Modeling Metal Nitrides for Interface Design in Lithium-Sulfur Batteries with GPUs and CPUs

Abstract

As current batteries reach their limits, finding new battery materials is crucial. Lithium-sulfur batteries are a promising next-generation technology but face three major issues: low active material utilization, cathode pulverization, and limited polysulfide conversion leading to anode corrosion. Nano-deposition of metal nitride (MNx, M = Ti, V, Zr, etc.) layers on the graphene sulfur cathodes could significantly improve conductivity and cycling performance. Nevertheless, the large number of potential metal candidates requires preliminary and efficient computational screening using density-functional theory (DFT). This modeling framework can be used to calculate many properties of the coatings and screen out poor candidates. Firstly, the surface-adsorption ability of metal nitride candidates for lithium polysulfide intermediates involved in the electrochemical cycle (Li2S, Li2S2, Li2S4, Li2S6, Li2S8, S8) must be greater than the adsorption by dioxolane and dimethyl ether electrolytes (>~0.99eV). Secondly, the electronic properties before and after adsorption must feature significant density of states near the Fermi level, as a possible indicator of good electrical conductivity. Lastly, the free-energy profiles for the sulfur reduction reaction (SRR) over the remaining candidates will be estimated to better understand the catalytic properties of the metals. Particular attention will be paid to the Li2S2 reduction to Li2S, the potential limiting step. The top catalyst candidates should allow for an exergonic reaction. Finally, this application serves as a case study for our modeling platform, and the relative merits of standard for CPUs and GPUs in terms of computation time and accuracy will be discussed. Careful analysis of binding energy results, densities of states, and energy profiles for the various metal candidates provides valuable insights into the design of experimentally viable lithium-sulfur batteries, as well as advanced interface design in the broader field of battery research.