L’objectif de cette thèse est de développer la caractérisation et le diagnostic non destructif de microbatteries « tout solide » par spectroscopie d’impédance électrochimique. Ces travaux s’appuient sur des microbatteries commerciales EnFilmTM EFL700A39, basées sur une architecture lithium métal Li/LiPON/LiCoO2. La caractérisation unitaire des couches actives, constituant ces microbatteries, a permis d’une part, d’identifier les principales propriétés de transport des ions Li+ dans l’électrolyte solide, et d’autre part, a permis de mettre en avant la présence de zones plus ou moins conductrices dans la couche active LiCoO2, pouvant engendrer des limitations électroniques et/ou ioniques lors du fonctionnement de la microbatterie. L’étude des microsystèmes complets par spectroscopie d’impédance électrochimique a ensuite été effectuée en fonction du taux de lithiation de l’électrode positive, du nombre de cycles, et du vieillissement calendaire de la microbatterie. Les résultats obtenus ont donné naissance à un circuit électrique équivalent permettant de modéliser le comportement (souvent indépendant) des différentes couches actives durant l’utilisation d’une microbatterie. Cette modélisation permet en outre de cibler les origines éventuelles de défaillances, soit après la fabrication, soit au cours du vieillissement d’une microbatterie. Les travaux additionnels effectués sur des systèmes lithium free (LiCoO2/LiPON/Cu) révèlent, quant à eux, une forte interaction électrochimique entre le lithium et le collecteur de cuivre (partiellement oxydé) et mettent en évidence l’importance capitale des premiers cycles de la cellule pour ses performances ultérieures / The goal of this work is to develop characterization and non-destructive diagnosis of all-solid-state lithium microbatteries, essentially by means of electrochemical impedance spectroscopy. This work is based on commercial microbatteries EnFilmTM EFL700A39, built with the lithium metal architecture Li/LiPON/LiCoO2. Firstly, the elemental characterization of active layers allowed us to identify the main properties of the ionic motion in the solid electrolyte layer. Secondly, characterization of the positive electrode (LiCoO2) revealed the existence of more or less conductive areas inside the layer. Theses areas can cause ionics or electronics limitations during battery operation. The study of the entire microsystems by electrochemical impedance spectroscopy was then performed according to lithiation rate (SOC), number of cycles, and battery aging. The results obtained allowed the building of an electrical equivalent circuit for modeling the behaviour of the different active layers of a microbattery in use. This model also allows targeting the origins of any failures after manufacturing or upon microbattery aging. Additional works on lithium free systems (LiCoO2/LiPON/Cu) reveals a strong electrochemical interaction between in situ deposited lithium and copper current collector (partially oxidized) and highlight the critical importance of the very first cycles of the cell for subsequent performance

The widespread deployment of wireless sensors in our homes, offices, factories and infrastructure has opened the door for system designers to create novel approaches for powering wireless sensor nodes. In recent years, energy harvesting has emerged as the power supply of choice for embedded system designers, enabling wireless sensors to be used in applications that previously were not feasible with conventional battery-powered designs. This report details the design and development of an energy harvesting wireless sensor from concept to production. Design constraints included the requirement to operate reliably in a wide variety of environments, the use of commercially available components, and a visually appealing form factor. The result is a very power-efficient, solar-powered wireless sensor that measures temperature, voltage, and illumination level at the solar cell and has an ultra slim form factor. / text

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.

All solid state Li-ion batteries (thin film micro batteries) have become inevitable for miniaturized devices and sensors as power sources. Fabrication of electrode materials for batteries in thin film form has been carried out with the existing technologies used in semiconductor industry. In the present thesis, radio frequency (RF) sputtering has been chosen for deposition of cathode material (ceramic oxides) thin films because of several advantages such as precise thickness control and deposition of compound thin films with equivalent composition. Conventional sputtering involves fabrication of thin film using custom made pellet according to the specification of sputter gun. However several issues such as target breaking are inevitable with the pellet sputtering. To forfend the issues, powder sputtering has been implemented for the deposition of various thin film cathodes in an economically feasible approach. Optimization of various process parameters during film deposition of cathode materials LiCoO2, Li2MnO3, LiNixMnyO4, mixed oxide cathodes of LiMn2O4, LiCoO2 and TiO2 etc., have been executed successfully by the present approach to achieve optimum electrochemical performance. Thereafter the optimized process parameters would be useful for selection of cathode layers for micro battery fabrication. Chapter 1 gives a brief introduction to the Li ion and thin film solid state batteries. It also highlights the advantages of powder sputtering compared to conventional pellet sputtering. In Chapter 2, the materials used and methods employed for the fabrication of thin film electrodes and analytical characterizations have been discussed. In chapter 3, implementation of powder sputtering for the deposition of LiCoO2 thin films has been discussed. X-Ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS) and electrochemical investigations have been carried out and promising results have been achieved. Charge discharge studies delivered a discharge capacity of 64 µAh µm-1 cm-2 in the first cycle in the potential range 3.0-4.2 V vs. Li/Li+. The possible causes for the moderate cycle life performance have been discussed. Systematic investigations for RF power optimization for the deposition of Li2-xMnO3-y thin films have been carried out. Galvanostatic charge discharge studies delivered a highest discharge capacity of 139 µAh µm-1cm-2 in the potential window 2.0-3.5 V. Thereafter, effect of LMO film thickness on electrochemical performance has been studied in the thickness range 70 nm to 300 nm. Films of lower thickness delivered higher discharge capacity with good cycle life than the thicker films. These details are discussed in chapter 4. In Chapter 5, fabrication and electrochemical performance of LiNixMnyO4 thin films are presented. LMO thin films have been deposited on nickel coated stainless steel substrates. The as deposited films were annealed at 500 °C in ambient conditions. Nickel diffuses in to LMO film and results in LiNixMnyO4 (LMNO) film. These films were further characterized. Electrochemical studies were conducted up to higher potential 4.4 V resulted in discharge capacities of the order of 55 µAh µm-1cm-2. In chapter 6, electrochemical investigations of mixed oxide thin films of LiCoO2 and LiMn2O4 have been carried out. Electrochemical investigations have been carried out in the potential window 2.0–4.3 V and a discharge capacity of 24 µAh µm-1cm-2 has been achieved. In continuation, TiO2 powder was added to the former composition and the deposited films were characterized for electrochemical performance. The potential window as well as the discharge capacity enhanced after TiO2 doping. Electrochemical characterization has been carried out in the potential window 1.4–4.5 V, and a discharge capacity of 135 µAh µm-1cm-2 has been achieved. Finally chapter 7 gives overall conclusions and future directions to the continuation of the work.

Li-ion thin film battery technology has attracted much attention in recent years due to its highest need in portable electronic devices. Development of new materials for lithium ion battery (LIB) is very crucial for enhancement of the performance. LIB can supply higher energy density because Lithium is the most electropositive (-3.04V vs. standard hydrogen electrode) and lightest metal (M=6.94 g/mole). LIBs show many advantages over other kind of batteries such as, high energy density, high power density, long cycle life, no memory effect etc. The major work presented in this thesis is on the development of nanostructured materials for anode of Li-ion battery. It involves the synthesis and analysis of grapheme nanosheet (GNS) and its performance as anode material in Li ion battery. We studied the synthesis of GNS over different substrates and performed the anode studies. The morphology of GNS has great impact on Li storage capacity. Tin and Tin oxide nanostructures have been embedded in the GNS matrix and their electrochemical performance has been studied. Chapter 1 gives the brief introduction about the Li ion batteries (LIBs), working and background. Also the relative advantages and characterization of different electrode materials used in LIBs are discussed. Chapter 2 discusses various experimental techniques that are used to synthesize the electrode materials and characterize them. Chapter3 presents the detailed synthesis of graphene nanosheet (GNS) through electron cyclotron resonance (ECR) microwave plasma enhanced chemical vapor deposition (ECR PECVD) method. Various substrates such as metallic (copper, Ni and Pt coated copper) and insulating (Si, amorphous SiC and Quartz) were used for deposition of GNS. Morphology, structure and chemical bonding were analyzed using SEM, TEM, Raman, XRD and XPS techniques. GNS is a unique allotrope of carbon, which forms highly porous and vertically aligned graphene sheets, which consist of many layers of graphene. The morphology of GNS varies with substrate. Chapter 4 deals with the electrochemical studies of GNS films. The anode studies of GNS over various substrates for Li thin film batteries provides better discharge capacity. Conventional Li-ion batteries that rely on a graphite anode have a limitation in the capacity (372 mAh/g). We could show that the morphology of GNS has great effect in the electrochemical performance and exceeds the capacity limitation of graphite. Among the electrodes PtGNS shown as high discharge capacity of ~730 mAh/g compare to CuGNS (590 mAh/g) and NiGNS (508 mAh/g) for the first cycle at a current density of 23 µA/cm2. Electrochemical impedance spectroscopy provides the various cell parameters of the electrodes. Chapter 5 gives the anodic studies of Tin (Sn) nanoparticles decorated over GNS matrix. Sn nanoparticles of 20 to 100nm in size uniformly distributed over the GNS matrix provides a discharge capacity of ~1500 mAh/g mAh/g for as deposited and ~950 mAh/g for annealed Sn@GNS composites, respectively. The cyclic voltammogram (CV) also shows the lithiation and delithiation process on GNS and Sn particles. Chapter 6 discusses the synthesis of Tinoxide@GNS composite and the details of characterization of the electrode. SnO and SnO2 phases of Tin oxide nanostructures differing in morphologies were embedded in the GNS matrix. The anode studies of the electrode shows a discharge capacity of ~1400 mAh/g for SnO phase (platelet morphology) and ~950 mAh/g for SnO2 phase (nanoparticle morphology). The SnO phase also exhibits a good coulumbic efficiency of ~95%. Chapter 7 describes the use of SnO2 nanowire attached to the side walls of the GNS matrix. A discharge capacity of ~1340 mAh/g was obtained. The one dimensional wire attached to the side walls of GNS film and increases the surface area of active material for Li diffusion. Discharge capacity obtained was about 1335 mAhg-1 and the columbic efficiency of ~86% after the 50th cycle. The research work carried out as part of this thesis, and the results have summarized in chapter 8.