http://www.digitaljournal.com/tech-and-science/science/dissolving-batteries-invented/article/472193

Dissolving batteries invented

Posted Aug 10, 2016 by Tim Sandle
Researchers have developed the world's first dissolving batteries. The main aim is to provide a positive environmental benefit, although the batteries are also energy efficient.
This new disposable battery  developed at Binghamton University  folds like an origami ninja star an...
This new disposable battery, developed at Binghamton University, folds like an origami ninja star and could power biosensors and other small devices.
Jonathan Cohen/Binghamton University
The new batteries self-destruct when exposed to either heat or liquid. As well as this remarkable property, which adds a covert operations benefit to the environmental advantages, the battery delivers 2.5 volts, which is sufficient to operate a standard calculator for 15 minutes. This may not seem that much, but as a proof-of-concept the battery could herald a new generation of easy-to-dispose of power sources.
The transient battery has been developed by a team led by Profressor Reza Montazami of Iowa State University. The dimensions of the battery are tiny: 5 millimeters in length, 1 millimeter thick and just 6 millimeters wide. Within this tiny structure is an anode, a cathode and an electrolyte separator encased within two layers of polyvinyl alcohol-based polymer (in other words, the standard functionality of a battery.)
In terms of dissolving, when the battery is placed in a liquid, like water, the polymer casing swells and the electrodes are broken apart. This act causes the structure to dissolve. By dissolving all that remains are some particles detectable only on the nanoscale.
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Discussing the dissolving activity further, when interviewed by the BBC, Professor Montazami said: "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 idea behind the battery could also apply one day to batteries that dissolve within the human body. This could reduce the risk of removing certain implantable medical devices that are powered by batteries. The present dissolving battery would not be suitable for this application because it uses lithium (which is toxic to the body); however the scientific concept means that once a biologically compatible electrolyte is found then work can begin on developing a battery than can harmlessly dissolve away with the human body.
The dissolving battery concept has been published in the Journal of Polymer Science, Part B: Polymer Physics. The research paper is headed "Physical–chemical hybrid transiency: A fully transient li-ion battery based on insoluble active materials."