Summary: Scientists at UC Berkeley have developed a jelly-like, non-toxic flexible lithium battery that can survive bending, twisting, and even being stabbed, while lasting through 500 charge cycles. Although its energy retention is lower than typical smartphone batteries, the innovation shows promise for use in flexible electronics and wearables.

While the new hotness in terms of batteries is, silicon-carbon, that’s not keeping scientists from continuing to innovate on lithium batteries. A team of scientists from UC Berkeley built a flexible, non-toxic, jelly-like battery that can survive being bent, twisted, and even being stabbed with a razor.

Flexible batteries aren’t new – in fact LG used them in phones like the LG G Flex many years ago – but they typically have significant drawbacks. Professor Liwei Lin at UC Berkeley says that “all such batteries could [only] operate [for] a short time, sometimes a few hours, sometimes a few days.” The battery built by its team has endured 500 complete charge cycles, which is about the number of cycles that most smartphone batteries are designed for.

One of the downsides to this flexible battery however, is energy performance. Most batteries that are rated for 500 cycles, are able to keep at least 80% of their capacity after 500 full cycles. This flexible battery was only able to retain about 60% of its capacity after 500 cycles. So there is still work to be done.

Professor Lin says that “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.” However, unfortunately, flexible packaging made of polymers or other stretchable materials can be easily penetrated by air or water. That will, obviously, react with standard electrolytes and generate loads of heat. Because of this, scientists started to experiment with quasi-solid-state hydrogel electrolytes in 2017.

What could this flexible battery be used in?

Despite the incredible thinness of Silicon-Carbon batteries, flexible batteries can still have a use. The team at UC Berkeley says that they expect these to be used in flexible electronics and wearables. This could allow for your smartwatch to have an even larger battery than it currently has. Something that OnePlus sort of solved by using a Silicon-Carbon battery in its OnePlus Watch 3.