Over the past year, incidents of lithium-ion (Li-ion) battery-related fires have been increasing globally, in part due to an increased demand for these batteries in electric vehicles, phones, laptops, scooters, and other devices, As a result, researchers are constantly on the prowl for alternatives that could improve safety, lower cost, and increase energy density.
The most consequential alternative seems to be solid-state batteries, which function by replacing flammable liquid electrolytes with solid materials, reducing fire risks and potentially increasing energy density. On the flip side, though, unwanted reactions at the interface between battery components frequently reduces performance and shortens battery life.
Recently, solid-state magnesium batteries have emerged as a promising next-generation energy technology. However, here, too, there’s a technical barrier to overcome: Instability inside these batteries is a major obstacle to their development.
Reactions Breed Better Magnesium Batteries
Addressing this issue, a research team from Japan’s Tohoku University developed a new way to improve solid-state magnesium batteries. Interfacial reactions between the solid electrolyte and electrode are usually considered harmful because they degrade battery performance over time. But the researchers found that in solid-state magnesium batteries, this side effect is actually essential for improving battery efficiency — as long as the reactions are carefully controlled.
The Tohoku University research has been published in the journal ACS Energy Letters (“Balancing Reactivity and Ion Transport in Mg Alloy Anodes via Secondary-Phase Engineering” by Qian Wang, Xue Jia, Ting Xu, Jianwei Li, Yungui Chen, Hao Li, and Yigang Yan).
Unexpected Benefit Could Lead to Longer-Lasting Energy Storage
The study highlights the importance of balancing chemical reactions and ion transport together when designing battery interfaces. By turning one of the field's biggest challenges into a functional advantage, the study opens a new direction for designing longer-lasting energy storage systems.
"For a long time, interfacial reactions were treated as something to avoid," said Hao Li, Distinguished Professor at Tohoku University's Advanced Institute for Materials Research. "But our results show that when these reactions are carefully guided rather than suppressed, they can help solid-state magnesium batteries perform far more effectively."
The researchers introduced tin into magnesium. The combination forms a stable compound known as Mg2Sn, which helps regulate reactions inside the battery.
To identify the most effective composition, the team tested several magnesium-based alloys containing different secondary phases and evaluated their electrochemical performance under battery operating conditions. Among the tested materials, the optimized magnesium-tin alloy demonstrated the best balance between interfacial stability, magnesium-ion transport, and long-term cycling performance.
By engineering the surface and internal structure of the anode, they enabled magnesium ions to move more efficiently through the battery. It also improved overall stability and created a more uniform magnesium deposition layer.
The optimized magnesium-tin alloy demonstrated significantly improved electrochemical performance, including more stable cycling behavior and enhanced magnesium-ion transport at the electrode-electrolyte interface. In solid-state battery tests, the Mg-Sn alloy remained stable for over 1,300 hours and achieved more than 400 times longer cycling performance than pure magnesium.
Turning Interfacial-Reaction Lemons into SSB Lemonade
As mentioned, for years, interfacial reactions inside solid-state magnesium batteries were seen as a major challenge limiting performance. However, the researchers' findings suggest that, when carefully controlled, these same reactions could become part of the solution.
As demand grows for safer and longer-lasting energy storage systems, the Tohoku University work offers a new way of thinking about battery design. Rather than treating interfacial reactions solely as a problem, researchers may be able to harness them to improve performance and extend battery life.
