Batteries are electrochemical devices capable of converting chemical energy into electrical energy through oxidation-reduction processes. The most used type of batteries was based on the usage of lithium (LIBs) and has continuously developed over the years to become the main and probably the only energy source used. For its extractive’s limitation and the continuous growing on this technology, in recent years the attention of industries has shifted to the development and study of an alternative battery systems capable of competing or surpassing LIBs technology. Sodium batteries (SIBs) are considered as an alternative to lithium batteries showing optimal mechanical and electronic properties for use in latest generation of electronic devices. This work is focused to the synthesizing and characterizing of two materials with different properties in terms of their crystal structure and their electron conductivity mechanism but both usable as active materials in the anodic comparison of a final cell. The first candidate was a composite consisting of black phosphorus (BP) and conductive carbon (SC65) and the latter a high entropy oxide (HEO) with a spinel structure composed by a equimolar distribution of nickel, iron, cobalt, manganese, and chromium. To obtain those materials, it was chosen to use of the high energy ball milling method, an eco-sustainable approach that avoids the use of organic solvents harmful to the environment. In the case of phosphorus, there is a structural conversion, through the kinetic energy transferred from the spheres of ball miller, from the tetragonal structure of the red phosphorus (RP) to an orthorhombic structure of the black phosphorus (BP), for the high entropy oxide - spinel (HS) a first grinding of the oxide precursors was made to allows the obtaining of a homogeneous powder that was heat-treated in order to realize a solid state reaction with the to obtaining of the pure spinel structure. The techniques that have been applied to characterize the materials that was synthesis are: 1)X-ray diffraction (XRD) 2)Raman spectroscopy: only in the case of the BP-C composite Once the samples are obtained and characterized, the next goal is to obtain a slurry with the optimal properties like: composition, reagents, viscosity and solid loading ideal for making an anode and the consequent characterization of the electrochemical properties. Once the slurry is obtained, it is spread using a manual tape caster and then the casted slurry is treated in a vacuum oven. For both, the phosphorus and the spinel, it was decided to use the coin cells types as a half-cell by mounting them in the same way, as regards the order of the various components of the cell and as regards the type of electrolyte (NaPF6 1M in EC:PC + 5%NaPFSi + 2%FEC) and the cathode used (Na metal). All analyses were performed on a coin cell and the following electrochemical characterization techniques were conducted using a BCS-810 battery tester: 1) Electrochemical impedance spectroscopy (PEIS) 2) Galvanostatic cycling with potential limitation (GCPL) 3) Pulsed cycling galvanostatic analysis (PGCA) From the GCPL, the BP-C composite shows excellent experimental capacity in comparison with the theoretical capacity with a yield of 65-70% and maintaining for all cycles an efficiency that oscillates between 90-100% for all cells. The HS presented an extremely low capacity value compared to the theoretical one expected (about 6%), one hypothesis is that sodium is not able to form an alloy capable of conducting unlike the case of lithium. As for the PGCA of the BP-C from the analysis it is possible to affirm the reversibility of the sodiation and desodiation process following the alternation of formation and dissociation of the Na3P species. The intensity of the peaks of the same cycle is comparable while the drop of the intensity value starting from the second cycle is in line with what has already been seen with the GCPL analyses.
Le batterie sono dispositivi elettrochimici in grado di convertire l'energia chimica in energia elettrica attraverso processi di riduzione dell'ossidazione. Il tipo di batterie più utilizzato si basa sull'utilizzo del litio (LIB) e si è continuamente sviluppato nel corso degli anni per diventare la principale e probabilmente l'unica fonte di energia utilizzata. Per la sua quantità limitata e la continua crescita della domanda, negli ultimi anni l'attenzione delle industrie si è spostata sullo sviluppo e lo studio di sistemi di batterie alternative in grado di competere o superare la tecnologia LIBs. Le batterie al sodio (SIB) sono considerate un'ottima alternativa mostrando delle proprietà meccaniche ed elettroniche ottimali per l'uso in dispositivi elettronici di ultima generazione. Questo lavoro è focalizzato sulla sintesi e caratterizzazione di due materiali con proprietà diverse in termini di struttura cristallina e meccanismo di conducibilità elettronica ma entrambi utilizzabili come materiali attivi nel confronto anodico di una cella finale. Il primo campione era un composito costituito da fosforo nero (BP) e carbonio conduttivo (SC65), il secondo ossido ad alta entropia (HEO) con una struttura di spinello composto da nichel, ferro, cobalto, manganese e cromo. Per ottenere questi materiali, è stato scelto di utilizzare il metodo ball miller ad alte prestazioni, un approccio ecosostenibile che evita l'uso di solventi organici dannosi per l'ambiente. Nel caso del fosforo, avviene una conversione strutturale, grazie all'energia cinetica trasferita dalle sfere del mulino, dalla struttura tetragonale del fosforo rosso (RP) a una struttura ortorombica del fosforo nero (BP), per lo spinello ad alta entropia (HS) è stata fatta una prima macinazione degli ossidi precursori per consentire l'ottenimento di una polvere omogenea che è stata trattata termicamente per realizzare una reazione allo stato solido con l'ottenimento della struttura pura dello spinello. Le tecniche che sono state applicate per caratterizzare dei materiali sono: i) diffrazione dei raggi X (XRD) ii) Spettroscopia Raman: solo nel caso del composito BP-C Una volta ottenuti e caratterizzati i campioni, l'obiettivo successivo è quello di ottenere uno slurry con proprietà ottimali come: composizione, reagenti, viscosità e solid loading ideali per realizzare un anodo e la conseguente caratterizzazione delle proprietà elettrochimiche. Una volta ottenuta la sospensione, questa viene stesa usando una doctor blade e trattata in una stufa da vuoto. Per entrambi si è deciso di utilizzare le coin cell come una semicella montandole allo stesso modo, sia per quanto riguarda l'ordine dei vari componenti della cella, sia per il tipo di elettrolita ( NaPF6 1M in EC: PC + 5% NaPFSi + 2% FEC) e il catodo utilizzato (Na metalllico). Tutte le seguenti tecniche di caratterizzazione elettrochimica sono state condotte utilizzando un tester batteria BCS-810: i) Spettroscopia di impedenza elettrochimica (PEIS) ii) Ciclo galvanico con potenziale limitazione (GCPL) iii) Analisi galvanostatica a ciclo pulsato (PGCA) Dal GCPL, il composito BP-C mostra un'eccellente capacità sperimentale rispetto alla capacità teorica con una resa del 65-70% e mantenendo per tutti i cicli un'efficienza che oscilla tra il 90-100% per tutte le celle. L'HS ha presentato un valore di capacità estremamente basso rispetto a quello teorico previsto (circa il 6%), un'ipotesi è che il sodio non è in grado di formare una lega capace di condurre. Per quanto riguarda la PGCA del BP-C dall'analisi è possibile affermare la reversibilità del processo di sodiazione e desodiazione in seguito all'alternanza di formazione e dissociazione delle specie Na3P. L'intensità dei picchi dello stesso ciclo è paragonabile mentre la caduta del valore di intensità a partire dal secondo ciclo è in linea con quanto già visto con le analisi GCPL.
ANODI INNOVATIVI PER BATTERIE A IONI SODIO: COMPOSITO FOSFORO NERO/CARBONIO & OSSIDO AD ALTA ENTROPIA (CoCrFeMnNi)3O4
MORINA, RICCARDO
2019/2020
Abstract
Batteries are electrochemical devices capable of converting chemical energy into electrical energy through oxidation-reduction processes. The most used type of batteries was based on the usage of lithium (LIBs) and has continuously developed over the years to become the main and probably the only energy source used. For its extractive’s limitation and the continuous growing on this technology, in recent years the attention of industries has shifted to the development and study of an alternative battery systems capable of competing or surpassing LIBs technology. Sodium batteries (SIBs) are considered as an alternative to lithium batteries showing optimal mechanical and electronic properties for use in latest generation of electronic devices. This work is focused to the synthesizing and characterizing of two materials with different properties in terms of their crystal structure and their electron conductivity mechanism but both usable as active materials in the anodic comparison of a final cell. The first candidate was a composite consisting of black phosphorus (BP) and conductive carbon (SC65) and the latter a high entropy oxide (HEO) with a spinel structure composed by a equimolar distribution of nickel, iron, cobalt, manganese, and chromium. To obtain those materials, it was chosen to use of the high energy ball milling method, an eco-sustainable approach that avoids the use of organic solvents harmful to the environment. In the case of phosphorus, there is a structural conversion, through the kinetic energy transferred from the spheres of ball miller, from the tetragonal structure of the red phosphorus (RP) to an orthorhombic structure of the black phosphorus (BP), for the high entropy oxide - spinel (HS) a first grinding of the oxide precursors was made to allows the obtaining of a homogeneous powder that was heat-treated in order to realize a solid state reaction with the to obtaining of the pure spinel structure. The techniques that have been applied to characterize the materials that was synthesis are: 1)X-ray diffraction (XRD) 2)Raman spectroscopy: only in the case of the BP-C composite Once the samples are obtained and characterized, the next goal is to obtain a slurry with the optimal properties like: composition, reagents, viscosity and solid loading ideal for making an anode and the consequent characterization of the electrochemical properties. Once the slurry is obtained, it is spread using a manual tape caster and then the casted slurry is treated in a vacuum oven. For both, the phosphorus and the spinel, it was decided to use the coin cells types as a half-cell by mounting them in the same way, as regards the order of the various components of the cell and as regards the type of electrolyte (NaPF6 1M in EC:PC + 5%NaPFSi + 2%FEC) and the cathode used (Na metal). All analyses were performed on a coin cell and the following electrochemical characterization techniques were conducted using a BCS-810 battery tester: 1) Electrochemical impedance spectroscopy (PEIS) 2) Galvanostatic cycling with potential limitation (GCPL) 3) Pulsed cycling galvanostatic analysis (PGCA) From the GCPL, the BP-C composite shows excellent experimental capacity in comparison with the theoretical capacity with a yield of 65-70% and maintaining for all cycles an efficiency that oscillates between 90-100% for all cells. The HS presented an extremely low capacity value compared to the theoretical one expected (about 6%), one hypothesis is that sodium is not able to form an alloy capable of conducting unlike the case of lithium. As for the PGCA of the BP-C from the analysis it is possible to affirm the reversibility of the sodiation and desodiation process following the alternation of formation and dissociation of the Na3P species. The intensity of the peaks of the same cycle is comparable while the drop of the intensity value starting from the second cycle is in line with what has already been seen with the GCPL analyses.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/11845