New self-destructing battery to power 'transient' devices

Scientists have developed a new lithium-ion battery that can dissolve in water within 30 minutes, an advance that may lead to the development of 'transient electronics' or self-destructing devices designed to keep military secrets out of enemy hands.
Self-destructing devices could also save patients the pain of removing a medical device, and allow environmental sensors to wash away in the rain, researchers said.
Making such devices possible is the goal of a relatively new field of study called "transient electronics."
These transient devices could perform a variety of functions - until exposure to light, heat or liquid triggers their destruction.

The latest development by researchers, including Reza Montazami from the Iowa State University in the US, is a self-destructing, lithium-ion battery capable of delivering 2.5 volts and dissolving or dissipating in 30 minutes when dropped in water.
The battery can power a desktop calculator for about 15 minutes. It 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," researchers said.

"Any device without a transient power source is not really transient. This is a battery with all the working components," Montazami said.
The transient battery is made up of eight layers, including an anode, a cathode and the electrolyte separator, all wrapped up in two layers of a polyvinyl alcohol-based polymer.
The battery itself is tiny - about 1 millimetre thick, 5 millimetres long and six millimetres wide.
Montazami said the battery components, structure and electrochemical reactions are all very close to commercially developed battery technology.
However, when you drop it in water, the polymer casing swells, breaks apart the electrodes and dissolves away.

According to Montazami, the battery does not completely disappear. It contains nanoparticles that do not degrade, but they 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, researchers said.
The findings were published in the Journal of Polymer Science, Part B: Polymer Physics.