Sulfur Cathode for High Performance Lithium Sulfur Batteries

Over the last few decades, electric vehicles (HEV, PHEV, BEV) have been developed as one of the solution to the CO₂emission problems. For the successful electric vehicles commercialization, batteries with high energy density are required. Among several kinds of batteries, the lithium sulfur battery is a very attractive candidate, because elemental sulfur has the highest theoretical capacity(1,672 mAh/g) and highest theoretical energy density(2,600 Wh/kg) of all known cathode materials. However, lithium sulfur battery has some problems about cycle life and sulfur utilization efficiency. Recently, a lot of researchers are focused on solving those problems.

In this research, electrochemical properties of lithium sulfur battery were investigated by applying mesoporous carbon and carbon fiber sheet to sulfur cathode. Mesoporous carbon with controllable pore sizes (4nm, 12nm, 25nm) was fabricated and the pores are filled with sulfur for mesoporous carbon/sulfur composites. The optimal pore size of mesoporous carbon was chosen by cell performance test. Carbon fiber sheet was also applied to cathode as a frame structure to have chemical reaction even higher thickness of electrode with maximum sulfur loading. Using those mesoporous carbon/sulfur composites and carbon fiber sheet, lithium sulfur pouch cell was designed, fabricated and tested.

As a result, the discharge capacity of lithium sulfur pouch cell shows 1,206 mAh/g_S with sulfur loading amount of 8.5mg/cm².