A Bendable Magnesium-Air Battery That Beats Platinum Without Using Any

The rechargeable battery inside a future electric vehicle needs to do two contradictory things well: pack enormous energy into a small space and cost almost nothing to produce. Lithium batteries handle the first requirement acceptably. They fail badly at the second. Lithium is not cheap, and platinum - used in many high-performance cathodes - is considerably less cheap. A research team at the University of Tsukuba has been working on a different design entirely, and their latest results suggest the trade-off may be smaller than assumed.

The battery in question uses magnesium rather than lithium. That choice alone cuts material costs dramatically - magnesium is abundant and inexpensive. The theoretical energy density of magnesium-air batteries is nearly identical to that of lithium-air systems, which is what made them attractive to begin with. The catch has always been chloride ions in the electrolyte. They corrode the battery's internal components over charge-discharge cycles, degrading performance faster than any serious application can tolerate.

The graphene solution to a corrosion problem

The Tsukuba team's solution is a cathode made from nitrogen-doped nanoporous graphene - a three-dimensional carbon structure with tiny holes running through it and nitrogen atoms embedded in the carbon lattice. This architecture does several useful things at once.

First, the nitrogen doping gives the material strong catalytic activity for the oxygen reduction reaction that powers the battery's discharge. Second, the porous structure creates physical space to accommodate discharge products and helps oxygen and ions move through the electrode efficiently. Third - and this is the part that matters most for magnesium-air chemistry - the graphene resists chloride attack far better than platinum does.

The team assembled a complete all-solid-state battery using commercially available magnesium metal as the anode and a polymer gel infused with magnesium chloride as the solid electrolyte. No platinum anywhere in the design. The resulting battery not only matched platinum-based systems but exceeded them in measured performance, according to results published in Chemical Engineering Journal.

Flexibility as a bonus

Solidifying the electrolyte into a gel rather than using a liquid had an unexpected benefit beyond improved safety: the battery became mechanically flexible. The researchers bent their device to 120 degrees and found no performance loss and no electrolyte leakage. That property is largely irrelevant for stationary storage or standard electric vehicle applications, but it opens possibilities in wearable electronics and conformable devices where rigid cells are a design constraint.

Is this ready for a car? Not yet. The gap between laboratory results and production-ready batteries is wide, and solid-state batteries of any chemistry face engineering challenges around scalability, manufacturing consistency, and long-term cycle stability that take years of development to address. The study demonstrates that the graphene cathode approach is viable in principle and outperforms a platinum baseline, which is meaningful progress, but it is an early-stage result.

Why magnesium, and why now

The timing of this research reflects a broader anxiety about critical materials. Lithium supply chains run through a small number of countries and are vulnerable to geopolitical disruption. Platinum is rarer still. The push to identify battery chemistries built from abundant, affordable, widely distributed materials has intensified as electric vehicle adoption has accelerated.

Magnesium hits most of the right criteria. It is the eighth most abundant element in Earth's crust. It is already produced industrially at scale for other applications. A rechargeable magnesium-air system that genuinely works - meaning one that can survive hundreds of charge-discharge cycles without falling apart to chloride corrosion - would represent a meaningful contribution to battery diversity.

The work was funded by the Suzuki Foundation and JSPS-Kakenhi grant JP24H00478, among other sources. Professor Yoshikazu Ito of the Institute of Pure and Applied Sciences led the research. Zhuang Xian, who contributed as a co-author, was supported by the JST-SPRING program.