Electron transfer discovery is a step toward viable grid-scale batteries

January 21, 2021

The liquid electrolytes in flow batteries provide a bridge to help carry electrons into electrodes, and that changes how chemical engineers think about efficiency.

The way to boost electron transfer in grid-scale batteries is different than researchers had believed, a new study from the University of Michigan has shown.

The findings are a step toward being able to store renewable energy more efficiently.

As governments and utilities around the world roll out intermittent renewable energy sources such as wind and solar, we remain reliant on coal, natural gas and nuclear power plants to provide energy when the wind isn't blowing and the sun isn't shining. Grid-scale "flow" batteries are one proposed solution, storing energy for later use. But because they aren't very efficient, they need to be large and expensive.

In a flow battery, the energy is stored in a pair of "electrolyte" fluids which are kept in tanks and flow through the working part of the battery to store or release energy. An active metal gains or loses electrons from the electrode on either side, depending on whether the battery is charging or discharging. One efficiency bottleneck is how quickly electrons move between the electrodes and the active metal.

"By maximizing the charge transfer, we can reduce the overall cost of flow batteries," said study first author Harsh Agarwal, a chemical engineering Ph.D. student who works in the lab of Nirala Singh, U-M assistant professor of chemical engineering.

Researchers have been trying different chemical combinations to improve it, but they don't really know what's going on at the molecular level. This study, published in Cell Reports Physical Science, is one of the first to explore it.

Researchers had believed that the negatively charged molecular groups from the acids provided more spots for electron transfer to take place on the battery's negative electrode. The findings from the team co-led by Singh and Bryan Goldsmith, the Dow Corning Assistant Professor of Chemical Engineering, tell a different story. Instead, the acid groups lowered the energy barrier of the electron transfer by serving as a sort of bridge between the active metal in the fluid--vanadium in this case--and the electrode. This helps the vanadium give up its electron.

"Our findings suggest that bridging may play a critical yet underexplored role in other flow battery chemistries employing transition metals," Singh said. "This discovery is not only relevant to energy storage but also fields of corrosion and electrodeposition."

The study shows that the reaction rate in flow batteries can be tuned by controlling how well the acid in the liquid electrolyte binds with the active metal.

"Researchers can apply this knowledge to electrolyte engineering or electrocatalyst development, both of which are important disciplines in sustainable energy," Agarwal said.

Agarwal and Singh measured the reaction rate between the vanadium and electrode for five different acidic electrolytes. To get a clearer picture of the details at the atomic level, the team used a form of quantum mechanical modeling, known as density functional theory, to calculate how well the vanadium-acid combinations bind to the electrode. This part of the study was undertaken by Goldsmith and Jacob Florian, a chemical engineering senior undergraduate student working in the Goldsmith lab.

At Argonne National Laboratory, Agarwal and Singh used X-ray spectroscopy to discover details about how the vanadium ions configured themselves when in contact with different acids. Density functional theory calculations helped interpret the X-ray measurements. The study also provides the first direct experimental verification of how water attaches to vanadium ions.
-end-
Image: https://docs.google.com/document/d/12zhpF3xUMztkFTI8tnuQc5dCOdSTYr_D1onvUbsMNCk/edit

The study is titled "The effect of anion bridging on heterogeneous charge transfer for V2+/V3+." The work was supported by the University of Michigan Office of Research. This research used the resources of the National Energy Research Scientific Computing Center, Argonne National Laboratory and the Canadian Light Source.

Nirala Singh
Bryan Goldsmith
Abstract of paper

University of Michigan

Related Energy Storage Articles from Brightsurf:

Reviewing multiferroics for future, low-energy data storage
Big data and exponential demands for computations are driving an unsustainable rise in global ICT energy use.

The perfect angle for e-skin energy storage
Researchers at DGIST have found an inexpensive way to fabricate tiny energy storage devices that can effectively power flexible and wearable skin sensors along with other electronic devices, paving the way towards remote medical monitoring & diagnoses and wearable devices.

Upcycling plastic waste toward sustainable energy storage
UC Riverside engineering professors Mihri and Cengiz Ozkan and their students have been working for years on creating improved energy storage materials from sustainable sources, such as glass bottles, beach sand, Silly Putty, and portabella mushrooms.

Chemists advance solar energy storage aimed at global challenges
Multi-university effort develops solar energy storage to enable decentralized electrification systems in remote areas.

Energy-saving servers: Data storage 2.0
A research team of Mainz University has developed a technique that will potentially halve the energy required to write data to servers and make it easier to construct complex server architectures.

Energy storage using oxygen to boost battery performance
Researchers have presented a novel electrode material for advanced energy storage device that is directly charged with oxygen from the air.

New material, modeling methods promise advances in energy storage
The explosion of mobile electronic devices, electric vehicles, drones and other technologies have driven demand for new lightweight materials that can provide the power to operate them.

Finding balance between green energy storage, harvesting
Generating power through wind or solar energy is dependent on the abundance of the right weather conditions, making finding the optimal strategy for storage crucial to the future of sustainable energy usage.

Diamonds shine in energy storage solution
QUT researchers have proposed the design of a new carbon nanostructure made from diamond nanothreads that could one day be used for mechanical energy storage, wearable technologies, and biomedical applications.

Gas storage method could help next-generation clean energy vehicles
A Northwestern University research team has designed and synthesized new materials with ultrahigh porosity and surface area for the storage of hydrogen and methane for fuel cell-powered vehicles.

Read More: Energy Storage News and Energy Storage Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.