Aqueous zinc-ion batteries use water-based electrolytes to transport charged particles between their electrodes. Unlike many lithium-based systems that rely on flammable organic solvents, water-based batteries carry a considerably lower fire risk and can potentially be manufactured from relatively abundant and inexpensive materials. These advantages have made them attractive for stationary energy-storage systems that collect electricity from renewable sources and release it when needed. Yet their practical performance has been limited by a fundamental trade-off: electrodes must accommodate enough ions to deliver high capacity while also allowing those ions to move rapidly during charging and discharging.

Zinc ions are appealing because each Zn²⁺ ion carries two units of positive charge, potentially contributing substantially to energy storage. However, their relatively large size and slower movement within an electrode can make it difficult to combine high capacity with fast operation. Protons, by comparison, are exceptionally small and can migrate through materials much more quickly. Their speed makes them attractive for rapid charge transfer, but protons have traditionally created serious problems in aqueous zinc-ion batteries. When they enter an electrode too early or in excessive numbers, they can trigger parasitic reactions and generate byproducts on the electrode surface. Those deposits can block pathways, disrupt zinc-ion transport, and gradually reduce battery performance.

Rather than suppressing proton activity, the KAIST team designed an electrode that controls when protons are allowed to participate. The material is a two-dimensional conductive metal–organic framework, or MOF, called Cu₃(HHTATP)₂. MOFs are porous crystalline structures assembled from metal centers and organic molecules, and their nanoscale channels can be chemically modified to influence how ions enter, move through, and bind within the material. In this case, the researchers introduced amine functional groups into the framework’s micropores. These chemical groups were designed to react with protons only after the electrode reached a specific voltage, effectively giving the material a built-in switching mechanism for sequential ion storage.

The result resembles filling a container with objects of different sizes. The electrode first stores the comparatively larger zinc ions while the battery operates in a higher-voltage range. As the voltage decreases, the amine groups become active and enable additional proton storage in the spaces and chemical environments that remain available. This order is crucial. If protons were admitted at the beginning of the process, they could generate surface byproducts before zinc ions had completed their storage step. By delaying proton participation, the electrode reduces competition between the two charge carriers and uses its porous architecture more efficiently.

Electrochemical measurements showed that zinc ions and protons contributed to energy storage in distinct voltage ranges. The research team used multiple X-ray analysis techniques to track the structural and chemical changes taking place inside the electrode, confirming that zinc ions were stored first and that protons entered afterward. The analyses also indicated that proton storage and release could be repeated, an important requirement for a rechargeable battery. Together, the results suggest that ion-storage sequence is not merely a side effect of electrode chemistry but can be deliberately engineered through molecular-level design.

The electrode achieved a storage capacity of 368.7 milliampere-hours per gram at a current density of 0.5 amperes per gram. Capacity expressed in milliampere-hours per gram indicates how much electrical charge can be stored per unit mass of active electrode material; a higher value means that a smaller quantity of material can hold more charge. The result is notable because aqueous zinc-ion batteries have often struggled to approach the combination of energy capacity and rapid ion transport associated with more established battery chemistries. By combining the charge contribution of zinc ions with the fast mobility of protons, the new material takes advantage of two different storage mechanisms within one electrode.

The material also retained 46.9 percent of its initial capacity when the charging and discharging rate was increased sixteenfold. Batteries commonly lose a significant portion of their storage capacity when operated rapidly because ions cannot move through the electrode quickly enough, and structural or chemical bottlenecks become more pronounced. Maintaining nearly half of the original capacity under such an accelerated condition suggests that the conductive two-dimensional framework and its controlled proton chemistry can support comparatively rapid electrochemical reactions. The electrode further maintained stable operation for more than 500 rapid charge–discharge cycles, indicating that the sequential process did not immediately destroy the material or permanently consume its proton-storage sites.

The study presents a broader design principle for battery research: ions that appear harmful under uncontrolled conditions may become useful when their reactions are separated in time and regulated by the molecular structure of an electrode. Professor Sarah S. Park, who led the KAIST research team, said that protons previously regarded as “troublemakers” could instead be used to store more energy, and that the principle might be applied to other electrode materials. The approach could be particularly relevant to large-scale energy-storage systems, where aqueous batteries offer safety and cost advantages but need higher energy density and faster response. The researchers now point toward the possibility of adapting sequential multi-ion storage to other porous conductive frameworks, potentially creating a new class of water-based batteries that combine rapid charging with greater energy storage.

Subject of Research: Sequential storage of zinc ions and protons in a conductive metal–organic framework for aqueous zinc-ion batteries.

Article Title: Sequential Zn²⁺–H⁺ Storage in a 2D Conductive Metal–Organic Framework for Advanced Aqueous Zinc-Ion Battery

Web References: https://doi.org/10.1016/j.chempr.2026.103129

References: Chem, DOI: 10.1016/j.chempr.2026.103129; article publication date: 7 July 2026.

Image Credits: KAIST

Keywords

Aqueous zinc-ion batteries, proton storage, zinc ions, metal–organic frameworks, conductive MOFs, Cu₃(HHTATP)₂, energy storage, fast charging, battery technology, sustainable batteries, large-scale energy storage, electrochemistry

Aluminum stands as one of the most abundant and cost-effective materials on Earth, making it an appealing candidate for battery anodes. Unlike lithium, which is constrained by geographical and geopolitical limitations, aluminum’s wide availability could democratize access to energy storage on a global scale. Moreover, aluminum’s trivalent nature theoretically offers a higher charge transfer capability, translating into greater energy density compared to monovalent metals. This intrinsic property drives the enthusiasm surrounding RABs as they promise a combination of affordability, safety, and performance that conventional batteries have struggled to achieve.

Despite these advantages, aluminum battery technology has long been hampered by fundamental electrochemical challenges. Key among them is the sluggish reaction kinetics associated with aluminum’s multiprotonic redox processes, which hinder rapid charging and discharging. Additionally, the notorious formation of passivation layers at the aluminum interface and corrosive electrolytes limit the battery’s lifecycle and capacity retention. Overcoming these obstacles has been the focal point of intensive research efforts aimed at unlocking aluminum batteries’ full potential for commercial deployment.

Recently, Chinese researchers have taken a significant stride forward by systematically reviewing and synthesizing the state-of-the-art advancements in rechargeable aluminum battery technology. Their comprehensive work highlights an innovative multi-ion cooperative strategy that leverages the synergistic interplay of various charge carriers within the electrolyte and electrode matrix. This approach addresses the kinetic bottlenecks by facilitating more efficient ion transport and charge transfer, thereby accelerating the electrochemical reactions that aluminum-based batteries typically struggle with.

Furthermore, the researchers delve into the multi-electron redox reaction mechanisms intrinsic to aluminum, which enable the transfer of three electrons per ion. This multi-electron process inherently enhances the charge capacity and energy density of the batteries. Traditional single-electron redox reactions are comparatively limited in their capability, thus this multipronged electron exchange holds the key to achieving both high capacity and long-term stability in RABs. Understanding and optimizing this mechanism is a critical breakthrough in ensuring that aluminum batteries can rival or even surpass the performance of lithium-ion counterparts.

The review also places emphasis on material engineering at the electrode and electrolyte interfaces to mitigate degradation phenomena. By fine-tuning the composition of electrolytes, employing novel ionic liquid salts, and designing protective coatings for the aluminum anode, researchers aim to suppress side reactions that degrade battery materials. These innovations contribute to enhanced cycle life, safety, and energy efficiency, essential attributes for real-world applications ranging from grid-scale energy storage to electric vehicles.

One remarkable aspect illuminated in the research is the scalability potential of RABs. Unlike lithium-ion batteries that rely heavily on expensive and geographically concentrated materials like cobalt and nickel, aluminum batteries utilize materials that are readily sourced and environmentally benign. This shifts the paradigm toward sustainable battery manufacturing with reduced supply chain risks and ecological footprint, which is critical as the world pushes toward electrification of its entire energy economy.

Moreover, safety concerns prevalent in lithium-based batteries—such as overheating and thermal runaway—are inherently lower in aluminum batteries owing to aluminum’s stable electrochemical characteristics and the non-flammable electrolytes typically employed. This enhances the operational safety profile of RABs, making them attractive for deployment in densely populated urban centers and remote locations where battery failures pose significant hazards.

Despite these promising developments, the review candidly acknowledges the remaining scientific and technical challenges that must be surmounted before RABs can realize their commercial promise. Electrolyte optimization remains a delicate balancing act to ensure ionic conductivity without compromising chemical stability. Additionally, managing volume changes in aluminum electrodes during cycling requires further materials innovation to prevent mechanical stresses that reduce battery lifespan.

In conclusion, the systematic assessment offered by these Chinese researchers charts a clear and plausible pathway for the future of aluminum-based energy storage. By exploiting the multi-ion cooperative strategies alongside harnessing the intrinsic multi-electron redox chemistry of aluminum, many of the entrenched limitations impeding aluminum batteries have been effectively negotiated. This represents a major leap toward the large-scale, practical use of rechargeable aluminum batteries.

As we stand at a crossroads where sustainable energy solutions are no longer optional but imperative, RABs emerge as a formidable contender capable of transforming global energy storage. These batteries are poised to supplement and potentially replace existing technologies, offering a blend of abundance, safety, cost-effectiveness, and enhanced performance. The continued deepening of our understanding and engineering of aluminum battery systems thus holds the promise of significantly advancing the clean energy revolution.

The implications of this breakthrough extend beyond mere academic curiosity, signaling a tangible shift in how we might power everything from portable electronics to national power grids without exacerbating environmental degradation. The technological maturation of aluminum batteries could catalyze innovations across multiple sectors, forging a resilient, sustainable, and economically viable energy future.

As research moves forward, collaboration between academia, industry, and government will be essential to scale up these laboratory successes into real-world battery systems. Investments in advanced materials synthesis, battery manufacturing infrastructure, and lifecycle assessment will chart the journey from potential to impact. Given aluminum’s global availability and environmental advantages, the widespread adoption of rechargeable aluminum batteries could revolutionize energy storage paradigms worldwide.

Ultimately, this comprehensive review not only highlights the ingenious chemical and physical strategies overcoming historical barriers but also serves as an inspiration for the global scientific community. It underscores the vitality of aluminum battery research in the urgent context of climate change and energy sustainability, encouraging renewed focus and resources toward this promising technology that could power the zero-carbon future.

Subject of Research: Rechargeable Aluminum Batteries (RABs) and their application in renewable energy storage

Article Title: Not provided

News Publication Date: Not provided

Web References: Not provided

References: Not provided

Image Credits: EurekAlert! media service

Keywords
Rechargeable aluminum batteries, energy storage, renewable energy, multi-ion cooperative strategy, multi-electron redox mechanism, battery technology, low-carbon energy, aluminum anode, electrolyte optimization, energy density, battery safety, electrochemical kinetics