Bending the Rules of Battery Design

The latest innovation in battery technology has brought a breath of fresh air to the industry. A new type of lithium-ion battery, designed to be flexible, safe, and sustainable, has been developed by researchers at the University of California, Berkeley. This breakthrough battery can withstand punctures, razor cuts, and even a full month of abuse without a single drop of lithium ion leaking out. At first glance, the battery looks like a simple patch of silicone, but beneath its soft and flexible exterior lies a revolutionary technology that could change the game for wearable devices, soft robots, and medical implants. The battery’s design is centered around a unique hydrogel that can stretch to more than 13 times its original length, heal itself after being sliced in two, and keep powering an LED light even as it’s twisted, folded, and stabbed.

What Makes this Battery So Special?

The battery’s electrolyte is a water-scarce zwitterionic hydrogel that allows it to operate at a voltage window of up to 3.11 volts without needing a rigid, hermetically sealed case.
The hydrogel is made up of a mix of quaternary ammonium and sulfonic acid groups that attract and trap lithium ions while binding water tightly enough to keep it from misbehaving.
The battery’s molecular makeup contains hydrogen bond donors and acceptors that snap back together after damage, allowing it to reassemble itself and recover from injuries.

Testing the Battery’s Limits

The researchers built full lithium-ion batteries with flexible, wavy electrodes and their innovative hydrogel. They then subjected the batteries to a series of rigorous tests, including twisting, bending, and stretching them up to 50% of their original length. They also stabbed the batteries repeatedly with needles and sliced them in half. In one particularly grueling test, the battery lit an LED even as it was being punctured five times in a row. After each injury, the battery was allowed to rest or was briefly heated to 70°C. Within minutes, it stitched itself back together. Ten cycles of cutting and healing resulted in less than a 10% change in resistance.

Long-Term Performance

The battery’s long-term performance was impressive, with it retaining 60% of its original capacity after 500 charge cycles. While this is less than the industry standard of 80%, the researchers argue that this is still a significant improvement over traditional lithium-ion batteries.

The Future of Battery Technology

The development of this new battery technology has far-reaching implications for the industry. Wearables, soft robots, and medical implants could become fully flexible, and the need for rigid packages could be a thing of the past. “The smartwatch is powered by a battery, but the band for this watch today performs only the mechanical function,” said Liwei Lin, the study’s senior author. “If you can replace the band with our battery, you have more area, more volume to work with. Instead of needing a recharge once a day, it could perhaps work for, like, a week.”
The team is exploring ways to increase the battery’s capacity using 3D porous electrodes and new cathode materials that can better exploit the gel’s high voltage window. They’re also looking into how the technology might work in other battery chemistries, including zinc or sulfur-based designs.

Conclusion

The development of this new battery technology is a significant breakthrough in the industry. It shows that a soft, safe, stretchable lithium-ion battery is not just possible, but it can survive real-world abuse and keep working. As the technology continues to evolve, we can expect to see more innovative applications in the future.