Automotive Battery Research Articles

Fundamental and solutions of microcrack in Ni-rich layered oxide cathode materials of lithium-ion batteries

Ni-rich layered transition metal oxide is one of the most promising cathode materials for the next generation lithium-based automotive batteries due to its excellent electrochemical performances. Nevertheless, its further applications are capped by the structural/interfacial instability during the prolonged charging/discharging, leading to severe performance fading and serious safety concerns. Here, we provide a comprehensive review about challenges and solutions to modify Ni-rich layered cathodes specifically for microcrack failure. Firstly, the mechanism of microcrack formation and evolution are concluded thoroughly. Secondly, recent advances in stabilizing the structure/interface of Ni-rich cathodes are summarized such as surface coating, cation/anion doping, composition tailoring, morphology engineering and electrolytes optimization. Furthermore, strategies to mitigate the microcrack and then boost the electrochemical performance of Ni-rich cathodes at the chemical & mechanical engineering level are presented. More importantly, outlook and perspectives to facilitate the practical application of Ni-rich layered cathodes toward electrical vehicle application are provided as well. The information compiled herein can promote the understanding of the microcracks of Ni-rich cathode materials, including its fundamental science, characterization method, and strategies for designing crack-free Ni-rich cathode materials. Furthermore, we provide a new idea for material modification, which is perspective strategy from crystallographic, structural mechanics and chemistry under the guidance of “chemical-mechanical” effect. • The mechanism of microcrack formation and evolution are concluded. • Recent advances in stabilizing the structure/interface of Ni-rich cathodes are summarized. • Strategies to mitigate the microcrack and then boost the electrochemical performance of Ni-rich cathodes are presented. • Main challenges and the future horizons are outlooked.

Research progress on recycling technology of waste lithium battery anode materials

In this paper, three kinds of recycling technologies for automotive lithium battery anode materials at home and abroad are introduced, including thermal metallurgy, hydrometallurgy and bio metallurgy. By comparison, the wet process with acid leaching precipitation extraction process has low requirements for equipment and energy consumption, and high leaching efficiency, which is an excellent technology easily introduced in industry.

Optimized lead-acid grid architectures for automotive lead-acid batteries: An electrochemical analysis

A variety of technological approaches of lead-acid batteries have been employed during the last decades, within distinguished fabrication features of electrode grid composition, electrolyte additives, or oxide paste additives embodiment. We proposed in this study, a particular path for improving the efficiency of positive grids by developing two novel geometry designs of lead-acid battery metallic grids. Our projection is based on a hierarchical approach that employed exclusively rectangular shapes for the structural configuration of grids. The intensity of current distribution was firstly evaluated by a numerical algorithm across the electrodes grid surface, thus allowing measuring the propagation of the electric charge emitted from each point inside of the grid. The novel fabricated prototypes were investigated by electrochemical impedance spectroscopy, following a controlled aging procedure. Two distinct parameters were investigated for evaluation of batteries lifetime: i) a time-dependent analysis of Constant Phase Element – Q parameter at 75% SoC partially discharged, and ii) the resonance frequency of the circuit. To confirm our improvements, we compared the data with the ones of an industrial grid model. An increment of battery lifetime was obtained for one prototype, with an estimation growth of 25% - 28% over the usual industrial electrode, while for the later a slightly improved lifetime efficiency of about 10% was resulted.

Structural Analysis in Reconfigurable Battery Systems for Active Fault Diagnosis

Conventional automotive battery systems consisting of a large number of battery cells pose a variety of challenges in terms of safety, reliability, lifetime, and energy efficiency. Reconfigurable battery systems (RBSs) are a promising solution to these issues of conventional battery systems. However, the large number of components in RBS also increases the fault probability. To meet this challenge on the way to fault tolerance, this article addresses fault isolation in an RBS, which comprises two switches per cell. Based on an electrothermal model, a structural analysis is performed and a sensor set with optimal fault isolation properties is found. Since the system consists of many equations, a novel algorithm is introduced to efficiently calculate minimal structurally overdetermined (MSO) subsystems for fault diagnosis. For each fault, the algorithm allows determining the MSO set that has the least number of equations. A complexity analysis of the algorithm reveals that the proposed algorithm is computationally significantly less expensive for systems with high redundancy, such as RBS, than existing algorithms that compute all MSO sets. Since the algorithm considers the switch states, it is suitable for active fault isolation through switches. The application to the RBS shows that the electrical equations are prioritized over the thermal equations due to the model uncertainties. A video file demonstrating the proposed graph-based algorithm with an example is attached to this article.

Simulation of heat dissipation model of lithium-ion battery pack

Lithium-ion power battery has become an important part of power battery. According to the performance and characteristics of lithiumion power battery, the influence of current common charge and discharge and different cooling methods on battery performance was analysed in this paper. According to the software simulation, in the 5C charge-discharge cycle, the maximum temperature of the cells with regular arrangement is 57.97°C, the maximum temperature of the cells with staggered arrangement is 55.83°C, and the maximum temperature of phase change cooling is 47.42°C. The most important thing is that the temperature difference between the cells with phase change cooling is only 5.5°C. Some simulation results of air cooling and phase change show that phase change cooling can control the heat dissipation and temperature rise of power battery well. The research in this paper can provide better theoretical guidance for the temperature rise, heat transfer and thermal management of automotive power battery.

Reduction of acid mist emission in formation process of Automotive lead acid battery manufacturing industry by means of an electrolyte additive

The sulphuric acid mist released during plate formation process of Automotive Lead Acid Battery manufacturing Industry is a major concern to environmental sustainability and there is a strong environmental drive to control its emission into the work environment. The present work is mainly aimed to reduce the acid mist emission at source itself without affecting the product performance. A “simple and salient” method to reduce the acid mist was carried out using an organic surfactant namely, “Sodium Lauryl Sulphate (SLS)” as an additive to the acid electrolyte. The best method of adding SLS into the electrolyte is by adding it to the required volume of electrolyte that was already filled. After addition of SLS, batteries are subjected to regular formation process. It is noteworthy that acid mist was noticeably reduced i.e. as high as 40% with the addition of SLS to the electrolyte. The study reveal that SLS is a cost effective and viable technique for acid mist reduction and therefore by making manufacturing of Automotive Lead Acid Batteries system in compliance with OSHA's regulations.

Interacting Multiple Model Strategy for Electric Vehicle Batteries State of Charge/Health/ Power Estimation

States estimation of lithium-ion batteries is an essential element of Battery Management Systems (BMS) to meet the safety and performance requirements of electric and hybrid vehicles. Accurate estimations of the battery’s State of Charge (SoC), State of Health (SoH), and State of Power (SoP) are essential for safe and effective operation of the vehicle. They need to remain accurate despite the changing characteristics of the battery as it ages. This paper proposes an online adaptive strategy for high accuracy estimation of SoC, SoH and SoP to be implemented onboard of a BMS. A third-order equivalent circuit model structure is considered with its state vector augmented with two more variables for estimation including the internal resistance and SoC bias. An Interacting Multiple Model (IMM) strategy with a Smooth Variable Structure Filter (SVSF) is then employed to determine the SoC, internal resistance, and SoC bias of a battery. The IMM strategy results in the generation of a mode probability that is related to battery aging. This mode probability is then combined with an estimation of the battery’s internal resistance to determine the SoH. The estimated internal resistance and the SoC are then used to determine the battery SoP which provides a complete estimation of the battery states of operation and condition. The efficacy of the proposed condition-monitoring strategy is tested and validated using experimental data obtained from accelerated aging tests conducted on Lithium Polymer automotive battery cells.

Опыт ЕС в построении стратегических цепочек добавленной стоимости: пример аккумуляторной отрасли

The article analyzes the EU’s experience in transformation of its industrial policy, which is designed to help the EU to overcome the gap with competitors in technology and innovation, as well as to set new standards for the functioning of industrial sectors in the conditions of greening and digitalization. The basic principles of building the strategic value chains are considered. The method of lifecycle analysis is used, as well as the theoretical basis of research on economic policy in new industries. Among the main principles on which support measures for new industries are based, we highlight the desire to ensure the legal and regulatory dominance of the EU, the desire for maximum transparency of business processes, the emphasis on the complex systemic effect for the entire European economy. The analysis of new projects implemented in the EU is conducted using the empirical base from the battery industry. The analysis includes the new instruments of industrial policy – Important Projects of the Common European Interest and others. An attempt has been made to assess the effectiveness of these mechanisms. It has been shown that the value-added chain of automotive batteries currently being built in the EU is not fully European, and dependence on suppliers of raw materials and services from third countries persists. The EU production spots are concentrated mostly in the middle parts of the value chain – like cell production and battery assembly. This configuration allows for regulatory opportunities in the industry, giving an advantage to European companies with extensive experience in measuring and reducing the climate footprint of their products. There are prerequisites for the involvement of a large number of small business players in the new chains and an increased diffusion of innovation. In addition, the EU is successfully addressing the challenge of demonstrating the potential of its Green Deal and increasing consumer confidence in new products.

Modelling Large Scale Manufacturing of Automotive Battery Cells – Impact of New Technologies on Production Economies

Modelling Large Scale Manufacturing of Automotive Battery Cells – Impact of New Technologies on Production Economies

Multi-length scale microstructural design of lithium-ion battery electrodes for improved discharge rate performance

Microstructural design strategies across multiple length scales for improved rate performance of automotive battery electrodes, assisted by physics-based microstructure-resolved model.

Applying optical coherence tomography for weld depth monitoring in remote laser welding of automotive battery tab connectors

This paper addresses in-process monitoring of weld penetration depth (WPD) during remote laser welding of battery tab connectors using optical coherence tomography (OCT). The research aims at studying the impact of welding process parameters on the accuracy of WPD measurements. In general, the highest measurement accuracy is achievable by positioning the OCT measuring beam toward the bottom of the keyhole. However, finding and maintaining the alignment between the OCT measuring beam and the bottom of the keyhole is a challenging task because of the dynamic changes in the size and shape of the keyhole itself. The paper addresses the above challenge by (1) developing welding process parameters for the Al-Cu thin foil lap joint (Al 1050 foil 450 μm and Ni-plated Cu foil 300 μm) using a novel adjustable ring mode (ARM) laser and (2) integrating OCT technology with two beams: one targeting the bottom of the keyhole and another as a reference to the part surface (TwinTec technology). The methodology is underpinned by the “Keyhole Mapping” approach, which helps one to identify the optimal placement of the OCT measuring beam with considerations to both measurement accuracy and stability of the keyhole. Findings indicated that welding with the ARM laser results in a more stable process, reduces fluctuations of the keyhole opening, and, therefore, helps one to improve the measurement accuracy by a factor of 50% (from the average error of 0.22 mm to 0.11 mm). Results further identified that the feasible operating window of the OCT measuring beam, corresponding to the highest measurement accuracy, is below 20 μm in length.

Authenticating Drivers Using Automotive Batteries

Automakers have been improving, or even trying to replace, key-based driver authentication solutions, owing to their vulnerability to cyber attacks and single-point-of-failures, as well as their inability of driver identification. In line with this effort, we design a novel driver authentication system using automotive batteries, called Batteries-as-Authenticators (BAuth), to mitigate the limitations of key-based solutions by providing a second-factor authentication. BAuth is an add-on module installed between vehicles and their batteries, which uses the batteries as sensors to validate drivers' identities and actuators to enable/disable the cranking of vehicle's engine. We have prototyped and evaluated BAuth on 6 regular/hybrid/electric vehicles. Our evaluation shows BAuth to authenticate the drivers with a 98.17 (2.84)% averaged true (false) positive rates and tolerate the dynamics caused by the aging/temperature/state-of-charge of batteries. Our user study corroborates BAuth's attractiveness to car owners.

Experimental and Numerical Investigation of the Behavior of Automotive Battery Busbars under Varying Mechanical Loads

Automotive high-voltage busbars are critical electrical components in electric vehicle battery systems as they connect individual battery modules and form the connection to the vehicle’s powertrain. Therefore, a vehicle crash can pose a significant risk to safety by compromising busbar insulation, leading to electrical short circuits inside the battery. In turn, these can trigger thermal chain reactions in the cell modules of the battery pack. In order to ensure a safe design in future applications of busbars, this study investigated the mechanical behavior of busbars and their insulation. Our results indicated that crashlike compressive and bending loads lead to complex stress states resulting in failure of busbar insulation. To estimate the safety of busbars in the early development process using finite element simulations, suitable material models were evaluated. Failure of the insulation was included in the simulation using an optimized generalized incremental stress state dependent model (GISSMO). It was shown that sophisticated polymer models do not significantly improve the simulation quality. Finally, on the basis of the experimental and numerical results, we outline some putative approaches for increasing the safety of high-voltage busbars in electric vehicles, such as choosing the insulating layer material according to the range of expected mechanical loads.

Drive circuitry of an electric vehicle enabling rapid heating of the battery pack at low temperatures.

SummaryHeating battery at low temperatures is fundamental to avoiding the range anxiety and the time-consuming charging associated with electric vehicles (EVs). One method for achieving fast and uniform battery heating is to polarize the cell under pulse currents. However, the on-board implementation of this method leads to an increase in the cost and size. Therefore, in this study, an adapted EV circuitry compatible with the existing one and an optimized operating condition are proposed to enable rapid battery heating. With this circuit, electricity transfer between the cells can be realized through a motor, leading to remarkably higher battery currents than those of the conventional circuit. The increase in the maximum heating currents (from 1.41C to 4C) resulted in a battery temperature rise of 8.6°C/min at low temperatures. This heating method exhibits low cost, high efficiency, and negligible effects on battery degradation, practical and promising on battery heating of EVs.

Future material demand for automotive lithium-based batteries

The world is shifting to electric vehicles to mitigate climate change. Here, we quantify the future demand for key battery materials, considering potential electric vehicle fleet and battery chemistry developments as well as second-use and recycling of electric vehicle batteries. We find that in a lithium nickel cobalt manganese oxide dominated battery scenario, demand is estimated to increase by factors of 18–20 for lithium, 17–19 for cobalt, 28–31 for nickel, and 15–20 for most other materials from 2020 to 2050, requiring a drastic expansion of lithium, cobalt, and nickel supply chains and likely additional resource discovery. However, uncertainties are large. Key factors are the development of the electric vehicles fleet and battery capacity requirements per vehicle. If other battery chemistries were used at large scale, e.g. lithium iron phosphate or novel lithium-sulphur or lithium-air batteries, the demand for cobalt and nickel would be substantially smaller. Closed-loop recycling plays a minor, but increasingly important role for reducing primary material demand until 2050, however, advances in recycling are necessary to economically recover battery-grade materials from end-of-life batteries. Second-use of electric vehicles batteries further delays recycling potentials.

Environmental Life Cycle Impacts of Automotive Batteries Based on a Literature Review

We compiled 50 publications from the years 2005–2020 about life cycle assessment (LCA) of Li-ion batteries to assess the environmental effects of production, use, and end of life for application in electric vehicles. Investigated LCAs showed for the production of a battery pack per kWh battery capacity a median of 280 kWh/kWh_bc (25%-quantile–75%-quantile: 200–500 kWh/kWh_bc) for the primary energy consumption and a median of 120 kg CO2-eq/kWh_bc (25%-quantile–75%-quantile: 70–175 kg CO2-eq/kWh_bc) for greenhouse gas emissions. We expect results for current batteries to be in the lower range. Over the lifetime of an electric vehicle, these emissions relate to 20 g CO2-eq/km (25%-quantile–75%-quantile: 10–50 g CO2-eq/km). Considering recycling processes, greenhouse gas savings outweigh the negative environmental impacts of recycling and can reduce the life cycle greenhouse gas emissions by a median value of 20 kg CO2-eq/kWh_bc (25%-quantile–75%-quantile: 5–29 kg CO2-eq/kWh_bc). Overall, many LCA results overestimated the environmental impact of cell manufacturing, due to the assessments of relatively small or underutilized production facilities. Material emissions, like from mining and especially processing from metals and the cathode paste, could have been underestimated, due to process-based assumptions and non-regionalized primary data. Second-life applications were often not considered.

Stabilized 3-D Foam for Ultra-Stable and Fast-Charging Lithium Metal Anode

Current lithium ion batteries almost reached the practical energy density and needs further innovation at materials chemistry and design. Lithium metal holds the highest specific capacity among the possible anode materials for Li-ion batteries. However, the complex and parasitic interfacial reaction between lithium metal and electrolyte hinders the practical application of lithium metal as anode in secondary batteries. Therefore, stabilizing the interface of lithium metal is crucial for their application in automotive batteries and grid-scale energy storage devices. In this study, the interface of the lithium metal anode was tailored using a simple and strategical approach by a) regulating uniform deposition and stripping of lithium ions on to the 3-D structured foam and b) stabilizing the cycle life of the anode. A facile and cost effective method was adopted to uniformly deposit the carbon material on to the 3-D scaffold. The performance was analyzed using various structural and electrochemical performance studies. As a result of this study, the Li-ion cell delivered a stable cycling performance of over 400 cycles with 98.5% Coulombic efficiency. Also, post-mortem analysis of the lithium metal anode was performed to establish fundamental understanding on the interfacial protection mechanism. These results provide valuable insights for advanced design of lithium metal anode with uniform protective coating.

Origins of Capacity Fade and Material Degradation in Ni-Rich NMC Li-Ion Batteries

Nickel-rich layered oxide cathode materials are promising candidates for automotive lithium-ion batteries due to their low cost and high reversible capacity.1 However, paired with graphite anodes these materials exhibit faster voltage and capacity fading compared to isostructural LiNixMnyCozO2 (NMC) cathodes with lower nickel content.2 In this work we will explore the origins of capacity fade and material degradation in graphite/LiNi0.8Mn0.1Co0.1O2 (NMC811) full cells. With a focus on strategically designed electrochemical protocols (see Fig. 1), the role of several key cycling parameters (e.g. upper cut-off voltage, time at high voltage, phase transitions) on the degradation are decoupled. The aging processes are quantified in terms of the full cell capacity retention, impedance rise, electrode slippage, and NMC cathode deterioration. We find that most full cell capacity loss and impedance rise is caused by increasing the upper cut-off voltage to >4.2 V, with the impedance increase largely driven by concomitant full state-of-charge (SOC) cycling. Time spent at high voltage (voltage holds) has less impact on these parameters. These findings are supported by electron microscopy and spectroscopy experiments (SEM, high-resolution TEM, and STEM-EELS) on cycled electrodes, which show clear evidence for cycle history dependent degradation including particle cracking, shearing, and surface reconstruction. Figure 1

The Effects of Non-Ideal, Lithiation-Based Active Material Volume Change on Mechano-Electrochemical Pouch Cell Simulation

Automotive battery manufacturers are working to improve individual cell and overall pack design by increasing their performance, durability, and range, while reducing cost; and active material volume change is one of the more complex aspects that needs to be considered during this process. In the study presented here, thermodynamically non-ideal (non-linear), lithiation-based volume change behavior for the anode and cathode active materials were incorporated into a previously developed mechano-electrochemical model.(1-4) Before, an ideal (linear) relationship between active material volume change and state-of-lithiation was assumed.Using the non-ideal active material volume change behavior, the changing thickness of an automotive relevant, large-format pouch cell was predicted while simulating cell discharge. Measurements were taken using an experimental setup capable of simultaneous mechanical and electrochemical operation and observation. Figure 1 shows that the mechano-electrochemical measurements prove to agree well with simulation when using non-ideal lithiation-based volume change as opposed to the previously assumed ideal volume change behavior.The resulting model was used to simulate other mechano-electrochemical phenomena including the effects of anode/cathode capacity ratio and changing pressure/porosity during cell discharge. This mechano-electrochemical model shows promise to help define operational parameters to mitigate negative effects from active material volume change and may act as a tool for developers to reduce the extensive electrochemical and mechanical testing required for the design of promising new batteries. References T. R. Garrick, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, Journal of The Electrochemical Society, 164, E3592 (2017).T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, Journal of The Electrochemical Society, 164, E3552 (2017).T. R. Garrick, K. Kanneganti, X. Huang and J. W. Weidner, Journal of The Electrochemical Society, 161, E3297 (2014).D. J. Pereira, J. W. Weidner and T. R. Garrick, Journal of The Electrochemical Society, 166, A1251 (2019).D. J. Pereira, M. A. Fernandez, K. C. Streng, X. X. Hou, X. Gao, J. W. Weidner, and T. R. Garrick, Journal of The Electrochemical Society, 167, 080515 (2020). Figure 1. Experimentally measured data and simulations using ideal and non-ideal active material volume change behavior for a NMC/LMO:Graphite pouch cell strain as a function of cell state-of-charge. Figure 1

High-Performance Lithium-Ion Negative Electrodes Based on Silicon Nanowires/Graphite Composites

Lithium-ion batteries (LIBs) have enabled significant technological progress in recent years and are considered the state-of-the-art technology for electrochemical energy storage.1 As the market for LIBs grows, so do the requirements for improvements concerning their energy and power density, especially with respect to their application in electric vehicles.2 As a consequence, extensive research efforts have been made towards the development of new and optimized materials that could provide the required leap in performance. Of particular interest are alternative anode materials to (partially) replace graphite and, thus, enable faster recharging of the battery cells.3 Non-toxic and abundant understoichiometric silicon oxide and elemental silicon are presently considered the materials of choice in this regard and have been incorporated already in commercial cells.3 In this work, we present the use of a silicon nanowires/graphite composite as active material for the negative electrode. The approach of using such composite is of great interest because it seeks to combine the advantages of the two components – i.e., the excellent cycling stability of graphite and the much higher specific capacity (3579 mAh g-1) and superior rate capability of silicon. The 1D silicon nanowire morphology compared to bulk silicon materials offers short Li+ transport pathways 4 and provides better contact with the graphite particles within the composite. This improved contact ensures first cycle coulombic efficiencies of well above 80% as well as very good cycling stability and high rate capability – even for high areal capacity electrodes – in half-cells and full-cells; the latter comprising NMC-type cathodes. A specific focus was set moreover on the investigation of the impact of (partially) pre-lithiated anodes, providing superior lithium-ion cycling stability with negligible capacity loss over hundreds of cycles. References M. Armand and J. M. Tarascon, "Building better batteries", Nature, 451, 652-657 (2008).D. Bresser et al., “Perspectives of automotive battery R&D in China, Germany, Japan, and the USA", J. Power Sources, 382, 176-178 (2018).J. Asenbauer et al., "The success story of graphite as a lithium-ion anode material – fundamentals, remaining challenges, and recent developments including silicon (oxide) composites", Sustain. Energy Fuels, DOI: 10.1039/D0SE00175A (2020).C. K. Chan et al., “High-performance lithium battery anodes using silicon nanowires", Nat. Nanotechnol., 3, 31–35 (2008).