A team of energy storage researchers based at Texas A&M University has identified a nanoscale bottleneck as the culprit behind low performance in lithium-ion batteries. The discovery could lead to the use of new, improved materials that enable a rechargeable battery to attain more of its maximum theoretical capacity and maintain it through more of its lifecycle.
Considering the widespread use of Li-ion energy storage tech, the discovery has significant implications for energy efficiency and energy conservation in the low-carbon economy of tomorrow.
What’s The Matter With Li-ion Energy Storage?
To be clear, lithium-ion technology is considered the gold standard for rechargeable batteries. However, the Texas A&M researchers have pinpointed what they’re calling a “ghost in the machine” that prevents battery-powered devices from getting the most out of every charge.
They’re also calling it a “traffic jam,” which is a bit less evocative than the reference to René Descartes’ mind-body dualism but a little more germane to the situation, metaphorically speaking.
Team leader Sarbajit Banerjee describes the basic problem:
Fundamentally, when you have a battery, every time you use it, it starts to die a little bit. The more you use it, the more it dies. Eventually, it becomes unusable. Theoretically speaking, you expect a certain performance from a battery, and you rarely ever get there…
Everyone who uses rechargeable batteries knows this, but until now researchers have not been able to put a label on the actual cause.
The team leveraged previous studies along with a Scanning Transmission X-Ray Microscope to simulate and track the movement of lithium ions through a Li-ion battery.
With the powerful imaging technology in hand, the researchers were able to directly observe the effect of small polarons for the first time (a polaron refers to an electron with an associated structural distortion):
In order to make way for additional lithium to enter the structure, the lithium ions need to diffuse, bringing their electrons in tow. But as a small polaron, it also has to carry along the structural distortion — a real drag for transport of charge in a material.
As described by the researchers, the distortion effectively acts as a trap that forms small “puddles of charge.” If linked up, they could move (think of raindrops on a slightly tilted surface), but they are too small to move on their own:
…they’re all stranded, and they can’t move to charge or discharge something. And so they go out and hang in different areas of the particle. They’re all sort of sitting, defining different regions, and they aren’t able to move easily.
Aside from providing a precise description of the problem, the researchers also concluded that the puddling is directly related to the materials structure of the cathode.
Rather than tinker around with the architecture, the team has set itself the ambitious task of coming up with “entirely new” materials.
If you want more details on the new energy storage breakthrough, you can look up the study in the journal Nature Communications under the title, “Mapping polaronic states and lithiation gradients in individual V2O5 nanowires.”
Texas And Energy Storage
Texas has been one of the historic epicenters of the US fossil fuel industry (a leading coal producer as well as oil and natural gas), but with the help of its considerable research facilities — and energy initiatives at its military bases — the state has also become a driving force behind innovation in the renewable energy and energy storage industries.
One example is a recently launched solar energy storage project designed to enhance reliability for an isolated “electricity island.”
Another is a 2013 project that involved constructing the nation’s largest wind energy storage facility, designed to serve as a test bed and research site for similar installations nationwide.
And, despite political objections to President Obama’s Clean Power Plan by Republican leadership in Texas, according to one study, the state is already on track to reach an impressive 88% of its clean power goals without enacting any new policies.
Another study indicates that Texas is in position to replace its coal power plant capacity with natural gas and wind, while still meeting its future electricity generating needs for the next 20 years.
All that activity is partly offsetting job losses in the state’s cratering fossil fuel sector, so it looks like the constituency for clean tech is growing in Texas. Why elected representatives decide not to represent that trend is another story.
Image: by Luis De Jesús via Texas A&M University: “Mapping electron density in order of increasing lithiation levels using spectral imaging. Each colored region corresponds to sites where electron density is localized, which also corresponds to high concentrations of Li-ions. ‘The stripes mark regions that have been extensively lithiated and reduced.'”
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