Correlation between structure and electrochemistry of LiMO2 cathode materials (M = Ni, Co)

Technical diversity and various knowledge is required for the understanding of undoubtedly complex system such as a Lithium-ion battery. The peculiarity is to combine different techniques that allow a complete investigation while the battery is working. Nowadays, research on Li-ion batteries (LIBs) is experiencing an exponential growth in the development of new cathode materials. Accordingly, Li-rich and Ni-rich NMCs, which have similar layered structure of LiMO2 oxides, have been recently proposed. Despite the promising performance on them, still a lot of issues have to be resolved and the materials need a more in depth characterisation for further commercial applications. In this study LiMO2 material, in particular M = Co and Ni, will be presented. We have focused on the synthesis of pure LiCoO2 and LiNiO2 at first, followed by the mixed LiNi0.5Co0.5O2. Different ways of synthesis were investigated for LCO but the sol-gel-water method showed the best performances. An accurate and systematic structural characterization followed by the appropriate electrochemical tests were done. Moreover, the in situ techniques (in-situ XRD and in situ OEMS) allowed a deep investigation in the structural change and gas evolution upon the electrochemically driven processes.

PEDOT:PSS thin films: Applications in Bioelectronics

Owing to their capability of merging the properties of metals and conventional polymers, Conducting Polymers (CPs) are a unique class of carbon-based materials capable of conducting electrical current. A conjugated backbone is the hallmark of CPs, which can readily undergo reversible doping to different extents, thus achieving a wide range of electrical conductivities, while maintaining mechanical flexibility, transparency and high thermal stability. Thanks to these inherent versatility and attracting properties, from their discovery CPs have experienced incessant widespread in a great plethora of research fields, ranging from energy storage to healthcare, also encouraging the spring and growth of new scientific areas with highly innovative content. Nowadays, Bioelectronics stands out as one of the most promising research fields, dealing with the mutual interplay between biology and electronics. Among CPs, the polyelectrolyte complex poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS), especially in the form of thin films, has been emphasized as ideal platform for bioelectronic applications. Indeed, in the last two decades PEDOT:PSS has played a key role in the sensing of bioanalytes and living cells interfacing and monitoring. In the present work, development and characterization of two kinds of PEDOT:PSS-based devices for applications in Bioelectronics are discussed in detail. In particular, a low-cost amperometric sensor for the selective detection of Dopamine in a ternary mixture was optimized, taking advantage of the electrocatalytic and antifouling properties that render PEDOT:PSS thin films appealing tools for electrochemical sensing of bioanalytes. Moreover, the potentialities of this material to interact with live cells were explored through the fabrication of a microfluidic trapping device for electrical monitoring of 3D spheroids using an impedance-based approach.

Sintesi e caratterizzazione di batterie tipo rocking chair basate sugli analoghi del blu di Prussia

La rapida espansione del mercato delle batterie incalza lo sviluppo di materiali elettrodici basati su elementi largamente disponibili sulla crosta terrestre, rispettosi dell'ambiente ed economicamente sostenibili. Nel presente elaborato si effettua lo studio di elettrodi basati sugli analoghi del blu di Prussia (PBA) come una classe di composti inorganici che presenta diverse proprietà elettrochimiche adatte per applicazioni legate all’energy storage. A tal riguardo, la sintesi del PBA ferro esacianocobaltato (FeHCC) è stata effettuata mediante un metodo di coprecipitazione semplice e poco costoso. L’utilizzo di tecniche analitiche quali XAS, PXRD, MP-AES e TGA ha permesso di ricavare la composizione del ferro esacianocobaltato, dell'esacianoferrato di titanio e del manganese esacianoferrato nonché diverse informazioni di carattere strutturale. In seguito, le prestazioni elettrochimiche degli elettrodi sono state valutate mediante voltammetria ciclica, utilizzando come agenti intercalanti gli ioni K+ e Na+ contenuti nel relativo elettrolita acquoso.Infine, grazie ai dati così ottenuti, è stato possibile assemblare e testare diversi layout di coin cell in configurazione rocking chair completamente basate su elettrodi PBA; anche in questo caso, la voltammetria ciclica e le tecniche galvanostatiche sono state utilizzate per valutare le prestazioni elettrochimiche e raccogliere informazioni sulla capacità gravimetrica ottenibile da questi dispositivi.

Thermodynamics of hydrogen absorption in Mg thin films and multilayers studied by electrochemical method

Electrochemical hydrogen loading is a technique used to produce and study the hydrogenation in metals starting from a liquid solution containing water. It is a possible alternative to another, well-established technique which loads hydrogen starting from its gas phase. In this work, the electrochemical method is used to understand the fundamental thermodynamics of hydrogen loading in constraint systems such as thin films on substrates, and possibly distinguish the role of interfaces, stresses and microstructure during the hydrogenation process. The systems under study are thin films of Pd, Mg/Pd, and Ti/Mg multilayers. Possible future technological applications may be in the field of hydrogen storage and hydrogen sensors. Towards the end, the experimental setup is modified by introducing an automatic relay. This change leads to improvements in the data analysis and in the attainable information on the kinetics of the systems.