A team of Chinese researchers belonging to the QIBEBT Institute has published a very important advance that will allow replace lithium with magnesium in electric vehicle batteries. Instead of magnesium ions, a copper-rich charge carrier, which is a highly conductive material, so that electricity flows freely allowing high energy output.

Magnesium batteries take advantage of natural benefits of this mineral over lithium. Being much more abundant, it eliminates the supply problem and reduces its cost. The price of magnesium is about $ 5,000 per ton, about half that of lithium. In addition, it offers higher energy and power density, even at room temperature. Last, and not least, since it is not a material prone to dendrite formation and to suffer failures in its internal structure, it is safer, since it avoids the risks of explosion and fire.

However, the materials used in this type of batteries for both the cathode and the electrolyte have been an obstacle in its development. The use of chloride in the electrolyte contributes to slow performance, which prevents these batteries from being commercially competitive while they cannot store and discharge large amounts of energy.

Researchers from the Qingdao Institute for Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS) have published the results of their research in the journal Angewandte Chemie. There they announce that are one step closer to creating an economically viable, high performance magnesium battery, using copper ions as charge carriers.

Chemical operation of the new copper ion manesium batteries.

During the recharging process, the high density of Mg2 + ions makes its diffusion in the electrolyte slow. Furthermore, the bonds between them and the anions are difficult to break, leading to a poor charge-discharge cycle. To address this problem, the strategy followed by the researchers has been to use another charge carrier for cathode chemistry: the Cu +. This dissolves in the electrolyte, which will be made up of magnesium and copper ions and boron anions (BCM). The concentration of the Cu + charge carrier in the solution is governed by an equilibrium between the electrode and the BCM electrolyte.

As the magnesium battery is discharged, the Cu + ions dissolve in the electrolyte and this in metallic copper forming a coating on the electrode. How copper is highly conductive, electricity then flows freely, allowing a high energy production.

In the laboratory, the experimental Mg / Cu battery has shown excellent performance retaining 80% of its original capacity after 200 charge-discharge cycles. In comparison, a commercial lithium-ion battery loses more than 20% of its original capacity after 1,000 cycles. While the Mg / Cu battery is not commercially viable, the research opens the way to compete with lithium batteries. According to the project director, Professor CUI Guanglei “we hope to reach the 1,000 cycle milestone in the next two years.” The next step is to design the cells as flexible bags, for which they will need to create their gel-based Cu + based electrolyte solution.

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