Structural Transitions in Monolayer MoS₂by Lithium Adsorption

Abstract

Based on first-principles calculations, we study the structural stability of the H and T phases of monolayer MoS 2 upon Li doping. Our calculations demonstrate that it is possible to stabilize the T phase of MoS 2 over the H phase through adsorption of Li atoms on the MoS 2 surface. Through molecular dynamics and phonon calculations we show that the T phase of MoS 2 is dynamically unstable and undergoes considerable distortions. The type of distortion depends on the concentration of adsorbed Li atoms and changes from zigzag-like to diamond-like when increasing the Li doping. There exists a substantial energy barrier to transform the stable H phase to the distorted T phases which is considerably reduced by increasing the concentration of Li atoms. We show that it is necessary that the Li atoms adsorb on both sides of the MoS 2 monolayer to reduce the barrier sufficiently. Two processes are examined that allow for such twosided adsorption, namely penetration through the MoS 2 layer and diffusion over the MoS 2 surface. We show that while there is only a small barrier of 0.24 eV for surface diffusion, the amount of energy needed to pass through a pure MoS 2 layer is of the order of 2 eV. However, when the MoS 2 layer is covered with Li atoms the amount of energy that Li atoms should gain to penetrate the layer is drastically reduced and penetration becomes feasible.

Understanding the structural, electrical, and optical properties of monolayer h-phase RuO2 nanosheets: a combined experimental and computational study

“…3, our NEB calculations estimated an activation energy barrier of 0.58 eV for the phase transition from distorted h-RuO 2 to distorted t-RuO 2 . A recent theoretical study of MoS 2 showed that h-MoS 2 is more stable than t-MoS 2 by 0.8 eV, and the activation barrier of the phase transition from t-MoS 2 to h-MoS 2 is 0.79 eV 25 . Although h-MoS 2 is more stable than t-MoS 2 , metastable t-MoS 2 induced by chemical exfoliation has been observed at room temperature 22,26 .…”

Electric field enhanced adsorption and diffusion of adatoms in MoS2 monolayer

“…As the NEB method has not been included into the main SIESTA code, in this study the diffusion barriers were calculated using a constrained method in the present work, in which the ions were constrained in the direction along the diffusion path, whereas it is allowed to relax in the direction perpendicular to the diffusion path. The diffusion path for the Li, Mg and Al atoms in the MoS 2 monolayer is from a T site to another nearest T site by passing through the metastable H site [38] as shown in Fig. 3 The diffusion coefficient varies exponentially with the diffusion barrier following an Arrhenius-like formula [58]:…”

“…Reducing the thickness of the graphite can significantly improve its energy capacity, and a mono-layer of graphene has much higher energy capacities of 600-1000 mAh/g [9,10]. Other types of monolayer materials such as molybdenum disulfide (MoS 2 ) [11], V 2 O 5 [12], and transition-metal nitride [13] have also received much attention to be used as the electrode materials for the LIBs. Recently, MoS 2 with a graphite-like layered structure has been explored as a new generation of renewable energy related materials, used as catalysts for dissociation of H 2 O [14], catalysts for hydrogen evolution reaction [15], and anode materials for the rechargeable ion batteries [16][17][18].…”

“…At the same time, the anode materials should have a large exothermic reaction energy for the transporting ions in order to achieve a large storage capacity [37]. The diffusion barriers for the Li and Na in a monolayer of MoS 2 calculated using density function theory (DFT) are 0.24 [38] and 0.68 eV [34] , respectively, and the Li mobility can be enhanced using the MoS 2 nanoribbons by reducing the dimensions [39]. Defects including single-and few-atom vacancies, antisite, and grain boundary are inevitable, thus the effects of defects on the electronic properties of the MoS 2 have been investigated [40,41].…”

Monolayer black phosphorus as potential anode materials for Mg-ion batteries

“…Currently, the other two-dimensional materials such as MoS 2 [6], V 2 O 5 [7] have also received much attention to be used as electrode materials for the LIBs. Two dimensional MoS 2 is a promising material for the LIBs with a large reversible storage capacity of 1290 mAhg -1 and a charge-carrier ~200 cm 2 V -1 s -1 [8].…”