I’m happy to announce that Iron Battery 2.0 has been accepted for publication in HardwareX, the peer reviewed journal for Open Source Hardware. Back in 2017, and with the help of some generous crowd funders, we set out to make a radically inexpensive and nontoxic battery. We made a lot of progress.
We took inspiration from the Edison cell iron electrode (invented more than 100 years ago). When iron oxidizes, it gives up electrons. In the Edison cell, those electrons are taken up by nickel. That transfer of electrons is what gives the usable electricity we want. To reverse the reaction and charge the battery, electrons are sucked out of the nickel and back into iron. But nickel is relatively expensive, and the Edison cell uses a concentrated and caustic alkaline electrolyte.
Back in 2017, we replaced the nickel with ferric iron and neutralized the electrolyte. This really hurts the energy density and performance of the battery. The energy was there, it just couldn’t discharge fast enough to give useful power. The plan was to use it for stationary applications, but it was still under-powered. It would take days to get all the energy out of Iron Battery 1.0. But it worked well enough to show that the idea was valid.
This low-power problem is called high internal resistance. So, the next step was to try to decrease the internal resistance. So, if we could reduce the distance the electrons had to travel, we should make a better battery. To help get the electrons close to the ferric iron, we added a lot of carbon black (a conductive carbon powder used in conductive inks). That’s how we made Iron Battery 2.0. It is a significant improvement in power, up to usable levels.
A single Iron Battery 2.0 cell can now deliver enough power to light up an LED (albeit with a little voltage booster circuit called a “Joule thief,” which has a great pun for a name). This is getting closer to practical level where this chemistry could store solar or wind energy on a larger scale.
The previous build video (Iron Battery 1.5) goes through the construction and the main recipe. The very detailed build instructions (including a list of all the materials and where to get them) are now available in the new publication.