High-Rate Performance of Antimony Chalcogenides (Sb2X3) Studied By Operando X-Ray Diffraction (XRD)
Authors: Skurtveit Amalie , Pastusic Andrew , Brennhagen Anders , Cavallo Carmen , Wragg David Stephen , Koposov Alexey 
Published: February 2024

Na-ion batteries (NIBs) represent an environmentally-friendly and sustainable alternative to Li-ion batteries (LIBs), owing to the higher abundance of Na compared to Li. [1] However, many challenges associated with the successful implementation of NIBs are yet to be addressed, which includes the optimization of the present set of materials. Among others, the development of high-performing anode materials as a replacement for conventionally used hard carbon is essential to deliver NIBs with high energy density. A class of materials promising for implementation in NIBs is based on the combined conversion/alloying reaction pathway as a main motive of their operating mechanism. [2] However, such conversion/alloying materials (CAMs) typically undergo a set of complex structural and chemical transformations during electrochemical cycling (formation of new phases, amorphization, etc). [3] Investigation of the (de)sodiation mechanism using advanced characterization techniques, such as operando X-ray diffraction (XRD), is therefore the key to revealing the true potential of these battery mechanisms.

Among many CAMs, Sb-based chalcogenides (Sb2X3, where X = O, S, Se, Te) have demonstrated superior electrochemical performance in NIBs. In the present work, the research efforts have been focused on elucidating the (de)sodiation mechanism of Sb2Se3/Sb (Sb-rich Sb2Se3) materials using operando XRD. The study reveals the true complexity of the (de)sodiation mechanism for Sb2Se3/Sb (Figure 1), where the active material passes through a combination of multiple phases (Na2Se, Na2Se4, Sb, NaSb, hexagonal Na3Sb, cubic Na3Sb) during sodiation, where some of these phases are amorphous.

One of the discovered benefits of such chalcogenide materials is the ability to operate at high cycling rates. Therefore, another objective of this study is to understand if and how the (de)sodiation mechanism change as a function of the C-rate. The preliminary operando XRD analysis suggests that kinetics plays a crucial role in the formation of certain phases during cycling leading to a rate-dependent cycling mechanism. Thus, a systematic study utilizing specific currents of 100 mA g-1, 1000 mA g-1, and 5000 mA g-1 have been applied to the Sb2Se3/Sb system to deepen the understanding of the (de)sodiation mechanism.

This presentation will underpin the fundamentals of the cycling mechanism of Sb2Se3/Sb using operando XRD as a function of cycling rates. A better knowledge of the various mechanisms by which sodium can move in and out of this material is crucial for our understanding and potentially mitigate the limited cycling stability that limits their practical usefulness.

References.

Hasa, I., et al., Challenges of today for Na-based batteries of the future: From materials to cell metrics. Journal of Power Sources, 2021. 482: p. 228872.

Skurtveit, A., et al., Benefits and Development Challenges for Conversion-Alloying Anode Materials in Na-Ion Batteries. Frontiers in Energy Research, 2022. 10.

Brennhagen, A., et al., Understanding the (De)Sodiation Mechanisms in Na‐Based Batteries through Operando X‐Ray Methods. Batteries & Supercaps, 2021. 4(7): p. 1039-1063.

Figure 1