Compositional and Structural Aspects of Li-rich Anti-perovskites as Li-ion Battery Cathodes

Mikhail V. Gorbunov

AutorIn

Mikhail V. Gorbunov

Titel

Compositional and Structural Aspects of Li-rich Anti-perovskites as Li-ion Battery Cathodes

Zitierfähige Url:

https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa2-836136

Erstveröffentlichung

2023

Datum der Einreichung

19.09.2022

Datum der Verteidigung

31.01.2023

Abstract (DE)

Alkali-metal ion battery cathode is the part which mostly defines its specific characteristics, thus, studies in this field are always important, to make the batteries fulfill the needs of the rapidly accelerating progress and growing market. Current dissertation represents a comprehensive physicochemical study of novel inorganic compounds with general formula of Li2MChO (M – Mn, Fe, Co; Ch– S, Se) and Pm-3m anti-perovskite structure. One of their key properties is the electrochemical activity, and rather high specific capacity, explained by a high amount of lithium which can be reversibly extracted per formula unit. Although the practical application of these materials as Li-ion battery cathodes is limited due to relatively low operation voltage and high requirements to synthetic conditions, outstanding chemical flexibility of the crystal structure turns the cubic anti-perovskites into excelsior model for studying the synergetic effects of various transition metal cations on the structural stability against lithium removal, as well as on the mechanism of charge compensation. The named investigations are mostly based on operando methods, using synchrotron radiation facilities, and the electrochemical activity of anti-perovskites provides an opportunity to conduct such experiments: while lithium is removed or inserted into the crystal lattice, the electrochemical cell is irradiated, allowing to observe the changes constantly. Such studies may bring use for the battery research in general and give certain hints for creation of new battery materials, in particular, high-entropy ones (if two transition metal cations, or two chalcogenide anions are combined in Li2MChO formula, the compound formally becomes a high-entropy one). Besides, an attempt to extend the research topic was done, introducing the double anti-Ruddlesden-Popper phases (double anti-perovskites). Their structure is layered, which is favorable for the reversible electrochemical alkali-metal, which is in this specific case sodium, extraction, however, as their cationic and anionic sublattices are formed by the same transition metal cations and by the same anions, as in cubic anti-perovskites, they suffer from the same issue of low operation voltage. Nevertheless, from this type of structure it is also possible to expect chemical flexibility, which makes them model compounds as well, but for investigations on layered cathode materials, which are rather common nowadays: one of the most typical examples of those is NMC, which is commercialized, but still has much of unrealized potential. In the end, this dissertation is considered by its author as primarily fundamental research, which is supposed to expand the knowledge in the field of physical chemistry of novel battery compounds, and to give certain keys for their development.

Freie Schlagwörter (EN)

Anti-perovskites, operando Methoden, XAS, XRD, LIB

Klassifikation (DDC)

540

Klassifikation (RVK)

VN 6057

GutachterIn