Tokyo University of Science


2023.02.09 Thursday

Beyond Lithium: A Promising Cathode Material for Magnesium Rechargeable Batteries

Scientists discover the optimal composition for a magnesium secondary battery cathode to achieve better cyclability and high battery capacity

Magnesium is a promising candidate as an energy carrier for next-generation batteries. However, the cycling performance and capacity of magnesium batteries need to improve if they are to replace lithium-ion batteries. To this end, a research team focused on a novel cathode material with a spinel structure, Mg1.33V1.67−xMnxO4. Following extensive characterization and electrochemical performance experiments, they have found a specific composition that could open doors to high-performance magnesium rechargeable batteries.

Beyond Lithium: A Promising Cathode Material for Magnesium Rechargeable Batteries

Lithium-ion batteries have remained unrivaled in terms of overall performance for several applications, as evidenced by their widespread use in everything from portable electronics to cellular base stations. However, they suffer from few important disadvantages that are difficult to ignore. For one, lithium is rather expensive, and the fact that it is being mined at an extreme pace does not help. Moreover, the energy density of lithium-ion batteries is not enough to grant autonomy to electric vehicles and heavy machinery. These concerns, coupled with the fact that the batteries are highly unsafe when punctured or at high temperatures, have caused scientists to look for alternative technologies.

Among the various elements being tested as efficient energy carriers for rechargeable batteries, magnesium (Mg) is a promising candidate. Apart from its safety and abundance, Mg has the potential to realize higher battery capacities. However, some problems need to be solved first. These include the low voltage window that Mg ions provide, as well as the unreliable cycling performance observed in Mg battery materials.

To tackle these issues, a research team led by Vice President and Professor Yasushi Idemoto from Tokyo University of Science, Japan has been on the lookout for new cathode materials for Mg batteries. In particular, they have been searching for ways to improve the performance of cathode materials based on the MgV (V: vanadium) system. Fortunately, as reported in a recent study made available online on 8 December 2022 and published in Volume 928 of the Journal of Electroanalytical Chemistry on 1 January 2023, they have now found the right track to success.

The researchers focused on the Mg1.33V1.67O4 system but substituted some amount of vanadium with manganese (Mn), obtaining materials with the formula Mg1.33V1.67−xMnxO4, where x goes from 0.1 to 0.4. While this system offered high theoretical capacity, more details about its structure, cyclability, and cathode performance needed to be analyzed to understand its practical utility. Accordingly, the researchers characterized the synthesized cathode materials using a wide variety of standard techniques.

First, they studied the composition, crystal structure, electron distribution, and particle morphologies of Mg1.33V1.67−xMnxO4 compounds using X-ray diffraction and absorption, as well as transmission electron microscopy. The analyses showed that Mg1.33V1.67−xMnxO4 has a spinel structure with a remarkably uniform composition. Next, the researchers conducted a series of electrochemical measurements to evaluate the battery performance of Mg1.33V1.67−xMnxO4, using different electrolytes and testing the resulting charge/discharge properties at various temperatures.

The team observed a high discharge capacity for these cathode materials-especially Mg1.33V1.57Mn0.1O4-but it also varied significantly depending on the cycle number. To understand why, they analyzed the local structure near the vanadium atoms in the material. "It appears that the particularly stable crystal structure along with a large amount of charge compensation by vanadium leads to the superior charge-discharge properties we observed for Mg1.33V1.57Mn0.1O4," remarks Prof. Idemoto. "Taken together, our results indicate that Mg1.33V1.57Mn0.1O4 could be a good candidate cathode material for magnesium rechargeable batteries."

Satisfied with the present findings and hopeful about what is to come, Prof. Idemoto concludes: "Through future research and development, magnesium batteries could surpass lithium-ion batteries thanks to the former's higher energy density."

Indeed, substituted MgV systems could eventually lead to the much awaited next-generation batteries. Let us hope the highly anticipated alternative to lithium for our rechargeable battery needs will be realized soon!

Authors  : Yasushi Idemoto1,2,3, Mina Takamatsu1, Chiaki Ishibashi1,2, Naoya Ishida1, Toshihiko Mandai3, Naoto Kitamura1,2
Title of original paper  : Electrochemical properties and crystal and electronic structure changes during charge/discharge of spinel type cathode-materials Mg1.33V1.67-xMnxO4 for magnesium secondary batteries
Journal  : Journal of Electroanalytical Chemistry
DOI  : 10.1016/j.jelechem.2022.117064
Affiliations  : 1Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, Japan.
2Research Group for Advanced Energy Conversion, Research Institute for Science and Technology, Tokyo University of Science, Japan.
3Center for Advanced Battery Collaboration, Center for Green Research on Energy and Environmental Materials, National Institute for Materials Science, Japan.
About The Tokyo University of Science

Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.

With a mission of "Creating science and technology for the harmonious development of nature, human beings, and society", TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.

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About Professor Yasushi Idemoto
from Tokyo University of Science

Yasushi Idemoto obtained his master's and PhD degrees in Chemistry and Engineering at Tokyo University of Science, where he has been an active researcher since 1989. He became a Full Professor in the Department of Pure and Applied Chemistry in 2008, and then became a Dean of Faculty of Science and Technology in 2016. He also became Vice President of the University in 2020. His key research areas are applied materials for batteries and fuel cells and physical and inorganic chemistry, and he has published well over 280 research articles on these topics. Moreover, Idemoto is a member of various scientific societies, as well as current Director of The Electrochemical Society of Japan.

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Funding information

This study was supported by JST ALCA-SPRING Grant Number JPMJAC1301, Japan.


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