Hydride ions possess a distinct advantage over metal ions traditionally used in electrochemical systems. Their negative charge and small size enable rapid conduction and facile reactivity at the electrode–electrolyte interface. However, the challenge has been identifying solid electrolytes capable of sustaining efficient hydride ion transport at ambient conditions, a hurdle that this new research has impressively overcome by synthesizing and optimizing a core-shell structured hydride conductor composed of 3CeH₃ encapsulated within BaH₂.

The core-shell material 3CeH₃@BaH₂ exhibits exceptional hydride ion conductivity at room temperature, with its ionic transport properties further enhancing upon heating above 60°C to achieve superionic conduction. The concept of superionic conduction typically involves dramatic increases in ionic mobility akin to liquid electrolytes while retaining the mechanical stability and safety features of solids. The high hydride ion mobility arises from an intricate synergy between the inner 3CeH₃ phase and the BaH₂ shell that facilitates continuous ionic pathways without severe lattice distortion or structural instability.

Building on this material breakthrough, the researchers successfully constructed a fully solid-state rechargeable battery using CeH₂ as the anode, 3CeH₃@BaH₂ as the solid electrolyte, and sodium aluminum hydride (NaAlH₄) as the cathode. This configuration uniquely harnesses hydride ions as the charge carriers, enabling reversible electrochemical reactions at room temperature without relying on volatile liquid electrolytes or susceptible metal dendrites that commonly compromise battery longevity and safety in metal-based systems.

The assembled battery demonstrated an exceptional initial specific capacity of 984 mAh per gram, a figure that surpasses many existing rechargeable battery materials. Although capacity retention diminished over 20 cycles, the cell maintained a considerable 402 mAh per gram at that stage, indicating promising stability and potential for further optimization. These findings reflect significant progress in both materials science and practical device engineering, marking a compelling step toward commercializable hydride ion batteries.

One of the most notable attributes of using hydride ions in energy storage lies in the potential elimination of dendrite formation, a pernicious problem in metal-based batteries. Dendrites—needlelike metallic protrusions that grow during repeated charge-discharge cycles—pose severe risks of short-circuiting and catastrophic failure. By contrast, hydride ions, as non-metallic charge carriers, inherently mitigate this risk, fostering safer and longer-lasting batteries that can be charged and discharged many times without the usual degradation pathways.

More importantly, these batteries operate efficiently under ambient conditions without the need for elevated temperatures or complex system management. This characteristic significantly reduces energetic overheads and enables simpler designs suitable for a broad array of applications, from portable electronics and electric vehicles to grid-scale energy storage and renewable energy integration. The solid-state nature ensures enhanced mechanical robustness and reduced flammability, addressing key safety concerns prevalent in liquid electrolyte batteries.

The electrochemical mechanisms underlying the hydride ion movement involve intricate redox processes at the CeH₂ anode and NaAlH₄ cathode interfaces. The reversible interconversion between CeH₂ and 3CeH₃ involves the absorption and release of hydride ions, while NaAlH₄ serves as a hydride ion reservoir with excellent electrochemical stability. This synergy supports sustained ionic flux and electromotive force critical for efficient battery cycling.

On the materials front, synthesizing the 3CeH₃@BaH₂ core-shell conductor required precise control of phase purity, crystallinity, and interface chemistry. The BaH₂ shell functions both as a protective layer preventing direct chemical degradation and as a high-conductivity medium facilitating hydride ion transfer. The core-shell architecture effectively stabilizes the superionic phase of 3CeH₃ and prevents the formation of undesired secondary phases or conductive bottlenecks.

From a theoretical perspective, the polarizability and hydration sphere dynamics of hydride ions place them in an advantageous position compared to standard metal cations. The energy landscape for ion migration within the BaH₂ lattice displays relatively low activation barriers, fostering rapid ionic movement even at moderate temperatures. This ion transport behavior may inspire the design of new classes of hydride conductors with tailored lattice architectures further optimized for high ionic conductivity and stability.

This study also signals a paradigm shift in the role of hydrogen chemistry in energy conversion. Traditionally relegated to gaseous fuel considerations or electrolyzer feedstocks, hydride ions are now emerging as versatile solid-phase charge carriers in advanced battery systems. The unique chemistry of hydrides enables distinct approaches to electrochemical storage, potentially bridging the gap between hydrogen fuel technologies and solid-state battery innovations.

Looking forward, these findings offer a promising platform to explore further hybrid hydride materials, scalable fabrication techniques, and full cell architectures integrating hydride ion conduction with high-capacity electrodes. Completing the engineering toolkit for hydride batteries will require tackling challenges such as long-term cycling stability, interface engineering, and manufacturability to bring this emerging technology from laboratory curiosity to market-ready products.

The implications of hydride ion batteries stretch far beyond portable energy storage devices. In principle, similar hydride conduction mechanisms could be employed in solid-state fuel cells that operate on hydrogen-based fuels or electrolyzers splitting water with high efficiency. This versatility underpins a potentially transformative role for hydride ions in the global transition to clean and sustainable energy systems, reducing reliance on scarce or toxic metals and leveraging Earth-abundant hydrogen chemistry.

In conclusion, the successful creation of a room temperature rechargeable all-solid-state hydride ion battery embodies a major advance in energy material science. By harnessing the unique properties of hydride ions within innovative core-shell materials, researchers have opened a new frontier for high-performance, safe, and versatile electrochemical devices. This breakthrough invites extensive future research and development that could redefine the landscape of energy storage and power conversion technologies for the coming decades.

Subject of Research:

Development of a room temperature rechargeable all-solid-state hydride ion battery based on core-shell hydride ion conduction materials.

Article Title:

A room temperature rechargeable all-solid-state hydride ion battery.

Article References:

Cui, J., Zou, R., Zhang, W. et al. A room temperature rechargeable all-solid-state hydride ion battery. Nature (2025). https://doi.org/10.1038/s41586-025-09561-3

Image Credits:

AI Generated

Hydride ions, characterized by their low mass and exceptional redox potential, have long tantalized scientists with their potential to serve as superior charge carriers. Unlike the conventional lithium-ion systems that dominate today’s energy landscape, hydride ion batteries operate on the transfer of H⁻ ions, offering advantages such as higher energy density and lower dendritic risks. Yet, progress has been derailed by the absence of suitable electrolytes capable of facilitating rapid hydride ion conduction at ambient temperatures, while also withstanding rigorous electrochemical and thermal conditions.

Addressing this critical bottleneck, the DICP team engineered an innovative core–shell composite hydride electrolyte, denoted as 3CeH₃@BaH₂, where cerium hydride (CeH₃) forms the core enveloped by a barium hydride (BaH₂) shell. This heterojunction-inspired design synergistically combines the intrinsic high ionic conductivity of CeH₃ with the robust structural stability of BaH₂. The resulting composite electrolyte exhibits remarkable hydride ion transport kinetics at room temperature, a feat previously unattainable with single-phase hydride materials.

The core–shell architecture operates on the principle that the BaH₂ shell not only safeguards the CeH₃ core from degradation but also contributes to an extended electrochemical window, ensuring the material’s resilience in repeated cycling. This intricate interplay between phases facilitates fast and stable conduction pathways for hydride ions, overcoming typical barriers of electrolyte decomposition and limited ionic movement encountered in prior research.

Building upon the electrolyte breakthrough, the team assembled an all-solid-state hydride ion battery consisting of a CeH₂ anode, the novel 3CeH₃@BaH₂ electrolyte separator, and a cathode composed of NaAlH₄—a classical hydrogen storage material prized for its reversible H− capacity. This choice of cathode not only underscores the battery’s sustainability but also leverages the well-understood hydrogen chemistry intrinsic to NaAlH₄, known for its compatibility with hydride ions. The novel battery design successfully achieved a high initial discharge capacity of 984 mAh/g at room temperature, confirming the electrolyte’s efficacy in practical application.

Over a series of 20 charge-discharge cycles, the battery maintained a capacity of 402 mAh/g, demonstrating promising cyclability and operational stability without significant degradation. Such retention rates hint at the core-shell electrolyte’s durability and the compatibility of hydride ion chemistry within a solid-state framework—issues that have plagued many experimental battery systems attempting to transcend liquid electrolytes’ limitations.

The hydride ion battery’s operating voltage was measured at an impressive 1.9 V in a stacked configuration, a voltage sufficient to power real-world devices such as a yellow light-emitting diode (LED) lamp, as demonstrated by the researchers. This clear proof-of-concept underscores the technology’s readiness for practical energy storage applications, highlighting its potential utility in portable electronics, electric vehicles, and possibly grid storage, where high energy density and safety are paramount.

One of the most compelling advantages of utilizing hydrogen-based charge carriers, specifically hydride ions, is the near elimination of dendrite formation—a notorious issue in lithium metal batteries that leads to short circuits and catastrophic failures. This intrinsic dendrite suppression greatly enhances battery lifespan and safety, pivotal factors for widespread commercial adoption. The all-solid-state nature further contributes to operational safety by circumventing volatile, flammable liquid electrolytes commonly used in current lithium-ion systems.

The implications of this technology extend beyond performance metrics. The use of earth-abundant and relatively inexpensive materials such as cerium and barium hydrides could moderate production costs, addressing critical economic barriers in next-generation battery manufacturing. Given that scalability remains a critical hurdle for any nascent battery technology, the simplicity and stability of these hydride compounds bode well for potential industrial deployment.

This success also opens up a broader landscape for hydride ion battery research, inviting deeper investigation into tuning hydride-based materials’ structural, electrochemical, and interfacial properties. Such tunability offers a promising pathway to optimize energy density, charge rates, and cycle life, potentially surpassing the capabilities of current lithium-ion and emerging sodium-ion battery technologies.

Moreover, the demonstration of fast hydride ion conduction at room temperature challenges longstanding assumptions about hydride mobility, which was traditionally viable only at elevated temperatures. This breakthrough shifts the paradigm, enabling energy storage devices to function efficiently under ambient conditions without resorting to complex thermal management systems—a crucial factor for consumer electronics and electric transportation.

By harnessing the synergy of novel material design and robust chemical understanding, Prof. CHEN Ping’s team has charted an exciting course toward viable, safe, and sustainable electrochemical energy storage solutions that could integrate seamlessly into the ever-evolving clean energy ecosystem. If further optimized and commercialized, hydride ion batteries may well become frontrunners in the pursuit of more efficient, environmentally friendly, and resilient power sources for the next century.

As the global push intensifies toward decarbonization and renewable energy integration, the development of innovative battery chemistries like the hydride ion system is essential. Its unique approach, centered on hydrogen-based ions and solid-state materials, situates it as a promising candidate to overcome prevailing battery challenges—ushering in an era where electrochemical devices combine performance, safety, and sustainability without compromise.

This study not only provides a compelling proof-of-concept for hydride ion batteries but also lays a foundational framework for future research into advanced hydride electrolytes. By expanding the fundamental understanding of hydride ion transport and battery assembly using core-shell heterostructures, this work amplifies the horizon of electrochemical science and lays the groundwork for next-generation energy storage technologies.

Subject of Research: Not applicable

Article Title: A room temperature rechargeable all-solid-state hydride ion battery

News Publication Date: 17-Sep-2025

Web References: http://dx.doi.org/10.1038/s41586-025-09561-3

Image Credits: Dalian Institute of Chemical Physics (DICP)

Keywords

Batteries, Electrolytes, Electrochemical cells