Researchers Develop Method for Improving Durability and Energy Storage Capacity of Lithium-Sulfur Batteries

Research conducted at the Gwangju Institute of Science and Technology (GIST) School of Earth Science and Environmental Engineering, Korea, has brought forward a method that improves the performance of lithium-sulfur batteries (LSBs). The research was led by Professor Jaeyoung Lee with support from the GIST Research Institute (GRI). 

An inorganic compound known as cobalt oxalate (CoC2O4) was introduced as an electrochemical catalyst at the anode interface of an LSB. This was done for the first time and the research team was able to identify the electrochemical catalyst reaction as the charging and the discharging process took place. Research findings collated by the GIST team were published in the journal ChemSusChem. 

 

Image used courtesy of GIST 

 

LIB’s have typically been considered the way forward concerning the provision of power for electronic consumer goods and electric vehicles (EVs). These batteries feature high energy density while remaining in a small size, a low-self discharge rate, more discharge cycles (with top-of-the-range batteries lasting for 1000 full charge cycles), and low maintenance. 

Among next-generation batteries, LSBs are thought to be the closest to commercialization. This is because they exhibit features that challenge those of LIBs. LSBs are also lightweight like LIBs, but the unit weight has an energy density of up to 2,100 Wh/kg. This makes it an ultra-high-capacity next-generation battery with a theoretical capacity of 5.4 times that of a LIB. LSBs have also gained significant attention because they are eco-friendly and low cost. 

 

Improving Capacity and Durability of LSBs 

Despite the perceived benefits of using LSBs, the commercialization of these batteries has been halted by their low life expectancy. This is brought on by the non-conductive properties of sulfur and the elution of lithium polysulfides created during the charging and discharging process. To help improve the performance of LSBs, the research team at GIST synthesized cobalt oxalate and added it to the positive electrode of the LSB. A simple chemical precipitation method was used to produce cobalt oxalate as an electrochemical oxidation/ reduction catalyst.

By using the cobalt oxalate electrochemical catalyst-based anodes, the GIST researchers were able to reduce the self-discharge generated from the passage of lithium polysulfide as it moved inside the cell. The catalyst-based anodes helped to absorb the generated lithium polysulfide on the catalyst and the surface of the positive electrode.  The researchers also confirmed that performance degradation did not impinge upon cell performance because of self-discharge. This was found to be the case even if the battery was left for about a week at about 1.5 times the level of conventional LSBs. 

 

 Professor Jaeyoung Lee. Image used courtesy of GIST.

 

In a recent press release, professor Lee commented: "The research results are most significant in securing capacity improvement and durability of lithium-sulfur batteries, which can implement high energy density at low cost through electrochemical catalyst reactions. Subsequent research is expected to contribute greatly to the development of next-generation energy storage technologies by gradually improving the durability of lithium-sulfur batteries."