First‐principles Screening of Transition‐Metal Doped FeS2 As Sulfur Cathode Host for Sulfur Redox Chemistry

Abstract

AbstractThe 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 affects 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.