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 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 space charge layer.
All-solid-state lithium-sulfur batteries (ASSLSBs) have the highly reversible characteristics owing to high redox potential, high theoretical capacity, high electronic conductivity, and low Li+ diffusion energy barrier in the cathode. Monte...
The sulfur cathode host Fe1‐xMxS2 (M = transition metal; x = 0, 0.125, and 0.25) for the sulfur redox chemistry is essential to facilitate the fast charge‐discharge kinetics of lithium‐sulfur‐batteries (LSBs). Applying first‐principles calculations, the formation energy, conductivity, work function, charge redistribution, chemical adsorption, and catalytic performance of Fe1‐xMxS2 are systematically investigated. Ti/V‐doped FeS2 has low lattice distortion and formation energy, and facilitates the Li+ diffusion due to charge redistribution. Chemical adsorption for polysulfides (LiPSs) is closely related to d‐band center of Fe1‐xMxS2. Li2S’s activation begins with the transfer of electrons from the electron‐rich metal center to the empty orbitals of Li2S. Gibbs free energy change of Li2S4 to Li2S determines the catalytic efficiency. Li2S deposition and decomposition affect the redox kinetics of sulfur. Ti/V‐doped FeS2 has superior conductivity, chemical adsorption, and has low thermodynamic barrier of Li2S deposition. Li2S decomposition tends to occur on Fe0.875Ti0.125S2(001) surface. In general, Ti/V‐doped FeS2, as the host material of the sulfur cathode, is more beneficial to the cycle performance of LSBs. The electrochemical properties of sulfur cathode host materials can be controlled by doping, and can be manipulated and optimized in a certain range through electronic structure and chemical composition design in LSBs.
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