Mya Le Thai's 200,000 Cycle Battery Experiment: What the UCI Breakthrough Achieved

A three month experiment with an extraordinary result

In a laboratory at the University of California, Irvine, doctoral researcher Mya Le Thai repeatedly charged and discharged an experimental electrode until it reached 200,000 cycles. After three months, researchers detected no loss of capacity or power and found no fractured nanowires. UCI announced the findings on April 20, 2016, when the study was published in ACS Energy Letters.

The material combined gold nanowires, a manganese dioxide coating and a gel electrolyte resembling Plexiglas. Its durability offered a possible answer to a stubborn problem: tiny wires that are useful for storing electrical energy tend to crack as they are used repeatedly.

The discovery also produced an arresting claim that a future laptop battery might last 400 years. That figure comes from converting the experimental cycle count into years at an assumed rate of use. The actual achievement was a laboratory electrode that survived 200,000 cycles during a test lasting three months.

Nearly a decade after the announcement, the nanowire result remains a laboratory proof of concept. Thai later earned her doctorate and moved into research on batteries for electric transportation. Her experiment continues to attract attention because it points to a way of keeping fragile battery materials intact through repeated use.

How a thin gel layer changed the experiment

Thai, a Vietnamese American researcher, was studying nanowires when she tried adding a thin gel coating to the experimental structure. The electrodes kept working as testing passed 10,000 cycles and, a few days later, 30,000. Testing eventually reached 200,000 cycles.

Reginald Penner, the study's senior author and then chair of UCI's chemistry department, described the unexpected discovery in the university's April 2016 announcement.

Mya was playing around, and she coated this whole thing with a very thin gel layer and started to cycle it," said Penner. "She discovered that just by using this gel, she could cycle it hundreds of thousands of times without losing any capacity.

Penner called the result surprising because comparable structures usually failed after 5,000 to 7,000 cycles. At those endpoints, the UCI electrode's 200,000 cycles amounted to roughly 29 to 40 times as many cycles. That comparison describes the improvement against the structures Penner discussed.

The accidental element was the success of the gel treatment. Establishing its value required sustained testing: Thai continued cycling the electrode for months, checking whether its electrical performance or physical structure deteriorated.

Why nanowires need protection

Nanowires are thousands of times thinner than a human hair. They conduct electricity well and offer a large surface area relative to their size, making them attractive building blocks for electrodes, the parts of a battery where charge is stored and released through electrochemical reactions.

Repeated charging and discharging puts stress on those structures. UCI explained that nanowires can expand and become brittle during use in a typical lithium ion battery. Cracks can then develop, breaking up material that needs to remain connected for the electrode to function effectively.

Thai's experimental structure had three main elements. A gold nanowire formed the core, manganese dioxide surrounded it, and a gel electrolyte covered the assembly. An electrolyte allows charged particles called ions to move through an energy storage device.

The researchers proposed that the gel plasticized the metal oxide. In everyday language, it may have made the coating more flexible, allowing it to tolerate movement without cracking. Keeping the structure intact helped the electrode preserve its performance through repeated cycles.

UCI reported that the tested electrode showed no detected loss of capacity or power and no fractured nanowires after the three month run. Capacity describes how much electrical charge a device can store; power describes how quickly it can deliver energy. Both matter to a useful battery.

What the performance figures mean

The experiment was also described as achieving average Coulombic efficiency of 94 to 96 percent. Coulombic efficiency compares the charge recovered during discharge with the charge put in during charging. A value of 94 percent means that about 94 units of charge were recovered for every 100 units supplied.

Capacity retention and Coulombic efficiency describe different aspects of performance. Capacity retention tracks whether the amount an electrode can store falls with repeated use. Coulombic efficiency tracks charge going in and coming out during cycling. An electrode can retain its storage capacity while returning a smaller amount of charge than it receives.

A Stanford nanobattery configuration developed in 2007 had previously reached 40,000 cycles. UCI's 200,000 cycles were five times that figure, although the devices used different configurations. Their designs and testing conditions therefore matter when comparing the results.

The laptop comparison is striking too. Against the 300 to 500 cycles commonly cited for a typical laptop battery, 200,000 is 400 to roughly 667 times as many cycles. Those numbers explain the excitement surrounding the experiment, while commercial development still requires a complete battery with suitable capacity, materials, safety and manufacturing costs.

Where the 400 year estimate comes from

The estimate assumes a laptop completes 1,000 charge cycles every two years, or 500 cycles a year. Dividing 200,000 cycles by 500 produces 400 years. Each step of that calculation is straightforward, but the calendar duration is an extrapolation from the laboratory result.

Thai's electrode reached its cycle count through continuous testing over three months. A battery in everyday use also spends time sitting partly charged, operates at changing temperatures and must work alongside other components. A finished product needs testing under the conditions its users will encounter.

The practical aim is longer service between replacements. For a laptop owner, that could mean keeping the same battery for more of the computer's useful life. For a vehicle manufacturer, it could mean an energy storage system that tolerates more charging and driving before replacement becomes necessary.

What researchers still needed to understand

UCI's May 2016 followup described further work to understand the manganese dioxide coating. Researchers could see that the gel kept the material from breaking into chunks, but they were still investigating how the material itself changed.

Penner, speaking as the senior author and chemistry department chair, explained the next scientific task.

"Mya's doing a bunch of studies now to try to get a better idea of what's going on with the manganese dioxide material. We know the gel prevents it from breaking up into chunks, but we don't know if what's left over is different from the material that would be there without the gel," Penner says.

Understanding that process matters for making the result repeatable and adapting it to other materials. If researchers can identify which properties of the gel and coating preserve the electrode, they can more deliberately design structures that withstand repeated charging.

The work was conducted in coordination with the Nanostructures for Electrical Energy Storage Energy Frontier Research Center at the University of Maryland. Funding came from the Basic Energy Sciences division of the U.S. Department of Energy.

From gold nanowires to practical batteries

Gold presents a cost problem for large scale production. Researchers have explored cheaper alternatives, including nickel, as a possible route toward a more economical design. Replacing the metal also requires checking whether the resulting electrode retains the durability of the original structure.

A complete commercial battery must combine long cycle life with enough stored energy, useful power, dependable safety and an affordable production process. The UCI result addressed a particular weakness in an experimental electrode: physical damage during repeated cycling. Turning that success into a product means meeting those other requirements together.

UCI identified computers, smartphones, appliances, cars and spacecraft as possible applications. Each would place different demands on a battery. A phone needs a compact energy supply; a vehicle needs a much larger system capable of delivering substantial power; spacecraft require dependable operation in demanding conditions.

Thai later became a principal scientist at Enevate, a U.S. battery technology company, working on advanced batteries for electric transportation. She has also applied for patents covering other inventions, including technology intended to delay thermal propagation between cells. Thermal propagation occurs when heat from a failing cell spreads to nearby cells.

No commercial launch date for the gold nanowire technology has been announced in the accounts of the work. Thai's later career shows her continued involvement in battery development, including durability and safety challenges beyond the original experiment.

The milestones behind the discovery

The story spans an earlier nanobattery result, months of laboratory cycling and two UCI announcements in 2016. Keeping those milestones together makes the age and scope of the discovery easier to follow.

• 2007: A different nanobattery configuration developed by Stanford researchers reached a reported 40,000 cycles.
• During UCI's experiment: Thai's gel coated electrode passed 10,000 and then 30,000 cycles before reaching 200,000 over three months.
• April 20, 2016: UCI announced the result, and the findings were published in ACS Energy Letters.
• May 16, 2016: UCI published a followup describing continuing research into how the gel affected manganese dioxide.
• After her doctorate: Thai joined battery research in industry and became a principal scientist at Enevate.

Thai described the result in terms of the electrode's improved physical stability and the possibility of building durable batteries. As the doctoral researcher leading the study, she said:

The coated electrode holds its shape much better, making it a more reliable option," Thai said. "This research proves that a nanowire-based battery electrode can have a long lifetime and that we can make these kinds of batteries a reality.

Key Points

• Mya Le Thai's UCI electrode completed 200,000 cycles over three months without detected capacity or power loss or fractured nanowires.
• The design combined gold nanowires, manganese dioxide and a gel electrolyte that researchers believed helped prevent cracking.
• The findings were published in ACS Energy Letters on April 20, 2016.
• The 400 year estimate comes from assuming 500 cycles annually; the laboratory test lasted three months.
• Gold costs and the requirements of a complete battery remain central to commercial development.
• Thai later became a principal scientist at Enevate, working on batteries for electric transportation.