Unlocking rechargeable aluminum batteries: Multi-ion synergy and multi-electron reactions drive next-generation energy storage

"Aluminum has unique advantages as an energy carrier, " said Prof. Chuan Wu, corresponding author of the review and professor at the Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology. “Its abundance and intrinsic safety make it highly attractive for grid-scale applications. But the critical question is how to enable fast kinetics and long-term reversibility when multivalent ions are involved.”

The review, titled Multi-Ion Synergy and Multi-Electron Reactions for Rechargeable Aluminum Batteries, synthesizes advances across four tightly connected fronts: (1) cathode materials design, (2) electrolyte formulation, (3) anode interface engineering, and (4) theory-guided discovery. Together, these strategies directly target the field’s core limitations—slow charge transport for multivalent ions, narrow electrolyte stability windows, cathode phase instability, and aluminum-anode dendrites and corrosion.

According to Wu, the charge storage behavior of RABs is no longer a single-ion or single-electron process. Instead, multiple species (including Al³⁺, AlCl₄⁻, AlCl₂⁺, AlCl²⁺) coexist in the electrolyte and participate in charge transfer, often in combination with multi-electron reactions at the cathode. The team systematically reviewed advances in inorganic and organic cathodes, from layered vanadium oxides and Prussian blue analogues to conducting polymers and quinone derivatives. Each class of materials shows unique advantages in accommodating multi-ion transport and enabling multi-electron pathways, but structural stability and long-term reversibility remain central challenges. "To unlock Al's full potential, we must engineer how multiple carrier species move and react together, and how many electrons each active site can transfer—this is the essence of multi-ion synergy and multi-electron reactions," Wu said.

Recent researches show progress in chloride-based ionic liquids, low-corrosive aluminum triflate systems, and cost-effective deep eutectic solvents. More importantly, multi-salt formulations have extended electrochemical stability windows above 4.0 V and significantly improved cycle performance. Additives that inhibit corrosion and interfacial passivation have also emerged as effective tools. Wu emphasized that electrolyte engineering is at the core of advancing RABs. "Electrolytes not only govern ion transport but also determine stability and compatibility at both electrodes," he said. "To achieve practical cells, the electrolyte must simultaneously deliver high ionic conductivity, a wide electrochemical window, and interfacial stability. This is the decisive factor for enabling high-voltage operation and long cycling life."

Although Al metal provides exceptional theoretical capacity, dendrite formation and surface corrosion hinder its long-term operation. Wu pointed out that strategies such as chemical surface reconstruction, protective coatings, three-dimensional current collectors, and advanced interfacial layers are showing promise.

The review also underscores the role of density functional theory, high-throughput screening, and machine learning in revealing ion diffusion pathways, predicting voltage plateaus, and identifying promising electrode–electrolyte combinations.

"The complexity of multi-ion and multi-electron reactions requires theoretical support," Wu said. "Computation helps us move beyond trial-and-error, guiding the rational design of materials with fast kinetics and structural stability."

Although some progress has been made in the research on RABs, Wu emphasized that a great deal of research is still needed. "We must deepen our understanding of multi-ion coordination chemistry, design adaptive solid–electrolyte interphases to stabilize interfaces, and integrate computational screening with experimental validation," he said. "Only then can we realize RABs with high energy density, long cycle life, and cost-effectiveness."

He added that interdisciplinary collaboration will be crucial: "Advancing RABs requires materials science, electrochemistry, and computational methods working together. By establishing clear design principles based on multi-ion synergy and multi-electron mechanisms, we can accelerate the path to practical applications."

Other contributors include Bo Long and Feng Wu, Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology.

The following authors have additional affiliations: Feng Wu and Chuan Wu, Yangtze Delta Region Academy of Beijing Institute of Technology.

This National Natural Science Foundation of China (Grant No. 22075028) supported this work.

Acknowledgement

Chuan Wu is a professor at Beijing Institute of Technology (BIT), where his interests are new energy materials, and advanced secondary batteries, including Li/Na/K/Al/Zn/Ca ion batteries. He received his Ph.D. degree in Applied Chemistry from BIT in 2002, followed by a 2-year postdoctoral fellowship in Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Dr. Wu is experienced in energy conversion and storage, has published 200+ peer reviewed papers, and got 70+ authorized patents; awarded First-Prize Award for invention and innovation by China Association of Inventions in 2021.Dr. Wu is a deputy editor of Energy Material Advances (a Science Partner Journal), a deputy secretary general of China Energy Storage and Power Batteries and Materials Professional Committee, a council member of the China Association of Inventions, a member of the National Standardization Technical Committees.