MAGNESIUM BATTERIES Unlocking new possibilities for magnesium batteries
Researchers in the U.S., in conjunction with the Toyota Research Institute of North America, have reported a ‘breakthrough’ in the development of magnesium batteries, a potential solution for realizing grid-scale energy storage systems.
There’s an ever-pressing need for grid-scale energy storage systems, and researchers have been searching for a way to make these viable by using materials that are more readily available and cheaper than lithium.
One potential alternative is the magnesium battery, however, scientists have struggled to build one that can operate at room temperature with a power density comparable to that of lithium-ion. This is down to the lack of a suitable cathode and electrolyte.
Now, researchers from the University of Houston, in conjunction with the Toyota Research Institute of North America (TRINA), claim to have developed a new cathode and electrolyte. This has allowed them to demonstrate a magnesium battery with a suitable power density that can operate at room temperature, the researchers say.
A new cathode and electrolyte
While magnesium ions can hold twice as much charge as lithium ions - making magnesium batteries a better alternative to lithium-ion batteries in theory - magnesium dissociation from electrolytes and its diffusion in the electrode are very slow at room temperature, meaning that current magnesium battery technology exhibits low power performance.
Scientists have already explored ways to address this problem. One way would be to improve the chemical reactions at higher temperatures. Another way would be to store magnesium cation in its complex form. Neither one of these approaches is practical in battery applications, however.
According to Yan Yao of the joint research team and author of a paper published in Nature Energy, new “groundbreaking” results have been achieved by combining both an organic quinone cathode and a new electrolyte solution based on boron clusters.
"We demonstrated a heterogeneous enolization redox chemistry to create a cathode which is not hampered by the ionic dissociation and solid-state diffusion challenges that have prevented magnesium batteries from operating efficiently at room temperature," Yao said. “This new class of redox chemistry bypasses the need of solid-state intercalation while solely storing magnesium, instead of its complex forms, creating a new paradigm in magnesium battery electrode design.”
TRINA researchers worked with the Houston team to develop the boron cluster anion electrolytes. Although these were initially found to have limitations in supporting high battery cycling rates—the rate at which a battery is discharged relative to its maximum capacity—the TRINA researchers were able to tweak their properties to change this.
“We had hints that electrolytes based on these weakly coordinating anions in principle could have the potential to support very high cycling rates, so we worked on tweaking their properties,” said Rana Mohtadi, a Principal Scientist in the materials research department at TRINA and co-corresponding author. “We tackled this by turning our attention to the solvent in order to reduce its binding to the magnesium ions and improve the bulk transport kinetics.”
According to the University of Houston press release, the magnesium battery demonstrated in this research has a power density almost “two orders of magnitude higher” than that achieved in previous magnesium battery works. By tailoring the properties of the membrane with enhanced intermediate trapping ability, the researchers were able to keep the battery operating for over 200 cycles with 82 percent stability.
"Our results set the direction for developing high-performance cathode materials and electrolyte solutions for magnesium batteries and unearth new possibilities for using energy-dense metals for fast energy storage," said Oscar Tutusaus of TRINA.