Emblems of a green energy era, rechargeable lithium-ion (Li-ion) batteries today are compact storehouses of power for everything from electric cars to solar grids. However, as the lithium metal they rely on is rare and costly, researchers such as those at the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE) are exploring more sustainable alternatives.
One promising candidate is magnesium (Mg), which is over 2,000 times more common than lithium and can hold more energy per unit volume. But there’s a catch: while batteries based on both metals shuttle ions between their negative and positive electrodes (anodes and cathodes) to store and release energy, magnesium has a bit more of a ‘sensitive’ personality.
“Over repeated charges and discharge cycles, an Mg-based anode tends to react with most conventional electrolytes, forming a solid film of Mg deposits on its surface,” explained Gaoliang Yang, A*STAR IMRE Scientist. “This film not only gradually makes the anode less reactive—an effect known as surface passivation—but its uneven texture can rapidly deplete electrolytes, cause poor cycling performance and create safety hazards.”
To make rechargeable Mg batteries more commercially viable, Yang, Senior Principal Scientist Zhi Wei Seh and other A*STAR IMRE researchers tackled the issues of surface passivation and uneven deposition, working with the A*STAR Institute of High Performance Computing (A*STAR IHPC); Nanyang Technological University, Singapore; University of Houston, US; ShanghaiTech University and Central South University, China; and the University of Chemistry and Technology, Czech Republic.
The team’s approach involved changing typical electrolytes by adding a molecule of 1-chloropropane (CP), which caused a protective, chloride-rich ‘bubble-wrap’ layer to form over the anode. Microscopy images revealed that CP altered how the Mg deposits formed, creating thin flat layers of hexagonal Mg crystals, or ‘platelets’, rather than thick whisker-like clumps.
“The CP-induced interphase layer reduces unwanted reactions and enhances the reversibility of Mg plating and stripping, which improves the battery’s rechargeability,” said Seh. “The smoother platelet structure is also safer as it prevents the formation of needle-like spikes, or dendrites, which can puncture the battery’s separator and potentially cause dangerous short circuits.”
The team electrochemically measured the new electrolyte’s Coulombic efficiency (CE), a critical metric of a battery’s lifespan and capacity. The CP-based electrolytes achieved an impressive CE of 99.79 percent, demonstrating stability over repeated cycles even at high current densities of 25 mA/cm², which typically challenge battery reliability.
“The high CE we achieved reflects minimal energy loss during charge/discharge cycles with negligible side reactions or irreversible effects,” said Yang. “This highlights the electrolyte’s potential for long-term use without significant performance loss in Mg batteries for real-world applications.”
Yang, Seh and colleagues plan to scale up testing with the new electrolyte in larger battery models, such as pouch cells. The team is also developing compatible cathode materials to further their progress towards safe, compact and energy-dense rechargeable Mg battery designs.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE) and the A*STAR Institute of High Performance Computing (A*STAR IHPC).
