There are a lot of teams trying to improve existing Li-Ion batteries or come up with completely new types of batteries. Some of them are already slowly reaching the market and significant changes should occur in the coming years. For example, Na-Ion sodium cells are already being produced, which should appear in the first motorcycles and electric cars this year, and several different types of solid-state cells are already being tested in cars, which often switch to metal lithium anodes. Scientists from the Illinois Institute of Technology (IIT), University of Illinois-Chicago (UIC) and Argonne National Labs present just such a thing. But while most solid-state cells are still basically Li-Ion with partial changes, this team showed Li-Air batteries, i.e. lithium-air cells. However, lithium ions are also used here. However, the principle itself is nothing new, it was already discovered half a century ago.
The reaction features a lithium metal anode and a porous structure as a cathode, which can provide oxygen molecules for the reaction. This is where the solid electrolyte separating these two electrodes comes into play, a composite of ceramic and polymer materials (contains nanoparticles of Li10GeP2S12). By being solid, it should offer greater security than liquid. The electrolyte used enables the transition of lithium ions 15 times faster than the solid electrolytes tested so far, but at the same time it represents a safety barrier for isolating the anode from direct access (and therefore explosion). But there is one more change. Until now, lithium-air batteries usually ended with LiO2 a Li2O2thanks to the new electrolyte and the formation of a coating preventing too much access of oxygen to the reaction (due to the amount of lithium ions) it is possible to continue up to Li2O, i.e. instead of one (LiO2) or two electrons (Li2O2) per oxygen molecule, there will be a transfer of four. The reaction catalyst is Mo3P, which is a relatively cheap material.
The tests showed that the batteries lost only 5% of their capacity after 1200 charging cycles (recall that Li-Ion lifetimes are usually given around 500-1000 cycles for a 20-30% decrease), which is a significantly better value (with the exception of Li- Ion LFP). But the most interesting parameter here is clearly the density. It reached 685 Wh/kg, which is 2.5 times more than today’s typical cells from the upper limit of the density spectrum, and about 2 times what should appear in the Li-Ion world in the next 2-3 years (e.g. NIO should start producing cars with semi-solid-state batteries with 360 Wh/kg) in these weeks. It is said that in the future the density of Li-Air batteries could reach up to 1000 Wh/kg.
If this 685 Wh/kg could be achieved even in series production (it certainly won’t happen soon, if ever), for example cells with 1 MWh for a tractor ensuring a range of 600-800 km would weigh only 1.5 tons, which is roughly the weight diesel engine with gearbox. The battery would, of course, be a few hundred kg heavier, because it is not just the cells, but also the packaging and other accessories, and the diesel tractor would have a few hundred more kg in diesel and other liquids. For a 100kWh battery for a passenger car, this would mean roughly 150 kg in cells, then the packaging itself, cooling and other components would add something.
