The diploma thesis deals with electrode materials for lithium-ions accumulators, concretely layered materials prepared via new methods. The main objective of this work is dealing with new procedures prepare electrodes of newly developed layered electrode materials and subsequently their measure. Another challenge was a theoretical analysis of newly developed layered electrode materials for positive and negative electrodes and their preparation of new procedures. In this work the detailed procedures for the preparation of individual electrodes, electrolytes and other issues associated with these preparations. There were describing batteries of general, primary and secondary lithium cells, fuel cells, Lithium-ion batteries, layered materials forming the electrodes and of course the history these cells. Practical work is focused on separate measurements layered electrode materials prepared by new processes and assessment of results for individual layered materials. In the practical part has been made that the newly prepared layered electrode materials offer higher capacity and voltage.

This thesis is interested in new materials for lithium – ion batteries. Two different samples were investigated, one intercalation and one conversion cathode material. The theoretical part is focused to the structure of cells, their advantages and disadvantages compared to other secondary batteries. Also other materials used in batteries are described. The practical part describes the preparation of cathode materials for subsequent testing by scanning elektron microscopy and thermogravimetric analysis. In conclusions two different materials were evaluated and compared with each other.

Les travaux présentés portent sur l’étude du HNBR (Hydrogenated Nitrile Butadiene Rubber), un polymère à base d’acrylonitrile, pour son application en tant que liant d’électrodes dans les batteries lithium ions. Cette thèse repose sur un partenariat avec l’entreprise Hutchinson (spécialisée dans le domaine des polymères) qui a cherché à développer un nouveau procédé pour la fabrication des électrodes. Ce procédé par voie fondue a soulevé la problématique du polymère liant utilisé dans les électrodes puisque ce dernier doit être compatible avec le procédé tout en étant utilisable dans des batteries. C’est dans l’optique de trouver et valider un tel polymère que s’inscrit cette thèse sur le polymère HNBR. En premier lieu, nous nous sommes concentrés sur les répercussions du traitement thermique, étape importante du procédé par voie fondue, sur le HNBR. Il a été conclu que le traitement thermique conduit à une réticulation du polymère aidant ainsi à la stabilité chimique du HNBR dans les électrolytes organiques des batteries. Ensuite, le HNBR a été introduit comme liant d’électrodes et a été analysé, avec le procédé de fabrication classique puis avec le nouveau procédé. Nous avons remarqué que le HNBR est un bon candidat pour être utilisé dans un système électrochimique car il y est stable sur une large gamme de potentiels et permet d’obtenir des performances en cyclage et en puissance intéressantes. Face à ce constat, la dernière partie des travaux s’est concentrée sur une analyse approfondie du système en étudiant les interactions entre les fonctions polaires du HNBR, les nitriles, et les ions lithium présents dans l’électrolyte. La combinaison polymère-sel-solvant a été étudiée pour comprendre comment chacun de ces paramètres impacte les propriétés électrochimiques du système et en particulier la conductivité. Nous avons remarqué qu’un taux d’acrylonitrile élevé est favorable à une plus haute conductivité et que le solvant, de par son affinité avec le HNBR, est également à considérer. / In this thesis, we have investigated an acrylonitrile-based polymer, HNBR (Hydrogenated Nitrile Butadiene Rubber), for its application in lithium ion batteries. This work relies on a partnership with the company Hutchinson (specialized in polymers) who was interested in developing a new process for the fabrication of electrodes. This melt-based process revealed problems regarding the polymer that is used as a binder for the electrodes as it needs to be compatible with the process as well as with the application in batteries. The aim of the thesis was therefore to find and validate a polymer meeting these requirements. Hence, HNBR was investigated. At first, we focused on the thermal treatment of HNBR, a key step of the melt-process. It was concluded that the thermal treatment leads to the cross-linking of HNBR, which is an asset because it increases the chemical stability of HNBR in the presence of the organic electrolyte. The following step was to introduce HNBR into the electrode formulation and investigate the performances of electrodes, made with the classical process and then with the melt process. It was found that HNBR is a good candidate to be introduced in an electrochemical system because it is stable over wide potential ranges and it allows interesting cycling and power performance. Faced with these findings, the last part of the study was to focus on analyzing the system more deeply by investigating the interactions between the HNBR polar functions, nitriles, and the lithium ions from the electrolyte. The ternary system polymer-salt-solvent was analyzed to understand the impact of each of these parameters on electrochemical properties, especially the conductivity. We noticed a high acrylonitrile content was beneficial to have a higher conductivity and that the solvent, regarding its affinity with HNBR, needs also to be considered.

Development of microsized batteries plays an important role in the design of in-situ electrochemical investigation systems and portable/wearable electronics. This emerging field intimately correlates with the topics of rechargeable batteries, nanomaterials, on-chip microfabrication, flexibility with reliable mechanical properties etc. Among the various energy materials, conversion-type materials have been proposed as high-energy-density alternatives to traditional intercalation-based materials. However, these materials usually show complex reaction processes accompanied by multi-reaction intermediates, which poses a great challenge to understand the chemical mechanisms. Benefiting from the merits of microsized battery devices, we develop a novel strategy to investigate and then optimize the electrochemical performance of a specific conversion-type material: nickel-iron oxide (NFO). Subsequently, this kind of materials are employed for flexible minimized energy storage systems. Unlike traditional characterization methods based on slurry-coated electrodes, micro-platforms directly probe the intrinsic electrochemical properties of a single active material in real-time due to the elimination of other additives. In this thesis, we firstly design a micro-lithium batteries (MLBs), based on a single “Swiss-roll” microtubular nanomembrane electrode. This platform enables us to investigate the electrochemical mechanisms of electrode materials in lithium batteries by in-situ Raman spectroscopy, electrical conductivity measurements, and electrochemistry characterization. With this designed MLBs, we systematically studied NFO nanomembranes. Using in-situ Raman spectroscopy during the delithiation/lithiation process, we monitored the transition of the chemical component directly. Guided by our investigations of micro-batteries, composite NFO nanomembrane electrodes were fabricated and tested in coin cells, which showed an excellent rate performance: 440 mAh g-1 at a high rate of 20 A g-1 and a long-term stable cycling performance over 1600 cycles. One step further, a flexible energy storage micro-device is achieved using such optimized materials. We demonstrate a thin, lightweight, and flexible micro-full lithium-ion battery based on nickel-iron oxide with a high-rate performance and energy density that can be repeatedly bent to 180° without structural failure and performance loss. It delivers a stable output capacity of 140 mAh g-1 over 1000 charge/discharge cycles. Meanwhile, the excellent rate performance guarantees high energy output up to 255 W h kg-1 at a high power density of 12000 W kg-1 at the microscale.

Ökad miljömedvetenhet ökar anpassningen till ett klimatsmart samhälle där helt eller delvis elektriska bilar blivit populära. Med ökat antal elektriska bilar på vägarna tillkommer risker, som tidigare inte funnits, i form av litium-jonbatterier. Elfordon målas upp som en stor brandrisk men är det korrekt?  Vid brand i ett parkeringsgarage under mark finns flera försvårande förutsättningar när räddningstjänsten ska utföra insats. Vid elfordonsbrand i parkeringsgarage under mark ökar komplexiteten ytterligare. På grund av begränsad forskning är osäkerheten fortfarande stor exempelvis om räddningstjänstens larmställ står emot toxisk brandrök, speciellt det farliga ämnet vätefluorid, som bildas vid elfordonsbrand.  Räddningstjänsten saknar tydliga riktlinjer för elfordonsbrand i parkeringsgarage under mark vilket är ett problem som behöver belysas och utredas. Arbetet omfattar en litteraturstudie, enkätundersökning och intervjustudie.  Medvetenheten om eventuella risker med elfordonsbrand i parkeringsgarage under mark är stor. Kunskapen hur riskerna ska hanteras vid insats är däremot bristfällig. Med högre befattning på räddningstjänsten och utbildningskrav höjs generellt kunskapsnivån. Oberoende om en person arbetar på räddningstjänstförbund, enskild kommuns räddningstjänst eller arbetsbefattning har individuellt intresse stor inverkan på personens kunskapsnivå kring elfordonsbrand. Resultatet av enkätundersökning och intervjustudie åskådliggjorde att riktlinjer för elfordonsbrand i parkeringsgarage under mark förekom i mindre utsträckning inom svensk räddningstjänst. Istället uppgav vissa räddningstjänster att allmänna riktlinjer för elfordonsbrand förekom och dessa kan appliceras på efterfrågat scenario.  Slutsatsen av utfört arbete är att nationell riktlinje för elfordonsbrand behöver upprättas. Riktlinjen bör inte vara specificerad till elfordonsbrand i parkeringsgarage under mark utan allmänt skriven. Myndigheten för samhällsskydd och beredskap bör som styrande organ leda samverkan med svensk räddningstjänst för upprättandet av nationell riktlinje.  Önskan med arbetets resultat är att belysa kunskapsbristen med förhoppning att berörda parter tar ansvar för att höja befintlig kunskapsnivå. Vidare att framtagandet av nationell riktlinje kring elfordonsbrand genomförs. För att möjliggöra detta behövs mer och ny forskning.  På grund av arbetet omfattning fanns inte möjlighet att undersöka innehåll och utformning av eventuell framtida riktlinje. Vid fortsatt arbete är detta något som bör undersökas. Befintliga riktlinjer kring elfordonsbrand i parkeringsgarage under mark bör också studeras vidare. / With increased environmental awareness the adaption to a more sustainable society with electrical and part-electrical vehicles have become more popular. With an increasing number of electrical vehicles, new risks have appeared on the roads in the form of lithium-ion batteries. Electrical vehicles are considered a major risk, but is this assumption completely true?  There are several aggravating conditions for the fire department in the event of underground parking garage fires. The involvement of an electrical vehicle will make the firefighting event more complex. Due to limited research there still is a great deal of uncertainties about the toxic fumes from fires in electrical vehicles. One example the performance of the fire fighters' clothing to resist the toxic gas hydrogen fluoride; many others exist.  The lack of guidelines for the fire department regarding electrical vehicle fires in underground parking garages needs to be highlighted and investigated further. The methods used in the report include literature studies, surveys, and interviews.  Awareness of the potential risks when electrical vehicles are burning in underground parking garages is satisfactory. On the other hand, the knowledge of how to manage these incidents is inadequate. The level of knowledge is generally higher when personnel on the fire department have a higher position with associated qualification requirements. It does not matter if a person works in a fire department in a union or if it’s driven by one county for the level of knowledge. Each individual's interest in the subject have influence over a person’s knowledge.  The survey and interviews illustrated that specific guidelines regarding fire in electrical vehicles in underground parking garages have minimal occurrence in the Swedish Fire Department. Instead, some fire departments declared that general guidelines for fires in electrical vehicles exists. These general guidelines can therefore be adapted to address fires in electrical vehicles in underground parking garages.  This study concludes that national guidelines need to be established. The guidelines should not be specific to electrical vehicle fires in underground parking garages. Instead they should be written in a general and broad representation to encompass electric vehicle fires. National guidelines should be developed by The Swedish Civil Contingencies Agency (MSB) in cooperation with the Swedish rescue services.  The desire with this report is to highlight the perceived lack of knowledge amongst stakeholders and for those involved to take responsibility to improve the existing knowledge platform. Further, it is suggested that national guidelines to be considered and potentially developed for fires involving electrical vehicles. To accomplish this additional research is needed as well as a broader understanding of electric car components and the considerations for firefighting.  The intention of this report was not to analyze the implementation of a national guideline regarding firefighting, building and parking design standards, fire mitigation efforts, etc. related to electric vehicles. As mentioned above, additional research for adapting a national study would be worthy for further consideration. Lastly, existing guidelines and standards should be further studied in order to modify and adopt to the changing landscape impacting electric vehicle use.

<p>Electrospinning has gained immense interests in recent years due to its potential application in various fields, including energy storage application. The V₂O₅/GO as a layered crystal structure has been demonstrated to fabricate nanofibers with diameters within a range of ~300nm through electrospinning technique. The porous, hollow, and interconnected nanostructures were produced by electrospinning formed by polymers such as Polyvinylpyrrolidone (PVP) and Polyvinyl alcohol (PVA), separately, as solvent polymers with electrospinning technique. </p> <p> </p> <p>In this study, we investigated the synthesis of a graphene-modified nanostructured V₂O₅ through modified sol-gel method and electrospinning of V₂O₅/GO hybrid. Electrochemical characterization was performed by utilizing Arbin Battery cycler, Field Emission Scanning Electron Microscopy (FESEM), X-ray powder diffraction (XRD), Thermogravimetric analysis (TGA), Mercury Porosimetery, and BET surface area measurement. </p> <p> </p> <p>As compared to the other conventional fabrication methods, our optimized sol-gel method, followed by the electrospinning of the cathode material achieved a high initial capacity of <b>342 mAh/g</b> at a high current density of 0.5C (171 mA/g) and the capacity retention of ~80% after 20 cycles. Also, the prepared sol-gel method outperforms the pure V₂O₅cathode material, by obtaining the capacity almost two times higher.</p> <p>The results of this study showed that post-synthesis treatment of cathode material plays a prominent role in electrochemical performance of the nanostructured vanadium oxides. By controlling the annealing and drying steps, and time, a small amount of pyrolysis carbon can be retained, which improves the conductivity of the V₂O₅ nanorods. Also, controlled post-synthesis helped us to prevent aggregation of electro-spun twisted nanostructured fibers which deteriorates the lithium diffusion process during charge/discharge of batteries.</p>

Die wachsende Weltbevölkerung und die stetigen Entwicklungen in der Industrie benötigen einerseits immer größere Mengen an Grundchemikalien und führen andererseits zu einem ständig steigenden Energiebedarf. Die Dissertation behandelt daher die Themen Zeolithe und Kathodenmaterialien, welche zwei aktuelle Forschungsschwerpunkte der chemischen Industrie darstellen. Der Fokus der Arbeit lag in der Steuerung der Partikelgröße durch die hydrothermale und mikrowellenunterstützte Kristallisation.

The battery is a component with significant impact on both the cost and environmental footprint of a full electric vehicle (EV). Consequently, there is a strong motivation to maximize its degree of utilization. Usage limits are enforced by the battery management system (BMS) to ensure safe operation and limit battery degradation. The limits tend to be conservative to account for uncertainty in battery state estimation as well as changes in the battery's characteristics due to aging. To improve the utilization degree, aging sensitive battery control is necessary. This refers to control that a) adjusts during the battery's life based on its state and b) balances the trade-off between utilization and degradation according to requirements from the specific application.  In state-of-the-art battery installations, only three signals are measured; current, voltage and temperature. However, the battery's behaviour is governed by other states that must be estimated such as its state-of-charge (SOC) or local concentrations and potentials. The BMS therefore relies on models to estimate states and to perform control actions. In order to realize points a) and b), the models that are used for state estimation and control must be updated onboard. An updated model can also serve the purpose of diagnosing the battery, since it reflects the changing properties of an aging battery. This thesis investigates identification of physics-based and empirical battery models from operational EV data. The work is divided into three main studies. 1) A global sensitivity analysis was performed on the parameters of a high-order physics-based model. Measured current profiles from real EV:s were used as input and the parameters' impact on both modelled cell voltage and other internal states was assessed. The study revealed that in order to excite all model parameters, an input with high current rates, large SOC span and longer charge or discharge periods was required. This was only present in the data set from an electric truck with few battery packs. Data sets from vehicles with more packs (electric bus) and limited SOC operating window (plug-in hybrid truck) excited fewer model parameters. 2) Empirical linear-parameter-varying (LPV) dynamic models were identified on driving data. Model parameters were formulated as functions of the measured temperature, current magnitude and estimated open circuit voltage (OCV). To handle the time-scale differences in battery voltage response, continuous-time system identification was employed. We concluded that the proposed models had superior predictive abilities compared to discrete and time-invariant counterparts.  3) Instead of using driving data to parametrize models, we also investigated the possibility to design the charging current in order to increase its information content about model parameters. This was formulated as an optimal control problem with charging speed and information content as objectives. To also take battery degradation into account, constraints on polarization was included. The results showed that parameter information can be increased without significant increase in charge time nor aging related stress. / Elekriska fordon utgör en allt större andel av världens fordonsflotta. Batteriet är en komponent med betydande påverkan både på fordonets kostnadoch dess miljö- och klimatpåverkan. Det är därför viktigt att försöka maximera batteriets utnytjandegrad. Användargränser upprätthålls av batterietsstyrsystem, såkallad BMS, för att garantera säker drift samt för att begränsabatteriets åldrande. Användargränserna tenderar att vara konservativa för attta höjd för osäkerhet i tillståndsestimeringen samt batteriets förändrade egenskaper under dess livstid. För att utöka utnyttjandegraden är ålderskänsligstyrning nödvändig. Med detta avses styrning som a) justeras under batterietslivstid och b) balancerar utnyttjande och prestanda på ett sätt som passar enspecifik applikation. Ombord på fordon mäts typiskt tre signaler; ström, spänning och temperatur. Batteriets beteende bestäms dock av andra tillstånd som måste estimeras, såsom dess laddnivåeller lokala koncentrationer och potentialer. BMS:enförlitar sig därför på modeller för att estimera interna tillstånd och utföra styrning. För att uppfylla punkterna a) och b) måste modellerna som användsuppdateras ombord i takt med att batteriet åldras. En uppdaterad modellkan också fungera som ett diagnostiskt verktyg eftersom det speglar batteriets förändrade egenskaper. Den här avhandlingen undersöker identifieringav fysikbaserade och empiriska modeller från kördata. Arbetet delas in i treseparata studier. 1) En global känslighetsanalys utfördes på parametrarna i en fysikbaseradmodell av hög ordning. Som inputsignal användes uppmätt ström från riktigaelfordon i drift. Parametrarnas effekt på både cellspänning och interna batteritillstånd analyserades. Studien visade att alla modellparametrar exciteradesav strömmen från ett helelektriskt fordon. Anledningen var att batteriernaanvändes inom ett brett SOC spann samt att den dragna strömmen var stor.I fordon med snävare SOC span och lägre strömmar var inte alla parametrarkänsliga. 2) Dynamiska parametervarierande modeller formulerades och identifierades från kördata. Den uppmätta temperaturen, samt strömmens storlekoch den estimerade tomgångsspänningen (OCV) användes till parameterberoenden. För att hantera skillnader i tidsskala mellan spänningssvarets olikakomponenter användes systemidentifiering i kontinuerlig tid. Vi kunde draslutsatsen att de föreslagna modellerna var överlägsna motsvarande diskretaoch konstanta modeller. 3) Istället för att använda kördata för att parametrisera modeller undersökte vi också möjligheten att designa laddförloppet för att öka dess informationsinnheåll. Detta formulerades som ett optimeringsproblem med laddtidoch informationsinnehåll i kostnadsfunktionen. För att även ta batteriets åldrande i beaktning, ansattses bivillkor på polariseringsspänningen. / <p>QC 20220516</p>

Self-activation is a process that takes advantage of the gases emitted from the pyrolysis process of biomass to activate the converted carbon. The pyrolytic gases from the biomass contain CO2 and H2O, which can be used as activating agents. As two common methods, both of physical activation using CO2 and chemical activation using ZnCl2 introduce additional gas (CO2) or chemical (ZnCl2), in which the CO2 emission from the activation process or the zinc compound removal by acid from the follow-up process will cause environmental concerns. In comparison with these conventional activation processes, the self-activation process could avoid the cost of activating agents and is more environmentally friendly, since the exhaust gases (CO and H2) can be used as fuel or feedstock for the further synthesis in methanol production. In this research, many types of biomass were successfully converted into activated carbon through the self-activation process. An activation model was developed to describe the changes of specific surface area and pore volume during the activation. The relationships between the activating temperature, dwelling time, yield, specific surface area, and specific pore volume were detailed investigated. The highest specific surface area and pore volume of the biomass-derived activated carbon through the self-activation process were up to 2738 m2 g-1 and 2.209 cm3 g-1, respectively. Moreover, the applications of the activated carbons from the self-activation process have been studied, including lithium-ion battery (LIB) manufacturing, water cleaning, oil absorption, and electromagnetic interference (EMI) shielding.

Bei der Assemblierung von Lithium-Ionen-Batterien ist ein zentraler Arbeitsschritt die Herstellung der elektrischen Verbindung von einzelnen Lithium-Ionen-Zellen in Reihen- und/oder Parallelschaltung. Dazu kommen in der Regel Überlappschweißverbindungen aus Blechen mit Dicken von unter 2 mm zum Einsatz. Typischerweise werden Eisen-, Aluminium- und Kupferwerkstoffe genutzt. Dieser Produktionsschritt ist wegen der Wichtigkeit für die gesamte Batteriefunktion in seiner Qualität zu überwachen. Im Rahmen dieser Arbeit wird ein dafür geeignetes Verfahren identifiziert. Es wurden Ultraschallprüfverfahren, Durchstrahlungsverfahren, die Messung des elektrischen Widerstands sowie thermografische Verfahren auf ihre Eignung zur Prüfung derartiger Überlappschweißverbindungen hin untersucht. Dabei zeigte sich, dass die nach dem Stand der Technik verfügbaren Verfahren im betrachteten Anwendungsfall wegen unzureichender Zugänglichkeit, mangelnder Fähigkeit der Fehlerdetektion oder wirtschaftlicher Gründe häufig nur eingeschränkt einsetzbar sind. Demzufolge war ein neues Verfahren zur Prüfung der Schweißnähte zur elektrischen Verbindung von Zellen zu entwickeln. Als Ansatz wurde die optisch angeregte Thermografie gewählt. Diese konnte erfolgreich eingesetzt werden, wenn ein Laser zur Anregung sowie eine Photonendetektorkamera zur Detektion genutzt wurde. Durch die Anwendung der Lockin-Thermografie konnten Rauscheinflüsse auf die Messung minimiert werden. Es konnte gezeigt werden, dass Lockin-Messungen auch dann ausgewertet können, wenn das gemessene Temperatursignal neben einer harmonischen Schwingung und Rauschen einen stetigen Temperaturtrend aufweist. Die Anwendung von im Rahmen der Arbeit entwickelten Abschirmelementen, die für die Anregungsstrahlung transparent und die von der genutzten Kamera erfassten Strahlung undurchlässig sind, erlaubte die Prüfung metallischer Schweißverbindung in der Nähe von hochabsorptiven Flächen. Unter Nutzung eines neu entwickelten Auswertealgorithmus, der auf die Kompensation des Effekts lateraler Wärmeflüsse im untersuchten Bauteil zielt, konnte die Ergebnisqualität der Thermografie hinsichtlich einer besseren optischen Korrelation der Ergebnisbilder zu Referenzprüfungen sowie einer verringerten Messunsicherheit der angebundenen Fläche verbessert werden. Insgesamt zeigte sich das Verfahren in seiner weiterentwickelten Form als für die Prüfung tauglich.:1 Einleitung 1.1 Motivation und Ziel 1.2 Einführung in die Arbeit 2 Stand der Technik 2.1 Lithium-Ionen-Batterien für Elektrofahrzeuge 2.1.1 Lithium-Ionen-Batterien im Vergleich zu anderen Energiespeichern in der Elektromobilität 2.1.2 Aufbau und Funktion von Lithium-Ionen-Batterien 2.2 Fertigungstechnik der Kontaktierung von Lithium-Ionen-Zellen 2.2.1 Kontaktierung von Lithium-Ionen-Zellen 2.2.2 Schweißverfahren zur Kontaktierung von Lithium-Ionen-Zellen 2.3 Schweißnahtanforderungen und -fehler 2.4 Zerstörungsfreie Prüfung von Kontaktierverbindungen 2.4.1 Qualitätssicherung von Kontaktierverbindungen 2.4.2 Anforderungen an zerstörungsfreie Prüfverfahren 2.4.3 Ultraschallprüfung 2.4.4 Durchstrahlungsprüfung 2.4.5 Messung des elektrischen Widerstands 2.4.6 Oberflächenprüfung 2.4.7 Infrarotthermografie 3 Vorauswahl eines geeigneten Verfahrens der zerstörungsfreien Prüfung 3.1 Untersuchte Verfahren 3.2 Ultraschallverfahren 3.3 Durchstrahlungsverfahren 3.4 Messung des elektrischen Widerstands 3.5 Infrarotthermografie 3.6 Verfahrensauswahl 4 Anwendung der optisch angeregten Thermografie zur Schweißnahtprüfung 4.1 Herausforderungen bei der Messung von Kontaktierschweißverbindungen von Lithium-Ionen-Batterien 4.2 Narzisseffekt und Perspektivenkorrektur 4.3 Techniken der optischen Anregung 4.4 Signalaufbereitung durch Lockin-Verfahren 4.4.1 Lockin-Thermografie 4.4.2 Lockin-Thermografie im Nicht-Gleichgewichtszustand 5 Unterdrückung des Einflusses von Reflexionen bei der thermografischen Prüfung von Kontaktierverbindungen 5.1 Hintergrund 5.2 Lösungsansatz 5.3 Werkstoffauswahl 5.4 Erprobung 6 Kompensation des Einflusses lateraler Wärmeströme 6.1 Mehrdimensionaler Wärmefluss 6.2 Simulation des Einflusses lateraler Wärmeströme 6.2.1 Simulationsmodell 6.2.2 Simulationsresultate 6.3 Entwicklung eines Kompensationsalgorithmus 6.3.1 Ansatz 6.3.2 Ergebnis 6.3.3 Sensitivitätsanalyse 6.3.4 Fazit der simulativen Untersuchung des Kompensationsalgorithmus 6.4 Umsetzung und Verifikation des Kompensationsalgorithmus 6.4.1 Untersuchte Proben 6.4.2 Emissionsgradmessung 6.4.3 Ergebnisqualität 6.4.4 Grenzen des Algorithmus 7 Zusammenfassung 8 Ausblick / The electrical connection of a multitude of lithium-ion cells is of high importance for producing lithium-ion batteries. These connections are usually carried out with lap welds of steel, aluminium and copper sheets with a thickness of less than 2 mm. Due to its importance the electrical connection should be subject to non-destructive evaluation. Therefore, a suitable method was identified to evaluate the electrical connection. Technologies based on ultrasonic, radiographic and thermographic evaluation as well as measurement of electrical resistance have been studied regarding their potential to non-destructively test aforementioned lap welds. It was found that in the studied case state of the art technologies are limited by restraints regarding accessibility, cycle time and detectability of ctitical flaws. Therefore, a new technique for non-destructive testing of lap welds between cell connections, had to be be defined. Optically excited thermography was considered a promising approach. Optically excited thermography was applied successfully using a laser as excitation source and a photon detector camera to record infrared radiation. The application of the lock-in principle allowed significant noise reduction. It was shown that the evaluation of temperature sequences using the lock-in algorithm does not depend on a temperature signal that shows strict harmonic behaviour but could also be applied when the raw temperature sequence incorporated a trend. The application of newly developed radiation shields, which are transparent to the wavelengths of the excitation signal, but opaque to the wavelengths of infrared detection, allowed thermographic testing of metal surfaces in proximity to highly absorbing surfaces. A new algorithm was developed for evaluating thermographic sequences aimed at reducing the impact of lateral thermal flux. It was proven to increase the quality of thermographic results in terms of visual correlation to reference technologies and measurement uncertainty of the joined area. Overall, the improved technology was found to be feasible for non-destructive testing of lap welds in lithium-ion batteries.:1 Einleitung 1.1 Motivation und Ziel 1.2 Einführung in die Arbeit 2 Stand der Technik 2.1 Lithium-Ionen-Batterien für Elektrofahrzeuge 2.1.1 Lithium-Ionen-Batterien im Vergleich zu anderen Energiespeichern in der Elektromobilität 2.1.2 Aufbau und Funktion von Lithium-Ionen-Batterien 2.2 Fertigungstechnik der Kontaktierung von Lithium-Ionen-Zellen 2.2.1 Kontaktierung von Lithium-Ionen-Zellen 2.2.2 Schweißverfahren zur Kontaktierung von Lithium-Ionen-Zellen 2.3 Schweißnahtanforderungen und -fehler 2.4 Zerstörungsfreie Prüfung von Kontaktierverbindungen 2.4.1 Qualitätssicherung von Kontaktierverbindungen 2.4.2 Anforderungen an zerstörungsfreie Prüfverfahren 2.4.3 Ultraschallprüfung 2.4.4 Durchstrahlungsprüfung 2.4.5 Messung des elektrischen Widerstands 2.4.6 Oberflächenprüfung 2.4.7 Infrarotthermografie 3 Vorauswahl eines geeigneten Verfahrens der zerstörungsfreien Prüfung 3.1 Untersuchte Verfahren 3.2 Ultraschallverfahren 3.3 Durchstrahlungsverfahren 3.4 Messung des elektrischen Widerstands 3.5 Infrarotthermografie 3.6 Verfahrensauswahl 4 Anwendung der optisch angeregten Thermografie zur Schweißnahtprüfung 4.1 Herausforderungen bei der Messung von Kontaktierschweißverbindungen von Lithium-Ionen-Batterien 4.2 Narzisseffekt und Perspektivenkorrektur 4.3 Techniken der optischen Anregung 4.4 Signalaufbereitung durch Lockin-Verfahren 4.4.1 Lockin-Thermografie 4.4.2 Lockin-Thermografie im Nicht-Gleichgewichtszustand 5 Unterdrückung des Einflusses von Reflexionen bei der thermografischen Prüfung von Kontaktierverbindungen 5.1 Hintergrund 5.2 Lösungsansatz 5.3 Werkstoffauswahl 5.4 Erprobung 6 Kompensation des Einflusses lateraler Wärmeströme 6.1 Mehrdimensionaler Wärmefluss 6.2 Simulation des Einflusses lateraler Wärmeströme 6.2.1 Simulationsmodell 6.2.2 Simulationsresultate 6.3 Entwicklung eines Kompensationsalgorithmus 6.3.1 Ansatz 6.3.2 Ergebnis 6.3.3 Sensitivitätsanalyse 6.3.4 Fazit der simulativen Untersuchung des Kompensationsalgorithmus 6.4 Umsetzung und Verifikation des Kompensationsalgorithmus 6.4.1 Untersuchte Proben 6.4.2 Emissionsgradmessung 6.4.3 Ergebnisqualität 6.4.4 Grenzen des Algorithmus 7 Zusammenfassung 8 Ausblick