Scientists from the University of Iowa have developed a water soluble battery that is able to deliver a charge capable of powering a desktop calculator for 15mins. The charge is 2.5 V. The battery dissolves in water in 30 minutes.
The discovery is being held as a major leap forward in the field of transient electronics, an area of research that for years has been trying to make temporary electronic devices that self-destruct or dissolve when a trigger is applied.
Whilst a major breakthrough was made last year with the development of water soluble silicon, many transient electronic devices still needed an external non-transient power source. Attempts to create a transient battery have until now been unsuccessful, as researchers had been unable to develop one that could, as the online journal Futurism reports, “demonstrate the power, stability and shelf life for practical use”.
As the research team outline in their report, published in the Journal of Polymer Science; Part B Polymer Physics, previous efforts have included, “a swallowable battery based on Zn and Pt electrodes and ceramic porous separator [with a] maximum potential of 0.42 V and current of 2.41 mA”; “edible water activated sodium batteries based on melanin electrodes where a potential of 0.6–1.06 V and current of 5–20 μA was achieved”; plus “An intrinsically transient battery capable of environmental resorption where Mg anode and biodegradable metals (Fe, W, or Mo) cathodes were used with a transient polymer casing [with] potentials ranging from 0.45 to 0.75 V”
But now a breakthrough has been made, which the technology journal Engadget describes as a, “one-millimeter-thick and five-millimeter-long device [that] uses typical lithium-ion technology. Unlike typical batteries though, it’s encased in a degradable polymer composite that swells and eventually breaks apart in water.”
The research team explained their use and selection of polymers, “PVA and PVA composites were used as binder, substrate, and casing materials, due to its ease of control over transiency rate and fabrication. Subsequently, PVA chains are eventually solvated and the membrane dissolves in the solvent. Lithium cobalt oxide, LiCoO2, (LCO), and Li4Ti5O12 (LTO) were used as the ultimate cathode and anode active materials, respectively.”
Although dissolvable, lead researcher, Reza Montazami, an Iowa State University assistant professor of mechanical engineering and an associate of the U.S. Department of Energy’s Ames Laboratory, was quick to point out that the battery doesn’t completely disappear. Instead, the battery contains “nanoparticles that do disperse as the battery’s casing breaks the electrodes apart”, something that he calls, “physical-chemical hybrid transiency.”
While the discovery is significant and has obvious practical uses, the researchers do warn that the product will not be for sale soon, as, “While promising, it will probably take some time before the team can make a version that can power more sophisticated electronics. They still have to figure out how to scale up a battery that has multiple layers and has such a complex structure.”
Development of the transient battery was supported by funding from Iowa State’s Presidential Initiative for Interdisciplinary Research and the department of mechanical engineering.
Whilst the battery is clearly a fantastic invention, entrepreneurs are now considering where the battery would be best used. The researchers themselves suggested on the Iowa State University website that, “Self-destructing electronic devices could keep military secrets out of enemy hands. Or they could save patients the pain of removing a medical device. Or, they could allow environmental sensors to wash away in the rain.”
All of which are great suggestions, but the question remains, “Where would you apply a self-destructing dissolvable battery?”