Tin alloy brings practical solid state magnesium batteries within reach

May 27, 2026

The new alloy design improves both stability and magnesium-ion transport inside solid-state batteries, helping address one of the long-standing challenges in next-generation battery technology.

(Nanowerk News) A magnesium tin alloy anode developed at Tohoku University has cycled more than 400 times longer than a pure magnesium anode in solid state battery tests (ACS Energy Letters, “Balancing Reactivity and Ion Transport in Mg Alloy Anodes via Secondary-Phase Engineering”). The improvement comes from a counterintuitive choice. Rather than blocking the chemical reactions that normally degrade the electrode surface, the researchers engineered the anode so those reactions form a stable intermetallic phase that improves ion transport and stability.

Key Findings

Solid state magnesium batteries are considered a candidate alternative to lithium-ion technology, with potential gains in safety, cost, and energy density. Instability inside the cell, particularly where the solid electrolyte meets the electrode, has remained a major obstacle to their development. Reactions at this interface typically degrade performance over time and are usually treated as something to eliminate. “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 (WPI-AIMR), “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 mechanism centers on Mg2Sn, a stable intermetallic phase that forms when tin is added to magnesium. By tuning both the surface and the internal structure of the alloy anode, the researchers used this phase to regulate chemistry at the interface, allowing magnesium ions to move more efficiently through the cell and producing a more uniform deposition layer during charging. To find the most effective composition, Qian Wang and co-authors ran a high throughput screen of magnesium binary compounds before testing several alloys with different secondary phases in electrochemical experiments. The optimized magnesium tin formulation outperformed the others on interfacial stability, magnesium ion transport, and long-term cycling. In solid state battery tests, the alloy remained stable for more than 1,300 hours and cycled more than 400 times longer than pure magnesium. Symmetric cell measurements showed stable plating and stripping behavior across current densities from 0.1 to 1 milliamp per square centimeter. The Tohoku findings point to a different approach to chemistry at the solid state interface in magnesium batteries. Alloying with tin produces a stabilizing intermetallic phase, allowing the team to use interfacial reactions to improve stability and ion transport rather than eliminate them.