Christopher McFadden

Researchers from Yale University have developed an innovative “holey” battery that is both flexible and breathable than conventional batteries. This could pave the way for making lithium batteries a perfect fit for wearable electronics.

Currently, most batteries are limited use in wearables, especially for applications that could result in significant wear and tear. “The rigid and non-breathable nature of conventional batteries has remained a significant limitation for wearable electronics, particularly in applications involving dynamic physical activities,” the team wrote in its paper published in Matter.

However, this new “holey” battery could solve many existing battery problems with a relatively simple solution. The team took a flexible lithium-ion battery pouch to achieve it and cut a series of horizontal and vertical rectangular holes into it. These kinds of batteries consist of a flat composite of materials that have a limited degree of flex.

They are also relatively easy to make and comprise conventional electrode materials and hot-pressed consumables.

“Holey” battery breakthrough

“This is especially useful for athletes or individuals who wear electronics for extended periods – smart clothing for fitness tracking, medical monitoring devices, and similar applications that demand both comfort and reliable performance,” explained Lin Xu, one of the team members.

By adding a series of holes, the team found that the battery pouch was very flexible while retaining much of its power. Simulation of the design also showed that the battery should be able to be stretched or folded 180 degrees without tearing.

“One challenge was maintaining enough active material to keep the battery’s energy density high – too many or too large holes would reduce the energy storage capacity,” said Xu.

“We had to balance mechanical stretchability with electrical performance.”

Not only that, but the team found that when the battery is stretched 10% or folded, the battery could resist physical stress and continue to power LED light bulbs. The team confirmed this by stretching and folding the battery over 100 times.

“Importantly, this architecture allows for a high areal energy density, achieving 7.2 mW h/cm2 in a single-layer pouch, which is scalable to 14.4 mW h/cm2 using double electrode layers,” the team highlighted.

A perfect fit for wearables

They also found that the new “holey” battery could better resist fluctuating temperatures and humidities. It appears the new battery is roughly twice as breathable as cotton.

To test the “holey” battery further, the team wove it into a lab coat to assess its performance when the wearer performed light exercises like running. The battery’s design dramatically improved its ability to dissipate heat and prevent the buildup of sweat underneath.

According to the research team, the battery still needs more wear-and-tear testing, so the researchers plan to test its performance in commercial health monitoring devices and sports gear.

They are also investigating how to scale up the best production – automated manufacturing must provide consistent hole placement and sealing to avoid leaks or short circuits in the battery pouch.

The study has been published in the journal Matter.