Academic literature on the topic 'Batteries au Li-Ion'

Efforts are being globally spent today to boost stored energy produced by renewable sources and to encourage a sustainable electric transportation. High-energy conversion systems like batteries can satisfy these demands in an efficient way. Although Li-ion batteries (LIBs) are the best batteries on the market in terms of energy content, a drastic change is desirable to increase both energy and power performance. In this context, Li/O2 is the next generation system due to the theoretical 10-fold higher specific energy than commercial LIBs (3500 vs. 250 Wh kg-1). The aim of this PhD thesis is the development of novel concepts and cell designs with the purpose to increase the performance of the aprotic Li and Li/O2 batteries. Specifically, a novel design of electrolyte (i.e. solvent-in-salt “SIS” solutions, where the salt-to-solvent ratio is higher than 1), and an innovative concept of semi-solid lithium redox flow air (O2) battery (SLRFAB) technology, based on the use of a O2-saturated semi-solid catholyte, have been proposed.

Les batteries lithium-ion sont présentes dans de nombreuses applications portables ou embarquées car leurs énergies massique et volumique et leur cyclabilité les placent en tête des autres technologies de stockage. Cependant, elles ne résistent pas aux fonctionnements abusifs et peuvent subir des emballements thermiques avec risque d’explosion. Par ailleurs, l’état des composants internes évoluant au cours du vieillissement de la batterie, son comportement en sécurité doit être considéré pour n'importe quel état de santé afin de mieux concevoir la gestion thermique des cellules et du pack batterie. Dans ce contexte, il est donc primordial de comprendre les mécanismes de dégradation de l’ensemble des composants internes d’un élément (matériaux d'électrodes, collecteurs, séparateur et électrolyte) lors d’un vieillissement en fonctionnement normal et le déroulement des évènements en conditions abusives pouvant aboutir à un scénario accidentel.Le séparateur doit alors être considéré comme le premier dispositif de sécurité intrinsèque car il assure la séparation physique entre l’électrode positive et négative. Il doit alors être étudié sur le plan de ses propriétés électrochimiques, mécaniques et thermiques. Pour cela, une méthodologie de caractérisation a été développée, mettant en œuvre un large panel de techniques de caractérisation physique et chimique, et appliquée sur des séparateurs issus de vieillissements en conditions normales et après surcharge. Différentes méthodes de lavage ont permis de discréditer l’évolution morphologique et électrochimique du polymère poreux sans l’interaction des résidus solides associées aux produits de dégradation de l’électrolyte. Ainsi, la porosité et la tortuosité de la matrice polymère, associées à la conductivité ionique du système séparateur/électrolyte, ont été pleinement étudiées.Il a pu être montré que, en accord avec la croissance de la SEI sur l’électrode négative graphite, sa porosité de surface se dégrade avec un encrassement des pores par accumulation de composés solides de la SEI. Aucune conséquence sur les propriétés mécaniques n’a été observée, mais les performances électrochimiques en puissance se dégradent fortement. Une évaluation face aux risques de court-circuit interne par percée dendritique a permis de montrer que la formation de dendrite est favorisée. Le séparateur en tant qu’organe de sécurité face aux risques mécaniques garde donc son efficacité tout au long de la vie de la batterie lithium-ion mais le risque de court-circuit est plus élevé<br>Lithium-ion batteries have undeniable assets to meet several of the requirements for embedded applications. They provide high energy density and long cycle life. Nevertheless, they can face irreversible damage during their lives which could cause safety issues like the thermal runaway of the battery and its explosion. It is then essential to understand the degradation mechanisms of all the internal components of an accumulator (i.e. electrode materials, collectors, separator and electrolyte) and the progress of events in abusive conditions that can lead to an accident scenario. The aim of this thesis is to work on the security aspects of Lithium-ion batteries in order to understand these degradation mechanisms and to help to prevent future incidents.Even if the degradation mechanisms of all the internal components are studied in this work, a special attention is given to the separator. This component is indeed one of the most important safety devices of a battery and have to be electrochemically, mechanically and thermally characterized after ageing. Different washing methods have been study in order to characterize the separator without any degradation product of the electrolyte which could interfere. Porosity and tortuosity associated with the ionic conductivity of the separator have been tested.The results show that even if the separator is electrochemically inactive, its porosity can decrease because of the degradation of the negative graphite electrode. Indeed, SEI components obstruct the surface porosity of the separator. This porosity change do not cause any mechanical degradation but decrease separator performances at high current rate and promote lithium dendrite growth

A new challenging application for Li-ion battery has arisen from the rapid development of micro-electronics. Powering Micro-ElectroMechanical Systems (MEMS) such as autonomous smart-dust nodes using conventional Li-ion batteries is not possible. It is not only new batteries based on new materials but there is also a need of modifying the actual battery design. In this context, the conception of 3D nano-architectured Li-ion batteries is explored. There are several micro-battery concepts that are studied; however in this thesis, the focus is concentrated on one particular architecture that can be described as the successive deposition of battery components (active material, electrolyte, active material) on free-standing arrays of nano-sized columns of a current collector. After a brief introduction about Li-ion batteries and 3D micro-batteries, the electrodeposition of Al through an alumina template using an ionic liquid electrolyte to form free-standing columns of Al current collector is described. The crucial deposition parameters influencing the nucleation and growth of the Al nano-rods are discussed. The deposition of active electrode material on the nano-structured current collector columns is described for 2 distinct active materials deposited using different techniques. Deposition of TiO2 using Atomic Layer Deposition (ALD) as active material on top of the nano-structured Al is also presented. The obtained deposits present high uniformity and high covering of the specific surface of the current collector. When cycled versus lithium and compared to planar electrodes, an increase of the capacity was proven to be directly proportional to the specific area gained from shifting from a 2D to a 3D construction. Cu2Sb 3D electrodes were prepared by the electrodeposition of Sb onto a nano-structured Cu current collector followed by an annealing step forcing the alloying between the current collector and Sb. The volume expansion observed during Sb alloying with Li is buffered by the Cu matrix and thus the electrode stability is greatly enhanced (from only 20 cycles to more than 120 cycles). Finally, the deposition of a hybrid polymer electrolyte onto the developed 3D electrodes is presented. Even though the deposition is not conformal and that issues of capacity fading need to be addressed, preliminary results attest that it is possible to cycle the obtained 3D electrode-electrolyte versus lithium without the appearance of short-circuits.

Coin cells with lithium and graphite electrodes were assembled using different combinations of graphite material and electrolyte. Specifically, three commercially available graphite materials and five electrolyte compositions were studied. The cells were discharge-charge cycled with varying parameters in order to determine the performance of the graphite materials and electrolytes. Particularly, a temperature chamber was employed to cycle some cells at temperatures between 0 and 40&#176;C to find the significance of the electrolyte composition and graphite material on the cell performance at these temperatures. The cycled cells were disassembled and samples from the graphite electrode soaked with electrolyte were prepared for thermal analysis, specifically differential scanning calorimetry (DSC). The thermal stability of the graphite electrodes and the influence from the graphite and electrolyte properties and the cycling parameters were analysed. In order to facilitate the interpretation of the results from discharge-charge cycling at different temperatures, DSC analysis from -80 to +50&#176;C was performed on the pure electrolytes.Confirming previous studies, it was found that both the thermal stability and cycling performance were highly influenced by the properties of a solid electrolyte interphase (SEI), situated between the graphite surface and the electrolyte and formed during cycling. The three graphites were good substrates for stable SEI formation, exhibited by high thermal stability after being cycled at room temperature. After cycling with a temperature program, subjecting the cells to temperatures between 0 and 40&#176;C, the thermal stability was generally reduced. This was attributed to increased SEI formation. The properties of both the electrolyte and graphite influenced the SEI and consequent thermal stability, though in different ways.The cell capacity was considerably reduced upon cycling at lower temperatures, such as 10 and 0&#176;C. The results indicate that the electrolyte properties, particularly the viscosity and resulting conductivity, played the most important role in determining the cell performance. Low viscosity electrolyte components should be utilised, maintaining the electrolyte conductivity even at reduced temperatures. The graphite properties did not influence the cell performance at the temperatures studied. Advice is given on which electrolyte components should be avoided to build Li-ion cells performing acceptably at temperatures from 0 to 40&#176;C.