Prediction of New Phase and Electrochemical Properties of Li₂S₂ for the Application of Li-S Batteries

Abstract

The intermediate product LiS plays a pivotal role in the charge/discharge process of lithium-sulfur batteries. However, the structural configuration and relevant properties of LiS are unclear. In this work, by using ab initio calculations, we present results of novel phases, average open circuit voltages ( Vs), and electronic properties of the stable LiS. Two new LiS phases are predicted: orthorhombic ( Cmca) and orthorhombic ( Immm) structures. The calculated Vs of hexagonal ( P6/ mmc), orthorhombic ( Cmca), and orthorhombic ( Immm) are 3.91, 3.95, and 3.88 V, respectively. In particular, the calculated band gap of the Immm structure is about 0.225 eV, which is smaller than that of LiS. The narrow band gap of LiS derives from the electronic lump between the Li s state and S 3p state for the orthorhombic structure. Therefore, the electronic properties of LiS are markedly influenced by the structural configuration.

Enhancing the Vickers hardness, melting point and thermodynamic properties of hafnium dodecaboride

“…It is well known that the structural stability is related not only to the thermodynamic stability but also to the dynamic stability. 66,67 Generally, the dynamic stability of a solid is measured by the phonon frequency. The imaginary phonon frequency means the dynamic instability, and vice versa.…”

The structural, mechanical, and thermodynamic properties of B2‐type TMZr (TM = Ru, Mo, Rh, Os, and Re) compounds from first‐principles calculations

“…It is well known that the dynamic stability of a solid is estimated by the phonon dispersion, which is related to the vibrational frequency. The vibration free energy of a solid is calculated by the quasi‐harmonic approximation ( QHA ) .…”

“…It is well known that the dynamic stability of a solid is estimated by the phonon dispersion, [39,40] which is related to the vibrational frequency.…”

First‐principles calculation of temperature‐dependent electronic transitions mechanism in V or Nb substituted BiFeO3

“…Density functional theory (DFT) calculations are a powerful method to study the electronic transitions in BFO . The reported literature shows that using DFT with GGA or GGA + U qualitatively predicts the electronic transitions related to the Fe─O octahedrons of BFO . These transitions are determined by both the p–d charge‐transfer transitions from the occupied O‐2p to the unoccupied Fe‐3d states, and the d–d transition between the Fe‐3d orbitals located at the top and bottom of the valence and conduction bands (CBs), respectively.…”

“…[26][27][28] The reported literature shows that using DFT with GGA or GGA + U qualitatively predicts the electronic transitions related to the Fe─O octahedrons of BFO. [29,30] These transitions are determined by both the p-d charge-transfer transitions from the occupied O-2p to the unoccupied Fe-3d states, and the d-d transition between the Fe-3d orbitals located at the top and bottom of the valence and conduction bands (CBs), [31][32][33] respectively. However, the quantitative calculation of the temperature effect on the electronic transitions in BFO has been rarely reported.…”