Metal nanoclusters and graphene boost lithium–sulfur batteries

The demand for efficient energy-storage systems is ever increasing, spurred by the emergence of intermittent renewable energy sources and the adoption of electric vehicles. In this regard, lithium–sulfur batteries (LSBs), which can store three to five times more energy than traditional lithium-ion batteries, have emerged as a promising 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 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 approaches, including cathode composites, electrolyte additives and solid-state electrolytes, have been employed to address these challenges, they all involve trade-offs that limit further development of LSBs.

Recently, atomically precise metal nanoclusters, aggregates of metal atoms ranging from 1nm to 3nm in size, have received considerable attention in materials research, including for LSBs, owing to their high designability and unique geometric and electronic structures. However, while many suitable applications for metal nanoclusters have been suggested, there are still no examples of their practical use.

Now, in a paper in Small, a team of researchers from Japan and China, led by Yuichi Negishi at the Tokyo University of Science (TUS), report harnessing the surface-binding property and redox activity of platinum (Pt)-doped gold (Au) nanoclusters, Au₂₄Pt(PET)₁₈ (PET: phenylethanethiolate), as a high-efficiency electrocatalyst for LSBs.

The researchers prepared composites of Au₂₄Pt(PET)₁₈ and graphene (G) nanosheets, which possess a large specific surface area, high porosity and a conductive network. They then used these composites to develop a battery separator that can accelerate the electrochemical kinetics of LSBs.

“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,” said Negishi.

This led to an improved energy density, longer cycle life, enhanced safety features and a reduced environmental impact, making the LSBs more environmentally 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,” said Negishi. “In addition, this study is expected to pave the way for all-solid-state LSBs with more novel functionalities.”

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 the adoption of renewable energy, promoting sustainability.

This story is adapted from material from the Tokyo University of Science, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.