In the relentless pursuit of advanced energy storage systems, researchers have now turned their focus toward aqueous Zn^2+/Zn||MnO_2/Mn^2+ batteries, systems characterized by their high voltage and formidable capacity potential. These batteries operate via electrodeposition and dissolution mechanisms, promising efficient and durable solutions for grid-level storage applications. However, a formidable obstacle has been the reliance on acidic conditions essential for the MnO_2/Mn^2+ conversion process, which unfortunately accelerates zinc corrosion, undermining battery longevity and performance. Overcoming this challenge has been a primary concern, prompting the investigation into novel electrolyte systems that can stabilize both electrodes under more benign, less corrosive conditions.
A groundbreaking stride in this domain has been achieved through the development of deep eutectic aqueous-organic electrolytes that strategically disrupt the hydrogen-bonding network of water molecules. By doing so, these novel electrolytes simultaneously enhance the reversibility of MnO_2 at the cathode and enable stable cycling of the zinc anode without initiating water decomposition, a traditional source of efficiency loss. This delicate balance is critical not only to extend the battery lifecycle but also to maintain high Coulombic efficiencies over thousands of cycles, a benchmark for commercial viability.
The innovative electrolytes bring a non-flammable character to the system, greatly improving safety parameters—a crucial factor for grid-scale storage where large quantities of energy are stored. By regulating the solvation structure of Zn^2+ cations and controlling the phase of deposited MnO_2, these eutectic solutions engineer the morphology of the cathode’s active material. This results in the formation of layered MnO_2 structures with facilitated ion-transport pathways that enhance the stripping efficiency, helping to unlock higher performance levels that were previously unattainable with aqueous electrolytes.
Notably, these electrolytes also elevate the oxygen evolution overpotential to levels significantly higher than the MnO_2 deposition potential, a breakthrough that completely suppresses the unwanted side reaction of oxygen evolution. This suppression is vital, as oxygen evolution is not only a wasteful process but can also produce gas bubbles that degrade electrode integrity and battery endurance. This mechanism underscores a novel electrochemical environment where the intrinsic stability of the battery components is decisively enhanced.
The local interfacial environment at the cathode is another arena where these deep eutectic electrolytes bring transformative changes. They create localized pH gradients at the electrode interface, a nuanced effect that critically impacts essential processes such as proton transport and MnO_2 stripping. This local pH modulation optimizes the cathode reactions in a manner that fosters more efficient and reversible electrochemical behavior, thereby driving the overall battery performance upwards.
This holistic approach addresses multiple interrelated challenges simultaneously—corrosion, electrolyte instability, parasitic gas evolution, and poor reversibility—thus marking a significant departure from piecemeal solutions previously explored. By focusing on intimate molecular-level interactions within the electrolyte, researchers have concretized a practical path toward achieving long cycle lives (>5,000 cycles) without the need for external acid additives, which have traditionally been used to maintain acidic conditions but at the cost of zinc metal corrosion.
The enhancement in Coulombic efficiency maintained over prolonged cycling not only cements the practicality of this system but also signifies a leap towards higher energy density zinc–manganese batteries. These advancements have profound implications for stationary energy storage applications that demand both safety and sustainability alongside performance. The strategy of rational electrolyte design emerging from this research pushes the frontier of aqueous battery technologies closer to their theoretical potential.
Behind these accomplishments lies a detailed understanding of zinc’s electrochemical behavior in complex electrolyte environments. Traditionally, zinc anodes suffer from dendritic growth and corrosion-induced shape changes that detract from cycling stability. In this eutectic medium, zinc’s solvation environment is modulated, promoting more uniform deposition and dissolution, which underpins the remarkable endurance demonstrated by these batteries. This design principle reflects a nuanced grasp of solvation dynamics and electrode interfacial science.
For the cathode, the phase and morphology control bestowed by the deep eutectic electrolytes directly impact the MnO_2 layer’s crystallinity and ionic pathways. This layer is neither too compact nor irregular, allowing faster ion transport and minimizing kinetic barriers associated with MnO_2 redox reactions. Such structural tuning is essential for unlocking higher capacities and operational voltages, both of which are critical to making zinc–manganese batteries commercially attractive.
The elimination of parasitic gas evolution, chiefly oxygen and hydrogen, has been a persistent challenge for aqueous battery chemistries. These side reactions not only squander energy but also present safety hazards due to pressure build-up and electrode damage. Raising the oxygen evolution overpotential well above the deposition potential acts as a gatekeeper, essentially preventing the onset of this undesirable reaction during cycling. This breakthrough offers a clearer path toward aqueous battery systems that can rival their non-aqueous counterparts.
Equally important is the ability of this electrolyte system to maintain a benign pH environment locally while facilitating proton transport for the MnO_2/Mn^2+ conversion. This balance mitigates acid-driven corrosion at the zinc side while simultaneously optimizing cathode kinetics, an intersection that had proven elusive until now. The creation of localized interfacial pH gradients represents an elegant self-regulating mechanism within the battery, enhancing both safety and efficiency.
The implications of this research stretch beyond zinc–manganese batteries alone. The concept of disrupting hydrogen bonding networks to design electrolytes with tailored solvation properties opens pathways for other aqueous battery chemistries hindered by water’s reactivity. Additionally, the extensive cycle life without acid additives indicates potential for reduced maintenance and greater system durability, attributes vital for grid-storage economics.
Moreover, these eutectic electrolytes’ non-flammable attributes catapult the battery technology into safer operations, a non-trivial advantage for stationary applications often located near populated areas. This safety profile, combined with high energy density and long-term stability, may attract widespread industry and governmental interest, catalyzing a shift in how sustainable energy infrastructures are designed.
The global approach employed in this research exemplifies the power of interdisciplinary collaboration, blending electrochemistry, materials science, and molecular engineering to realize a practical solution. Such integrative methodologies underscore the future of battery innovation, where holistic understanding catalyzes technological leaps rather than incremental improvements.
As this new generation of zinc–manganese batteries moves from the laboratory toward commercial applications, questions remain regarding scalability and cost-effectiveness of these novel eutectic electrolyte formulations. However, the foundational proof-of-concept demonstrated promises a compelling avenue for further exploration and optimization by both academic and industrial research communities.
In summary, these aqueous eutectic electrolytes stand to redefine the landscape of zinc–manganese energy storage by resolving long-standing bottlenecks of corrosion, electrolyte instability, and parasitic reactions. This breakthrough augurs well for high-energy, safe, and durable batteries necessary for the energy transition and the integration of renewable sources—marking a pivotal advancement in the quest for sustainable power solutions.
Subject of Research: Electrolyte engineering in aqueous Zn^2+/Zn||MnO_2/Mn^2+ batteries to achieve stable, high-performance, and long-cycle-life energy storage without acid-induced corrosion and parasitic gas evolution.
Article Title: Aqueous eutectic electrolytes suppress oxygen and hydrogen evolution for long-life Zn||MnO_2 dual-electrode-free batteries.
Article References:
Li, J., Li, C., Liu, B. et al. Aqueous eutectic electrolytes suppress oxygen and hydrogen evolution for long-life Zn||MnO_2 dual-electrode-free batteries. Nat Energy (2026). https://doi.org/10.1038/s41560-025-01958-8
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41560-025-01958-8
Tags: advanced energy storage technologiesaqueous Zn2+/Zn batteriesaqueous-organic electrolyte developmentbattery lifecycle extensiondeep eutectic electrolyteselectrodeposition mechanismsgrid-level energy storagehigh Coulombic efficiencyMnO2 electrode efficiencynon-flammable battery systemssustainable energy solutionszinc corrosion prevention
