��������

Boron-Alloyed Silicon Nanoparticle Anodes can improve the performance for lithium-Ion Batteries.��

By mixing some boron with your silicon you can make a more robust battery electrode!

With a theoretical energy density ten times higher than graphite, Silicon (Si) has inspired interest as a next generation anode active material for lithium-ion batteries. In the general analogy, this is building a more robust parking lot for the charged state. When you charge and discharge a lithium-ion battery, on a molecular scale this is achieved by the pumping in, and pumping out of lithium ions (cars going in and out of the parking lot), which come with a significant volume change. (This would be like the floors of a multi-story parking lot changing size as cars drive in and out. Realistic on the atomic scale, not so much on the car-scale…) Silicon-based anodes have been found to be unstable to this constant change in volume which can lead to instability and failure. One strategy to address this is to move from having the silicon anode being a solid slab, to being a series of nanoparticles, which helps to reduce this mechanical stress, but this comes with another problem, the increased surface area of the particles allows more chemical side reactions, which is another big problem. There has been much research investigating the materials science and surface chemistry to reduce the unwanted side reactions. A key finding from recent research is that the best way to prevent unwanted side reactions is to essentially isolate the silicon surface from the electrolyte media it is in. This is where this research, led by RASEI Fellow Nate Neale, comes in.

By mixing, or alloying, the silicon with boron, the anodes were found to perform better and last longer. The more boron added to the nanoparticles, the more robust they were. In fact, the team saw a 3x improvement in lifetime by incorporating boron. The team proposes that by making the nanoparticles out of a mixture of silicon and boron, the presence of the boron creates an “electric double layer” effect, essentially providing a protective layer at the surface of the nanoparticle, shielding from the unwanted side reactions. This saw some real improvements in the performance of the electrolytes, not just a 3x improvement in the calendar lifetime, but an 82.5% capacity retention after 1000 cycles, the pure silicon electrodes reached the end-of-life (<80% capacity retention) in fewer than 400 cycles under similar conditions.

Boron creates a strong electrical field at the nanoparticle surface that attracts and concentrates ions from the surrounding electrolyte, forming a stable, dense layer that acts like a permanent shield. This work reveals an underexplored parameter in the design and optimization of silicon anodes that could prove valuable in the next-generation of lithium-ion batteries.

This breakthrough could accelerate the adoption of silicon anodes in battery applications, such as electric vehicles, where longer-lasting batteries are essential to address range anxiety. The research team is now working to identify the optimal silicon-boron ratio that maximizes both capacity and longevity, potentially bringing us closer to the next generation of high-performance lithium-ion batteries.

How Molecular Shape Impacts Battery Performance: New Insights for Flow Batteries

Making seemingly minor molecular changes to the structure of charge storage chemicals can have significant impacts on the performance of redox flow batteries.

Redox Flow Batteries offer a promising solution for large-scale energy storage. Unlike the lithium-ion batteries in your phone, flow batteries store energy in liquid electrolytes that flow through the system. This design allows them to store massive amounts of energy for long periods, making them ideal for stabilizing electrical grids.

However, making these batteries practical requires finding the right chemical compounds that are stable, efficient, and cost effective. This article describes collaborative research that includes teams led by RASEI Fellow Mike Toney and former RASEI Fellow Mike Marshak. The teams were exploring the optimization of chromium-based compounds as charge carriers. The aim was that by changing the structure of the organic chelate ligand that surrounds the chromium atom, they could better understand the relationship between structure and performance and use that understanding to design more efficient systems.

Two very similar chromium compounds were prepared; CrPDTA and CrPDTA-OH, which differ only by the addition of a single hydroxyl group (-OH) on the organic framework. Hydroxy groups are often added to compounds to improve their solubility in water, but in this case the team observed a drop in the performance of the molecule. The hydroxylated compound showed:��

• Slower reaction rates – The CrPDTA-OH transferred electrons 100 times more slowly than the non-hydroxylated.
• Reduced efficiency – battery efficiency dropped from 99.3% to 98.2%.
• Increased hydrogen gas production – more energy was wasted producing unwanted hydrogen gas in a side reaction instead of being stored.

It’s kind of like if some of the cars had one flat tire. They are going to be worse at transporting charge back and forth, and they might do things you don’t want them to.

Using a suite of advanced characterization techniques the team discovered that the addition of the hydroxyl group caused a distortion of the molecular shape around the central chromium ion. This distorted shape weakened the bonds between the metal atom and the organic chelate ligand, which reduced the efficiency of electron transfer.

This research reveals a fundamental principle for designing redox flow battery materials: molecular geometry matters immensely. The chromium atom needs to adopt an octahedral arrangement to work efficiently. Any distortion of this shape leads to reduced performance. This study also confirms why maintaining the precise structure is so important. It prevents water molecules from interfering with the chromium atom, which would cause the unwanted production of hydrogen gas instead of energy storage.

Researchers Discover The Hidden ‘Dance’ Of Ions That Could Inform The Design Of Grid-Scale Energy Storage

Insights into the processes of charge movement in the electrolyte could inform future battery design

The electrolyte of the battery is the highway that connects the two parking lots together. This research that brings together an international collaborative team, including researchers from three US universities, three National labs, and researchers from the United Kingdom and Switzerland, and RASEI Fellow Mike Toney, reveals important features of this highway in zinc-ion based batteries.

While most people are familiar with lithium-ion batteries in their phones and devices, zinc-ion batteries offer compelling advantages for large-scale electricity storage. Zinc is more abundant and thus affordable, zinc-ion batteries use water-based electrolytes that are much less likely to overheat or explode, Zinc-ion batteries can pack a lot of energy into a small space, they are very energy dense.

The electrolyte is the media through which the charged ions pass through during charge and discharge cycles. In our metaphor the electrolyte is the highway on which the cars travel back and forth. The properties of the electrolyte can dictate a number of features of the batteries performance, how fast it charges, how long it lasts, and how much energy it can store. This research has explored how these ions, or ‘cars’, act during transport, and they have observed that it is not plain driving, the ions cluster and form convoys as they move through the electrolyte. The way the zinc sulfate ions travel is far more dynamic and complex than previously understood.

Using advanced x-ray techniques in combination with advanced computer modeling the team were able to explore the molecular structure of the electrolyte at different stages of the charge / discharge cycle. They found that the ions don’t just float around independently, instead they form clusters, like cars forming a convoy. It was observed that the zinc ions surround themselves with exactly six water molecules and clusters formed in a range of sizes, from just 2 ions all the way up to 22 ions.

You might expect that they clusters would move more slowly, like a traffic jam on the highway, but the team found that while the clusters do reduce conductivity, the battery still works. Critical to this is the timing of the clusters. The clusters are incredibly short lived, existing for only picoseconds (trillionths of a second) at a time. Instead of having a traffic jam, it is like having really busy traffic that is moving so fast that it is constantly reorganizing itself and so it never actually gets stuck.

This offers insights that can be applied in future battery designs; Ions form diverse, temporary partnerships that vary in size and composition, the system is constantly undergoing reorganization, transport happens both through vehicular motion (cars moving through the highway), and hopping between clusters (it would be like someone jumping from car to car in an action movie). These insights could improve future electrolyte design which could improve battery performance and potentially open the door to new battery chemistries that could be used for a broader range of applications, such as grid-scale storage.

By developing a more informed understanding of how charge is transported in electrolytes we can improve our designs in the future. Instead of trying to avoid cluster, we can harness it to improve the efficiency of charge transport in battery technologies.

��

Inside the battery: X-Ray Vision Reveals How Sodium Really Moves and Stores Energy

Sodium-ion batteries have the potential to be game changers for grid-scale storage with their abundance, low cost, and sustainability advantages over existing lithium-ion technologies. A key hurdle in their development is that we don’t yet fully understand how sodium actually moves and stores energy on the molecular level. This international collaboration, led by RASEI Fellow Mike Toney, uses cutting-edge X-ray techniques and computational modeling, provides insight into these promising battery chemistries.

Sustainable battery technologies are central to the modern power grid and meeting the growing demand of electrification technologies, such as electric vehicles. Among the growing array of battery chemistries Sodium-Ion Batteries (NIBs) address many of the challenges associated with lithium-ion batteries, and can even benefit from the work done to bring lithium-ion technologies to scale. This is swapping out the cars in our analogy from lithium-ions to more affordable sodium-ions. Sodium is one of the most abundant elements on Earth, making it dramatically more affordable and sustainable than lithium. While NIBs don’t yet match the energy density of lithium-ion based designs, they are ideal for grid storage applications where space is less constrained, but cost and sustainability matter enormously. Furthermore, NIBs can be produced using lithium-ion manufacturing facilities, enabling rapid deployment without the associated infrastructure costs.

The main hurdle has been developing anode materials that efficiently store and release sodium ions. Hard carbon shows promise but understanding exactly how sodium storage works at the molecular level remained elusive—a critical gap for large-scale manufacturing.

This research uses a combination of advanced X-ray spectroscopy techniques and computational modeling to peer inside the electrodes of a working NIB to watch the storage process unfold in real-time. Put simply they explored the details of a three step system where sodium ions first attach to surface defects in the hard carbon, then squeeze between the carbon layers, and finally cluster into the pores of the anode, providing insights and a road map for the design of NIBs in the future.

To gain more information about the details of these processes the team using X-ray total scattering, a technique that bounces high-energy X-rays off atoms and analyzes the scattered pattern to map exactly where atoms are positioned relative to each other. Think of it like echolocation to see in the dark, but for atomic structures! By taking a series of ‘snapshots’ of the NIBs at different stages of charging, the researchers could track how sodium atoms moved and arranged themselves during the process. The X-ray data reveals amazing levels of detail, revealing distinct signatures for different types of sodium storage, distinguishing between sodium atoms stuck to the surface defects of the hard carbon and those squeezed between carbon sheets, and those atoms clustered in pores.

Through a combination of these experimental results and advanced computational modeling the team were able to piece together a three-stage sequence to better understand the movement of sodium ions during charging. First, the sodium ions target high-energy defect sites on the hard carbon surfaces, like easy to access parking spots with the strongest attraction. In the second stage, as the prime parking spots fill up, sodium begins what the researchers call “defect-assisted intercalation’, where the defects are used as entry points to slip between the carbon layer (like cars going to other levels of a multistory parking lot), causing the carbon layers to expand slightly. In the third stage, in the low-voltage plateau region, sodium continues to intercalating between the layers, while also filling up the nanoscale pores and forming metallic clusters. Crucially the evidence from the X-ray analysis shows that the size of these clusters is dependent on the pore size – larger pores in the carbon processed at higher temperatures produced bigger sodium clusters, directly linking the battery’s microstructure to its storage capacity.

This molecular-level understanding has the potential to transform NIB development from educated guesswork into precision engineering. Guided by this three stage roadmap, battery researchers can now strategically design hard carbon materials, altering defect concentrations to optimize initial storage, controlling pore sizes to maximize capacity, while balancing these factors to minimize the irreversible trapping that reduces overall battery lifetimes. The combined X-ray spectroscopy and computational modeling technique demonstrated in this research has the potential to provide a powerful new toolkit for studying other battery chemistries in the future. By revealing more about how sodium energy storage works, this research brings us closer to sustainable solutions for grid-scale energy storage, a critical piece in the puzzle for a modern, resilient, and sustainable energy economy.

��