Theoretical and experimental understanding of Li2S crystal structure and its isotropic ion conduction mechanism

Lithium sulfide is a crucial material for Li-S solid electrolytes, as it serves as the costly precursor in the research and development of solid-state batteries. This study introduces an economical carbothermal reduction method for synthesizing Li 2 S powder. Physicochemical studies are conducted to assess the crystallinity, morphology, homogeneity, and oxidation state of the produced Li 2 S powders. DFT calculations are utilized to visualize the crystal structure and atomic sites in Li 2 S. Electrochemical impedance spectroscopy analysis examines the ionic conductivity of the prepared pellets at specific temperatures. NVT-Molecular Dynamics method is applied to evaluate the diffusion coefficient of Li 2 S crystal structure at both low and high temperatures. A high concentration of disordered defects correlates with excellent ionic behavior at T = 700 K. The Nudged Elastic Band study demonstrates the activation energy (E Li+ ) for Li ion hopping between neighboring and distant Li sites. The low activation barrier and identification of lithium ion conduction channels confirm that Li 2 S is an isotropic ionic conductor. • Li 2 S powder is synthesized using an economical carbothermal reduction method. • Density Functional Theory and Molecular Dynamics are used to analyze the structural and Li-ionic migration mechanisms. • The Nudged Elastic Band method is employed to understand the isotropic hopping behavior of Li ions. • Electrochemical impedance spectroscopy method is applied to analyze the ionic conductivity