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New Activation Strategy Could Make Magnesium Batteries Commercially Viable

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In a new study published in ACS Nano, researchers from the Korea Institute of Science and Technology (KIST) report the development of a new activation strategy that allows magnesium-based batteries to work without the use of corrosive additives.

The researchers say that their findings may lead to new low-cost, mass-producible, high-energy-density batteries that could be a commercially viable alternative to lithium-ion batteries.

The need for lithium battery alternatives

Lithium-ion batteries have become one of the most popular forms of energy storage in the world, largely due to their high energy density and favorable charge cycle properties. However, the production of lithium batteries also requires significant amounts of other rare earth metals, such as cobalt, which are only found in a small number of countries. Concerns over the future safety and reliability of this supply chain have prompted researchers to begin investigating alternative next-generation rechargeable batteries which use more abundant materials.

Magnesium-based batteries are one of these promising alternatives. Magnesium forms divalent ions (Mg2+), whereas lithium ions are monovalent (Li+).  As a result, magnesium has the potential to achieve extremely high energy densities. Indeed, a pure magnesium metal anode can deliver a volumetric capacity around 1.9 times larger than lithium metal.

So why are we not already walking around with magnesium batteries in our phones or in our cars? Magnesium is a highly reactive metal, and its reactivity with common electrolytes causes significant issues with charging and discharging magnesium-based secondary batteries. Previous studies have side-stepped this issue by using alternative electrolytes to produce functional magnesium batteries, but this requires corrosive additives that are not conducive to commercial scale-up and use.

Now, KIST researchers believe that a new artificial protective layer designed for use with magnesium metal components and common electrolytes could be the key to unlocking further magnesium battery development.

New technology enables magnesium batteries to work with safer electrolytes

By dipping the magnesium metal anodes into a reactive alkyl halide solution prior to battery cell assembly, the KIST researchers were able to synthesize an artificial magnesium alkyl halide oligomer coating on the surface of the metal.

They found that when a specific reaction solvent was used, nanostructures would form on the metal surface, which in turn enabled the dissolution and deposition of magnesium. This effectively nullified the risk of extreme reactions between the magnesium and the non-corrosive electrolytes.

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Using this new activation step, the researchers demonstrated that the overpotential for a magnesium battery without corrosive additives can be reduced from more than 2 V to under 0.2 V when charging and discharging in common electrolytes. Additionally, the Coulombic efficiency  — the ratio of total charge extracted from a battery to the total charge put into it over a full cycle — can be increased from around 10% to more than 99.5%. Higher Coulombic efficiencies indicate that a battery will lose less capacity in each charge/discharge cycle, extending its potential lifespan.

The new magnesium battery operated safely through more than 990 charging cycles, which the researchers say proves the potential of these batteries for commercial use.

"This work provides a new direction for the existing magnesium secondary battery research, which has been using corrosive electrolytes that prevent the formation of interfacial layers on magnesium metal surfaces," said lead study author Dr. Minah Lee of KIST. "It will increase the possibility of low-cost, high-energy-density magnesium secondary batteries based on common electrolytes suitable for energy storage systems.“

Next-generation rechargeable batteries

Rechargeable magnesium batteries have the potential to offer a higher volumetric capacity than lithium batteries, while also using elements that can be more easily and reliably sourced through the global supply chain. Both of these aspects make magnesium batteries a very attractive alternative for commercial development. With this new magnesium activation technique, the KIST researchers have demonstrated highly efficient magnesium cycling, marking an important step forward in the mass production of commercial magnesium batteries.

Reference:  Jeon AR, Jeon S, Lim G, et al. Reversible magnesium metal cycling in additive-free simple salt electrolytes enabled by spontaneous chemical activation. ACS Nano. 2023;17(10):8980-8991. doi: 10.1021/acsnano.2c08672

This article is a rework of a press release issued by the Korea Institute of Science and Technology. Material has been edited for length and content.