Molecular Dynamic Behavior of Lithium Atoms in a Flat Silicene Pore on a Copper Substrate
- PDF / 1,334,523 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 79 Downloads / 224 Views
ICAL PHYSICS OF NANOMATERIALS
Molecular Dynamic Behavior of Lithium Atoms in a Flat Silicene Pore on a Copper Substrate A. E. Galasheva, b, *, O. R. Rakhmanovaa, b, and A. V. Isakova aInstitute
of High-Temperature Electrochemistry, Ural Branch, Russian Academy of Sciences, Yekaterinburg, 620137 Russia bYeltsin Ural Federal University, Yekaterinburg, 620002 Russia *e-mail: [email protected] Received May 13, 2019; revised July 11, 2019; accepted July 22, 2019
Abstract—The processes of lithization/delithization in a flat slit-like pore formed from defective silicene sheets and located on a copper substrate are considered in a molecular dynamic (MD) simulation. Depending on the type of the defects (mono-, bi-, tri-, hexavacancies), such a pore can hold up to 67, 86, 60, and 23 lithium atoms during the entire MD calculation with the duration of up to 1 ns without being destroyed. As a result of the intercalation/deintercalation cycle, the structure of defective silicene changes, especially in the presence of tri- and hexavacancies. With the increase in the size of the defects, the mobility of the lithium atoms in the silicene pore also increases. The shape of the silicene sheets is not restored after delithization, and the volume of the space enclosed between them slightly changes. Effective use of silicene in lithium-ion batteries assumes that only mono- and bivacancies are present in its sheets. Keywords: molecular dynamics, silicene, copper substrate, lithization, delithization, mobility coefficient DOI: 10.1134/S1990793120040053
INTRODUCTION The use of batteries with a high energy density, long lifetime, and low cost is a key factor for consumer electronics, electric cars, and energy storage in grids [1–3]. The operation of lithium-ion batteries is based on the phenomenon of intercalation of lithium into the material of the electrode. Upon the charging of a battery, lithium is extracted from the material of the positive electrode and it is intercalated into the material of the negative electrode most often fabricated from graphite. Upon its discharge, these processes are reversed. One of the main characteristics of an electrode is its intercalation capacity, determined as the quantity of electricity imparted to the electrode upon full charging and calculated per the unit mass or volume. In particular, in the case of the full charging of a carbon electrode, the intercalation capacity is 372 mA h g−1. For a silicon electrode, this characteristic has a value of 4200 mA h g−1 [4]. The rate of the intercalation/deintercalation reaction is determined by the rate of diffusion of lithium in the solid phase. The coefficient of diffusion of lithium in the process of lithization/delithization, e.g., in bilayer graphene at room temperature, is 7 × 10−5 cm2/s [5]. To avoid a significant change in the volume (almost fourfold in the case of the use of crystalline silicon) during the intercalation of lithium, it is proposed to use negative electrodes made of thin-film materials [6–10]. Autonomous bilayer silicene does
Data Loading...
