Researchers from the University of Houston and the Toyota Research Institute of North America (TRINA) have developed a new cathode and electrolyte that could help magnesium batteries compete with lithium-ion.
The teams have demonstrated a magnesium battery capable of operating at 25oC and delivering a power density comparable to that offered by lithium-ion batteries.
The breakthrough results came from combining both an organic quinone cathode and a new tailored boron cluster-based electrolyte solution.
Researchers say the new battery is nearly two orders of magnitude higher than the power density achieved by previous magnesium batteries, and was able to continue operating for more than 200 cycles with around 82% capacity retention, showing high stability.
The findings were published in the journal Nature Energy.
Previously, researchers have tried two ways to prevent magnesium dissociation from electrolytes and its diffusion in the electrode: improving the chemical reactions at elevated temperatures; and storing magnesium cation in its complex forms. However, neither approach is practical.
Yan Yao (pictured), professor of electrical and computer engineering at the University of Houston and co-corresponding author for the paper, said: “We demonstrated a heterogeneous enolisation redox chemistry to create a cathode that is not hampered by the ionic dissociation and solid-state diffusion challenges that have prevented magnesium batteries from operating efficiently at room temperature.
“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 made advancements in the magnesium battery field, including developing highly recognised, efficient electrolytes based on boron cluster anions. However, these electrolytes had limitations in supporting high battery cycling rates.
Rana Mohtadi, a principal scientist in the materials research department at TRINA and co-corresponding author, said: “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.
“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.”
“We were fascinated that the magnesium plated from the modified electrolyte remained smooth even under ultrahigh cycling rates. We believe this unveils a new facet in magnesium battery electrochemistry.”
The work is in part a continuation of earlier efforts described in 2018 in Joule.