Scientists discover the optimal composition for a magnesium secondary battery cathode to achieve better cyclability and high battery capacity
Tokyo University of
Science
February 9, 2023 -- 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.
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!
https://www.tus.ac.jp/en/mediarelations/archive/20230206_7710.html
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