Crack open your phone case and you’ll likely find a familiar label on the battery: ‘Li-ion’, or lithium-ion. Thanks to its excellent energy density and discharging abilities, lithium makes up the bulk of battery electrolytes used everywhere from personal electronics to electric vehicles.
Yet the world’s lithium supplies are struggling to keep up with demand, especially as economies transition to renewables. In search of lithium alternatives, researchers such as Zhigen Yu, a Senior Principal Scientist at the A*STAR Institute of High Performance Computing (A*STAR IHPC), are turning to metals such as magnesium.
“Magnesium is earth-abundant, non-toxic and cheap, enabling scalable and sustainable battery products,” said Yu. Magnesium ions (Mg2+) can also theoretically carry twice the electrical charge of lithium ones, offering further boosts to battery storage and charging speeds.
However, research on aqueous (water-based) Mg2+ energy storage is still in its early stages, Yu noted. Several major challenges persist: strong interactions between Mg2+ and host materials limit their usable capacity, the Mg2+ storage mechanism is poorly understood, and traditional cathode materials exhibit low conductivity when interacting with Mg2+.
To enhance Mg2+ battery designs, Yu and A*STAR IHPC Distinguished Principal Scientist Yong-Wei Zhang, as well as colleagues from A*STAR IHPC; Liaoning University, China; and RMIT University, Australia, recently tested a performance-boosting strategy: the use of a novel organic-inorganic composite as a cathode. Using hydrothermal treatment, the team coated manganese (III) oxide (Mn2O3)—a mineral commonly used in magnets and electronics—with ethylenediamine (EDA), an organic base for many industrial chemicals.
“Mn2O3 offers a high theoretical energy capacity versus traditional cathode materials. Organic materials like EDA can also capture and store charged particles, adding to that capacity,” Yu said. “The coupled structure helps speed up the movement of charged Mg2+ in and out of the cathode.”
When the team tested their prototype cathode in an aqueous Mg2+ battery and studied it with X-ray diffraction tools, they found that the EDA coat reduced the otherwise strong electrostatic interaction between Mg2+ and the cathode, improving the flow of charged ions. As the battery discharged, EDA molecules also acted like ‘clamps’ that plucked Mg2+ from the electrolyte fluid, boosting the cathode’s storage capacity and cycling stability.
Compared to a pure Mn2O3 cathode with similar energy density, the EDA-Mn2O3 cathode also produced an approximately 1.5 times higher discharge capacity, as reported by the team.
“Our study demonstrates that organic-inorganic coupling can unlock synergistic effects that significantly enhance energy storage and performance,” said Yu. “It suggests that future energy storage systems can greatly benefit from the intelligent integration of organic functionalities into traditional inorganic materials.”
In the future, the team aims to investigate other organic molecules to fine-tune ion capture and exchange not just for Mg2+, but other potential electrolytes. With the aid of high-throughput computational simulations and machine learning, they also aim to screen new organic-inorganic combinations to accelerate the discovery of new electrode materials.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of High Performance Computing (A*STAR IHPC).
