Tiny 'transient' lithium-ion battery dissolves in water

Have you heard of ‘transient electronics’? It sounds a bit like something out of James Bond — self-destructing electronic devices that keep military secrets out of enemy hands and environmental sensors that wash away in the rain — but it’s based on fact, not fiction. The devices perform their functions until exposure to light, heat or liquid triggers their destruction.

The latest development to come out of this research is a self-destructing lithium-ion battery capable of delivering 2.5 V and then dissolving within 30 minutes when dropped in water. It can power a desktop calculator for about 15 minutes.

According to its creator Reza Montazami, an Iowa State University assistant professor, this is the first transient battery to demonstrate the power, stability and shelf life for practical use.

“Unlike conventional electronics that are designed to last for extensive periods of time, a key and unique attribute of transient electronics is to operate over a typically short and well-defined period, and undergo fast and, ideally, complete self-deconstruction and vanish when transiency is triggered,” the research team wrote in their paper in the Journal of Polymer Science, Part B: Polymer Physics.

“Any device without a transient power source isn’t really transient,” Montazami said. “This is a battery with all the working components. It’s much more complex than our previous work with transient electronics.”

The battery itself is tiny — just 1 x 5 x 6 mm — and the battery components, structure and electrochemical reactions are all very close to commercially developed battery technology. When it’s dropped in water, the polymer casing swells, breaks apart the electrodes and dissolves away. It doesn’t completely disappear, however — it contains nanoparticles that don’t degrade but do disperse as the battery’s casing breaks the electrodes apart.

Larger batteries with higher capacities could provide more power, but they also take longer to self-destruct, the researchers said. The paper suggests applications requiring higher power levels could be connected to several smaller batteries.