In a groundbreaking advancement poised to transform the landscape of clean energy storage, researchers at the Institute of Science Tokyo have unveiled a novel hydrogen battery capable of operating at an unprecedentedly low temperature of 90 °C. This innovative device employs a solid-state electrolyte that transports hydride ions (H⁻) with remarkable efficiency, enabling reversible hydrogen storage and release without the burdensome high-temperature requirements traditionally associated with hydrogen storage technologies. This breakthrough addresses one of the most formidable obstacles in the hydrogen economy: safe, efficient, and practical hydrogen storage.
Hydrogen, as a clean fuel, holds tremendous promise for decarbonizing energy systems and powering next-generation vehicles. However, its storage has been plagued by fundamental difficulties. Conventional storage methods demand cryogenic temperatures near -253 °C or extreme pressures exceeding 350 bar, imposing significant safety, economic, and logistical challenges. Solid-state storage in metal hydrides, particularly magnesium hydride (MgH₂), presents an alluring alternative due to its high theoretical hydrogen capacity. Yet, harnessing this material in practical devices has been hindered by the necessity to operate at temperatures above 300 °C, which is energy-intensive and mechanically taxing over time.
The team at Science Tokyo has ingeniously integrated MgH₂ into a battery-like cell architecture, utilizing a newly developed solid electrolyte with the formula Ba₀.₅Ca₀.₃₅Na₀.₁₅H₁.₈₅. This electrolyte exhibits superionic conduction of hydride ions through an anti-α-AgI-type crystal lattice—a structure that facilitates rapid H⁻ ion mobility via face-sharing tetrahedral and octahedral sites. Remarkably, the material demonstrates significant ionic conductivity at room temperature (2.1 × 10⁻⁵ S cm⁻¹) and maintains electrochemical stability throughout repeated cycling. Such attributes enable the battery to shuttle hydride ions efficiently between the electrodes at temperatures far below those previously deemed necessary.
Operationally, the MgH₂ functions as the anode where, during charging, it releases hydride ions that travel through the solid electrolyte to the cathode, comprised of hydrogen gas. Here, the hydride ions are oxidized, liberating molecular hydrogen. During discharge, the process reverses as hydrogen gas at the cathode is reduced back to hydride ions, which migrate through the electrolyte to react with magnesium metal at the anode, reforming MgH₂. This reversible electrochemical mechanism effectively stores and releases hydrogen fuel on demand, all within a thermally manageable regime under 100 °C.
Empirical evaluations reveal that this solid-state hydrogen battery achieves the full theoretical capacity of MgH₂, approximately 2,030 mAh g⁻¹, equating to 7.6 weight percent hydrogen storage. This performance surpasses earlier electrochemical attempts hampered by poor ion transport and limited reversibility, laying a foundation for durable, high-capacity hydrogen storage solutions. The battery’s ability to undergo repeated charge-discharge cycles without significant capacity degradation highlights its robustness and application potential.
Prior approaches to magnesium hydride hydrogen storage involved thermal absorption and desorption at elevated temperatures ranging from 300 to 400 °C. These methods were inherently inefficient due to their high energy cost and slow kinetics, along with undesirable side reactions that compromised longevity. Alternatively, electrochemical storage employing liquid electrolytes at lower temperatures was limited by insufficient hydrogen-ion mobility, precluding attainment of theoretical storage limits. The innovation from Science Tokyo’s researchers circumvents these issues by integrating a solid electrolyte that combines high ionic conductivity with chemical stability and compatibility with magnesium hydride.
Dr. Takashi Hirose, along with colleagues Assistant Professor Naoki Matsui and Institute Professor Ryoji Kanno, spearheaded this research within the Research Center for All-Solid-State Battery. Their work, slated for publication in Science on September 18, 2025, marks a pivotal step toward practical hydrogen energy systems. The team’s success in lowering operational temperature while maintaining capacity and reversibility challenges long-held assumptions regarding the trade-off between temperature and storage performance.
One of the notable technical details of this electrolyte lies in its carefully engineered composition, where barium, calcium, and sodium ions occupy body-centered lattice positions, creating conducive pathways for hydride ion migration. This strategic incorporation of multiple cations tunes the crystalline environment to optimize ionic transport properties. The superionic conduction facilitated by this anti-α-AgI-type lattice is a rare achievement in solid electrolytes designed for hydrogen ion transport, making it a cornerstone of the battery’s operation.
From an application standpoint, this hydrogen battery could revolutionize energy carriers for a wide array of industries. Presently, the challenges of hydrogen storage limit the feasibility of hydrogen-powered vehicles and impede the broader adoption of hydrogen fuel cells. The ability to store substantial amounts of hydrogen safely at low temperatures and moderate pressures opens pathways to integrate hydrogen energy more seamlessly into transportation, stationary power generation, and grid storage. Moreover, the elimination of hazardous liquid electrolytes and reliance on solid-state materials enhances the device’s safety profile.
This development aligns with broader global efforts to transition to sustainable energy systems. Hydrogen, when produced via renewable sources, offers a zero-emission fuel that can decarbonize sectors that are otherwise difficult to electrify. By overcoming storage obstacles, the newly developed hydrogen battery could accelerate the realization of hydrogen’s potential, reducing dependency on fossil fuels and helping mitigate climate change effects.
The successful demonstration of hydride ion conduction in a solid electrolyte also has implications beyond hydrogen storage. It could inspire new research directions in the design of solid-state ionic conductors for other energy conversion and storage technologies. Solid-state batteries with similar ionic transport mechanisms might exhibit improved stability, energy density, and safety compared to current lithium-ion technologies.
Despite this leap forward, the path to commercialization will require further validation including scale-up, integration with real-world systems, and long-term durability testing under varied environmental conditions. However, the promising laboratory results provide a strong foundation for continued development. Collaborative efforts between industry and academia could expedite the transition from prototype devices to market-ready technologies.
In summary, the Institute of Science Tokyo’s solid-state hydrogen battery represents a significant advance in clean energy technology. By achieving high-capacity, reversible hydrogen storage at a remarkably low operating temperature using a novel hydride ion-conducting electrolyte, it overcomes key limitations that have stalled hydrogen’s widespread adoption. This innovation not only paves the way for safe and practical hydrogen storage but also energizes the broader hydrogen economy, potentially igniting a transformative shift in how we produce, store, and utilize clean energy in the coming decades.
Subject of Research:
Not applicable
Article Title:
High-Capacity, Reversible Hydrogen Storage Using H⁻-Conducting Solid Electrolytes
News Publication Date:
18-Sep-2025
Web References:
http://dx.doi.org/10.1126/science.adw1996
Image Credits:
Institute of Science Tokyo (Science Tokyo)
Keywords
Hydrogen storage, Chemical engineering, Physical sciences, Conductivity, Environmental sciences, Applied sciences and engineering
