UH, Toyota researchers develop new cathode and electrolyte for high-power Mg battery rivaling Li-ion
Researchers from the University of Houston and the Toyota Research Institute of North America (TRINA) report in Nature Energy that they have developed a new cathode and electrolyte—previously the limiting factors for a high-energy magnesium battery—to demonstrate a magnesium battery capable of operating at room temperature and delivering a power density comparable to that offered by lithium-ion batteries.
Magnesium batteries have long been considered a potentially safer and less expensive alternative to lithium-ion batteries, but previous versions have been severely limited in the power they delivered.
Here we report a heterogeneous enolization chemistry involving carbonyl reduction (C=O↔C–O−), which bypasses the dissociation and diffusion difficulties, enabling fast and reversible redox processes. This kinetically favored cathode is coupled with a tailored, weakly coordinating boron cluster-based electrolyte that allows for dendrite-free Mg plating/stripping at a current density of 20 mA cm−2.
The combination affords a Mg battery that delivers a specific power of up to 30.4 kW kg−1, nearly two orders of magnitude higher than that of state-of-the-art Mg batteries. The cathode and electrolyte chemistries elucidated here propel the development of magnesium batteries and would accelerate the adoption of this low-cost and safe battery technology.—Dong et al.
Magnesium ions hold twice the charge of lithium, while having a similar ionic radius. As a result, magnesium dissociation from electrolytes and its diffusion in the electrode, two essential processes that take place in classical intercalation cathodes, are sluggish at room temperature, leading to the low power performance.
One approach to addressing these challenges is to improve the chemical reactions at elevated temperatures. The other circumvents the difficulties by storing magnesium cation in its complex forms. Neither approach is practical.
Yan Yao, Cullen Professor of Electrical and Computer Engineering at the University of Houston and co-corresponding author for the paper, said the groundbreaking results came from combining both an organic quinone cathode and a new tailored boron cluster-based electrolyte solution.
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. 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.—Yan Yao,
Yao, who is also a principle investigator with the Texas Center for Superconductivity at UH (TcSUH), is a leader in the development of multivalent metal-ion batteries. His group recently published a review article in Nature Energy on the roadmap to better multivalent batteries.
TRINA researchers have made tremendous advancements in the magnesium battery field, including developing highly recognized, efficient electrolytes based on boron cluster anions. However, these electrolytes had limitations in supporting high battery cycling rates.
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.—Rana Mohtadi, a Principal Scientist in the materials research department at TRINA and co-corresponding author
The work is in part a continuation of earlier efforts described in 2018 in Joule (earlier post) and involved many of the same researchers.
In addition to Yao and Mohtadi, coauthors include first authors Hui Dong, formerly a member of Yao’s lab and now a post-doctoral researcher at the University of Texas at Austin, and Oscar Tutusaus of TRINA; Yanliang Liang and Ye Zhang of UH and TcSUH; and Zachary Lebens-Higgins and Wanli Yang of the Lawrence Berkeley National Laboratory. Lebens-Higgins also is affiliated with the Binghamton University.
The new battery is nearly two orders of magnitude higher than the power density achieved by previous magnesium batteries. The battery was able to continue operating for over 200 cycles with around 82% capacity retention, showing high stability. We can further improve cycling stability by tailoring the properties of the membrane with enhanced intermediate trapping capability.—first author Hui Dong
Dong, H., Tutusaus, O., Liang, Y. et al. (2020) “High-power Mg batteries enabled by heterogeneous enolization redox chemistry and weakly coordinating electrolytes.” Nat Energy doi: 10.1038/s41560-020-00734-0
Yanliang Liang, Hui Dong, Doron Aurbach and Yan Yao (2020) “Current status and future directions of multivalent metal-ion batteries” Nature Energy doi: 10.1038/s41560-020-0655-0