Ab Initio Molecular Dynamics Simulations of Amorphous Metal-Polysulfides as Cathode Materials for Lithium-Ion Batteries

Lithium-sulfur batteries offer a few advantages, including high energy density and low cost, compared to our current battery technology. However, various polysulfide intermediates formed during charging and discharging lead to the polysulfide shuttle effect, which hinders their commercial application. It has been shown that amorphous metal sulfides can reduce the formation of polysulfides, although a fundamental understanding is lacking. In this research, amorphous molybdenum and titanium sulfides with different sulfur concentrations were generated by the simulated melt-quench process using ab initio molecular dynamics simulations. Different numbers of lithium ions were added at the cathode/electrolyte interface to simulate the electrochemical conversion process in these materials. It is observed that the behavior of amorphous metal sulfides is different from that of sulfur, and the formation and diffusion of lithium polysulfides have been greatly reduced. Insights obtained from this work could help to develop new strategies to effectively inhibit the polysulfide shuttle effect.