different form factors using NMC–graphite chemistry during prolonged cycling at moderate operating conditions. A physics-based aging model for lithium-ion batteries is introduced, incorporating side reactions such as solid electrolyte interface (SEI) formation, SEI reformation due to graphite layer cracking, and lithium plating. During cycling, the cell temperature increases with time for all form factors due to internal heat generation. Notably, larger form factor cells experience higher temperatures, attributed to their inferior surface-to-volume ratio for heat dissipation, thereby accelerating both SEI formation and triggering lithium plating in subsequent cycles. This accelerated aging manifests in increased heat generation and prolonged charging for larger cells. The 4680 cell showed the highest rate of capacity loss with a 20% reduction over 480 cycles as compared to the 600 cycles of the 18650 cell. Highlighting accelerated aging in the larger cells due to suboptimal heat dissipation, this study underscores the pressing need for advanced thermal management strategies tailored to the unique challenges posed by larger cells.

State of health estimation of lithium-ion battery cell based on optical thermometry with physics-informed machine learning

Effective thermal management and accurate state of health (SOH) estimation of lithium-ion batteries is crucial for ensuring their safety, reliability, and longevity. This study presents three innovative physics-informed machine learning-based SOH estimation techniques trained and demonstrated using experimental temperature data. Temperature distribution measurements were obtained using optical frequency domain reflectometry with optical fibers embedded in a cylindrical lithium-ion battery cell under various SOH. One of the trained model accurately predicted the SOH of a cell within 2% with only a 10-minute measurement. This technique also enables the estimation of SOH for individual cells connected in series or parallel within a battery module or pack simultaneously, thereby reducing the overall SOH estimation uncertainty without the need for disassembly. Furthermore, this not only highlights the necessity of precise thermal management in maintaining battery health but also offers a practical and efficient solution for real-time SOH monitoring in battery systems.

Thermal runaway behaviour of a cylindrical lithium-ion battery during charge and discharge processes: A comprehensive numerical study

Lithium-ion batteries (LIBs) may experience thermal runaway (TR) accidents during charge and discharge processes. To ensure the safe operation of batteries, it is very important to analyse the TR characteristics during charge and discharge processes. In this work, we have developed a coupled electrochemical thermal (ECT) – TR (ECT-TR) model for a commercial 18,650 type 2.6 Ah NCM523/graphite battery. This model allows for the examination of TR features under different ambient temperatures, effective heat transfer coefficients (h), and C-rates during both charge and discharge processes. We first analysed the temporal evolution of the battery's surface center temperature and the heat generated by chemical reactions under a spectrum of environmental variables. Subsequently, we introduce a battery risk map that delineates distinct zones, including the safe zone, battery chemical reaction zone, battery failure zone, and TR zone, across varying environmental conditions. The results suggest that the battery's TR risk during the charge process exceeds that during the discharge process, with both exhibiting reduced risk compared to that during the cycle process. However, it is noteworthy that the risk of accelerated battery aging due to chemical reactions is more pronounced in the discharge process compared to the charge process.

Numerical investigation and optimization of liquid battery thermal management system considering nanofluids, structural, and flow modifications under high discharge cycles

The thermal management of electric vehicle (EV) batteries continues to be a pressing challenge preventing wider EV adoption due to performance and safety concerns. Liquid battery thermal management systems (BTMSs) are the most commercially viable thermal management option due to their high heat transfer efficiency and compact design, despite these promising features, the current liquid BTMS designs suffer from high energy consumption and temperature gradients which severely affect the BTMS performance. To address these issues, this study numerically investigated the influence of various liquid BTMS design parameters for a 12 cylindrical lithium-ion battery module. The study evaluated 21 different BTMS configurations based on the maximum battery temperature, temperature difference, pressure drop, and energy consumption. Based on the selected evaluation criteria, The optimized liquid BTMS design (one cooling block, bidirectional flow, 0.0015 kg/s mass flow rate, 4 mm cell spacing, continuous operation strategy with hybrid CuO-MgO-TiO2 water 0.5 % concentration nanofluid) maintained the maximum temperature and temperature difference at 31.34 and 5.3 °C respectively, a 4.3 % and 21.1 % improvement compared to the base design, with a total pressure drop of 12.84 Pa when operated under 35 °C ambient temperature and 3C discharge rate. Proving the effectiveness of the proposed liquid BTMS design.

Effect of Electrode Curvature on Cell Behavior in Cylindrical Lithium-Ion Batteries

Lithium-ion batteries come in various form factors, with cylindrical lithium-ion batteries featuring electrodes wound in a jellyroll shape. This winding process introduces curvature to the electrodes, resulting in varying curvatures depending on the radius of the jellyroll.In this study, we investigated the influence of electrode curvature within cylindrical lithium-ion batteries on battery performance. We fabricated single-coated electrode pouch cells using an NCM622 cathode and graphite-silicon composite anode. We developed devices to simulate various curvatures based on the radius of the jellyroll and applied these devices to the pouch cells to analyze the effect of curvature on the cell’s charging and discharging behavior.The results revealed that changes in electrode curvature, depending on the radius of the jellyroll, alter the area available for reaction at the anode. As a result, the potential of the anode changed, leading to a corresponding change in the potential of the cathode at the same full cell's cut-off charging voltage. Additionally, we observed differences in cathode/anode utilization depending on whether they were on the inner or outer coated surface, even with the same curvature. Particularly, we found an increased risk of lithium deposition when the curvature is large with the anode on the outer coated surface. Furthermore, these effects influence changes in silicon utilization in the anode, affecting the thickness expansion and degradation differences in the anode. Consequently, the non-uniformity of cell reactions due to electrode curvature increases. Therefore, we propose methods for designing cylindrical lithium-ion batteries to minimize such non-uniformity in reactions.Our research emphasizes the importance of curvature within cylindrical lithium-ion batteries and its impact on battery performance by elucidating the mechanism of battery performance changes due to electrode curvature. These findings are expected to contribute to the design and development of cylindrical lithium-ion batteries. Figure 1

Properties of Wedge Wire Bonded Connection Between a Composite Copper Core Aluminum Shell Wire and an 18650 Cylindrical Lithium-Ion Battery Cell.

Wedge wire bonding is a solid-state joining process that uses ultrasonic vibrations in combination with compression of the materials to establish an electrical connection. In the battery industry, this process is used to interconnect cylindrical battery cells due to its ease of implementation, high flexibility and ease of automation. Wire materials typically used in battery pack manufacturing are pure or alloyed aluminum and copper. While copper wires possess better electrical properties, the force used in the bonding process can lead to cell isolator damage and cell thermal runaway. This is an unacceptable result of the bonding process and has led to the development of new types of composite wires containing a copper core embedded in an aluminum shell. This material has the advantage of high copper electrical and thermal conductivity combined with less aggressive bonding parameters of the aluminum wire. The aim of this study was to establish a process window for the wedge wire bonding of 400 µm composite copper-aluminum Heraeus CucorAl Plus wire on the surface of a BAK 18650 battery cell. This study was conducted using a Hesse Bondjet BJ985 CNC wire bonder fitted with an RBK03 bond head designed for the bonding of copper wires. The methods used in this study included light and scanning electron microscopy of bond and battery cell cross-sections, shear testing on the XYZtec Sigma bond tester system, and energy dispersive spectroscopy. The results were compared with a previous study conducted using a wire of the same diameter and made out of high-purity aluminum.

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.

Decoupling the influence of impact energy and velocity on dynamic failure of cylindrical lithium-ion batteries

Ensuring battery safety in electric vehicles during crashes is crucial due to the complexities of battery failure under dynamic loading. This study presents a dynamic test apparatus that isolates the effects of impact energy and velocity. Experiments show that impact energy primarily drives battery failure, with impact velocity also influencing outcomes. Notably, the battery demonstrates mitigated electrical failure within a specific impact energy range, which is lower than the threshold for failure characterized by a sudden voltage drop due to major fractures. The self-discharging rate of the impaired batteries within this range exhibits randomness, likely caused by complex electrode contact conditions following minor separator fractures and subsequent deformation recovery. Interestingly, under similar impact energy, electro-mechanical failure exhibits a nonlinear “severe-mild-severe” pattern as velocity increases, differing from the typical strain-rate effect observed in components like separators. X-ray computerized tomography and dynamic material behavior analysis reveal this anomaly as a competition between strain-rate hardening of materials and inertia effect of electrolyte flow and wound structure. The findings highlight that different factors dominate battery failure under varying impact velocities. This research enhances understanding of the energy- and velocity-dependent responses of lithium-ion batteries, aiding in optimizing battery designs for improved safety during collisions.

Fault detection of cylindrical lithium-ion battery under Markov switching

Fault detection of cylindrical lithium-ion battery under Markov switching

Study on the evolution laws and induced failure of series arcs in cylindrical lithium-ion batteries

With the increase of voltage level in energy-storage and power battery system, the electrical safety phenomenon of battery systems has received extensive attention. The issue of series arcs caused by electrical failure such as loose connections in battery systems has become increasingly serious. However, research on series arcs in battery systems is still in its early stages. Therefore, to investigate arc-related disasters in batteries, this study establishes an experimental platform to simulate series arc faults. Taking positive electrode terminal arcs as the focused point, this study explores the evolutionary patterns of battery-related arcs and under different conditions, and analyzes the hazardous effects on batteries. The results indicate that stable arcs can be generated in batteries with different states of charge (SOC) when the system voltage is 200 V and the circuit current is 2C. At the same time, the arc can melt the battery casing to form holes, leading to electrolyte leakage, and triggering battery short-circuit and open-circuit failures. The research findings of this study fill a gap in the field of battery system arc safety and are of vital importance for enhancing the safety performance of arc protection.

Parameterization and heat generation investigation of cylindrical lithium batteries based on a reconstructed electrochemical-thermal coupling model

To comprehensively investigate the electrochemical and thermal behaviors of cylindrical lithium-ion batteries (LIBs), an appropriate reconstructed electrochemical-thermal coupling model (RETM) is first established to parameterize the LIBs, and the simulation differences of different geometric configurations are quantitatively studied from two perspectives as temperature and voltage. Based on this RETM, a comprehensive method to obtain battery information by scanning electron microscopy, actual measurement and parameter estimation algorithm is further proposed and analyzed. Additionally, the heat generation rate (HGR) and the heat distributions of the cylindrical battery are carefully explored and a novel HGR verification method of the RETM is proposed and illustrated. Finally, the simulation and experimental results validate the superiority and effectiveness of the proposed RETM and HGR analysis method. This work could help other researchers predict the electrochemical and thermal behavior of batteries under different applicable conditions more effectively.

Obtaining parallax-free X-ray powder diffraction computed tomography data with a self-supervised neural network

In this study, we introduce a method designed to eliminate parallax artefacts present in X-ray powder diffraction computed tomography data acquired from large samples. These parallax artefacts manifest as artificial peak shifting, broadening and splitting, leading to inaccurate physicochemical information, such as lattice parameters and crystallite sizes. Our approach integrates a 3D artificial neural network architecture with a forward projector that accounts for the experimental geometry and sample thickness. It is a self-supervised tomographic volume reconstruction approach designed to be chemistry-agnostic, eliminating the need for prior knowledge of the sample’s chemical composition. We showcase the efficacy of this method through its application on both simulated and experimental X-ray powder diffraction tomography data, acquired from a phantom sample and an NMC532 cylindrical lithium-ion battery.

Insights into Thermal Runaway of Cylindrical Lithium-ion Batteries by Internal Temperature Sensors

Insights into Thermal Runaway of Cylindrical Lithium-ion Batteries by Internal Temperature Sensors

Dynamic response analysis of cylindrical lithium-ion battery under impact loadings: A theoretical study

The prediction of serious deformation for lithium-ion batteries (LIBs) under impact loadings becomes an important challenge for engineering application. In this paper, a theoretical model is developed to investigate the dynamic responses of cylindrical LIBs based on the membrane factor method. The cylindrical LIB is simplified as double-layer structure consisting of the casing and jellyroll. The plastic yield criterion is established by utilizing tensile yield strengths and the corresponding membrane factor fn is defined. The dynamic responses of the cell under radial impact loading are explored. The accuracy of this method is verified by the corresponding finite element (FE) results. In addition, a comprehensive quantitative analysis of the governing factors of fn is conducted under different boundary conditions. Using the theoretical model, the response characteristics of the cell under different initial velocities and masses are investigated. The approximate equation for the variation of the maximum deflection with initial velocity and the saturation impact time are presented. The tendency of the deformation changing with size and tensile properties of the cell is obtained. These researches will provide technical support for the failure prediction and structural safety design of cylindrical cells.

Distribution strategy of flexible phase change materials for pouch battery thermal management considering temperature non-uniformity

Flexible composite phase change materials (CPCMs) have been extensively studied in the thermal management of cylindrical lithium-ion batteries and proven to have a good cooling effect. However, passive cooling of pouch lithium-ion batteries with severe uneven temperature distribution has not received the attention it deserves. The thermal management of pouch battery based on passive cooling of flexible PCMs considering the heat-generating structure of pouch batteries needs to be further studied. Herein, CPCMs with different thermal conductivity were prepared, and four different distribution modes of CPCMs, including partial coverage and complete coverage, were applied to thermal management of pouch battery. Results indicated that the maximum temperature (Tmax) and maximum temperature difference (ΔTmax) can be kept separately within 35 °C and 5 °C in the passive thermal management of a single battery except upper coverage at discharge rate of 5C, and the middle coverage (case B) showed excellent temperature control in partial coverage cases. Equally noteworthy was that the increase in thermal conductivity increased the ΔTmax in partial coverage cases, while showing the opposite trend for full coverage (case ABC). Furthermore, only passive cooling of pouch battery pack did not meet the safety requirements under the discharge rate cycle of 5C. Under the active–passive combination mode, case B can control the Tmax (32.22 °C) and ΔTmax (4.69 °C) within a safe range, which was superior to case ABC (Tmax = 35.53 °C, ΔTmax = 5.04 °C). This conclusion provides technical support for the pouch battery to seek economic, stable and efficient thermal management.

Using fins to enhance heat transfer of cylindrical lithium-ion batteries immersed in electrical insulating oil

This work focused on designing the heat dissipation fins for cylindrical lithium-ion batteries to quickly transfer the heat generated inside the battery to the surrounding immersed insulating oil. The measured instantaneous heat generation rate of a single battery at the discharge rates of 1.0C and 1.5C was adopted as the internal heat source to simulate the surface temperature field of two series and two parallel (2S2P) battery modules immersed in insulating oil in three-dimensional space, respectively. The numerical simulation method has been validated by experimental results, indicating that the scheme of using this internal heat source is feasible. Then, this method was continued to be used to simulate the temperature rise characteristics during higher rate 2.5C discharge processes when the heat transfer was enhanced by circular or serrated fins. The cooling effects of three heat exchange enhancement methods (no fins, circular fins, and serrated fins) were compared under the operating conditions of 25 °C ambient temperature, and 1 g·s−1 rated insulation oil circulation mass flow rate. The maximum temperatures of the batteries in the module were 40.3 °C, 38.4 °C, and 37.5 °C, respectively. The maximum temperature differences between the batteries in the module were 1.63 °C, 1.59 °C, and 1.51 °C, respectively. Therefore, the serrated fins had the best thermal management effect. The orthogonal method was used to analyze the influence of the external structure and quantity of fins, as well as the insulation oil circulation mass flow rate, on heat transfer efficiency, and it was determined that the most significant factor is the mass flow rate of insulation oil. The final optimal parameters suitable for the 2S2P battery module were obtained, which were 16 serrated fins for each battery, with a fin height of 6 mm, a fin width of 3 mm, and a mass flow rate of 7 g·s−1.

Thermal management characteristics of a novel cylindrical lithium-ion battery module using liquid cooling, phase change materials, and heat pipes

To improve the thermal performance of large cylindrical lithium-ion batteries at high discharge rates while considering economy, a novel battery thermal management system (BTMS) combining a cooling plate, U-shaped heat pipes, and phase-change material (PCM) is proposed for 21700-type batteries. The effects of variables such as the contact angle between a corrugated aluminum plate (CAP) and the battery, the coolant flow direction in the cooling plate, the type of PCM, and the coolant flow velocity on the thermal characteristics of the batteries in the BTMS are investigated, and the advantages of this coupling cooling strategy relative to a single active cooling or a single active and passive cooling combination strategy are discussed. The results indicate that a corrugated aluminum plate is beneficial for significantly improving the temperature uniformity of the batteries. A staggered flow-direction scheme of adjacent channels significantly improves the temperature uniformity relative to the other inlet flow modes. The thermal performance of the batteries in the BTMS using paraffin and expanded graphite (PA/ EG) is superior to that with pure paraffin or paraffin and copper foam (PCF), with temperature uniformity improved by 44.6 % and 16.0 %, respectively. Increasing the coolant flow velocity can decrease the maximum temperature of the batteries and significantly reduce the heat dissipation share of PCM, resulting in a decrease in the temperature uniformity of the batteries in the BTMS. Meanwhile, compared with pure liquid cooling or a combination of liquid cooling and heat pipe or PCM, the proposed coupling BTMS not only reduces the maximum temperature of the batteries and further improves the temperature uniformity, but also significantly reduces the operating energy consumption of the BTMS.