doctoral thesis
Ava Rajh (Author), Matjaž Kavčič (Mentor)

Abstract

This thesis presents the development and application of novel characterization methodologies for studying structural and chemical changes in next generation battery technologies. This research focuses on the development and application of photon-in/photon-out spectroscopies, in particular X-ray Raman Scattering (XRS) and Laboratory X-ray Emission Spectroscopy (XES), which are used to circumvent certain limitations of the conventional X-ray absorption spectroscopy. XRS is a non-resonant inelastic photon scattering technique that overcomes the shallow probing depth limitations of traditional soft X-ray methods, enabling analysis of light elements in bulk samples and operando measurements. It was implemented for the study of structural changes in carbon anodes during Na-ion battery discharge/charge cycle and to characterize the electrochemical processes in metal-organic batteries. By analyzing the C K-edges, XRS provided information about structural changes in the hard carbon anodes as a result of initial carbonization temperature and Na insertion during cycling. The study of Na K-edges was used for characterization of Na species in the solid electrolyte interface. In the study of metal-organic batteries, XRS was used to record O K-edge spectra to monitor changes in the amount of carbonyl bonds in samples and to provide insight into the redox mechanism and reaction intermediates within the organic cathodes. The interpretation of experimental results was supported by density functional theory calculations of XAS spectra of target elements. XES enables the use of laboratory excitation sources and, when paired with high-resolution crystal Bragg spectrometers, it can achieve chemical characterization comparable to the conventional synchrotron-based XAS. Such laboratory approach improves accessibility of advanced elemental characterization in battery analysis. The feasibility of XES was demonstrated by tracking the chemical state of sulfur and characterizing sulfur species during the charge/discharge cycles of Li-S batteries.

Keywords

X-ray emission spectroscopy;Raman scattering;density functional theory;next generation batteries;

Data

Language: English
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UL FMF - Faculty of Mathematics and Physics
Publisher: [A. Rajh]
UDC: 543.427.3:621.352(043.3)
COBISS: 229418499 Link will open in a new window
Views: 103
Downloads: 25
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Other data

Secondary language: Slovenian
Secondary title: Karakterizacija strukturnih sprememb v baterijah z ramansko in emisijsko spektrometrijo rentgenskih žarkov
Secondary abstract: V disertaciji predstavljam razvoj in uporabo naprednih rentgenskih spektroskopskih metod za preučevanje strukturnih in kemijskih sprememb v novi generaciji baterijskih sistemov. Osredotočila sem se na razvoj in uporabo spektroskopij foton-noter/foton-ven, in sicer predvsem na rentgensko Ramansko sipanje (XRS) in laboratorijsko rentgensko emisijsko spektroskopijo (XES), ki presežeta nekatere omejitve konvencionalne rentgenske absorpcijske spektroskopije. XRS je neresonančno neelastično sipanje fotona, ki odpravlja omejitev majhne vdorne globine rentgenskih žarkov z energijo v območju mehke rentgenske svetlobe in omogoča analizo lahkih elementov v razsežnih vzorcih. Uporabila sem jo za preučevanje strukturnih sprememb v ogljikovih anodah med ciklom praznjenja/polnjenja Na-ionskih baterij in za karakterizacijo elektrokemijskih procesov v kovinsko-organskih baterijah. Z analizo spektra XRS na robu K v ogljiku sem določila strukturne spremembe v anodah iz trdega ogljika, ki so posledica začetne temperature karbonizacije in vstavljanja Na v C strukturo med baterijskim ciklom. Izmerjene spektre robov K na Na sem uporabila za karakterizacijo vezave natrija v trdo elektronsko pregrado. Pri raziskavah kovinsko organskih baterij sem uporabila XRS za meritve absorpcijskega roba K v kisiku, ki omogoča spremljanje količine karbonilnih vezi v vzorcih in s tem karakterizacijo procesa redukcije kisika. Eksperimentalne rezultate sem podprla z izračuni absorpcijskih spektrov tarčnih elementov v okviru teorije gostotnih funkcionalov. XES omogoča uporabo laboratorijskih virov vzbujanja in v kombinaciji z visoko ločljivimi Braggovimi kristalnimi spektrometri določitev kemijskega stanja elementa, ki je po natančnosti primerljiva s konvencionalno sinhrotronsko metodo XAS. XES sem uporabila za karakterizacijo elektrokemijskih procesov v bateriji Li-S. S pomočjo izmerjenih spektrov K\(\beta\) sem sledila redukciji elementarnega žvepla v vmesne produkte preko večih ciklov polnjenja in praznjenja baterije.
Secondary keywords: rentgenska emisijska spektroskopija;rentgensko ramansko sipanje;teorija gostotnih funkcionalov;baterije naslednje generacije;
Type (COBISS): Doctoral dissertation
Study programme: 0
Thesis comment: Univ. v Ljubljani, Fak. za matematiko in fiziko, Oddelek za fiziko
Pages: 151 str.
ID: 26206903