While lithium-ion (Li-ion) batteries are essential for powering today’s world, their drawbacks are driving a search for other options. Scarcity is one factor; experts project that global lithium demand could outstrip supply within the next five years. Li-ion batteries also involve a range of environmental and safety considerations throughout their lifespan, from the land degradation linked with lithium extraction to the fire hazards posed by damaged batteries.
Magnesium (Mg) presents a promising alternative: more abundant than lithium and cheaper to source, the metal’s electrochemical properties also make Mg-based batteries inherently safer than their lithium-based counterparts, noted Zhi Wei Seh, a Senior Principal Scientist at the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE).
“Rechargeable Mg batteries (RMBs) rarely form dendrites: small, spiky metal deposits on battery anodes that damage the system over time. RMBs are also less chemically reactive than lithium-based systems,” Seh explained. “These two features collectively make RMBs less likely to short-circuit or trigger thermal runaway: an effect where the battery overheats uncontrollably.”
In practice, though, RMBs have struggled to perform at the level of Li-ion batteries, as conventional designs typically exhibit low energy capacities and poor rechargeability. Seh pointed to two main electrochemical limitations at fault: Mg anode passivation, where a coating forms over Mg anodes and hampers the free flow of battery ions; and uneven Mg electrodeposition, which destabilises the battery and eventually causes short circuits.
To overcome these limitations, Seh, A*STAR IMRE Scientist Deviprasath Chinnadurai and their colleagues worked alongside collaborators from the A*STAR Institute of High Performance Computing (A*STAR IHPC) and ShanghaiTech University, China, to test the effects of a new multifunctional organic additive—1-bromooctane, or OctylBr—on a conventional RMB electrolyte, magnesium bis(hexamethyldisilazide) (Mg(HMDS)2).
“OctylBr is designed to simultaneously mitigate anode passivation and promote uniform, planar Mg deposition, enabling both higher capacity and stable battery cycling,” said Seh.
Through scanning electron microscopy (SEM) studies, the team confirmed that the inclusion of OctylBr helped create an even spread of flat, consistent hexagonal Mg structures across Mg anodes. Computer simulations also indicated that the additive smoothed out Mg ion flow in Mg(HMDS)2, resulting in a more consistent electric field.
In practical tests, the team found that an experimental RMB system built on Mg(HMDS)2 with added OctylBr achieved up to 3,600 hours of Mg cycling, sharply contrasting with the zero-hour cycling lifespan of Mg(HMDS)2 alone.
“Notably, the reported 3,600-hour cycle life is highly competitive with lithium systems, which typically exhibit cycling lifetimes of 800 to 3,500 hours in similar conditions,” added Seh.
While promising, the team’s findings may take time to reach real-world devices. “There are two main issues to address before these additives can be integrated into commercial manufacturing: ensuring their scalability, and maintaining full compatibility with existing cell fabrication and assembly protocols,” said Seh.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE) and A*STAR Institute of High Performance Computing (A*STAR IHPC).
