Computer study of the structure and thermal stability of a monolayer mos2 film on a diamond substrate

MoS2 is a promising candidate for next-generation electrical and optoelectronic devices. The use of chemical vapor deposition allows obtaining high-quality MoS2 monolayers on a diamond substrate. However, it is not clear how firmly the MoS2 monolayer is held on the diamond substrate at a high temperature and how the structure of the MoS2 monolayer changes after its deposition on the diamond substrate and subsequent heating on it. In this paper, the molecular dynamics method is used to study the stability of single-layer MoS2 in the temperature range of 250 – 550 K. The molybdenum disulfide film on a diamond substrate structure is studied by constructing Voronoi polyhedra. Polyhedra were built around Mo atoms, and faces are formed by neighboring S atoms. The distributions of polyhedrons by the number of faces were found. These distributions were also calculated for truncated polyhedra obtained by eliminating small geometric elements. A comparison of the obtained statistical distributions for a MoS2 monolayer on a diamond substrate with the corresponding characteristics of an autonomous monolayer MoS2 indicates a significant change in the structure of the monolayer. This change is a result of its deposition on the diamond substrate. When the temperature reaches 550 K, the MoS2 film is completely separated from the substrate. There is a singularity near this temperature, which indicates the thermal instability of the system under investigation. © 2019, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved

Computational study of lithium intercalation in silicene channels on a carbon substrate after nuclear transmutation doping

Silicene is considered to be the most promising anode material for lithium-ion batteries. In this work, we show that transmutation doping makes silicene substantially more suitable for use as an anode material. Pristine and modified bilayer silicene was simulated on a graphite substrate using the classical molecular dynamics method. The parameters of Morse potentials for alloying elements were determined using quantum mechanical calculations. The main advantage of modified silicene is its low deformability during lithium intercalation and its possibility of obtaining a significantly higher battery charge capacity. Horizontal and vertical profiles of the density of lithium as well as distributions of the most significant stresses in the walls of the channels were calculated both in undoped and doped systems with different gaps in silicene channels. The energies of lithium adsorption on silicene, including phosphorus-doped silicene, were determined. High values of the self-diffusion coefficient of lithium atoms in the silicene channels were obtained, which ensured a high cycling rate. The calculations showed that such doping increased the normal stress on the walls of the channel filled with lithium to 67% but did not provoke a loss of mechanical strength. In addition, doping achieved a greater battery capacity and higher charging/discharging rates. © 2020 by the authors.Russian Science Foundation, RSF: 16-13-00061Funding: This work was supported by the Russian Science Foundation (grant number 16-13-00061)

Silicene Anodes for Lithium-Ion Batteries on Metal Substrates

This article discusses heterogeneous materials containing silicene, which can be a promising anode for lithium-ion batteries. In addition to the current collector on an ultrathin insulator, the anode includes sheets of silicene spaced 0.75 nm apart. One of these sheets is on a metal substrate. Using the molecular dynamics method, we study new anode materials obtained from silicene on various metal substrates. In terms of the degree of filling of the anode and its mechanical strength, preference is given to Ni (111) and Cu (111) substrates. The highest degree of crystallinity of the packing is realized in a silicene channel on an Ag (111) substrate. The smallest local normal stresses appear in the channel walls on the Al (111) substrate. The voltage profile is defined as a function of the concentration of Li adsorbed on a two-layer silicene. The charge capacity of a two-layer freestanding silicene was estimated based on the study of its local destruction. Each of the considered metal substrates has a significant effect on the electronic properties of single-layer silicene, which leads to its metallization. The calculated partial densities of the electronic state allow us to establish the causes of the occurrence of metallic conductivity in silicene. © 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.Russian Science Foundation, RSF: 16-13-00061This work was supported by the Russian Science Foundation [the grant number 16-13-00061]

Physical aspects of the lithium ion interaction with the imperfect silicene located on a silver substrate

Epitaxy of Si on a silver substrate is the main method to obtain silicene. The latter does not separate from the substrate. In the present paper, the possibility of using silicene on a silver substrate as an anode for lithium-ion batteries is studied by the method of molecular dynamics. Structural and mechanical effects arising from the motion of a Li + ion through a planar channel formed by a perfect and defective two-layer silicene are studied. Generally, the defect stability and silicene sheet integrity are independent of the Ag(001) or Ag(111) substrate type. The transverse vibrations of Si atoms in the channel have a significant effect on the motion of lithium ions. This effect is taken into account by using the interference factor that describes the slowing down of the motion of the Li + ion in the channel. The dependence of this coefficient on the size of vacancy defects in silicene is determined. The presence of the substrate makes this dependence less relevant. The stress distribution in the defective silicene while driving a lithium ion along the planar silicene channel is calculated. The strongest stresses in the silicene are created by forces directed perpendicular to the strength of the external electric field. These forces dominate in the silicene channel placed on the substrates of both types. © 2018, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.Acknowledgements. This study is supported by the Russian Science Foundation (project no. 16‑13‑00061)

Computer Test of a Modified Silicene/Graphite Anode for Lithium-Ion Batteries

Despite the considerable efforts made to use silicon anodes and composites based on them in lithium-ion batteries, it is still not possible to overcome the difficulties associated with low conductivity, a decrease in the bulk energy density, and side reactions. In the present work, a new design of an electrochemical cell, whose anode is made in the form of silicene on a graphite substrate, is presented. The whole system was subjected to transmutation neutron doping. The molecular dynamics method was used to study the intercalation and deintercalation of lithium in a phosphorus-doped silicene channel. The maximum uniform filling of the channel with lithium is achieved at 3% and 6% P-doping of silicene. The high mobility of Li atoms in the channel creates the prerequisites for the fast charging of the battery. The method of statistical geometry revealed the irregular nature of the packing of lithium atoms in the channel. Stresses in the channel walls arising during its maximum filling with lithium are significantly inferior to the tensile strength even in the presence of polyvacancies in doped silicene. The proposed design of the electrochemical cell is safe to operate. Copyright © 2020 American Chemical Society

Computational Study of Lithium Intercalation in Silicene Channels on a Carbon Substrate after Nuclear Transmutation Doping

Silicene is considered to be the most promising anode material for lithium-ion batteries. In this work, we show that transmutation doping makes silicene substantially more suitable for use as an anode material. Pristine and modified bilayer silicene was simulated on a graphite substrate using the classical molecular dynamics method. The parameters of Morse potentials for alloying elements were determined using quantum mechanical calculations. The main advantage of modified silicene is its low deformability during lithium intercalation and its possibility of obtaining a significantly higher battery charge capacity. Horizontal and vertical profiles of the density of lithium as well as distributions of the most significant stresses in the walls of the channels were calculated both in undoped and doped systems with different gaps in silicene channels. The energies of lithium adsorption on silicene, including phosphorus-doped silicene, were determined. High values of the self-diffusion coefficient of lithium atoms in the silicene channels were obtained, which ensured a high cycling rate. The calculations showed that such doping increased the normal stress on the walls of the channel filled with lithium to 67% but did not provoke a loss of mechanical strength. In addition, doping achieved a greater battery capacity and higher charging/discharging rates. © 2020 by the authors.Russian Science Foundation, RSF: 16-13-00061Funding: This work was supported by the Russian Science Foundation (grant number 16-13-00061)

Elementary Unit for A Lithium-Ion Battery and Battery Based on It

FIELD: battery production. SUBSTANCE: invention relates to materials of lithium-ion batteries with high specific energy. An elementary unit of a battery consists of current collectors, an anode, a cathode, an electrolyte and an insulator. Thin–film electrolytes are used as electrolytes, lithium-cation-conducting materials are used as cathodes. A multilayer graphite-silicene composition is used as an anode with a ratio of 5 monoatomic layers of silicene on a graphite substrate of 4-8 monoatomic layers of graphene. The silicene sheets are separated by a gap of 0.24-0.75 nm. The graphite substrate is preferably made of 8 layers and is coated with silicene on both sides. A lithium-ion battery is made from parallel connected elementary cells placed in a housing isolated from the external environment of the atmosphere. The cells can be connected mirrorlike relative to the plane parallel to the plane of the silicene. EFFECT: increase in the number of discharge/charge cycles of the battery to 5000 and above without reducing the specific capacity of the anode below 3500 mAh/g in the operating temperature range (from -50 to 100°C), reducing the size and weight of the lithium-ion battery, eliminating the volumetric expansion of the anodes of the elementary cells and the lithium-ion battery as a whole. 5 cl, 2 dwg, 1 tbl.Изобретение относится к материалам литий-ионных аккумуляторов с высокой удельной энергией. Элементарная ячейка аккумулятора состоит из токосъемников, анода, катода, электролита и изолятора. В качестве электролитов используют тонкопленочные электролиты, в качестве катодов – катионпроводящие по литию материалы. В качестве анода используют многослойную графит-силиценовую композицию при соотношении 5 моноатомных слоев силицена на графитовую подложку из 4-8 моноатомных слоев графена. Силиценовые листы разделены зазором 0,24-0,75 нм. Графитовая подложка предпочтительно выполнена из 8 слоев и с обеих сторон покрыта силиценом. Из параллельно соединенных элементарных ячеек, размещенных в изолированном от внешней среды атмосферы корпусе, изготавливают литий-ионный аккумулятор. Ячейки могут быть соединены зеркально относительно плоскости, параллельной плоскости силицена. Технический результат заключается в увеличении числа циклов разряда/заряда аккумулятора до 5000 и выше без снижения удельной емкости анода ниже 3500 мА·ч/г в диапазоне рабочих температур (от -50 до 100°С), уменьшении размеров и массы литий-ионного аккумулятора, исключении объемного расширения анодов элементарных ячеек и литий-ионного аккумулятора в целом. 2 н. и 3 з.п. ф-лы, 2 ил., 1 табл