Flexible solid electrolyte unlocks high-performance fuel cells across extreme temperatures

Researchers at Kumamoto University （Japan）have unveiled a groundbreaking solid electrolyte material that could revolutionize fuel cell technology. Derived from natural clay minerals, this innovative membrane offers high proton conductivity and exceptional hydrogen gas barrier properties—unlocking new possibilities for low- to mid-temperature fuel cells.

Fuel cells traditionally rely on proton-conducting oxides that require operating temperatures above 500 °C, limiting their use in compact or mobile applications. A　team from Institute of Industrial Nanomaterials, Kumamoto University, led by Assistant Professor Kazuto Hatakeyama and Professor Shintaro Ida, has developed a flexible solid electrolyte composed of monolayer silicate nanosheets with the formula H₀.₃₇Al₁.₆₇Mg₀.₃₅Fe₀.₁₁Si₃.₉O₁₀(OH)₂(H₂O)₂.₆. This material achieves proton conductivities of 2.3×10^-3 S/cm @10 °C, 6.2×10^-3 S/cm @100 °C and 8.7×10^-3 S/cm @140 °C under 100% relative humidity—comparable to or exceeding current polymer-based electrolytes like Nafion.

What sets this membrane apart is its dual performance: it not only conducts protons efficiently but also blocks hydrogen gas more than 100 times better than Nafion. This combination of properties is critical for fuel cell safety, efficiency, and longevity.

When applied to hydrogen fuel cells, the membrane enabled a maximum current density of 1080 mA/cm² and a power output of 264 mW/cm² at 90 °C. Even more impressively, the fuel cell operated stably across a wide temperature range from −10 °C to 140 °C—making it suitable for both cold climates and high-demand automotive environments.

“This is a major step toward sustainable, high-performance fuel cells that don’t rely on expensive or environmentally burdensome materials,” said Professor Ida. “Because the raw material—montmorillonite clay—is abundant and low-cost, this technology has real potential for scalable, eco-friendly energy solutions.”