Researchers from China's Lanzhou University and Japan's Tokyo University of Science have harnessed the surface binding property and redox activity of platinum (Pt)-doped gold (Au) nanoclusters, Au24Pt(PET)18 (PET: phenylethanethiolate, SCH2CH2Ph), as a high-efficiency electrocatalyst in lithium–sulfur batteries (LSBs).
Lithium–sulfur batteries (LSBs) can store three to five times more energy than traditional lithium-ion batteries and so they have emerged as a promising energy storage solution. LSBs use lithium as the anode and sulfur as the cathode, but this combination poses challenges. One significant issue is the “shuttle effect,” in which intermediate lithium polysulfide (LiPS) species formed during cycling migrate between the anode and cathode, resulting in capacity fading, low life cycle, and poor rate performance. Other problems include the expansion of the sulfur cathode during lithium-ion absorption and the formation of insulating lithium–sulfur species and lithium dendrites during battery operation. While various strategies, such as cathode composites, electrolyte additives, and solid-state electrolytes, have been employed to address these challenges, they usually involve trade-offs and considerations that limit further development of LSBs.
This work follows the recent attention given to atomically precise metal nanoclusters, aggregates of metal atoms ranging from 1–3 nanometers in size, owing to their high designability as well as unique geometric and electronic structures. However, while many suitable applications for metal nanoclusters have been suggested, there are still no examples of their practical applications. This is what the research team set out to change in its recent work.
The researchers prepared composites of Au24Pt(PET)18 and graphene (G) nanosheets with a large specific surface area, high porosity, and conductive network, using them to develop a battery separator that accelerates the electrochemical kinetics in the LSB. “The LSBs assembled using the Au24Pt(PET)18@G-based separator arrested the shuttling LiPSs, inhibited the formation of lithium dendrites, and improved sulfur utilization, demonstrating excellent capacity and cycling stability,” highlights Tokyo University of Science's Prof. Yuichi Negishi. The battery showed a high reversible specific capacity of 1535.4 mA h g−1 for the first cycle at 0.2 A g−1 and an exceptional rate capability of 887 mA h g−1 at 5 A g−1. Additionally, the capacity retained after 1000 cycles at 5 A g−1 was 558.5 mA h g−1.
These results highlight the advantages of using metal nanoclusters in LSBs. They include improved energy density, longer cycle life, enhanced safety features, and a reduced environmental impact of LSBs, making them more environment-friendly and competitive with other energy storage technologies.
“LSBs with metal nanoclusters may find applications in electric vehicles, portable electronics, renewable energy storage, and other industries requiring advanced energy storage solutions. In addition, this study is expected to pave the way for all-solid-state LSBs with more novel functionalities,” highlights Prof. Negishi. In the near future, the proposed technology can lead to cost-efficient and longer-lasting energy storage devices. This would help reduce carbon emissions and support renewable energy adoption, promoting sustainability.