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June 2016

Scientists See Electron Bottleneck in Simulated Battery

An international team of scientists working at the Molecular Foundry has revealed how interactions between electrons and ions can slow down the performance of a material considered key to the next generation of batteries.

As the appetite grows for more efficient vehicles and mobile devices based on cleaner, renewable energy sources, so does the demand for equally efficient, lightweight and energy-dense batteries that pack more punch, last longer and charge or discharge more quickly. The compound vanadium pentoxide, with its layered atomic structure, has grabbed the spotlight as a potential nanostructured material for state-of-the-art lithium-ion batteries because it can provide a greater surface area for the arrival and insertion of lithium ions. That quality makes vanadium pentoxide a good candidate as a cathode, the part of a battery where electrons and lithium ions enter.

“The speed with which electrons can enter and exit the cathode determines how much power the battery can provide and how quickly it can be recharged, both critical factors to consider in the world of mobile electronics or electrification of our automotive fleet,” said David Prendergast, staff scientist at the Molecular Foundry, a DOE Office of Science User Facility located at Berkeley Lab.

But despite vanadium pentoxide’s potential, it has yet to be widely adopted commercially because of its less-than-stellar performance when put to the test in the real world.

The new findings shed light on the slowdown, showing that the flow of electrons in vanadium pentoxide nanowires gets bogged down as it interacts with lithium ions in a phenomenon known as “small polaron formation.” The study is led by Sarbajit Banerjee, professor of chemistry at Texas A&M University and a user of Berkeley Lab’s The Molecular Foundry. Banerjee’s team worked with Prendergast and postdoctoral fellow Yufeng Liang on this discovery through a user project at the Molecular Foundry.

The Banerjee group made 2D maps of the electronic properties of synthesized vanadium pentoxide nanowires serving as a model lithium-ion cathode using Scanning Transmission X-ray Microscopy at The Canadian Light Source. They came to the Molecular Foundry to interpret their findings.

Read the full press release.