Li-S Batteries: Sulfur Cathodes Prepared by Suspension Spraying

Kurzfassung

In the last few decades lithium-sulfur batteries have attracted increasing attention due to their high theoretical energy density (~2500 Wh/kg), low cost and environmental friendliness. However these batteries suffer from poor observed capacity and cycle life which is mainly due the low electrical conductivity of sulfur (5×10−30 S/cm at 25 ◦C), electrochemical irreversibility (i.e. the dissolved polysulfides) and morphology change of the cathode material upon cycling. Even though capacity improvements have been achieved by addressing the above mentioned problems, the observed capacities of the batteries lie below their theoretical values. In addition to that, the cycle life of the batteries still needs to be improved. The focus of this work is to investigate the performance of sulfur cathodes produced by suspension spraying. Dedicated suspensions were developed by mixing carbon black, binder, sulfur and suitable additives to achieve a homogenous distribution of each phase. These suspensions were sprayed onto aluminium based current collectors, resulting after spraying and drying in a core-shell like microstructure with a sulfur containing active material core and a carbon coating disposed on the active sulfur core. Structural and chemical characterization of the prepared cathodes was performed by several techniques such as SEM, EDX, XRD and AFM. Batteries containing prepared cathodes were electrochemically characterized and evaluated. Additionally, various microscopic and material analysis techniques were used to characterize microstructural and chemical changes of the cathodes upon cycling.