Researchers from the Monash Energy Institute, with colleagues from CSIRO, have used a saccharide-based binder system to develop a durable sulfur cathode with minimal polysulfide escape in a lithium-sulfur battery.

The saccharide-based binder system regulates polysulfides due to its reducing properties. The binder also promotes the formation of viscoelastic filaments during casting which endows the sulfur cathode with a desirable web-like microstructure.

In an open-access paper published in Nature Communications, the team reports 97% sulfur utilization with a cycle life of 1000 cycles and a high capacity retention (1106 mAh g⁻¹ even after 500 cycles and around 700 mAh g⁻¹ after 1000 cycles) while achieving >99% columbic efficiency (CE).

To demonstrate the robustness of the binder system, the researchers manufactured cathodes with a high loading of 10.5 mg cm⁻², achieving an areal capacity of 12.56 mAh cm⁻² with >98% CE. A pouch cell prototype showed an initial capacity around 1200 mAh g⁻¹.

… the viability of many emerging technologies, for example in aviation, require lighter-weight batteries. One such technology could be lithium-sulfur batteries (Li-S): which theoretically store as much as five times the energy of Li-ion and have a realizable specific energy of 400–600 Wh kg⁻¹. They can be made from materials that are readily and sustainably available around the world. Until now, the realization of Li-S batteries has been challenging, mainly due to the instability of both electrodes, which results in a short cycle life of the battery. The power performance of the Li-S system is also inherently slow, particularly when the sulfur cathode is loaded to the required levels, mainly due to poor ion diffusion across the thickness of the cathode.

… Our cathode design concurrently provides expansion tolerance, strong polysulfide crossover limitation, and ion diffusion highways via nano-structuring—and it can be fabricated at scale from commonly sourced materials. These beneficial properties holistically mitigate the damage to the lithium metal anode, from which short circuits typically originate, ending the cycle life.

—Huang et al.

In theory, lithium-sulfur batteries could store two to five times more energy than lithium-ion batteries of the same weight. However, in use the electrodes can deteriorate rapidly. There are two reasons for this: the positive sulfur electrode suffered from substantial expansion and contraction weakening it and making it inaccessible to lithium, and the negative lithium electrode became contaminated by sulfur compounds.

Last year the Monash team demonstrated they could open the structure of the sulfur electrode to accommodate expansion and make it more accessible to lithium. Now, by incorporating glucose into the web-like architecture of the electrode they have stabilized the sulfur, preventing it from moving and blanketing the lithium electrode.

While many of the challenges on the cathode side of the battery has been solved by our team, there is still need for further innovation into the protection of the lithium metal anode to enable large-scale uptake of this promising technology—innovations that may be right around the corner.

—Dr Mahdokht Shaibani, second author

The process was developed by the Monash team with significant contribution from Dr Matthew Hill’s research group in CSIRO Manufacturing.

The Lithium-sulfur Battery Research Program at Monash University has been supported by the Commonwealth Government through the Australian Research Council and the Department of Industry, Innovation and Science. In addition, the work has also been supported by Cleanfuture Energy, Australia, an Australian subsidiary of the Enserv Group of Thailand.

Enserv Australia hopes to develop and manufacture the batteries in Australia, the world’s largest producer of lithium.

We would be looking to use the technology to enter the growing market for electric vehicles and electronic devices. We plan to make the first lithium-sulfur batteries in Australia using Australian lithium within about five years.

—Mark Gustowski, Managing Director of Enserv Australia

Resources

• Huang, Y., Shaibani, M., Gamot, T.D. et al. (2021) “A saccharide-based binder for efficient polysulfide regulations in Li-S batteries.” Nat Commun 12, 5375 doi: 10.1038/s41467-021-25612-5