Sulfur Infiltrated Carbon Aerogels as new Cathode Material for LiS high Energy Batteries

Abstract

Lithium-Sulfur Batteries are one of the promising technologies for future energy storage applications. This technology has the potential of a specific capacity of 1675 mAh g-1, which is significantly higher than common lithium-ion battery cathode materials. Furthermore sulfur is an attractive active material due to its low cost and its environmental sustainability. However, the commercialization of lithium-sulfur batteries faces some challenges. Beside the insulating nature of sulfur one of the main problems is the solubility in the electrolyte. This leads to the so called "shuttle-mechanism" where dissolved sulfur diffuses to the lithium metal anode to react without contributing to the energy storage reaction mechanism. Thus this phenomenon leads to poor coulombic efficiency and fast degradation of the cell. Different ways to suppress the shuttle-mechanism were investigated. One way is to optimize the conductive carbon structure to hinder the sulfur diffusing to the anode. The use of carbon aerogels allows influencing pore size and geometry to form a bimodal conductive carbon matrix. With an additional melting or evaporating process after mixing carbon aerogels and sulfur it is possible to hold sulfur steric inside the pores. Another approach is to evaporate sulfur and trap S2 inside small nano pores (< 0.5 nm). To optimize and understand the interaction of sulfur and porous systems different kinds of carbon aerogels and infiltration processes were combined and analyzed.