The demand for efficient energy storage systems is steadily on the rise, primarily due to the growing use of intermittent renewable energy sources and the widespread adoption of electric vehicles. Within this context, lithium-sulfur batteries (LSBs) have emerged as a promising solution, offering the potential to store three to five times more energy compared to traditional lithium-ion batteries.
LSBs function by using lithium as the anode and sulfur as the cathode, but they come with significant challenges. One prominent issue is the “shuttle effect,” where intermediate lithium polysulfide (LiPS) compounds formed during cycling tend to move between the anode and cathode, leading to issues such as capacity degradation, limited lifespan, and subpar performance at high discharge rates.
Additionally, there are problems related to the expansion of the sulfur cathode during lithium-ion absorption and the creation of insulating lithium-sulfur compounds and lithium dendrites during battery operation. Various approaches, such as cathode composites, electrolyte additives, and solid-state electrolytes, have been employed to tackle these hurdles, but they often involve trade-offs and considerations that hinder further LSB development.
Recently, researchers have turned their attention to atomically precise metal nanoclusters, which are clusters of metal atoms typically measuring between 1 to 3 nanometers in size. These nanoclusters have gained substantial interest in materials research, including their potential application in LSBs, due to their high design flexibility and unique geometric and electronic characteristics.
Although many promising applications for metal nanoclusters have been proposed, there have been few practical implementations thus far. However, a recent collaborative study led by Professor Yuichi Negishi of Tokyo University of Science (TUS), featuring researchers from Japan and China, has made significant strides. They harnessed the surface binding properties and redox activity of platinum (Pt)-doped gold (Au) nanoclusters, specifically Au24Pt(PET)18 (PET: phenylethanethiolate, SCH2CH2Ph), as a high-efficiency electrocatalyst in LSBs, as detailed in their latest research publication in the journal Small.
The collaborative research involved Assistant Professor Saikat Das from TUS, alongside Professors Deyan He and Junior Associate Professor Dequan Liu from Lanzhou University, China.
The research team created composite materials by combining Au24Pt(PET)18 with graphene (G) nanosheets, which possess a substantial specific surface area, excellent porosity, and a conductive network. These materials were employed to fabricate a battery separator designed to accelerate the electrochemical processes within lithium-sulfur batteries (LSBs).
According to Professor Negishi, “LSBs utilizing the Au24Pt(PET)18@G-based separator effectively put a stop to the problematic movement of LiPSs, prevented the formation of lithium dendrites, and significantly improved the utilization of sulfur. This resulted in outstanding battery capacity and cycling stability.”
The battery exhibited an impressive reversible specific capacity of 1535.4 mA h g−1 during the first cycle at 0.2 A g−1 and demonstrated remarkable performance at high discharge rates, with a specific capacity of 887 mA h g−1 at 5 A g−1. Even after 1000 cycles at 5 A g−1, it retained a capacity of 558.5 mA h g−1.
These findings underscore the benefits of incorporating metal nanoclusters into LSBs, which encompass enhanced energy density, prolonged cycle life, improved safety features, and a diminished environmental footprint. This makes LSBs more eco-friendly and competitive when compared to other energy storage solutions.
Professor Negishi suggests that “LSBs featuring metal nanoclusters hold promise for applications in electric vehicles, portable electronics, renewable energy storage, and various industries in need of advanced energy storage solutions. Moreover, this study is anticipated to open the path toward all-solid-state LSBs with innovative functionalities.”
In the near term, this technology could lead to cost-effective, longer-lasting energy storage devices, contributing to the reduction of carbon emissions and the advancement of renewable energy adoption, thereby promoting sustainability.
Source: Tokyo University of Science