Glutamine as electrolyte additive and electrode binder for high capacity and stability in lithium-sulfur batteries.

Abstract

Lithium-sulfur batteries (LSB) are expected to be the next generation of LIB due to many advantages such as outstanding theoretical energy densities and environmental-friendly characteristics. However, many challenges still remained such as poor stability, liquid LiPS dissolution, and unstable interface on Li-anode. In this study, we introduced glutamine, which is one of the amino-acid materials, as electrolyte additives and binder materials on enhancing the performance of LSB. glutamine is an environmentally safe and cost-effective material. And, the molecular structure of glutamine is a polar surface charge containing both two amine and carboxyl groups. Considering the properties of glutamine, we observed the reduced overvoltage for Li plating process and improved long-term performance stability. It indicates that Li dendrite formation was effectively suppressed resulting from the uniform Li-ion flux by the glutamine-containing electrolyte. Also, we confirmed that the electrochemical kinetics of LiPS was enhanced through electrochemical analyses. Meanwhile, mechanical adhesion of electrode was enhanced by hydrogen bonding. And glutamine binder ensures the intimate contacts between active sulfur and conductive carbon. As a result, glutamine using the electrolyte additives and binder materials helped improve cell stability at high C-rate and mitigate the cell degradation rate for long-term cycles.