Electromobility Applications Research Articles

Scaling of ultrashort-pulsed laser structuring processes for electromobility applications using a spatial light modulator

The structuring of lithium-ion battery (LIB) electrodes and the diffusion media (DM) for polymer electrolyte membrane fuel cells (PEMFCs) with ultrashort laser pulses enables improved performance characteristics of both technologies. However, the transfer of the approaches from a laboratory scale to a commercial use has previously been hindered by the low average output power of ultrashort-pulsed (USP) laser beam sources and the limited productivity of single-beam structuring using scanning optics. Recent advancements in the development of USP laser systems have led to a steady increase in the available output power, thereby enabling new fields of applications. This study aims at accelerating the USP laser structuring of LIB electrodes and DM for PEMFCs to industrially relevant processing rates by comparing a single-beam with a multibeam structuring process regarding ablation characteristics and quality. For the multibeam strategy, the shape of the laser beam was modified by a spatial light modulator (SLM). In addition to microholes, the insertion of microchannels was investigated to demonstrate the high flexibility of state-of-the-art SLMs. The geometry of the created structures was measured with a laser scanning microscope, and the different layers were tested for their geometrical and electrochemical properties to compare both technologies. The results confirmed that applying an SLM enables high-quality microstructures with significantly higher structuring rates. Furthermore, this contribution includes a theoretical analysis of the specifications required for a laser setup to reach an industrially relevant productivity of the structuring processes.

Cycle-Life Curves Determination and Modelling of Commercially Available Electric Vehicle Batteries

In recent decades, there has been a growing concern about the trend of global emissions, and in particular those of the transport sector. In this context, the electric vehicle is a promising technology, with some barriers still to be overcome. Among these deficiencies everything related to storage technology is found. In this sense, lithium-ion batteries are one of the options to be considered, although it is necessary to continuously monitor the state of health. Cycle life vs DoD curves are very useful for characterizing profitability in any application that considers battery storage, as well as life cycle optimization studies. Cycle life refers to the number of charge-discharge cycles that a battery can provide before performance decreases to an extent that it cannot perform the required functions (e.g., 80% compared to a fresh one in electromobility applications). In this paper, a model for calculating the Cycle Life vs DoD curves is proposed, applied to a commercially available electric vehicle, the Renault Zoe. Modelling results show R squared coefficient of determinations above 0.9890.

The effect of in-source spatial beam shaping on the laser welding of e-mobility metals and alloys

Electromobility applications require several welded connections using demanding materials often in dissimilar combinations. Copper, aluminium, or steel alloys are laser welded for energy storage and traction related components. On the one hand, high power fiber laser sources provide in-source beam shaping solutions able to modify the irradiance profile towards ring-shaped beams. On the other hand, research focused on the effect of the beam shapes on the melting mechanisms and process quality is still in progress. This work studies the effect of different beam profiles on AISI301LN, AA6082 and pure Cu with a 5 kW fiber laser. Linear trends of power over penetration depth as a function of speed confirms the validity of employing the lumped heat capacity model for ring-shaped beams. Moreover, the specific melting fluence is observed to exhibit an exponential decaying trend with the proportion of power allocated in the fiber core, irrespective of tested material.

Technological Alternatives for Electric Propulsion Systems in the Waterway Sector

The trend in the development of maritime and river propulsion systems is to make a transition from hydrocarbon to more environmentally friendly solutions. This contributes positively to the solution of the problems identified by the International Maritime Organization (IMO) regarding the high emissions of polluting gases emitted by maritime transportation. Currently, there is a wide variety of systems available due to the development of mobility technologies focused on decarbonization. This paper presents an analysis of technological alternatives for boats with electromobility applications and propulsion systems in the waterway field. First, a description of the operation of boats with electric motors, the different energy sources, and the alternative propulsion options is presented. Then, the electromobility technologies are characterized, analyzing the different configurations between the power source and the propulsion system. The results show a comparative table of technologies and their advantages and disadvantages. In addition, the most environmentally friendly technologies present significant challenges for large-scale implementation due to their recent development. In the short term, hybrid systems technologies present advantages over the others, as current systems are available, with the addition of equipment with higher efficiency and lower environmental impact.

Wire bond contact defect identification in battery modules of electric vehicles using pulses and differential voltage analysis

Automotive battery packs for electromobility applications consist of a large number of interconnected battery cells. Different cell-to-busbar joining techniques are utilized, with cylindrical cells frequently being contacted using wire bonding. Failure of individual connections can occur due to strong vibrations during operation and improper stress, making detection by the battery management system a necessity. This study investigates the identification of an electrical wire bond failure in a state-of-the-art electric vehicle module of a Lucid Air with 10 series-connected and 30 parallel-connected cells (10s30p). Four individual cells were characterized extensively in order to generate a simulation model taking into account parameter scatter. The failure case under investigation was simulatively incorporated in one parallel circuit and subsequently replicated in experimental validation measurements at the module level. The results show that this defect can be detected using pulses of C/3 or higher currents at various states of charge. An even more robust detection is achieved using differential voltage analysis of constant current C/20 discharge voltage trajectories. This defect identification method does not require any additional measurement sensors beyond the voltage taps and sensors provided by the manufacturer – with one voltage sensor per parallel circuit – and can therefore be implemented during electric vehicle usage, e.g. at dedicated service checks. A discussion on the applicability and scalability as well as the limitations of the method is provided. All measurement data of the state-of-the-art Lucid battery system is available as open source alongside the article.

Concerted ionic-electronic conductivity enables high-rate capability Li-metal solid-state batteries

Enabling the fast charge and discharge of Li-metal solid-state batteries paves the way towards their deployment in electro-mobility applications, which require high-energy and power with safety guaranteed. Solid-state batteries using polyethylene oxide as the polymer matrix are appealing candidates although currently limited to relatively slow rate capability arising from high solid-solid interfacial resistance and sluggish lithium-ion mobility at the solid electrolyte. In this work, the engineering design and optimization of composite electrodes with multi-walled carbon nanotubes lead to high performance Li metal solid-state cells, showing a high-capacity retention at rates up to 4C. The electrode formulations including the elongated architectures exhibit a concerted ionic-electronic diffusion in the catholyte polymer enabling fast Li-ion transport, enhancing the electronic percolation and increasing the interfacial reaction kinetics and exchange current density. The solid-state battery with LiFePO4 electrode shows an unprecedented capacity retention of 92% during 800 cycles at 2C. The promising performance at high-rates of this approach is also extended to electrodes with a high-voltage active material.

Pore formation and melt pool analysis of laser welded Al-Cu joints using synchrotron radiation

Known as challenging material combination, the welding of aluminium and copper, both with strongly different thermophysical properties, causes joining failures such as pores, cracks or intermetallic phases in the solidified welding area. To investigate the mixing of the materials and the occurrence of pores, the laser welding process is observed with synchrotron radiation which visualizes the phase boundaries between solid, liquid and gaseous material phases. This allows the visualization of pore formation and density differences of the materials inside the melt pool. In this investigation, pore formation in front and bottom of the keyhole is observed. The movement of the bubbles in the melt pool can be tracked until solidification at the material transition. Regarding the intermixing of the materials, the high-speed images show a fluctuating copper flow towards the keyhole and a material mixing over the entire aluminium melt pool depth. By understanding the mechanisms, compensatory measures for an improved process can be developed to enable the usability of aluminium and copper connections, for example in electromobility applications.

Towards Rechargeable Aluminum Metal Batteries for Low-Temperature Space & Electromobility Applications

Rechargeable aluminum metal batteries are promising next-generation electrochemical energy storage devices due to the high energy density, inherent safety, low cost, earth abundance, and recyclability of aluminum. Aluminum batteries using graphite cathodes and chloroaluminate-containing electrolytes have recently been the focus of intense research in the energy storage and electroplating community, particularly due to their fast-charging capabilities. Engineered graphite cathodes have been shown to exhibit supercapacitor-like rate performance since chloroaluminate anions intercalate into graphite with significant pseudocapacitive characteristics1,2. Batteries with high considerable pseudocapacitive charge storage3 are especially attractive for energy storage systems that need to function at low temperatures and ideally exhibit high specific power. For example, robotic spacecraft that embark on planetary science missions often have typical mission temperature targets of -40 to -60 °C. However, state-of-the-art lithium-ion batteries with predominant faradaic diffusion-limited charge storage suffer from lithium plating, dendritic growth, and severe capacity loss at low temperatures. While organic electrolyte mixtures have been developed that enable moderate low-temperature performance, new battery concepts, including those using ionic liquid electrolytes, are needed to enable new paradigms for low-temperature space missions and electromobility.Herein we present, for the first time, results towards rechargeable aluminum-graphite batteries designed specifically for low-temperature applications that demonstrate high capacity retention and favorable electrochemical kinetics at temperatures down to -40 °C. We first disentangle quantitatively the faradaic diffusion-limited, pseudocapacitive, and capacitive contributions to the overall charge storage for different graphite materials. Moreover, we shed light on the relationships between graphite structure, ion mass transport, and the overall rates of electrochemical aluminum deposition/dissolution and chloroaluminate anion intercalation. We then develop ionic liquid electrolytes with mixed anion-cation compositions to impart disorder and disrupt crystallization at low temperatures. The resulting aluminum-graphite batteries were characterized by variable-temperature and rate cyclic voltammetry (CV), galvanostatic cycling, electrochemical impedance spectroscopy (EIS), and solid-state nuclear magnetic resonance (NMR) spectroscopy to understand their reaction mechanisms and factors limiting their rate performance. The ionic liquid electrolyte mixtures were also characterized by a combination of differential scanning calorimetry (DSC) and electrochemical methods to understand their freezing points and electrochemical stability. The results provide fundamental insights into the design of aluminum-graphite batteries for low-temperature space and electromobility applications.

Enabling Aqueous Processing of Prussian White Cathodes for Sodium Ion Cells By Understanding the Effect of Structural Water

Sodium-ion batteries (SIBs) have been identified as one of the most promising alternative technologies for future stationary large-scale storage and light electromobility applications. Indeed, the potential cost decrease with respect to the lithium-ion technology, and the sustainability provided by using Earth abundant elements lead to lower economic and geopolitical impact.[1,2] Great achievements in terms of materials development have been reported in the recent years. However, further work is still needed to fully understand the structure-function correlation in several SIB materials. Easy-synthesis Prussian blue analogues (PBAs) have attracted much attention as potential cathode material in SIBs. Their open framework structure with large interstitial spaces allows a range of different compositions and enables fast Na+ insertion/extraction. However, a key factor affecting the electrochemical performance of PBAs is the crystal water in the structure arising from aqueous synthesis environments.[3] Thus, many have investigated improved synthesis methods aiming at reducing crystal water and associated structural defects.[4] Goodenough et al[5] firstly reported the improved electrochemical stability of PBAs through dehydration converting Na-rich monoclinic Na2MnFe(CN)6 to a rhombohedral structure. More recent studies, including Zhou et al[6] and Chou et al[7], further highlighted the negative impact of structural water on electrochemical performance. So far, the water sensitivity of PBAs has hindered aqueous electrode processing as demonstrated by the several studies conducted on N-methyl pyrrolidone-based electrodes. A more comprehensive understanding of the effect of crystal water and the induced degradation processes is necessary for obtaining high-performance electrode materials produced through environmentally friendly aqueous processing.Herein, we investigate the electrochemical behaviour of an aqueous-processed Fe-based Prussian white (PW) cathode material (Na2-x Fe[Fe(CN)6]1-y·zH2O).[8] The use of such material and processing matches the requirements for low toxicity, cost, and resource abundance in large-scale applications. We uniquely show that, by carefully tuning the water content in the PW structure, the electrochemical performance can be significantly improved. As structural water is removed by tuning the temperature and vacuum conditions during the electrode preparation, the crystallinity of the structure can be controlled, and optimal electrochemical behaviour can be achieved. Moreover, with the combination of cyclic voltammetry, impedance spectroscopy, X-Ray diffraction, X-ray absorption spectroscopy and scanning electron microscopy, we elucidate the activity of the low spin/ high spin Fe2+/3+redox reactions, the Na+ transport properties and the electrode’s structural and morphological changes. This allows to understand holistically the effect of crystal water on the electrochemical performance of PW cathodes. We then demonstrate that our approach is scalable and can be applied to different cell formats representing a step forward in the upscale of sustainable and low-cost sodium-ion cells.

Near-instantaneous battery End-of-Discharge prognosis via uncertain event likelihood functions

The prediction of the time of occurrence of future events has been studied for decades in various scientific disciplines. Such events have historically been defined as moments where variables of interest (or indicators) hit pre-determined thresholds (i.e. the first-hitting time). Recently, semi-closed mathematical expressions were reported in the literature to analytically characterize the probability distribution of the occurrence time of future events, extending the event triggering criteria based on thresholds to a more general and intuitive threshold-less approach, where the occurrence of events is declared through the use of uncertain event likelihood functions. The End-of-Discharge time prognosis problem is formalized in this article via the definition of uncertain event likelihood functions. Moreover, a novel numerical method is proposed to compute the probability distribution of its future time of occurrence based on this conceptualization and exploiting the capability of uncertain event likelihood functions to assimilate uncertainty in analytic expressions. A case study related to energy autonomy in electromobility applications is considered; specifically an electric bicycle. Obtained results show that the proposed method achieves an extraordinary level of convergence in less than a tenth of a second, while the same level of convergence using Monte Carlo simulations under the traditional threshold crossing approach takes hours to be achieved.

Unifying Criteria for Calculating the Levelized Cost of Driving in Electro-Mobility Applications

The Levelized Cost of Driving (LCOD) calculates how much it costs to drive a vehicle, per kilometer, over the vehicle lifespan, and it is typically measured in USD/km. LCOD has been widely applied to assess and compare the performance of Electric Vehicles (EVs) and Internal Combustion engine Vehicles (ICVs). Unfortunately, there is no common methodology to establish how to compute LCOD. As authors use different criteria to determine which elements are relevant in LCOD, it is difficult to compare results. To overcome this issue, we re-introduce the LCOD concept, where the most relevant expenditures and incomes are included. This novel LCOD definition also incorporates key elements that are sometimes neglected, such as the second life of batteries in EVs, EV battery degradation models, and stochastic models, to characterize daily operation. The proposed methodology is applied to assess the cost of using EVs as taxis in the city of Quito, Ecuador.

Parametric optimization of the effective thermal conductivity for a three-phase particle-filled composite

Functionalized materials, consisting of a particle-filled polymer matrix, enable a considerable increase in thermal conductivity compared to standard plastics. This is particularly important in electromobility applications, e.g. in encapsulated circuit boards, to ensure sufficient thermal management. In this paper, a method for the optimization of the effective thermal conductivity (ETC) by considering electrically insulating composites is presented. To show the diversity of microstructural design options by using different filler/matrix compositions, the method is introduced by taking a particle-filled plastic with three phases and high contrast in the conductivities of the individual phases as example. Particles with different sizes and shapes in the micrometer range are considered. The task of setting a target ETC is formulated as a parameter optimization problem. The ETC is determined by microstructure simulation and numerical homogenization where virtually created representative volume elements (RVEs) are used. To study the influence of the different design variables, metamodeling and sensitivity analysis techniques are introduced. It turns out, that only the filler volume fraction, the aspect ratio and the proportions of the individual fillers are sensitive parameters. After neglecting non-sensitive parameters, global optimization in the reduced design space using an evolutionary algorithm is performed. The novelty of the paper is that several fillers with different microstructural parameters, such as diameter, aspect ratio and shape, are included as design variables in the structural optimization. Since the evaluation of the objective function of the structural optimization problem is very expensive, a cheaper surrogate model is introduced in the paper. This approach allows an efficient computation of microstructural realizations with a target ETC and can be extended to other microstructures and effective properties as well.

Reliability Evaluation of Lithium-Ion Batteries for E-Mobility Applications from Practical and Technical Perspectives: A Case Study

Evaluation of the reliability of the components of electric vehicles (EVs) has been studied by international research centers, industry, and original equipment manufacturers over the last few years. Li-ion batteries are the main sensitive component of an EV’s E-power train. In other words, the Li-ion batteries for electromobility applications are one of the main components of an EV, which should be reliable and safe over the operational lifetime of the EV. Thus, investigating how to assess the reliability of the Li-ion battery has been a highly recommended task in most European projects. Moreover, with the increase in the number of new EVs made by European car companies, there has been a competition for market acquisition by these companies to win over customers and gain more market share. This article presents a comprehensive overview of the evaluation of the reliability of Li-ion batteries from practical and technical perspectives. Moreover, a case study for assessing reliability from practical and technical perspectives has been investigated.

Functional Safety BMS Design Methodology for Automotive Lithium-Based Batteries

The increasing use of lithium batteries and the necessary integration of battery management systems (BMS) has led international standards to demand functional safety in electromobility applications, with a special focus on electric vehicles. This work covers the complete design of an enhanced automotive BMS with functional safety from the concept phase to verification activities. Firstly, a detailed analysis of the intrinsic hazards of lithium-based batteries is performed. Secondly, a hazard and risk assessment of an automotive lithium-based battery is carried out to address the specific risks deriving from the automotive application and the safety goals to be fulfilled to keep it under control. Safety goals lead to the technical safety requirements for the next hardware design and prototyping of a BMS Slave. Finally, the failure rate of the BMS Slave is assessed to verify the compliance of the developed enhanced BMS Slave with the functional safety Automotive Safety Integrity Level (ASIL) C. This paper contributes the design methodology of a BMS complying with ISO 26262 functional safety standard requirements for automotive lithium-based batteries.

Enhancement of Structural, Electrochemical, and Thermal Properties of High-Energy Density Ni-Rich LiNi0.85Co0.1Mn0.05O2 Cathode Materials for Li-Ion Batteries by Niobium Doping.

Ni-rich layered oxide LiNi1-x-yCoxMnyO2 (1 - x - y > 0.5) materials are favorable cathode materials in advanced Li-ion batteries for electromobility applications because of their high initial discharge capacity. However, they suffer from poor cycling stability because of the formation of cracks in their particles during operation. Here, we present improved structural stability, electrochemical performance, and thermal durability of LiNi0.85Co0.1Mn0.05O2(NCM85). The Nb-doped cathode material, Li(Ni0.85Co0.1Mn0.05)0.997Nb0.003O2, has enhanced cycling stability at different temperatures, outstanding capacity retention, improved performance at high discharge rates, and a better thermal stability compared to the undoped cathode material. The high electrochemical performance of the doped material is directly related to the structural stability of the cathode particles. We further propose that Nb-doping in NCM85 improves material stability because of partial reduction of the amount of Jahn-Teller active Ni3+ ions and formation of strong bonds between the dopant and the oxygen ions, based on density functional theory calculations. Structural studies of the cycled cathodes reveal that doping with niobium suppresses the formation of cracks during cycling, which are abundant in the undoped cycled material particles. The Nb-doped NCM85 cathode material also displayed superior thermal characteristics. The coherence between the improved electrochemical, structural, and thermal properties of the doped material is discussed and emphasized.

Co-Sintering Study of Na0.67[Ni0.1Fe0.1Mn0.8]O2 and NaSICON Electrolyte–Paving the way to High Energy Density All-Solid-State Batteries

Sodium is a promising candidate for stationary storage applications, especially when the demand for lithium-ion batteries increases due to electromobility applications. Even though its energy density is lower, Na-ion technology is estimated to lead to a cost reduction of 30% compared to Li-ion technology. To improve safety as well as energy density, Na-based all-solid-state-batteries featuring solid electrolytes such as beta-alumina and sodium superionic conductors and cathode materials such as Na3V2(PO4)3 and NaxCoO2 have been developed over the past years. However, the biggest challenge are mixed cathodes with highly conductive interfaces, especially when co-sintering the materials. For example, a promising sodium superionic conductor type Na3Zr2Si2PO12 electrolyte sinters at 1,250°C, whereas the corresponding Na3V2PO12 cathode decomposes at temperatures higher than 900°C, posing a bottleneck. Thus in this paper, we synthesized Na0.62 [Ni0.10Fe0.10Mn0.80]O2 as cathode material for all-solid-state sodium-ion batteries via a relatively cheap and easy solution-assisted solid state reaction processing route. The thermal investigations of the pure cathode material found no degradation up to 1,260°C, making it a perfect match for Na3.4Zr2Si2.4P0.6O12 electrolyte. In our aim to produce a co-sintered mixed cathode, electron microscopy investigation showed a highly dense microstructure and the elemental mapping performed via energy dispersive X-ray spectroscopy and secondary ion mass spectrometry confirm that Na3.4Zr2Si2.4P0.6O12 and Na0.62 [Ni0.10Fe0.10Mn0.80]O2 do not react during sintering. However, the active cathode material forms a sodium rich and a sodium deficient phase which needs further investigation to understand the origin and its impact on the electrochemical performance.

(Invited) Surface Characterisation of Ni-Rich NMC Materials Stored in Various Environments

In order to obtain higher energy densities for electromobility applications, the market is now heading towards high-nickel content NMCs. However, these materials suffer from severe gassing issues decreasing the cycle life and causing safety problems. While it is agreed that the O2 evolution is coming from oxygen lattice oxidation at the end of charge, the source of CO and CO2 gassing is still under debate.In this context, we report here a systematic study of NMC811 pristine material surface contaminations obtained after storage in different controlled environments. We use a multi-analytical approach involving combined MAS-NMR, XPS and STEM-EELS to provide a full material characterisation before cycling. The chemical environment of the Li present in the paramagnetic bulk of the material is successfully determined by means of 7Li MAS-NMR at low field (200 MHz). High field 7Li MAS-NMR (500 MHz) allows the quantification of the surface diamagnetic Li. Low field 1H MAS-NMR gives insights on the proton bulk and surface environments. STEM-EELS mapping is performed with both high energy and high spatial resolution using our new TEM/STEM Themis Z G3 (Thermo Fisher Scientific) equipped with a double camera GIF spectrometer. We obtain a good multi-elemental chemistry mapping quantification as well as the accurate analysis of the fine structure of the L3/L2 Ni edges thanks to the use of an excited monochromator.Putting together all characterisation results, we achieved a thorough analysis of primary particles surface contamination after different controlled storage conditions, that will be correlated with gassing measurements and cell cycling stability.

Particle-Filtering-Based Prognostics for the State of Maximum Power Available in Lithium-Ion Batteries at Electromobility Applications

Nowadays, electric vehicles such as cars and bicycles are increasing their popularity due to the rising environmental consciousness. The autonomy required by these means of transport has marked a significant and steady growth in the development of battery technologies. In this sense, it is crucial to estimate and prognosticate critical parameters of battery packs such as the State of Charge (SOC), the State of Maximum Power Available (SoMPA), and the Failure Time. All these indicators are relevant to determine if both the energy stored in the battery of electric vehicles and power specifications are sufficient to successfully complete a required route, avoiding battery preventive disconnection before arrival. In this regard, this paper presents a novel approach to estimate and prognosticate the SOC and SoMPA of Lithium-Ion batteries in the context of electromobility applications. The proposed method uses the formulation of an optimization problem to find an analytical relationship between the SOC and the SoMPA; whereas the battery pack is modeled in terms of both the polarization resistance and the SOC. Particle filtering algorithms are used to compute online estimates and prognostic results, while the characterization of the usage profile of the battery bank is achieved using probability-based models (Markov chains). The problem of battery monitoring for an electric bicycle is used as a case study to validate the proposed scheme, when driven in flat and sloped routes to generate different usage profiles. It is demonstrated that the proposed methodology allows to successfully prognosticate both SOC and SoMPA when the future discharge current profile is characterized in terms of probability-based models.

Intermetallics for Anodes in Li-Ion Batteries: Sb-Sn-Ti Alloys

Li-ion batteries (LIBs) are most frequently used in various handheld devices such as notebooks, cell phones or cameras. However, for load leveling and electro-mobility applications, key performance indicator parameters such as specific capacity, volumetric energy and power density, cyclability, lifetime, and safety have to be improved. In this regard, new electrode materials have to be designed for the next generation of LIBs. Among possible candidates for anode materials are intermetallic alloys which show significantly higher theoretical capacities than the currently used graphite. Additionally, such intermetallics are expected to be safer than graphite due to their higher lithiation potentials, which are sufficient to avoid the dendritic growth of lithium during charge.Many metals and alloys are able to form intermetallic phases with Li. For example, when Li17Sn4 is generated via lithiation of Sn, a theoretical charge capacity of 982 mAh per gram of Sn is obtained at the maximum Li-concentration of 81.31 at.% Li [1] (compare to 372 mAh per gram of carbon). A serious drawback of metallic active anode materials, however, is the mechanical degradation of the electrode upon cycling and the resulting short lifetime of the cell. The main reason for this is the embrittlement caused by the large volume changes on lithiation/delithiation (>180 %) starting from pure Sn. There are many attempts to overcome this phenomenon by, for example, adding carbonaceous fillers, using partial liquid intermetallic electrodes which show self-healing effects, or taking advantage of the in-situ precipitation of inactive matrix phases on lithiation. The latter can be achieved using multi-component Sb-Sn-Ti alloys instead of the pure metals Sb, Sn or binary Sb-Sn compounds. In such cases, full lithiation leads to the formation of Li3Sb and Li7Sn2 islands distributed in a fine grained inactive Ti-matrix. On de-lithiation, however, nano-crystalline Sb-Ti and Sn-Ti compounds are expected to form [2,3]. The Ti-based matrix buffers the volume expansion, mechanically stabilizes the electrode material and even improves its electronic conductivity compared to, e.g. carbonaceous filler materials.For the targeted design of such anodes, a fundamental understanding of the phase constitution, chemical thermodynamics and structural features of Li-Sb-Sn-Ti alloys is desirable. These data provide us with valuable information on the compounds which are formed during lithiation including their structures, stabilities and phase equilibria. In order to fully describe the behavior of such complex ternary and quaternary materials systems, self-consistent thermodynamic descriptions developed using the calculation of phase diagrams (CALPHAD) method are necessary. Such assessments allow us to not only calculate and graphically represent the phase equilibria but also enables the prediction of the electrochemical performance via calculation of the temperature-dependent e.m.f values for both stable and metastable states of the electrode. However, the simulative and predictive qualities of the thermodynamic models rely heavily on the generation of comprehensive experimental data, which are required as inputs for the assessment of the modelling parameters.As a first step, we studied the phase relations and crystal structures in the ternary Sb-Sn-Ti and Li-Sb-Sn sub-systems by means of XRD, thermal analysis and SEM/EDX. Isothermal sections at different temperatures are presented as well as the crystal structure of new ternary compounds. Based on this information, selected Ti-Sb-Sn alloys were processed into electrodes and subjected to electrochemical testing vs Li+/Li via galvanostatic cycling, cyclic voltammetry, and titration. Additionally, ex-situ XRD was applied to study the structural changes of the electrode active materials during the lithiation process.[1] Reichmann T., Gebert C., Cupid D., J. Alloys Compd., 2017, 714, 593[2] Sougrati M.T., Fullenwarth J., Debenedetti A., Fraisse B., Jumas J.C., Monconduit L., J. Mater. Chem., 2011, 21, 1069[3] Marino C., Sougrati M.T., Gerke B., Pöttgen R., Huo H., Menetrier M., Grey C.P., Monconduit L., Chem. Mater., 2012, 24, 4735

Automotive battery pack manufacturing – a review of battery to tab joining

Automotive battery packs used for electromobility applications consist of a large number of individual battery cells that are interconnected. Interconnection of the battery cells creates an electrical and mechanical connection, which can be realised by means of different joining technologies. The adaption of different joining technologies greatly influences the central characteristics of the battery pack in terms of battery performance, capacity and lifetime. Selection of a suitable joining technology, therefore, involves several considerations regarding electrical and mechanical properties and an assessment of production and operational conditions. Particularly, during the operation of an electric vehicle, challenges and mutual dependencies of the electrical and mechanical system emerge. The present work provides an overview of interdisciplinary challenges occurring at joints which are exposed to electrical current with a strong focus on interconnecting batteries for electric cars. It summarizes common quality criteria for the joining technologies and recombines those with criteria deduced from an electrical engineering point of view. Scientific literature concerning different joining technologies in the field of battery manufacturing is discussed based on those criteria. The most common joining techniques are ultrasonic welding, wire bonding, force fitting, soldering, laser beam welding, and resistance welding. Besides those, friction stir welding, tungsten inert gas welding, joining by forming and adhesive bonding are presented.