NREL researchers (left to right) Seoung-Bum Son, Steve Harvey, Andrew Norman and Chunmei Ban working with a time-of-flight secondary ion mass spectrometer, which allows them to investigate material degradation and failure mechanisms at the micro- to nano-scale. Photo: Dennis Schroeder / NREL.Scientists at the US Department of Energy's National Renewable Energy Laboratory (NREL) have discovered a new approach for developing a rechargeable non-aqueous magnesium-metal battery.
A proof-of-concept paper published in Nature Chemistry describes how the scientists pioneered a method for combining the reversible chemistry of magnesium metal with noncorrosive carbonate-based electrolytes and then tested the concept in a prototype cell. This technology possesses potential advantages over lithium-ion batteries – notably, higher energy density, greater stability and lower cost.
"Being scientists, we're always thinking: what's next?" said Chunmei Ban, a scientist in NREL's Materials Science department and corresponding author of the paper. The dominant lithium-ion battery technology is approaching the maximum amount of energy that can be stored per volume, she said, so "there is an urgent need to explore new battery chemistries" that can provide more energy at a lower cost.
"This finding will provide a new avenue for magnesium battery design," said Seoung-Bum Son, a scientist at NREL and first author of the paper. Other co-authors from NREL are Steve Harvey, Adam Stokes and Andrew Norman.
An electrochemical reaction powers a battery, as ions flow through a liquid (electrolyte) from the negative electrode (cathode) to the positive electrode (anode). For batteries using lithium, the electrolyte is a salt solution containing lithium ions. To allow the battery to be recharged, this electrochemical reaction must be reversible.
Magnesium (Mg) batteries theoretically contain almost twice as much energy per volume as lithium-ion batteries. But previous research encountered an obstacle: chemical reactions with the conventional carbonate electrolyte created a barrier on the surface of magnesium that prevented the battery from recharging. The magnesium ions could flow in a reverse direction by using a highly corrosive liquid electrolyte, but that barred the possibility of a successful high-voltage magnesium battery.
In seeking to overcome these roadblocks, the researchers developed an artificial solid-electrolyte interphase from polyacrylonitrile and magnesium-ion salt that protected the surface of the magnesium anode. This protected anode demonstrated a markedly improved performance.
The scientists assembled prototype cells to prove the robustness of the artificial interphase and were able to show promising results: the cell with the protected anode permitted reversible Mg chemistry in the carbonate electrolyte, which had never been demonstrated before. The cell with the protected Mg anode also delivered more energy than a prototype without the protection and continued to do so during repeated cycles. Furthermore, the group also demonstrated that the magnesium-metal battery was rechargeable, which provides an unprecedented avenue for simultaneously addressing the anode/electrolyte incompatibility and the limitations on ions leaving the cathode.
In addition to being more readily available than lithium, magnesium has other potential advantages over the more established battery technology. First, magnesium releases two electrons to lithium's one, thus giving it the potential to deliver nearly twice as much energy as lithium. Second, magnesium-metal batteries do not suffer from the growth of dendrites, which are crystals that can cause short circuits and consequently dangerous overheating and even fires, making potential magnesium batteries much safer than lithium-ion batteries.
This story is adapted from material from NREL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.