Friday, 16 April 10:00

The title of this webinar is: “Engineering the crystallinity of MoS2 for potassium-ion batteries”

ABSTRACT

Two-dimensional transition metal dichalcogenides (TMDs) are being heavily studied in battery research due to their structural uniqueness and interesting electrochemical mechanisms. They undergo a two-step electrochemical process that includes an intercalation reaction and a subsequent conversion reaction, where the former uses van der Waals gaps to accommodate ions and the latter causes the reduction of transition metals upon continuous ion insertion. Synthetic methods of layered TMDs are designed primarily focusing on high capacities derived from the conversion reaction, which often is a collective result of several contributors such as composites and carbon incorporation. In this talk, I will summarise our use of MoS2 as a potassium-ion battery (PIB) anode and decouple a critical factor, crystallinity, from the contributors. I will show that a lower degree of crystallinity can alleviate diffusional limitation of the intercalation reaction in storing K-ions, whereas a higher degree of crystallinity can ensure the structural stability of MoS2 layers and promote surface charge storage during the conversion reaction. Building on these observations, I will demonstrate a defect and interlayer engineering to exploit the van der Waals gaps as a natural asset to intercalate K-ions in MoS2 via transforming the ion diffusion from two dimensional to three dimensional.

Reference

  1. Y. Xu, F. Bahmani, et al., Nanoscale Horiz., 2019, 4, 202.
  2. Y. Dong, Y. Xu, et al., Small, 2019, 15, 1900497.

ABOUT THE PRESENTER

Dr Yang Xu received his PhD in chemistry at the University of Science and Technology of China in 2011 under the supervision of Prof. Yi Xie. His PhD research focused on vanadium-based nanomaterials and their applications in aqueous lithium-ion batteries, for which he received Chu Yuet Wah Chinese Academy of Sciences Award for Outstanding Doctoral Student. He carried out postdoctoral research at Boston College and the University of Alberta, where he worked on thin films for photoelectrochemical water splitting in the group of Prof. Dunwei Wang in the US and sodium-ion batteries in the group of Prof. David Mitlin in Canada. He then worked as a senior scientist and group leader at the Technical University of Ilmenau in Germany from 2013 to 2019, where he continued his research on sodium-ion batteries and started investigating in potassium-ion batteries. In 2019, he was appointed Lecturer in Electrochemical Energy Storage in the Department of Chemistry at University College London. His research presently focuses on beyond-lithium battery chemistries and devices, encompassing design of electrode materials with structural defects, understanding of the ion transport and storge associated with defects, and solid-liquid interfaces towards local electrochemical reactivity. His group is also interested in exploiting metal anode batteries based on conversion reactions.