(97g) Characterization of Polymer Binders to Improve Cyclability of Lithium-Sulfur Batteries

New emerging technologies such as hybrid electric vehicles and fully electrified vehicles require higher energy densities than Li-ion can provide. As a result, we must look into different battery chemistries that can supply adequate power to these systems. Li-S has been identified as a potential candidate to replace the Li-ion. There are many issues preventing commercialization of the Li-S battery and it’s poor cycling performance is a major obstacle to be overcome. This work focuses on using polymer binders to prevent the detrimental “shuttle effect” in these batteries. Poly-acrylic acid (PAA), carboxymethyl cellulose (CMC) and a tri-block copolymer (SBAS) were identified as potential candidates for use as binders in Li-S batteries. Various electrochemical techniques and SEM were used to characterize their abilities to improve cycle performance. From an analysis of the charge capacity and coulombic efficiencies vs the cycle number, a mixture composed of PAA:SBAS was shown to have the quickest and most stable cycling performance. Addition of SBAS to CMC or PAA improved the initial capacity and performance of the battery. SEM images revealed that the choice of binder could affect the sulfur distribution on the electrode. Electrochemical impedance spectroscopy (EIS) was used to study the resistances inherent with these binders. We proposed that the two-time constants observed in the spectra was similar to Gamry’s proposed model of a failed coating. The first semi-circle was attributed to the capacitance across the polymer coating and the second semi-circle was attributed to the double layer formed near the electrode.