State-of-the-art magnesium-ion batteries are all about to become the next big thing for huge increase in the density of energy storage - double, actually, if magnesium ions are present in the same density as lithium ions.
5/14/15 5:00 am chumakdenis 1
Researchers at the University of Illinois at Chicago have developed a battery that outperforms the lithium-ion technology used in electric vehicles.
The research is part of the Joint Center for Energy Storage Research, a Department of Energy Innovation Hub led by Argonne National Laboratory that aims to achieve revolutionary advances in battery performance.
They have shown they can replace the lithium ions, each of which carries a single positive charge, with magnesium ions, which have a plus-two charge, in battery-like chemical reactions, using an electrode with a structure like those in many of today's devices.
They did what?
If you are good at chemistry, you should know that the Li-ion battery essentially works by using lithium ions to ferry electrons back and forth between a positive and a negative electrode.
These are basically electrical freighters that load up with electrons on the negative side of the battery and, when given the proper signal, sail on over to the positive side to offload their cargo - this is discharging a battery, and when the electrons leave the lithium carriers at the other side, they can flow down their gradient and create a current to power our device. The now-empty lithium freighters are bound to the positive electrode, but they can be reloaded by running the current backwards. The now electron-laden molecule naturally dissociates and sails back to the first, storage electrode. Once all available ions are thus stored in a high energy state, the battery is recharged.
The freighter analogy works well because, just as cargo comes in units of shipping containers, electricity comes in units of electrons. A lithium ion is, for the purposes of batteries, going to be able to hold only a single electron; Li1+ is the ion we typically use in Li-ion batteries. But magnesium is most readily usable in the form of Mg2+ ions, meaning that it could ferry a maximum of two electrons per freighter-trip across the battery.
That allows a huge increase in the density of energy storage - double, actually, if magnesium ions are present in the same density as lithium ions.
"Because magnesium is an ion that carries two positive charges, every time we introduce a magnesium ion in the structure of the battery material we can move twice as many electrons," says Jordi Cabana, UIC assistant professor of chemistry and principal investigator on the study.
"We hope that this work will open a credible design path for a new class of high-voltage, high-energy batteries," Cabana said.
Every battery consists of a positive and negative electrode and an electrolyte. The electrodes exchange electrons and ions, which are usually of positive charge. Only the ions flow through the electrolyte, which is an electric insulator so as to force the electrons to flow through the external circuit to power the vehicle or device.
To recharge the battery, the exchange is reversed. But the chemical reaction is not perfectly efficient, which limits how many times the battery can be recharged.
"The more times you can do this back and forth, the more times you will be able to recharge your battery and still get the use of it between charges," Cabana said.
"In our case, we want to maximize the number of electrons moved per ion, because ions distort the structure of the electrode material when they go in or leave. The more the structure is distorted, the greater the energy cost of moving the ions back, and the harder it becomes to recharge the battery."
"Like a parking garage, there are only so many spaces for the cars," Cabana said. "But you can put a car in each space with more people inside without distorting the structure."
Having established that magnesium can be reversibly inserted into electrode material's structure brings us one step closer to a prototype, said Cabana.
Well, let’s wish Cabana and her research team good luck with that and wait for more good news from them.
*Do you think that this technology will make it to EV market?
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