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Tohoku researchers develop disordered rock-salt oxide cathode for rechargeable magnesium batteries

Researchers at Tohoku University have developed a novel rock-salt oxide cathode material for rechargeable magnesium batteries (RMBs) that enables efficient charging and discharging even at low temperatures. An open-access paper detailing the findings is published in the Journal of Materials Chemistry A.

The study showcases a considerable improvement in magnesium (Mg) diffusion within a rock-salt structure, a critical advancement since the denseness of atoms in this configuration had previously impeded Mg migration. By introducing a strategic mixture of seven different metallic elements, the research team created a crystal structure abundant in stable cation vacancies, facilitating easier Mg insertion and extraction.


Schematics of the battery and present cathode material. The present material contains many metal elements as cations due to the effect of the high configurational entropy. ©Tohoku University

This represents the first utilization of rock-salt oxide as a cathode material for RMBs. The high-entropy strategy employed by the researchers allowed the cation defects to activate the rock-salt oxide cathode.

The development also addresses a key limitation of RMBs: the difficulty of Mg transport within solid materials. Until now, high temperatures were necessary to enhance Mg mobility in conventional cathode materials, such as those with a spinel structure. However, the material unveiled by Tohoku University researchers operates efficiently at just 90 °C, demonstrating a significant reduction in the required operating temperature.

Lithium is scarce and unevenly distributed, whereas magnesium is abundantly available, offering a more sustainable and cost-effective alternative for lithium-ion batteries. Magnesium batteries, featuring the newly developed cathode material, are poised to play a pivotal role in various applications, including grid storage, electric vehicles, and portable electronic devices, contributing to the global shift towards renewable energy and reduced carbon footprints.

—Tomoya Kawaguchi, lead author


  • Tomoya Kawaguchi, Masaya Yasuda, Natsumi Nemoto, Kohei Shimokawa, Hongyi Li, Norihiko L. Okamoto, and Tetsu Ichitsubo (2024) “Securing cation vacancies to enable reversible Mg insertion/extraction in rocksalt oxides”, Journal of Materials Chemistry A doi: 10.1039/D3TA07942B



From the linked paper:

' The theoretical reversible capacity, potential, and energy density of M7O are 240.4 mA h g−1, ∼2.3 V vs. Mg2+/Mg (Fig. S1 in the ESI†), and 553 W h kg−1, respectively. '

If 553Wh kg is the theoretical specific energy, then that is not a lot more than the practical present energy density of lithium batteries, which should improve more.

So it looks as though they are not going to take over powering BEVs anytime soon.

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