I'm happy to announce that the all-iron battery 2.0 has been accepted for publication in the peer review journal Hardware X, the Journal of Open Source Hardware. For those of you who may be new here, back in 2017, we set out to develop an open source all-iron radically inexpensive battery with the help of some very generous crowd funders. To accomplish this, we started with iron because iron is one of the most abundant elements on earth, as well as being one of the most radically and widely exploited elements in the human economy. Humans produce on the order of a billion tons of iron per year every year, and iron has some properties that we can use if we want to make a battery. Now, using an iron electrode in a battery is not particularly new. The Edison battery invented more than a hundred years ago uses an iron anode. In the Edison cell, when the iron anode oxidizes or rust gives up electrons, and those electrons are transferred over to a nickel cathode, which accepts those electrons and is reduced. To reverse the reaction and charge the battery, electrons are forced out of the nickel and back into the iron to make iron metal again. But nickel is relatively expensive, and the Edison cell uses a caustic potassium hydroxide electrolyte, which is honestly dangerous. So, back in 2017, we set out to replace the nickel electrode with an iron based electrode. It was drastically reduced the performance of the battery. Unfortunately, that means this battery won't power any cars. The battery would have to be bigger than the car itself. The idea was that we could use it for stationary applications where it doesn't have to move and it's weight isn't a problem. Maybe it could eventually be used to store renewable energy, solar, or wind. Unfortunately, by the time we were done, it was still underpowered even for these sort of stationary applications. So, we set out to improve it more recently. But here's how the battery works in general. So, first let's define our terms. There are three kinds of iron, iron metal or iron zero. Ferris iron or iron 2 plus, and ferric iron or iron 3 plus. One iron metal oxidizes or rusts becomes mostly iron 2 plus, ferris iron. It gives up electrons in the process or is oxidized. We used ferric iron to take up those electrons, where upon it is reduced to ferris iron. So, as the battery is discharged, it generates ferrous iron in general. And as the battery is charged, we regenerate the iron metal at the end of the iron 3 plus or ferric iron at the cathode. We have to include a membrane for the battery to balance its charge. We don't want those electrons to build up a static electric charge on either side. And so, to balance that, we need to move ions around. So, in this case, we didn't want to use that caustic potassium hydroxide. So, we used a more neutral solution with plenty of ions to move through the membrane and balance that charge. Now, we showed the iron battery 1.0 could charge and discharge many times. But, it could only do so very, very slowly. Meaning that it would take something like 48 to 72 hours to fully discharge or charge the cell, even at maximum discharge rate, it would still take days to discharge. So, this is not ideal for any application. Only the most low power circuits can use this sort of battery. Now, this is called high internal resistance, meaning that the battery itself acts as a very intense resistor to the flow of electricity. This is not ideal. And so, we set out to reduce that high internal resistance for iron battery 2.0. So, we tried a bunch of things, but we worked under the following hypothesis that the electrons had to flow through the electrons. So, we tried to get through the electrolyte to get to the iron 3 plus, because iron 3 plus is non-conductive, and that flow through the electrolyte was slow and was causing the whole battery to be low power. So, we figured if we could reduce the distance from the current collector to the iron 3 plus, we would increase the power of the battery. To do that, we included a bunch of carbon black, which is a conductive form of carbon often used in conductive inks, to carry the electrons from the carbon current collector as close as possible to the iron 3 plus. We also improved the electrolyte salt mix slightly. It turns out that sodium isn't really necessary, where ion in the mix was necessary, without the sulfate chloride and potassium, the cell simply wasn't as able to charge and discharge. We also slightly improved the procedure for neutralizing the electrolyte to pH 7.5, and that was in the last update video, the 1.5 version. So, that's how we improved the battery. The updates are all available, and the link is in the description for iron battery 2.0. It now can deliver a more useful amount of energy per second, has a higher power density, and I think at this point it's getting close to a practical level. We now have enough power from a single iron battery 2.0 cell to illuminate an LED. Iron battery 1.0 required 6 cells in series to generate that much power. If we were to scale up to the size of a shipping container or about 100 meters cubed, we'd have enough power and energy to supply about four efficient homes for several days. In more technical terms, we went from a power density of about 1 milliwatt per liter, which is really tiny, up to almost 250 milliwatt per liter. So a significant improvement. The construction is equivalent to iron battery 1.5, the video link is in the description below, and the detailed instructions, including a bill of materials, and a link to all of our resources on where we bought all of our parts, is available at the paper, which is also linked in the description below. So there it is, that's the end of the iron battery story on this blog. I will update here if we have any more progress. My co-author, Deepak Kwarela, is still working on this a little bit in his PhD thesis, and if he has another publication, I'll be delighted to update that here. But for the most part, we'll be moving on to other topics on this blog. So if you're interested in this kind of thing or science in general, I hope you'll tune back in. We will be updating on the things that I'm interested in here. And also you can check out the paper at HardwareX in the link below, and you can check out my blog at PeterAllenLab.com. Thanks for watching.