Automotive Battery Research Articles

The impact of the degree of automation on the configuration of a car battery assembly line

This paper presents the concept of an automotive battery assembly line. The line includes in its structure fully and semi-automated assembly sockets, as well as manual assembly sockets. The transport between the sockets is carried out using an AGV autonomous trolley system. The selection of the assembly process execution method was based on an analysis of the technical feasibility of the process as well as an analysis of the occupation time of individual assembly stations. The resulting line structure indicates to what extent the automation of the assembly process contributes to a change in material flow and influences the way the process is carried out, including a variety of technical means used. The paper presents an analysis of the use of particular workstations. This analysis was used to optimise the flow of the component assembly line. Maximum utilisation of the resources involved in the production process was used as a criterion for optimisation.

Laser-based battery pack disassembly: a compact benchmark analysis for separation technologies

The global decarbonization will have to be driven by the e-mobility sector to achieve the climate goals. End-of-life battery packs therefore need to be recycled efficiently and sustainably so that a cost-competitive circular economy can be adopted. In current process approaches, once the battery is discharged, disassembly is typically performed manually in a process that is not automated and dangerous to workers. To disassemble, first the battery cover must be removed, whereby current technological approaches focus on screw connections, which are difficult to loosen due to their condition after many years in the vehicle and cause poor automation capability. Another alternative is to mechanically mill the battery cover, which creates chips inside the battery pack that can cause short circuits. Waterjet cutting, which is also a process approach, faces the challenge of water getting into the battery pack, which can also lead to short circuits. Therefore, there is a need for new technological approaches which can dismantle an automotive battery pack productively with enhanced safety standards for workers and batteries. For this purpose, this paper performs a compact benchmark analysis of different separation technologies to identify initial potentials and challenges for laser-based disassembly of automotive battery packs.

Fast and Energy-Efficient Compound Self-Heating of Automotive Batteries Based on Electrochemical-Thermal-Stress Aging Model

Fast and Energy-Efficient Compound Self-Heating of Automotive Batteries Based on Electrochemical-Thermal-Stress Aging Model

Amplitude–Frequency Decoupled Heater and Integrated Strategies for Automotive Batteries Based on Inverter and Motor

Amplitude–Frequency Decoupled Heater and Integrated Strategies for Automotive Batteries Based on Inverter and Motor

An Evaluation of the Environmental Impacts and Economic Performance of Automotive Battery Recycling: Bangladesh Perspective

An Evaluation of the Environmental Impacts and Economic Performance of Automotive Battery Recycling: Bangladesh Perspective

Experimental Analysis of Thermal Runaway Energy Release of an Automotive Li-Ion Battery Cell

Thermal runaway (TR) reactions of lithium ion cells pose a particular risk to the safety of battery systems. Beside the energy remaining in the cell body, particles and gases exiting the cell during the venting process cause major thermal load for adjacent cells and further system components [1]. In addition, high energy particles can act as an ignition source in the presence of ignitable venting gases and oxygen [2]. Therefore, measurements minimizing the risk of thermal propagation (TP) caused by venting ejecta material and the ignition of combustible gases are introduced on system level. For the dimensioning of the measures, the energy transported by venting particles and gases is identified as a crucial parameter. Depending on the amount of transported energy, the gas cooling distance as well as the complexity of the particle separation structure differ. Simulation methods are used to evaluate the effectiveness of such system measures. More information is needed regarding energy release to accurately predict the system behavior in simulations and to use them as a tool for design.Introducing a novel approach for TR tests enables the determination of the energy remaining in the cell body, separated from the energy transported by venting ejecta. The test setup combines a calorimeter combined with a cyclone separator placed inside an autoclave reactor. The TR energy release of 156 Ah prismatic lithium ion cells have been analyzed using the setup. Venting particles and gases transported a main part of the released energy out of the cell during the TR. Using an analytical approach, the energy transferred to the calorimeter is calculated. The obtained data can be used for validating simulation models for predicting the impact of venting reactions on TP.

New Method for Designing Robust External Short-Circuit Protection Systems at Different Scales

External short circuit is one of the failure modes of Li-ion and other batteries that potentially leads to serious damage such as, overheating and/or thermal runaway. Therefore in this work we test and analyse the short circuit behaviour of different system sizes from coin cells, 10Ah pouch cells and upto large scale automotive high voltage battery packs. It was found that the complex short circuit behavior can be described by 3 regions independently of the size of the battery. In the first region 274C-rate is observed which is mainly governed by the cell's double and diffusion layer discharge. In the second region, the current drops significantly to 50–60C-rate where mass transport becomes the current limiting factor. The maximum temperature is reached and cell rupture, venting and electrolyte leakage may occur. Then the current stabilizes at the maximum mass transport region independently of the external short circuit. This complex time behavior need to be covered by different fuses, circuit breaker and intelligent battery management system. The protection strategy depends on several factors, which makes the design process complex. We introduce the normalized resistance ratio which allows the comparison of external shorts with different external resistance and cells and with different capacities. We demonstrate that the estimation of the maximum external short circuit current derived in this work is more accurate than other calculations at different levels. Furthermore we developed and present a generalized visualisation of the full time-current window which potentially help scientists and engineers to design more robust external short circuit protection systems. With this method we also demonstrate that the currently used external short circuit design methods may potentially lead to unsafe regions especially in the soft short region. We also propose a testing protocol which can be applied in standards, regulations without jeopardizing the safety of testing personnels and infrastructure.

(Invited) Sensor Integration in Lithium-Ion Cells from a Systems Perspective

The cell temperature is a critical factor that impacts performance, safety and longevity of batteries. For the optimum operating strategy, therefore, maximum and minimum cell temperature must be available to the BMS at all times. This is a challenge, however, because typical automotive batteries use more than a hundred cells and the cells themselves do not exhibit a homogeneous temperature.For this reason, it was and is particularly important in the development of lithium-ion batteries to measure the temperatures at the relevant points - and thus often also inside the cells themselves.In the first part, an overview of the current state of research on cell-internal temperature measurement will be given and the efforts to transfer these approaches into application will be further discussed. In particular, the technical requirements at the system level will be discussed, but also the difficulties of industrialization.In addition to the integration of sensors, the determination of temperature from already existing variables such as cell voltage and current has already been described in many approaches. In particular, the application of impedance spectroscopy has reached a level that can be described as ready for industrialization. After an overview of the current state of research, the requirements for application in the target system will be addressed and the necessary further research is discussed.

Needle penetration studies on automotive lithium-ion battery cells: Influence of resistance between can and positive terminal on thermal runaway

Thermal runaway (TR) can be initiated by the heat dissipated from an internal short circuit (ISC). In prismatic cells, a crucial type of ISC is located between the cell can on positive potential and the first anode layer. To enhance the safety, the potential of the can could be adjusted by increasing the ISC resistance, i.e., realizing a floating can, whereas a universal automotive prismatic cell has a can on potential in contrast. This work demonstrates that the floating can mitigates the ISC current and possibly prevents ISC from leading to TR using an advanced needle penetration test. Moreover, the ISC current was quantitatively measured, proving that there is no significant ISC current between floating can and outmost anode, while the ISC with can on potential can cause TR. To demonstrate that such difference originates only from the increased resistance, the equivalence in thermal behaviors between the two types of cans was analyzed by a heat-wait-seek test in an accelerating rate calorimeter. This work provides not only a guidance on designing a safer prismatic cell but also a prospect how the optimized needle penetration test can bring a deeper insight into the internal processes of Lithium-ion cells during mechanical abuse.

Thermal runaway propagation in automotive lithium-ion batteries with NMC-811 and LFP cathodes: Safety requirements and impact on system integration

Thermal runaway propagation mitigation is a prerequisite in battery development for electric vehicles to meet legal requirements and ensure vehicle occupants’ safety. Thermal runaway propagation depends on many factors, e.g., cell spacing, intermediate materials, and the entire cell stack setup. Furthermore, the choice of cell chemistry plays a decisive role in the safety design of a battery system. However, many studies considering cell chemistry only focus on the cell level or neglect the energetic impacts of safety measures on system integration. This leads to a neglect of the conflict of objectives between battery safety and energy density. In this article, a comprehensive analysis of the thermal runaway propagation in lithium-ion batteries with NMC-811 and LFP cathodes from a Mini Cooper SE and Tesla Model 3 SR+ is presented. The focus is set on the identification of differences in battery safety, the derivation of safety requirements, and the evaluation of their impact on system integration. A comparative analysis identified significantly higher safety requirements for Graphite | NMC-811 than for Graphite | LFP cell chemistries. Regarding cell energy, thermal runaway reaction speed is nine times faster in NMC-811 cells and five times faster considering the whole propagation interval than LFP cells. However, since LFP cell chemistries have significantly lower energy densities than ternary cell chemistries, it must be verified whether the disadvantages in energy density can be compensated by advanced system integration. An analysis of cell-to-pack ratios for both cell chemistries has revealed that, based on average values, the gravimetric disadvantages are reduced to 16%, and the volumetric disadvantages can be completely compensated for at the pack level. However, future research should further focus on this issue as an accurate safety-related design depending on cell chemistry could enable a cost–benefit evaluation under the constraints of safety standards in the development of batteries for electric vehicles.

Internal Heating Techniques for Lithium-Ion Batteries at Cold Climates: An Overview for Automotive Applications

Lithium-ion (Li-ion) batteries suffer from substantial capacity and power degradation at low temperatures, severely deteriorating the performance of battery-based transportation electrification. To overcome this issue, different preheating techniques have been proposed to recover the performance of Li-ion batteries in cold climates. Among these, internal heating schemes are more promising than traditional conductive and convective approaches owing to their superiorities in terms of high efficiency, rapid speed, and uniform temperature distribution. This paper reviews various internal heating methodologies developed in recent years for Li-ion batteries, including mutual pulse current heating, alternating current heating, compound heating, and all-climate-battery based heating. Specifically, the effects of low temperatures on Li-ion batteries are first outlined in terms of cell performance and electrochemical characteristics. Then, the heat generation mechanism during internal heating is briefly described, based on which the internal temperature monitoring methods are also investigated considering the temperature gradient. Next, a comprehensive literature survey on different internal heating schemes with their basic principles, benefits, and drawbacks is presented. Finally, future trends of internal heating methods to benefit automotive battery performance are discussed in terms of key technologies, promising opportunities, and challenges.

Comprehensive Analysis on Power Factor Correction Circuit

With the development of industrial power electronics, the current era can be called the "world energy era". Energy has never been more important, especially with the growing demand for today's "green" energy sources. power factor correction circuits have become an integral part of most current AC voltage input power applications, whether it is automotive battery power, portable energy storage (such as power banks), traditional server power, or lighting systems. However, the basic principles of power factor correction converters are rarely described in detail. This paper will summarize and illustrate the basic principle of the power factor correction circuit, and first introduce the research background of power factor correction technology; At the same time, three operating modes of power factor correction circuit are analyzed: continuous on-mode (CCM), critical on-mode (CRM) and discontinuous on-mode (DCM), and their advantages and disadvantages are to be further discussed. In addition, the PFC converters with optimized topology and excellent performance will be introduced, and the application prospect and prospect of three-phase PFC converters will be presented.

Shell Shape Influence on Latent Heat Thermal Energy Storage Performance during Melting and Solidification

Phase-change materials have various applications across industries from thermal energy storage through automotive battery temperature management systems to thermal stabilisation. Many of these applications are shell and tube structures with different shell shapes. However, it is not yet known how the shape of the shell affects the melting, solidification times, and heat transport processes in such structures. To fill this research gap, seventeen shell shapes/orientations were compared using a simulation study. The well-known and validated enthalpy porosity algorithm implemented in the Fluent 2021R2 software was used. The numerical calculations were preceded by the measurement of thermal conductivity, phase change enthalpy, and specific heat during melting and solidification of the phase-change material. The shortest melting time was achieved for a semi-circular shell shape in the downward position, which was 44% shorter than the reference circular case. The shortest solidification times were recorded for an isosceles trapezium in an upward orientation relative to the reference circular case. Therefore, it is possible to significantly reduce the melting time in shell-and-tube systems as a result of the appropriate selection of the shell shape.

Development of a High-Frequency Test System to Study the Wear of Ultrasonic Welding Tools

In current automotive lithium-ion battery manufacturing, Ultrasonic Metal Welding (USMW) is one of the major joining techniques due to its advantages in welding multiple thin sheets of highly conductive materials. The sonotrode, serving as the welding tool, transmits high-frequency oscillation to the joining parts. Due to the high frequency of thermal-mechanical loading, the knurl pattern on the sonotrode wears with an increasing number of welds, which significantly influences the welding process, resulting in poor joint quality. In this study, a high-frequency test system was developed to investigate the wear mechanisms of the sonotrode. Based on the comparable relative motion to the welding process, the thermal-mechanical loadings on the contact area were analyzed. As the oscillation amplitude of the sonotrode increased, the estimated frictional force between the sonotrode and the copper counter body remained constant, while an increase in the sliding distance was observed in the contact area. Temperature development showed a strong correlation with mechanical loading. A first approach of continuous testing was performed but was limited due to the failure of the copper counter body under ultrasonic stimulation.

Influence of the Cell Type on the Physical Processes of the Mechanical Recycling of Automotive Lithium-Ion Batteries

Lithium-Ion Battery (LIB) manufacturers produce different cell formats (prismatic, cylindrical, pouch, etc.) with different casing materials (steel or aluminium) and cell chemistries (e.g., NMC, NCA, LFP, etc.) for application in electric vehicles. By law, these cells have to be recycled after their lifetime. This study investigates the influence of different cell types on the outcome of a standardized mechanical recycling process consisting of crushing, sieving and air classification. The aim of the study is to find out whether different cell types can be processed together or whether the recovery and product quality can be improved by processing them separately. Pouch cells require low energy consumption for crushing compared to cylindrical and prismatic cells. Steel as a casing material increases the energy requirement during crushing compared to aluminium. The particle size distribution of several product fractions varies significantly between the different cell types. During air classification, the separator, anode, and cathode show a similar separation behaviour and can be processed with the same settings, whereas for the separation of the casing metals, different settling velocities need to be applied depending on the casing material.

Arcing in Li-Ion Batteries

Lithium-Ion battery cells and automotive battery systems are constantly improving as a result of the rising popularity of electric vehicles. With higher energy densities of the cells, the risks in case of failure rise as well. In the worst case, a fast exothermic reaction known as thermal runaway can occur. During thermal runaway, the cell can emit around 66% of its mass as gas and particles. An experimental setup was designed and showed that the gas-particle-vent of a cell going through thermal runaway can cause electric breakthroughs. These breakthroughs could start electric arcing in the battery system, which could lead to additional damages such as burning through the casing or igniting the vent gas, making the damage more severe and difficult to control. Uncontrollable battery fires must be prevented. The emitted gas was analyzed and the ejected particles were examined to discuss the potential causes of the breakthroughs.

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.

Selective Module-to-Cell Equalizer With Internal AC Heating Capability for Automotive Lithium-Ion Batteries at Subzero Temperatures

Selective Module-to-Cell Equalizer With Internal AC Heating Capability for Automotive Lithium-Ion Batteries at Subzero Temperatures

Study on the Life Cycle Assessment of Automotive Power Batteries Considering Multi-Cycle Utilization

This article utilizes the research method of the Life Cycle Assessment (LCA) to scrutinize Lithium Iron Phosphate (LFP) batteries and Ternary Lithium (NCM) batteries. It develops life cycle models representing the material, energy, and emission flows for power batteries, exploring the environmental impact and energy efficiency throughout the life cycles of these batteries. The life cycle assessment results of different power battery recycling process scenarios are compared and analyzed. This study focuses on retired LFP batteries to assess the environmental and energy efficiency during the cascade utilization stage, based on a 50% Single-Cell Conversion Rate (CCR). The findings of the research reveal that, in terms of resource depletion and environmental emission potential, LFP batteries exhibit lower impacts compared to NCM batteries. The use of hydrometallurgy in recovering LFP power batteries leads to minimal life cycle resource consumption and environmental emission potential. During the cascade utilization stage of LFP batteries, significant benefits are noted, including a 76% reduction in mineral resource depletion (ADP e) and an 83% reduction in fossil energy depletion (ADP f), alongside notable reductions in various environmental impact factors. Simultaneously, considering the sensitivity of life cycle assessment indicators and their benefit percentages to different CCRs, it is observed that ODP exhibits the highest sensitivity to CCR changes, while evaluation indicators such as HTP, AP, and GWP show relatively lower sensitivity. This study can provide an effective reference for the establishment of an energy saving and emission reduction evaluation system of power batteries.

Automated feature extraction to integrate field and laboratory data for aging diagnosis of automotive lithium-ion batteries

Automated feature extraction to integrate field and laboratory data for aging diagnosis of automotive lithium-ion batteries