The Akron Legal News

OSU researchers gaining ground on electric cars' battery problem

KEITH ARNOLD
Special to the Legal News
Published: September 1, 2016

Since the arrival of the electric car to the marketplace, the well known, oft-cited shortcomings of the vehicles have been limited driving distance and inefficient batteries that — in the extreme — present the threat of fire.

Engineers at The Ohio State University may have cracked the code on both counts with development of technology controlling how charge flows inside a battery.

The technology, which was inspired by the manner in which living cell membranes transport proteins in the body, is the best bet yet to improve the rate of charge for most electric cars — 0.4 miles per minute, according to Vishnu-Baba Sundaresan, lead researcher and assistant professor of mechanical and aerospace engineering at the university.

Results of the National Science Foundation-funded study, which appear in the journal Energy & Environmental Science, suggest that the membrane may enable development of a new category of fast-charging, powerful batteries called “redox transistor batteries” for automobiles that feature a greater travel range per single charge.

Analysis of top-of-the-line hybrid and electric car batteries resulted in engineers concluding that automakers have hit a performance limit: The very best eco-friendly cars travel about 200 miles on an eight-hour charge, while gas-powered cars cover the same distance after only a minute spent at the pump.

Sundaresan is optimistic the new technology will allow for battery-charging performance of tens of miles per minute.

“That’s still an order of magnitude away from the equivalent measure in gasoline, but it’s a place to start,” Sundaresan said in a press release.

The problem with batteries in use in today’s hybrid and electric cars is storage of the charge, the research found.

“Research over the last 50-plus years has focused on advancing the chemistry of battery electrodes to increase capacity,” Sundaresan said. “We’ve done that, but the increase in capacity has come at the cost of robustness and the ability to rapidly charge and discharge batteries.

“Electric vehicle design is mature enough now that we know the limit they’re reaching is because of the chemistry of lithium-ion batteries.”

In the “ionic redox transistor,” the charge, or energy, is stored in a liquid electrolyte, allowing electric car motorists to empty and refill just as they would the tank of a gasoline-fueled engine.

“For everyday commuting, the electrolyte can be simply regenerated by plugging it into a power outlet overnight or while parked at the garage,” Sundaresan said. “For long road trips, you could empty out the used electrolyte and refill the battery to get the kind of long driving range we are accustomed to with internal combustion engines.

“We believe that this flexibility presents a convincing case for weaning our dependence on internal combustion engines for transportation.”

The membrane separators in today’s lithium-ion batteries conduct charge and keep separate the anode and the cathode, but lose charge over time on account of leakage between the anode and cathode, also known as self-discharge, according to doctoral student Travis Hey, who assisted Sundaresan in the study.

The chemical reaction results in heat and a gradual power drain. In extreme instances, however, the reaction results in the batteries overheating and catching fire — a phenomenon called thermal runaway, the study detailed.

Like cell membranes in living tissue that behave differently for different biological functions, Sundaresan and Hery posit that openings in the cell wall respond to the electrical charge of molecules to expand or contract.

In tests, when the battery is charging or discharging, the conductive polymer shrinks to open the holes. Likewise, when the battery isn’t in use, the polymer swells to close the holes.

Engineers found that the membrane reliably controlled charging and discharging in batteries powered by ions of lithium, sodium and potassium.

In an experiment, researchers connected batteries to an LED light and programmed the holes to open and close in precise patterns.

The membrane allowed the batteries to function normally, but reduced charge loss to zero when the batteries were not in use, results indicated.

Ohio State is expected to license the technology to industry for further development.

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