Battery Experiments Give 100K Charging Cycles With Key Ingredient Change

Battery researchers at the University of California-Irvine replace an expensive ingredient with a cheap one and see intriguing promise.

batteries, smartphones, mobile devices, tablets, lithium-ion batteries, rechargable batteries, University of California-Irvine, Reginald Penner

After swapping a key chemical ingredient for a different substance, researchers at the University of California-Irvine are optimistic about a new technology that could help make batteries that could be recharged more than 100,000 times for smartphones, laptops, tablets, smartwatches and other portable electronics.

The researchers, who have been experimenting using fragile, super-thin nanowires as a conduit for moving energy in batteries for portable devices, found that the structures would only allow about 5,000 recharging cycles before failing, Reginald M. Penner, a chemistry professor at UC-Irvine, told eWEEK. The nanowires, which are far thinner than a human hair, were being suspended in a liquid made from cobalt-oxide, which is commonly used in lithium-ion batteries.

The cobalt-oxide is corrosive to the nanowires, leading to their failure during the experiments, he said. But when a graduate student, Mya Le Thai, replaced the cobalt-oxide with a gel substance made from manganese-dioxide, the number of charging and recharging cycles could be repeated to 100,000 or more, said Penner. The researchers just published a paper on their work.

While the experiments are still very early, he said, they show promise in potentially solving a problem that has long vexed researchers who have been trying to use nanowire technology in lithium-ion batteries for the last six years.

Today's lithium-ion batteries use a thin film that can allow a much lower number of charging and recharging cycles, causing the battery lifespan issues seen in a wide range of portable devices, according to Penner.

The nanowires are much more efficient, but were being adversely affected by their short lifespans using cobalt-oxide, he said. Once the switch was made to manganese-oxide, which he said is essentially dirt, the number of possible recharging cycles increased tremendously. Now, the manganese-oxide gel could advance the use of nanowires in lithium-ion batteries because it seems to make the nanowires more reliable for long-term use.

"It's the first baby step in what makes these nanowires more practical for real-world batteries," Penner told eWEEK. "This just turns out to be an unexpected and important observation."

What will be needed now, he said is 20 to 100 more research papers that look at the same processes to dive more deeply into the science seen at UC-Irvine so other researchers can find out why the gel does what it does in the batteries.

"There's still a lot more to be done," he said.

Nanowires are incredibly thin strands of carbon that are very efficient at moving stored ions inside batteries, said Penner. "Because the nanowires are [shaped as] all surface area, ions can get into the nanowires way more efficiently than they can get into a film" in today's batteries. "This is why in battery science everybody is working on nanowires."

The old-style cobalt-oxide causes corrosion in films, too, but the surface area of the material is wider, allowing it to survive longer than the thin nanowires each time they are charged and discharged, he said. Manganese-oxide is much cheaper than cobalt-oxide, which also can reduce costs for battery makers in the future, he said.

Ongoing experiments at UC-Irvine are being done with layers of nanowires, laid out like shag carpets and super-thin thicknesses of the latest gel.

"To make this shag carpet and put the gel layer on it is a serious endeavor," said Penner. "It takes a lot of work and optimization. There are lots of practical issues you'd have to resolve, but in principal that could be possible in terms of real-world production."