Metal Nanoclusters For Stable Lithium Sulfur Batteries

Tokyo University of Science researchers have developed a graphene separator embedded with platinum-doped gold nanoclusters for lithium sulfur batteries. But issues like formation of lithium polysulfides and lithium dendrites lead to capacity loss and raise safety concerns.

Yet lithium sulfur batteries (LSBs) offer a higher energy storage potential and with the new separator have enhanced lithium-ion transport and facilitate redox reactions. This breakthrough addresses the long-standing issues associated with LSBs, setting the stage for their commercialization.

The researchers report has been published in the journal Small.

The demand for efficient energy storage systems is ever increasing, especially due to the recent emergence of intermittent renewable energy 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 hopeful 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 involve trade-offs and considerations that limit further development of LSBs.

Recently, atomically precise metal nanoclusters, aggregates of metal atoms ranging from 1-3 nanometers in size, have received considerable attention in materials research, including on LSBs, 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.

The latest collaborative study has been published in the journal Small, where the team of researchers from Japan and China, led by Professor Yuichi Negishi of Tokyo University of Science (TUS), has 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 LSBs.

The work is co-authored by Assistant Professor Saikat Das from TUS and Professor Deyan He and Junior Associate Professor Dequan Liu from Lanzhou University, China.

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.

Professor Negishi noted, “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.”

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,” highlighted 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.

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Some folks think the lithium sulfur chemistry is a very promising battery solution. Maybe someday, but in truth even with that 300 to 500% capacity gain potential, several chemistries are much closer to commercial practicality.

That theoretical capacity is a sure motivator. So this chemistry is going to get more attention and there may be a multiple problems solution breakthrough.

Then there is a bit of concern about things built with platinum-doped gold. Hints of not low cost. . .

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