Scientists made a stretchable lithium battery you can bend, cut, or stab
The Li-ion batteries that power everything from smartphones to electric cars are usually packed in rigid, sealed enclosures that prevent stresses from damaging their components and keep air from coming into contact with their flammable and toxic electrolytes. It’s hard to use batteries like this in soft robots or wearables, so a team of scientists at the University California, Berkeley built a flexible, non-toxic, jelly-like battery that could survive bending, twisting, and even cutting with a razor.
While flexible batteries using hydrogel electrolytes have been achieved before, they came with significant drawbacks. “All such batteries could [only] operate [for] a short time, sometimes a few hours, sometimes a few days,” says Liwei Lin, a mechanical engineering professor at UC Berkeley and senior author of the study. The battery built by his team endured 500 complete charge cycles—about as many as the batteries in most smartphones are designed for.
Power in water
“Current-day batteries require a rigid package because the electrolyte they use is explosive, and one of the things we wanted to make was a battery that would be safe to operate without this rigid package,” Lin told Ars. Unfortunately, flexible packaging made of polymers or other stretchable materials can be easily penetrated by air or water, which will react with standard electrolytes, generating lots of heat, potentially resulting in fires and explosions. This is why, back in 2017, scientists started to experiment with quasi-solid-state hydrogel electrolytes.