Professor Hee Tak Kim of the Department of Chemical and Biomolecular Engineering, alongside a research team from the Advanced Battery Center in the KAIST Institute for the NanoCentury, successfully developed a donut-shaped lithium sulfide (Li2S) anode that can be used to produce a long-lasting, high-energy-density lithium-sulfur battery. Research Professor Fangmin Ye of the center was the first author of the research paper, which was published on the online edition of Advanced Science on May 7.
One of the main concerns regarding electric cars is their limited range. The normally-used lithium-ion batteries have a low energy density, which limits the range available for the vehicles from a single charge. For this reason, research on the development of higher-energy-density lithium-sulfur batteries has been ongoing for more than 10 years. Despite this, it had been difficult to develop a battery with a long life cycle due to the weak reversibility of the lithium anode in these types of batteries.
The researchers at the Advanced Battery Center attempted to solve this problem by utilizing a graphite cathode, instead of one made from lithium, and a lithium sulfide anode. Due to the excellent life cycle of the graphite cathode and the high capacity of the lithium sulfide anode, a battery with this configuration has significantly better energy density and longevity. However, due to the high cost of lithium sulfide and the unavailability of an electrode and electrolyte design technology that satisfies the life cycle of these two electrodes simultaneously, the commercial development of such a battery seemed questionable.
To overcome these limitations, the research team produced a donut-shaped lithium sulfide anode from relatively inexpensive lithium sulfate (Li2SO4). This oddly-shaped anode, which has an empty interior, showed high repulsion and discharge reversibility due to its improved rate of lithium ion transmission. By also utilizing a high-concentration salt electrolyte, which showed exceptional durability as it formed a stable membrane on the surface of the graphite cathode, the team was able to successfully implement a lithium-sulfur battery that utilizes a graphite cathode and a lithium sulfide anode.
The developed battery had an energy density that was 30 percent higher than those of existing lithium-ion batteries and it showed to have a life span of more than 600 cycles. It is expected that the donut-shaped lithium sulfide anode will be easily adopted in the industry due to the low price of its raw materials and its simple manufacturing process.