Global warming and depletion in fossil fuels have forced the society to search for alternate, clean sustainable energy sources. An obvious solution to the aforesaid problem lies in electrochemical energy storage systems like fuel cells and batteries. The desirable properties attributed to these devices like quick response, long life cycle, high round trip efficiency, clean source, low maintenance etc. have made them very attractive as energy storage devices. Compared to many advanced battery chemistries like nickel-metal hydride and lithium - ion batteries, metal-air batteries show several advantages like high energy density, ease of operation etc. The notable characteristics of metal - air batteries are the open structure with oxygen gas accessed from ambient air in the cathode compartment. These batteries rely on oxygen reduction and oxygen evolution reactions during discharging and charging processes. The efficiency of these systems is determined by the kinetics of oxygen reduction reaction. Platinum is the most preferred catalyst for many electrochemical reactions. However, high cost and stability issues restrict the use of Pt and hence there is quest for the development of stable, durable and active electrocatalysts for various redox reactions. The present thesis is directed towards exploring the electrocatalytic aspects of titanium carbonitride. TiCN, a fascinating material, possesses many favorable properties such as extreme hardness, high melting point, good thermal and electrical conductivity. Its metal-like conductivity and extreme corrosion resistance prompted us to use this material for various electrochemical studies. The work function as well as the bonding in the material can be tuned by varying the composition of carbon and nitrogen in the crystal lattice. The current study explores the versatility of TiCN as electrocatalyst in aqueous and non-aqueous media. One dimensional TiC0.7N0.3 nanowires are prepared by simple one step solvothermal method without use of any template and are characterized using various physicochemical techniques. The 1D nanostructures are of several µm size length and 40 ± 15 nm diameter (figure 1). Orientation followed by attachment of the primary particles results in the growth along a particular plane (figure 2). (a) (b) (c) Figure 1. (a) SEM images of TiC0.7N0.3 nanowires (b) TEM image and (c) High resolution TEM image showing the lattice fringes. (a) (b) (d) Figure 2. Bright field TEM images obtained at different time scales of reaction. (a) 0 h; (b) 12 h; (c) 72 h and (d) 144 h. The next aspect of the thesis discusses the electrochemical performance of TiC0.7N0.3 especially for oxygen reduction. Electrochemical oxygen reduction reaction (ORR) reveals that the nanowires possess high activity for ORR and involves four electron process leading to water as the product. The catalyst effectively converts oxygen to water with an efficiency of 85%. A comparison of the activity of different (C/N) compositions of TiCN is shown in figure 3. The composition TiC0.7N0.3 shows the maximum activity for the reaction. The catalyst is also very selective for ORR in presence of methanol and thus cross-over issue in fuel cells can be effectively addressed. Density functional theory (DFT) calculations also lead to the same composition as the best for electrocatalysis, supporting the experimental observations. Figure 3. Linear sweep voltammetric curves observed for different compositions of titanium carbonitride towards ORR. The next chapter deals with the use of TiC0.7N0.3 as air cathode for aqueous metal - air batteries. The batteries show remarkable performance in the gel- and in liquid- based electrolytes for zinc - air and magnesium - air batteries. A partial potassium salt of polyacrylic acid (PAAK) is used as the polymer to form a gel electrolyte. The cell is found to perform very well even at very high current densities in the gel electrolyte (figures 4 and 5). Figure 4 Photographs of different components of the gel - based zinc - air battery. (a) (b) Figure 5. a) Discharge curves at different current densities of 5, 20, 50 and 100 mA/cm2 for zinc-air system with TiC0.7N0.3 cathode b) Charge – discharge cycles at 50 mA/cm2 for the three electrode configuration with TiC0.7N0.3 nanowire for ORR and IrO2 for OER and Zn electrode (2h. cycle period). Similarly, the catalytic activity of TiC0.7N0.3 has also been explored in non-aqueous electrolyte. The material acts as a bifunctional catalyst for oxygen in non- aqueous medium as well. It shows a stable performance for more than 100 cycles with high reversibility for ORR and OER (figure 6). Li-O2 battery fabricated with a non-aqueous gel- based electrolyte yields very good output. (a) (b) (c) Figure 6. Galvanostatic charge –discharge cycles. (a) at 1 mA/cm2 (b) specific capacity as a function of no. of cycles (c) photographs of PAN-based gel polymer electrolyte. Another reaction of interest in non –aqueous medium is I-/I3-. redox couple. TiC0.7N0.3 nanowires show small peak to peak separation, low charge transfer resistance and hence high activity. The catalyst is used as a counter electrode in dye sensitized a solar cell that shows efficiencies similar to that of Pt, state of the art catalyst (figure 7). (a) (b) (c) Figure 7 (a) Cyclic voltammograms for I-/I3 - redox species on TiC0.7N0.3 nanowires (red), TiC0.7N0.3 particle (black) and Pt (blue). (b) Photocurrent density - voltage characteristics for DSSCs with different counter electrodes. TiC0.7N0.3 nanowire (black), TiC0.7N0.3 particle (blue), Pt (red). (c) Photograph of a sample cell. (a) (b) (c) (d) Figure 8 a) Comparison ORR activity for (i) NiTiO3(black), (ii) N-rGO (red), (iii) NiTiO3 – N-rGO (green) and (iv) Pt/C (blue) (b) Linear sweep voltammograms for OER observed on NiTiO3 – N-rGO composite (black), NiTiO3 (brown), N-rGO (blue), glassy carbon (red) in 0.5 M KOH. (c) Galvanostatic discharge curves of NiTiO3 – N-rGO as air electrode (d) Charge – discharge cycle at 5 mA/cm2 for the rechargeable battery with 10 min. cycle period. The last part of the thesis discusses about a ceramic oxide, nickel titanate. The electrocatalytic studies of the material towards ORR and OER reveal that the catalyst shows remarkable performance as a bifunctional electrode. A gel - based zinc - air battery fabricated with nickel titanate – reduced graphene oxide composite shows exceptional performance of 1000 charge-discharge cycles in the rechargeable mode (figure 8). Of course, the primary battery configuration works very well too The thesis contains seven chapters on the aspects mentioned above with summary and future perspectives given as the last chapter. An appendix based on TiN nanotubes and supercapacitor studies is given at the end.

Le facteur clé limitant le déploiement des accumulateurs au lithium métal est dû à la formation de dendrites de lithium métallique à l'anode au cours de la recharge. Une solution consiste à employer un électrolyte solide polymère. Un copolymère à blocs est composé d'un ou plusieurs blocs conducteurs à base de POE (poly(oxyde d'éthylène)), linéaire ou branchée, dopés en sel de lithium (LiTFSI) et de blocs de renforts mécaniques qui idéalement mitigent la croissance dendritique. Ces matériaux ont la particularité de s'auto-assembler en domaines nanométriques. Les interfaces entre les domaines génèrent de bonnes propriétés mécaniques à l'échelle macroscopique tandis que localement la dynamique des chaînes POE demeure élevée, assurant la conduction ionique.Ce travail de thèse porte sur les caractérisations physico-chimiques d'électrolytes copolymères, selon différentes architectures (diblocs, triblocs et étoilées) et de l'optimisation de leurs compositions. Une étude fondamentale des polymères dopés en sel a mis en évidence les principaux mécanismes de transport ionique, ainsi que l'impact des groupes terminaux à faible masse molaire sur la conductivité et la viscosité. Cette étape a permis de sélectionner les meilleurs candidats. L'étude de la stabilité des électrolytes vis-à-vis du lithium a été menée. Après avoir formulé des cathodes, des batteries plastiques ont été assemblées et testées avec succès par cyclages galvanostatiques, en température [40°C-100°C] et à des régimes élevés. Enfin, un prototype de 6 mAh a réalisé plus de 400 cycles à des régimes C/4 et D/2 à 100°C. / The key limiting factor for the deployment of Lithium metal batteries is the formation of lithium dendrites at the anode during recharge. One solution consists in the use of a solid polymer electrolyte. A bloc copolymer is composed of one or several conductive blocks based on PEO (poly(ethylene oxide)), linear or branched, doped with a lithium salt (LiTFSI) and reinforced blocks that ideally mitigate the dendritic growth. These materials can self-organize in nanometric domains. The interfaces between the domains generate sufficient mechanical properties at the macroscopic level whilst, locally, the PEO chain dynamics remain high, ensuring ionic conduction.This thesis deals with physico-chemical characterizations of these copolymer electrolytes, with different architectures (diblock, triblock and star shaped), and the optimization of their composition. A fundamental study of doped polymers highlighted the main mechanisms of ionic transport and the impact of the end groups at low molar mass on conductivity and viscosity. This step enabled a selection of the best candidates to be made. A study of the electrolyte stability with respect to lithium was carried out. After the formulation of cathodes, plastic batteries were assembled and successfully tested by galvanostatic cycling under temperature [40°C-100°C] and high regime. Finally, a 6 mAh prototype realised more than 400 cycles under the regime C/4 and D/2 at 100°C.

Les matériaux dits de conversion à base de Sb et Sn, utilisés comme électrodes, apparaissent comme des composés particulièrement intéressants compte tenu de leur forte capacité théorique. Le matériau TiSnSb a été récemment développé en tant qu’électrode négative pour batteries lithium-ion. Ce matériau est capable d’accueilir, de façon réversible, 6,5 Li par unité formulaire, ce qui correspond à une capacité spécifique de 580 mAh/g. Dans le domaine des batteries lithium-ion, les propriétés de l’interface électrode/électrolyte (« solid electrolyte interphase », SEI), formant une couche de passivation protectrice à la surface des électrodes sont considérées comme essentielles pour les performances au sens large des batteries. Cet aspect représente le sujet majeur traité dans ce travail de thèse. Dans cet optique, nous avons tout d'abord étudié les propriétés électrochimiques de l'électrode TiSnSb sous divers aspects, dont les effets du régime de cyclage, l’influence de la nature des additifs au sein de l’électrolyte ainsi que l’utilisation de liquides ioniques à température ambiante (RTILs). En particulier, un système d'électrolyte à base de RTILs a été développé et optimisé vis-à-vis des performances électrochimiques. Afin de caractériser l’interface électrode-électrolyte, deux techniques de caractérisation majeures ont été utilisées : la Spectroscopie Photoélectronique à Rayonnement X (XPS) et la Spectroscopie d'Impédance électrochimique (EIS). Cette étude a permis de cibler certains paramètres essentiels liant les aspects performances électrochimiques à la nature de l’interface électrode-électrolyte. / In the past decades, the need for portable power has accelerated due to the miniaturization of electronic appliances. It continues to drive research and development of advanced energy systems, especially for lithium ion battery systems. As a consequence, conversion materials for lithium-ion batteries, including Sb and Sn-based compounds, have attracted much intense attention for their high storage capacities. Among conversion materials, TiSnSb has been recently developed as a negative electrode for lithium-ion batteries. This material is able to reversibly take up 6.5 Li per formula unit which corresponds to a specific capacity of 580 mAh/g. In the field of lithium-ion battery research, the solid electrolyte interphase (SEI) as a protective passivation film formed at electrode surface owing to the reduction of the electrolyte components, has been considered as a determinant factor on the performances of lithium-ion battery. Thus it has been a focused topic of many researches. However, little information can be found about the formation and composition of the SEI layer formed on TiSnSb conversion electrode at this time. With the aim to investigate the influences of the SEI layer on the performances of composite TiSnSb electrode, we first studied the electrochemical properties of the electrode from various aspects, including the effects of cycling rates, electrolyte additives, as well as room temperature ionic liquids (RTILs). Especially, a RTILs-based electrolyte system was developed and optimized by evaluating its physicochemical properties to be able to further improve the performances of TiSnSb electrode. In order to characterize the SEI layer formed at electrode surface, we performed X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). This study allowed to target some essential parameters concerning electrochemical performances linked with the nature of the solid electrolyte interphase.*

The magnificent development of on-board solutions for electronics has resulted in the race towards scaling down of autonomous micro-power sources. In order to maintain the reliability of miniaturized devices and to reduce the power dissipation in high density memories like CMOS RAM, localized power for such systems is highly desirable. Therefore these micro-power sources need to be integrated in to the electronic chip level, which paved the way for the research and development of rechargeable thin film batteries (TFB). A Thin film battery is defined as a solid-state electrochemical source fabricated on the same scale as and using the same type of processing techniques used in microelectronics. Various aspects of deposition and characterization of LiCoO2/LiPON/Sn thin film battery are investigated in this thesis. Prior to the fabrication of thin film battery, individual thin film layers of cathode-LiCoO2, electrolyte-LiPON and anode-Sn were optimized separately for their best electrochemical performance. Studies performed on cathode layer include theoretical and experimental aspects of deposition of electrochemically active LiCoO2 thin films. Mathematical simulation and experimental validation of process kinetics involved in sputtering of a LiCoO2 compound target have been performed to analyze the effect of process kinetics on film stoichiometry. Studies on the conditioning of a new LiCoO2 sputtering target for various durations of pre-sputtering time were performed with the help of real time monitoring of glow discharge plasma by OES and also by analysing surface composition, and morphology of the deposited films. Films deposited from a conditioned target, under suitable deposition conditions were electrochemically tested for CV and charge/discharge, which showed an initial discharge capacity of 64 µAh/cm2/µm. Studies done on the deposition and characterization of solid electrolyte layer-LiPON have shown that, sputtering from powder target can be useful for certain compounds like Li3PO4 in which breaking of ceramic target and loss of material are severe problems. An ionic conductivity of 1.1 x10-6 S/cm was obtained for an Nt/Nd ratio of 1.42 for a RF power density of 3 W/cm2 and N2 flow of 30 sccm. Also the reasons for reduction in ionic conductivity of LiPON thin films on exposure to air have been analyzed by means of change in surface morphology and surface chemistry. Ionic conductivity of 2.8 x10-6 S/cm for the freshly deposited film has dropped down to 9.9 x10-10 S/cm due to the reaction with moisture, oxygen and carbon content of exposed air. Interest towards a Li-free thin film battery has prompted to choose Sn as the anode layer due to its relatively good electrochemical capacity compared with other metallic thin films and ease of processing. By controlling the rate of deposition of Sn, thin films of different surface morphology, roughness and crystallinity can be obtained with different electrochemical performance. The reasons for excessive volume changes during lithiation/delithiation of a porous Sn thin film have been analyzed with the aid of physicochemical characterization techniques. The results suggest that the films become progressively pulverized resulting in increased roughness with an increase in lithiation. Electrochemical impedance data suggest that the kinetics of charging becomes sluggish with an increase in the quantity of Li in Sn-Li alloy. Thin film batteries with configuraion LiCoO2/LiPON/Sn were fabricated by sequential sputter deposition on to Pt/Si substartes. Pt/Cu strips were used as the current collector leads with a polymer packaging. Electrochemical charge/discharge studies revealed discharge capacities in the range 6-15 µAh/cm2/µm with hundreds of repeated cycles. TFB with a higher capacity of 35 µAh/cm2/µm suffered capacity fade out after 7 cycles, for which reasons were analyzed. The surface and cross-sectional micrographs of cycled TFB showed formation of bubble like features on anode layer reducing integrity of electrolyte-anode interface. The irreversible Li insertion along with apparent surface morphology changes are most likely the main reasons for the capacity fade of the LiCoO2/LiPON/Sn TFB.

Multifunctional batteries with enhanced safety performance have received considerable attention for their applications at extreme conditions. However, few batteries can endure a mix‐up of battery polarity during charging, a common wrong operation of rechargeable batteries. Herein, a polarity‐switchable battery based on the switchable intercalation feature of graphite is demonstrated. The unique redox‐amphoteric intercalation behavior of graphite allows a reversible switching of graphite between anode and cathode, thus enabling polarity‐switchable symmetric graphite batteries. The large potential gap between anion and cation intercalation delivers a high midpoint device voltage (≈average voltage) of ≈4.5 V. Further, both the graphite anode and cathode are kinetically activated during the polarity switching. Consequently, polarity‐switchable symmetric graphite batteries exhibit a remarkable cycling stability (96% capacity retention after 500 cycles), a high power density of 8.66 kW kg−1, and a high energy density of 227 Wh kg−1 (calculated based on the total weight of active materials in both anode and cathode), which are superior to other symmetric batteries and recently reported dual‐graphite or dual‐carbon batteries. This work will inspire the development of new multifunctional energy‐storage devices based on novel materials and electrolyte systems.

No description available.

The electrification within the automotive industry goes faster than ever, which drives an increased demand for more knowledge about batteries. Vehicle manufacturers should be able to tell how long the batteries will last and have a service program for electrified vehicles, just as there is for traditional, fuel-driven ones. Scania is in the process of developing new service methods for their hybrids and fully electrified vehicles where this thesis has been a part of this development by investigating the possibilities of having a workshop test to measure the capacity of the propulsion batteries.  During the thesis, essential parameters for cycling the batteries and measure the capacity with high accuracy have been identified and investigated by conducting lab tests. In parallel to defining the properties of a successful capacity measurement, the implementation of such a measurement at a workshop has been studied alongside a brief discussion about scheduling strategies. Conducting a capacity measurement in a workshop environment introduce new challenges, and the critical question arises, how long can the capacity measurement take? It is identified that the state of charge window size, the temperature, and the relaxation time are essential parameters to control. From the experimental part of the thesis, it can be concluded that the start temperature should lay in the range of 15-25 °C with a relaxation time of 5-10 minutes providing a satisfying accuracy. A SOC window size of 20-80% seems to be the most optimal balance between time spent and accuracy in the measurement. Furthermore, it is identified that the workshop's equipment is heavily influencing the time it takes to conduct a test. It is concluded that it is necessary to be able to charge and discharge the batteries. / Elektrifieringen av fordons industrin går snabbare än någonsin, vilket driver en högre efterfrågan på mer kunskap om batterier. Fordons tillverkare ska kunna redogöra för hur länge batterierna kan användas och ha ett service program för elektrifierade fordon, likt det som redan finns för traditionella, bränsledrivna fordon. Scania håller på att utveckla nya service metoder för sina hybrider och elektriska fordon där detta examensarbete har varit en del av denna utveckling genom att undersöka möjligheterna kring en verkstadsmetod för att mäta kapaciteten hos framdrivnings batterier.  Under examensarbetet har väsentliga parametrar för cykling av batterier och mätning av kapacitet med hög noggrannhet identifierats och undersökts med laboratorietester. Parallellt med arbetet för att definiera egenskaperna hos en precis kapacitets mätning har implementationen av en sådan mätning i en verkstad studerats tillsammans med en kort diskussion om strategier för schemaläggning av dessa tester. Det introducerar nya utmaningar att utföra kapacitets mätningen i en verkstad och den viktiga frågan uppstår, hur lång tid tar en sådan kapacitets mätning? Det har identifieras att SOC fönster storleken, temperaturen och relaxeringstiden är essentiella parametrar att kontrollera. Slutsatserna är att temperaturen bör ligga i intervallet 15-25 °C med en relaxeringstid på 5-10 minuter ger en tillfredställande noggrannhet. Ett SOC fönster motsvarande 20-80% är förefaller vara den mest optimala i avvägningen mellan tidsåtgång och precision. Vidare kan den tillgängliga utrustningen på verkstaden pekas ut som en starkt påverkande faktor till tiden det tar att utföra ett sådant verkstadstest.

The anode-free battery concept is proposed to pursue the aspiration of energy-dense, rechargeable metal batteries, but this has not been achieved with dual-ion batteries. Herein, the first anode-free Zn–graphite battery enabled by efficient Zn plating–stripping onto a silver-coated Cu substrate is demonstrated. The silver coating guides uniform Zn deposition without dendrite formation or side reaction over a wide range of electrolyte concentrations, enabling the construction of anode-free Zn cells. In addition, the graphite cathode operates efficiently under reversible bis(trifluoromethanesulfonyl)imide anion (TFSI−) intercalation without anodic corrosion. An extra high-potential TFSI− intercalation plateau is recognized at 2.75 V, contributing to the high capacity of graphite cathode. Thanks to efficient Zn plating–stripping and TFSI− intercalation–deintercalation, an anode-free Zn–graphite dual-ion battery that exhibits impressive cycling stability with 82% capacity retention after 1000 cycles is constructed. At the same time, a specific energy of 79 Wh kg−1 based on the mass of cathode and electrolyte is achieved, which is over two times higher than conventional Zn–graphite batteries (<30 Wh kg−1).

Depuis la mise en évidence des potentialités du phosphate LiFePO4 comme électrode positive de batteries lithium-ion, un très fort regain d'intérêt pour les phosphates de fer est actuellement observé. Dans cette optique de recherche de nouveaux matériaux, notre intérêt s'est porté sur la phase Na3Fe3(PO4)4 et sur des monophosphates de fer et de manganèse de type alluaudite LiXNa1-XMnFe2(PO4)3. Leurs structures, respectivement en couche et en chaines, en font de bons candidats pour des applications en tant que matériau d'électrode pour des batteries au lithium ou au sodium. Notre étude porte donc, d'une part, sur la synthèse et la caractérisation structurale de ces phases, et d'autre part sur leurs propriétés physiques et électrochimiques.

Crystalline polymer/salt complexes can conduct, in contrast to the view held for 30 years. The alpha-phase of the crystalline poly(ethylene oxide)₆:LiPF₆ is composed of tunnels formed from pairs of (CH₂-CH₂-O)ₓ chains, within which the Li⁺ ions reside and along which the latter migrate.¹ When a polydispersed polymer is used, the tunnels are composed of 2 strands, each built from a string of PEO chains of varying length. It has been suggested that the number and the arrangement of the chain ends within the tunnels affects the ionic conductivity.² Using polymers with uniform chain length is important if we are to understand the conduction mechanism since monodispersity results in the chain ends occurring at regular distances along the tunnels and imposes a coincidence of the chain ends between the two strands.² Since each Li⁺ is coordinated by 6 ether oxygens (3 oxygens from each of the two polymeric strands forming a tunnel), monodispersed PEOs with the number of ether oxygen being a multiple of 3 (NO = 3n) can form either “all-ideal” or “all-broken” coordination environments at the end of each tunnel, while for both NO = 3n-1 and NO = 3n+1 complexes, both “ideal” and “broken” coordinations must occur throughout the structure. A synthetic procedure has been developed and a series of 6 consecutive (increment of EO unit) monodispersed molecular weight PEOs have been synthesised. The synthesis involves one end protection of a high purity glycol, functionalisation of the other end, ether coupling reaction (Williamson's type ether synthesis³), deprotection and reiteration of ether coupling. The parameters of the process and purification methods have been strictly controlled to ensure unprecedented level of monodispersity for all synthesised samples. Thus obtained high purity polymers have been used to study the influence of the individual chain length on the structure and conductivity of the crystalline complexes with LiPF₆. The results support the previously suggested model of the chain-ends arrangement in the crystalline complexes prepared with monodispersed PEO² over a range of consecutive chain lengths. The synthesised complexes constitute a series of test samples for establishing detailed mechanism of ionic conductivity. Such series of monodispersed crystalline complexes have been studied and characterised here (PXRD, DSC, AC impedance) for the first time. References: 1. G. S. MacGlashan, Y. G. Andreev, P. G. Bruce, Structure of the polymer electrolyte poly(ethylene oxide)₆:LiAsF₆. Nature, 1999, 398(6730): p. 792-794. 2. E. Staunton, Y. G. Andreev, P. G. Bruce, Factors influencing the conductivity of crystalline polymer electrolytes. Faraday Discussions, 2007, 134: p. 143-156. 3. A. Williamson, Theory of Aetherification. Philosophical Magazine, 1850, 37: p. 350-356.