Coupling of Solvent Vapor Pressure and Binder Solubility for Rational Coordination in Li-S Batteries

Abstract

Nowadays, the attention on energy storage systems is increasing along with technological advancements. Especially, the development of electric vehicles and portable devices such as smartphones demands high energy density batteries. Various post-Li-ion batteries have been researched in order to replace the conventional Li-ion battery, which has a low energy density due to its intercalation-based mechanism. The Li-S battery is one of the most promising post-Li-ion batteries for the following attractive features: (i) high theoretical capacity up to 1675 mAh/g, (ii) natural abundance, and (iii) a low price. In spite of aforementioned advantages, several obstacles hinder the commercialization and scaling-up of the Li-S battery. First, end-products of charge/discharge reaction are electrically insulating sulfur and Li2S, respectively. Furthermore, the dissolution and irreversible loss of polysulfides cause severe capacity fading during cycles. In this thesis, research is largely focused on the cathode materials and structure to address the problems mentioned above. In Chapter 1, principles, challenges and previous approaches of the Li-S battery will be briefly introduced. In Chapter 2, the protection layer coating strategy will be accounted. First, sulfur cathodes were fabricated with two different nanostructured carbons. Then, an additional carbon layer was directly coated on the sulfur cathode via the simple doctor-blade method by utilizing chloroform solvent and polyethylene binder. With this strategy, a thin and lightweight carbon layer was constructed on the sulfur cathode and resulted in excellent electrochemical performances.