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Il mio progetto di dottorato è incentrato sul riciclaggio delle batterie agli ioni di litio, con particolare attenzione allo sviluppo di approcci ecologici e sostenibili per riciclare le materie prime presenti nelle LIB di scarto utilizzando un nuovo tipo di solventi organici chiamati Deep Eutectic Solvents (DES). Come primo DES, abbiamo riportato un metodo innovativo ed ecologico che utilizza un DES composto da acido lattico (HBD) e cloruro di colina (HBA) per il recupero efficiente e semplice di metalli preziosi da LiNi0,8Co0,2O2 (LNC). Abbiamo degradato con successo Li, Co e Ni dai materiali catodici, raggiungendo un'efficienza notevole del 100%. Un aspetto degno di nota del nostro lavoro è l'introduzione di un approccio in due fasi per il recupero di Li, Co e Ni da LiNi0,8Co0,2O2, che ha portato a rese elevate e a una purezza eccezionale. Il ciclo di riciclo è stato chiuso dalla risintesi e dalla caratterizzazione elettrochimica di LNC utilizzando il Li, il Ni e il Mn precedentemente recuperati. Il secondo DES proposto è composto da cloruro di colina, acido citrico e glicole etilenico in un rapporto molare di 1:1:1. Questa formulazione di DES mira a un'efficiente gestione dei rifiuti. Questa formulazione DES mira a degradare efficacemente il materiale catodico LiCoO2 attraverso un processo riduttivo. Il secondo DES proposto è composto da cloruro di colina, acido citrico e glicole etilenico in un rapporto molare di 1:1:1. Questa formulazione di DES mira a degradare efficacemente il materiale del catodo LiCoO2 attraverso un processo riduttivo. Il materiale catodico è stato completamente degradato con rese di estrazione superiori al 97% sia per il Li che per il Co. Sottoponendo il DES usato a un trattamento di 2 ore a 500°C, siamo riusciti a separare e recuperare Co3O4 e LiCl con una purezza sufficiente per essere utilizzati nella risintesi di LiCoO2. Per dimostrare la fattibilità del nostro approccio, abbiamo risintetizzato un nuovo lotto di LiCoO2 dal prec, My PhD project is centered around the recycling of lithium-ion batteries with a focus on developing environmentally friendly and sustainable approaches to recycle the raw materials present in waste LIBs by using a new type of organic solvents called Deep Eutectic Solvents (DES). As first DES, we present an innovative and environmentally friendly proof-of-concept that utilizes a DES composed by lactic acid (HBD) and choline chloride (HBA) for the efficient and straightforward recovery of valuable metals from LiNi0.8Co0.2O2 (LNC). We successfully leach Li, Co and Ni from the cathode materials, achieving a remarkable 100% efficiency. A noteworthy aspect of our work is the introduction of a two-steps approach for the recovery of Li, Co, and Ni from LiNi0.8Co0.2O2, resulting in high yields and exceptional purity. The recycling cycle was closed by the resynthesis and electrochemical characterization of LNC using the previously recovered Li, Ni and Mn. The second DES proposed is composed by choline chloride, citric acid, and ethylene glycol in a molar ratio of 1:1:1. This DES formulation aims to efficiently degrade LiCoO2 cathode material through a reductive process. The cathode material was fully degraded with extraction yields of over 97% for both Li and Co. Despite recover the DES, we developed an optimized thermal treatment method. By subjecting the used DES to a 2-hour treatment at 500°C, we successfully separated and recovered Co3O4 and LiCl with sufficient purity to be utilized in the resynthesis of LiCoO2. To demonstrate the viability of our approach, we resynthesized a new batch of LiCoO2 from the precursor obtained and the material was full electrochemically characterized and compare with a commercial LCO. As the last DES studied, we wanted to replace the more common choline chloride as HBD with other type of choline salt. We select choline citrate (CC) in combination with ethylene glycol (EG). The presence of the citrate ion instead of the chloride ion makes the

Understanding water drop impact on meshes is valuable to design passive systems for atmospheric water collection. By investigating water drop impact on hydrophobic and superhydrophobic surfaces, here, we identify the different drop impact outcomes and build outcome maps within the pertinent parameter spaces, based on Weber number and contact angles. Furthermore, we quantitatively evaluate critical factors such as the captured volume and spray characteristics of the penetrating liquid and also measure the drop rebound time, reporting that full rebound occurs on superhydrophobic meshes surfaces even at high We numbers, as the Cassie-Baxter wetting state is maintained.

Anche se i continui miglioramenti registrati dalle batterie agli ioni di litio (LIB) negli ultimi decenni hanno permesso la produzione di dispositivi di accumulo dell'energia affidabili e performanti, la densità di energia di questo sistema è ancora inferiore ai requisiti dell'industria, in particolare per le specifiche richieste dal settore automobilistico. Di conseguenza, molto interesse è attualmente rivolto allo sviluppo di nuove categorie di dispositivi di accumulo dell'energia in grado di immagazzinare e fornire maggiori quantità di energia per unità di massa e volume. Un'alternativa promettente è rappresentata dalle batterie al litio metallico (LMB), ossia dispositivi ricaricabili che sfruttano un anodo di litio metallico al posto di quello grafitico comunemente impiegato nelle LIB. Questa sostituzione migliora notevolmente la densità energetica delle batterie, consentendo al contempo l'utilizzo di catodi di conversione ad alta capacità come lo zolfo. Tuttavia, l'elevata reattività del Li metallico e la deposizione disomogenea di ioni Li sulla sua superficie, che porta alla crescita di pericolose dendriti responsabili di cortocircuiti, ostacolano l'implementazione delle LMB basate su elettroliti liquidi. Di conseguenza, una grande attenzione è attualmente rivolta allo sviluppo di elettroliti allo stato solido (SSE) che, possedendo una migliore stabilità meccanica unita a una ridotta infiammabilità, possono mitigare le suddette carenze. Pertanto, la mia tesi si è concentrata sullo sviluppo di una nuova generazione di elettroliti compositi, in grado di combinare le promettenti caratteristiche fornite da elettroliti ceramici e polimerici., Even if the continuous improvements experienced by lithium-ion batteries (LIBs) in the past decades have enabled a mass scale production of reliable and performant energy storage devices, the energy density of this system still falls short from the industry requirement, particularly for the specications required by the automotive sector. Consequently, a lot of interest is currently devoted to the development of new categories of energy storage devices able to store and deliver higher quantities of energy for unit of mass and volume. A promising alternative is represented by lithium metal batteries (LMBs), i.e. rechargeable devices that exploit an anode of metallic lithium in place of the graphitic one commonly employed in LIBs. This replacement greatly improves the gravimetric and volumetric energy density of the batteries, simultaneously enabling the use of high-capacity conversion cathodes such as sulphur. However, the high reactivity of metallic Li and the inhomogeneous deposition of Li-ions on its surface, which leads to the growth of dangerous dendrites responsible of shortcircuiting, are hindering the implementation of LMBs based on liquid electrolytes. As a consequence, great attention is presently directed towards the development of solid state electrolytes (SSEs) that, possessing an improved mechanical stability coupled with reduced flammability, can mitigate the aforementioned shortcomings. Therefore, my thesis focused on the development of next-generation of composite solid-state electrolytes able to couple the benifical properties of polymer and ceramic materials.

Batteries based on organic electrolytes have been raising safety concerns due to some associated fire/explosion accidents caused by the unusual combination of highly flammable organic electrolytes and high energy electrodes. Nonflammable aqueous batteries are a good alternative to the current energy storage systems. However, what makes aqueous batteries safe and viable turns out to be their main weakness, since water molecules are prone to decomposition because of a narrow electrochemical stability window (ESW). In this perspective we introduce aqueous batteries and then discuss the state-of-the-art of water-in-salt (WIS) electrolytes for aqueous energy storage systems. The main strategies to improve ESW are reviewed, including: (i) the use of fluorinated salts to make a solid electrolyte interphase (SEI); (ii) the use of cost-effective and highly soluble salts to reduce water activity through super concentration; and (iii) the use of hybrid electrolytes combining the advantages of both aqueous and non-aqueous phases. Then, we discuss different battery chemistries operated with different WIS electrolytes. Finally, we highlight the challenges and future technological perspectives for practical aqueous energy storage systems, including applications in stationary storage/grid, power backup, portable electronics, and automotive sectors.

Among the materials for the negative electrodes in Li-ion batteries, oxides capable of reacting with Li+ via intercalation/conversion/alloying are extremely interesting due to their high specific capacities but suffer from poor mechanical stability. A new way to design nanocomposites based on the (Ti/Sn)O2 system is the partial oxidation of the tin-containing MAX phase of Ti3Al(1-x)SnxO2 composition. Exploiting this strategy, this work develops composite electrodes of (Ti/Sn)O2 and MAX phase capable of withstanding over 600 cycles in half cells with charge efficiencies higher than 99.5% and specific capacities comparable to those of graphite and higher than lithium titanate (Li4Ti5O12) or MXenes electrodes. These unprecedented electrochemical performances are also demonstrated at full cell level in the presence of a low cobalt content layered oxide and explained through an accurate chemical, morphological, and structural investigation which reveals the intimate contact between the MAX phase and the oxide particles. During the oxidation process, electroactive nanoparticles of TiO2 and Ti(1-y)SnyO2 nucleate on the surface of the unreacted MAX phase which therefore acts both as a conductive agent and as a buffer to preserve the mechanical integrity of the oxide during the lithiation and delithiation cycles.

Poiché le batterie agli ioni di litio (LIBs) continuano a essere utilizzate sempre più ampiamente nella nostra vita quotidiana, aumentano anche i problemi di sicurezza. Ciò è in gran parte dovuto alle frequenti segnalazioni di incidenti di combustione ed esplosione, che sono direttamente collegati alla natura altamente infiammabile degli elettroliti utilizzati nelle LIBs. Le batterie acquose sembrano essere un'alternativa più sicura, ma la loro limitata densità di energia, che deriva dalla stretta finestra di stabilità elettrochimica (ESW) dell'acqua, è un grosso limite. Lo studio qui presentato ha avuto come obiettivo l’ampliamento dell'ESW degli elettroliti acquosi, utilizzando strategie innovative come la super-concentrazione (SC) e l'approccio dell'elettrolita ibrido. Inoltre, sono state sviluppate anche nuove fasi NASICON con l'obiettivo di ottimizzare i materiali elettrodici. Nella prima parte della tesi CH3COOK, altamente solubile, è stato selezionato come principale componente e miscelato con CH3COONa per formare elettroliti acqua-in-sale (WIS) a cationi misti con concentrazioni variabili. Le proprietà fisico-chimiche ed elettrochimiche di queste soluzioni sono state studiate utilizzando misurazioni termiche, reologiche, elettriche, elettrochimiche e spettroscopiche. La soluzione più concentrata, 20m CH3COOK + 7m CH3COONa, è risultata fornire il miglior compromesso tra proprietà di trasporto e stabilità elettrochimica, mostrando una conducibilità di 21,2 mS cm-1 a 25°C e un ESW di 3,2 V. Analizzando i legami idrogeno in questi elettroliti concentrati, sono state ottenute informazioni riguardo il loro impatto sull'ESW. Le analisi Raman hanno anche aiutato a comprendere la rete di interazioni, le variazioni di stato con la temperatura e la cinetica di cristallizzazione. Come prova delle performances, LiTi2(PO4)3 è stato in grado di inserire e disinserire reversibilmente ioni Na+ a un potenziale di circa -0,7 V rispetto a SHE nell'elettrolita ca, Ever-increasing demands for lithium-ion batteries give rise to several safety concerns all over the world, capturing the attention of the scientific community and socio-economical stakeholders . This is largely due to frequent reports of combustion and explosion incidents, which are directly linked to the highly flammable nature of the electrolytes used in LIBs. Aqueous batteries appear to be a safer alternative but the limited energy density of aqueous batteries is a major drawback, resulting from the narrow electrochemical stability window (ESW) of water. This study aims to widen the ESW of aqueous electrolytes using innovative strategies such as super-concentration (SC) and hybrid electrolytes. New NASICON phases were also developed with the aim of minimizing the issues that may arise from the electrodes point of view. In the first part of the thesis SC approach was used to expand the ESW of aqueous electrolytes. Highly soluble CH3COOK was mixed with CH3COONa to form mixed-cation water-in-salt (WIS) electrolyte solutions with varying concentrations. The physicochemical and electrochemical properties of these solutions were thoroughly investigated using a range of techniques, including thermal, rheological, electrical, electrochemical, and spectroscopy measurements. The most concentrated solution, 20m CH3COOK+7 m CH3COONa, gives the best compromise between transport properties and stability, displaying a conductivity of 21.2 mS cm-1 at 25°C and ESW of 3.2 V. Raman spectroscopy allowed to gain insights into the interaction between phase components and emerging structural features in concentrated solutions. By analyzing the hydrogen bonding motifs in these solutions, we gained insight into their impact on the ESW. Raman analyses also helped to understand the interactions network, the phase evolution with temperature and the crystallization kinetics. As a proof-of-concept LiTi2(PO4)3 was shown to reversibly insert/de-insert Na+ ions at approximately -0.7 V vs. SHE in

Highly concentrated aqueous binary solutions of acetate salts are promising systems for different electrochemical applications, for example, energy storage devices. The very high solubility of CH3COOK allows us to obtain water-in-salt electrolyte concentrations, thus reducing ion activity and extending the cathodic stability of an aqueous electrolyte. At the same time, the presence of Li+ or Na+ makes these solutions compatible with intercalation materials for the development of rechargeable alkaline-ion batteries. Although there is a growing interest in these systems, a fundamental understanding of their physicochemical properties is still lacking. Here, we report and discuss the physicochemical and electrochemical properties of a series of solutions based on 20 mol kg-1 CH3COOK with different concentrations of CH3COONa. The most concentrated solution, 20 mol kg-1 CH3COOK + 7 mol kg-1 CH3COONa, gives the best compromise between transport properties and electrochemical stability, displaying a conductivity of 21.2 mS cm-1 at 25 °C and a stability window of up to 3 V in “ideal” conditions, i.e., using a small surface area and highly electrocatalytic electrode in a flooded cell. Careful Raman spectroscopy analyses help to address the interaction network, the phase evolution with temperature, and the crystallization kinetics.

Scopo della tesi sono state la sintesi, la caratterizzazione fisico-chimica ed elettrochimica di materiali elettrodici per batterie a ioni sodio. Le batterie a ioni sodio sono una delle più interessanti alternative alle batterie agli ioni litio, per via del loro basso costo e della solo sostenibilità, che le rende interessanti candidati per applicazioni in molti settori, come ad esempio quello dell’accumulo dell’energia proveniente da fonti rinnovabili. Uno degli step mancanti necessari alla loro commercializzazione, tuttavia, è lo sviluppo di materiali elettrodici ad alte prestazioni. Il focus della ricerca è stato quindi posto sulle applicazioni che una particolare classe di materiali, quella degli ossidi, può avere, sia come materiali anodici che come materiali catodici. Questa categoria è stata scelta per il basso costo e l’alta abbondanza dei materiali. Riguardo ai materiali anodici testati, diverse nanofibre di ossidi di ferro sono state sintetizzate con la tecnica dell’elettrospinning. Questi materiali sono stati poi dopati con altri metalli di diversa valenza. La struttura dei materiali così ottenuti è stata caratterizzata con l’utilizzo di svariate tecniche, per capire l’effetto degli elementi dopanti sulla struttura cristallina e sulle performances elettrochimiche. Come materiali anodici sono stati caratterizzati anche elettrodi di ossido di piombo elettrodepositato, che reagiscono con un meccanismo di conversione ed alligazione. In questo caso, l’investigazione ha riguardato la possibilità di ottenere elettrodi blended tramite scambio galvanico Riguardo ai materiali catodici, la ricerca si è focalizzata sulla classe di ossidi stratificati di formula NaxTmO2 (con Tm = Mn, Ni). In questo caso, l’oggetto della ricerca sono stati l’ottimizzazione del percorso e delle condizioni di sintesi di P2-Na0.67Mn0.67Ni0.33O2, per controllarne la sua morfologia e ottimizzarne le performances elettrochimiche. Particolare attenzione è stata data anche alla stab, Aim of the thesis have been the synthesis, the physicochemical and the electrochemical characterization of electrode materials for sodium-ion batteries. Sodium-ion batteries have emerged as the most promising alternative to lithium-ion ones, due to their low cost and their sustainability that makes them interesting candidates for application in many sectors, such as the in the one of renewable energies. One of the steps necessary for their commercialization is, however, the development of high-performance electrode materials. The focus of the investigation has been put on the applications that a special class of materials, the one of oxides, can have, both as anodes and both as cathodes. This class has been chosen for the general abundance and low cost of those materials. Concerning anodic materials different doped iron oxide nanofibers prepared with electrospinning technique have been synthesize and studied. The structure of those materials has been characterized with a multi-technique approach, to understand the effect of the doping atoms on the structure of the material and on the electrochemical performances. As anode material also electrodeposited lead oxide electrodes, reacting with a conversion and alloying mechanism, have been characterized. In this case, investigations have regarded the stabilization of the electrochemical performances and the possibility of obtaining blended electrode through galvanic displacement. Concerning cathodic materials, the focus of the research has been put on the class of layered oxides of general formula NaxTmO2 (with Tm = Mn, Ni). In this case, the object of the research has been the optimization of the synthesis pathway and of the synthesis conditions of P2-Na0.67Mn0.67Ni0.33O2, to control its morphology and to optimize its electrochemical performances. Particular attention has been given also to the stabilization of this materials at high potentials, that has been achieved performing an inorganic inert coating on the particl

Dynamic Electrochemical Impedance Spectroscopy is a valuable tool to investigate kinetic parameters of non-Faradic processes in symmetric Electrochemical Double Layer Capacitors. Compared to classic Electrochemical Impedance Spectroscopy, the dynamic technique measures the impedance under non-equilibrium condition removing the stationarity requirement and, at the same time, giving the frequency-dependent information of a dynamic process in presence of overpotential. Despite not being a new technique, there is an inherent complexity in the signal sampling and data manipulation to obtain the impedance spectra down to low frequencies (the interesting band for energy storage devices impedance). Few methods to compute the impedance from sampled signals are reported in the literature and under development. For this work the Dynamic Multi-Frequency Analysis algorithm was used to compute the impedance and reconstruct the cyclic voltammetry profile as well. The time-dependency of the kinetic parameters, namely capacitances of double layer and adsorption phenomenon, were extracted from equivalent circuit model regression and the adsorption time constants with a graphical analysis of the impedance spectra dataset during a full charge/discharge cycle. The values of the adsorption capacitance from the model regression are, on average, compatible with the values computed with a common formula showing the reliability of the model regression. The use of a three-electrode compact cell allowed the characterization of both active electrodes independently during operation showing a strong potential dependence on the active material properties. Furthermore, the impedance showed the presence of a side reaction (likely oxygen evolution) connected to the increase of adsorption and double layer capacitances localized on the positive electrode in a clearer way than what was possible to observe from the voltametric profile.

Sodium-ion batteries have recently aroused the interest of industries as possible replacements for lithium-ion batteries in some areas. With their high theoretical capacities and competitive prices, P2-type layered oxides (NaxTMO2) are among the obvious choices in terms of cathode materials. On the other hand, many of these materials are unstable in air due to their reactivity toward water and carbon dioxide. Here, Na0.67Mn0.9Ni0.1O2 (NMNO), one of such materials, has been synthesized by a classic sol-gel method and then exposed to air for several weeks as a way to allow a simple and reproducible transition toward a Na-rich birnessite phase. The transition between the anhydrous P2 to the hydrated birnessite structure has been followed via periodic XRD analyses, as well as neutron diffraction ones. Extensive electrochemical characterizations of both pristine NMNO and the air-exposed one vs sodium in organic medium showed comparable performances, with capacities fading from 140 to 60 mAh g-1 in around 100 cycles. Structural evolution of the air-exposed NMNO has been investigated both with ex situ synchrotron XRD and Raman. Finally, DFT analyses showed similar charge compensation mechanisms between P2 and birnessite phases, providing a reason for the similarities between the electrochemical properties of both materials.