Reconstruction and electronic properties of β-Li₃PS₄|Li₂S interface

Abstract The morphology and properties of the interface between solid electrolyte and electrode have important impacts on all-solid-state lithium-sulfur batteries’ performance. We used the first-principles calculations to explore the interface between Li2S cathode and β-Li3PS4 (lithium thiophosphate, LPS) solid electrolyte, including lattice structure, mechanical, electrical properties, interface contact type, and charge distribution in real space. It is found that the interface is significantly reconstructed, and the Li atoms at the interface move mainly parallel to the interface plane. The interface density states introduce metallic properties, mainly contributed by the Li-s and S-s, -p orbitals in Li2S and S-p orbitals in LPS. The highest occupied molecular orbitals of the LPS electrolyte are lower than the electrochemical potential (Fermi level) of the Li2S cathode, thus the electrolyte and cathode materials are reasonable and stable in thermodynamics. Interface density of states shows electrons on the interface do not penetrate from Li2S into LPS, and do not leak electrons to cause electron conduct in LPS. Besides, the interface is an n-type Schottky barrier with a barrier value of 1.0 eV. The work-function of the interface indicates that there is a space charge layer (SCL) by the redistribution of electrons, which is in agreement with the result of interface charge density difference. The electron/hole pairs will be separate, realizing high current charge and discharge capability because of the SCL.