What is a Water-Based Battery?
A Breakthrough in 2026: Neutral Electrolytes and Organic Polymer Anodes
Why This Matters: The Li-Ion Problem
Applications and Current Limitations
The Broader Trajectory
References and Further Reading
The global energy transition has a storage problem. According to the International Energy Agency (IEA), meeting the COP28 commitment to triple renewable capacity by 2030 will require global battery storage capacity to increase sixfold, reaching 1500 GW, with battery systems accounting for 90% of that growth.1
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This demand has intensified scrutiny of the dominant technology: lithium-ion (Li-ion) batteries. Concerns about supply chain fragility, thermal safety, end-of-life toxicity, and the environmental cost of mining cobalt (Co) and nickel (Ni) have pushed researchers toward alternatives. A study published in February 2026 in Nature Communications has raised the ceiling on what aqueous, or water-based, batteries can achieve.2
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What is a Water-Based Battery?
An aqueous battery uses a water-based electrolyte instead of the organic solvent electrolytes found in conventional Li-ion cells. In standard Li-ion batteries, lithium salts dissolved in flammable organic solvents create both fire risk and disposal complications.2
Aqueous batteries replace this with water-based solutions, making them inherently non-flammable and less costly to produce. Research in Nature Reviews Clean Technology confirms this makes them well-suited for grid-scale battery energy storage systems (BESS), where large electrolyte volumes make fire-suppression infrastructure critical, but also very expensive.3
The trade-off has historically been performance. Water-based electrolytes constrain the electrochemical window, therefore limiting energy density compared to Li-ion electrolytes. These water-based electrolytes also tend toward extreme acidity or alkalinity, corroding metal electrode components over time, a process known as electrolyte decomposition, which can generate hydrogen and oxygen gas and, in severe cases, cause rupture.2
A Breakthrough in 2026: Neutral Electrolytes and Organic Polymer Anodes
A 2026 study published in Nature Communications addresses these failure modes with a design that departs from standard aqueous battery chemistry in two important ways.2
First, the researchers synthesized covalent organic polymers (COPs), rigid, porous structures built from nitrogen (N) and carbon (C), for use as the negative electrode (anode). Unlike metal-based anodes, these organic structures are built around dense carbonyl functional groups, which efficiently attract positive ions.
The specific compound developed, hexaketone-tetraaminodibenzo-p-dioxin (HKT), combines a high-density carbonyl configuration with a tetraaminodibenzo-p-dioxin backbone that preserves the molecule’s flat geometry across repeated charge cycles. This structural stability is what underpins the battery’s extended cycle life.2
Second, and critically, the electrolyte is neutral (pH 7). Most aqueous batteries use strongly acidic or alkaline solutions to achieve the conductivity needed to move ions efficiently.
The design developed in Chen et al. (2025) maintains that conductivity at neutral pH by matching the electrolyte chemistry to the COP’s ion-storage mechanism, which preferentially coordinates magnesium (Mg2+) and calcium (Ca2+) ions rather than the protons or hydroxide ions that drive side reactions in extreme-pH systems.2
The results are notable. In testing, the HKT-COP anode demonstrated 120,000 charge cycles with a specific capacity of up to 112.8 mAh g-1. When paired with a compatible cathode, the full cell achieved a voltage interval of 2.2 V and a specific energy of up to 48.3 Wh kg-1.2
Grid batteries operate at an average of roughly 1.1 cycles per day; at that rate, 120,000 cycles represents an operational lifespan of approximately 300 years before meaningful degradation.2
Equally significant is disposal. The neutral electrolyte used in the study is chemically equivalent to tofu brine, a magnesium sulfate solution, meaning it can be discarded directly into the environment without the hazardous waste protocols that acidic or alkaline aqueous electrolytes and organic Li-ion electrolytes require.2
Why This Matters: The Li-Ion Problem
A 2024 review in the Journal of Occupational Medicine and Toxicology found that mining cobalt, lithium (Li), manganese (Mn), and nickel poses risks including water contamination, soil degradation, and occupational toxicity.4
Cobalt extraction in the Democratic Republic of the Congo generates sulfuric acid that infiltrates waterways. Similarly, lithium brine mining in the Atacama basin extracts saline groundwater from water-scarce ecosystems. A 2024 lifecycle analysis further noted that forced and child labor remain features of artisanal cobalt mining.5
At the end of life, Li-ion cells disposed of in landfills can leach heavy metals into soil and groundwater and are prone to difficult-to-suppress thermal-runaway fires.5 The aqueous battery sidesteps these concerns: its active components (carbon- and nitrogen-based organic polymers, with magnesium (Mg) and calcium (Ca) as working ions) are abundant, non-toxic, and require none of the extraction processes that constrain Li-ion supply chains.2
Applications and Current Limitations
Aqueous batteries are best suited to stationary, grid-scale storage. This is not a disqualifying constraint as grid storage is precisely where low cost, non-flammability, and longevity matter most, and where lower energy density matters least, since systems can be sized up without transport weight penalties.
The 48.3 Wh kg-1 specific energy is considerably below the 150–300 Wh kg-1 range of commercial Li-ion cells and below some competing aqueous chemistries.6
A Nature Communications study demonstrated a copper hexacyanoferrate aqueous battery with 95% round-trip energy efficiency at high discharge rates.7 This is a benchmark for grid-suitable aqueous systems. The 2026 design does not report comparable round-trip efficiency figures, and independent replication at scale is pending.
These are open questions rather than fundamental barriers.
The Broader Trajectory
The 2026 Nature Communications study sits within a broader shift in aqueous battery research. A 2025 review in Communications Materials cataloged advances in covalent organic frameworks (COFs), which are structurally similar to the COPs used here, for multivalent-ion batteries, and identified design principles for neutral-pH ion storage.8
The convergence of neutral-electrolyte chemistry, organic electrode materials, and multivalent ions represents a maturing area of research rather than an isolated result.
Whether water-based batteries displace Li-ion at scale depends on manufacturing cost at volume, grid integration, and energy density improvements. The IEA’s net zero prediction requires 25% annual growth in battery storage deployment through 2030 at a total investment of $800 billion.1
This timeline is too compressed for any nascent technology to capture a dominant share. The long-term consideration is whether the industry continues to scale a technology with geopolitical raw-material constraints and environmental end-of-life liabilities, or begins transitioning to chemistries that do not carry those costs.
The Chen et al. study does not resolve that question, but it demonstrates, under controlled conditions, that an aqueous battery can be built from abundant organic materials, cycled 120,000 times without meaningful degradation, and disposed of without environmental harm. No commercial Li-ion system currently offers all three simultaneously.
References and Further Reading
- International Energy Agency. Batteries and Secure Energy Transitions. IEA Special Report, April 2024. Available at: https://www.iea.org/reports/batteries-and-secure-energy-transitions
- Chen, H., et al. (2026) An aqueous battery using an electrolyte with a pH of 7 and suitable for direct environmental discard. Nature Communications.17(1). https://doi.org/10.1038/s41467-026-69384-2
- Luo, X., Espinosa-Leal, L., Saadabadi, S.A., et al. (2025). Battery technologies for grid-scale energy storage. Nature Reviews Clean Technology. https://doi.org/10.1038/s44359-025-00067-9
- Mancini, F., Marzi, I., Sisto, R., Cerini, S., Abbate, C,. (2024) Occupational, environmental, and toxicological health risks of mining metals for lithium-ion batteries: a narrative review of the PubMed database. Journal of Occupational Medicine and Toxicology. 19(33). https://doi.org/10.1186/s12995-024-00433-6
- Domingues, A. M., de Souza, R. G., and Luiz, J. V. R. (2024). Lifecycle social impacts of lithium-ion batteries: Consequences and future research agenda for a safe and just transition. Energy Research & Social Science, 118. https://doi.org/10.1016/j.erss.2024.103756
- Hasan, M. M., Haque, R., Jahirul, M. I., Rasul, M. G., Fattah, I. M. R., Hassan, N. M. S., and Mofijur, M. (2025). Advancing energy storage: The future trajectory of lithium-ion battery technologies. Journal of Energy Storage, 120. https://doi.org/10.1016/j.est.2025.116511
- Wessells, C.D., Huggins. R.A., Cui, Y. (2011). Copper hexacyanoferrate battery electrodes with long cycle life and high power. Nature Communications. https://doi.org/10.1038/ncomms1563
- Zhu, L., Wang, L., Chen, J., Zhang, R., Li, Y. (2025) Covalent organic framework-based cathodes for beyond lithium-ion batteries. Communications Materials. 6(78). https://doi.org/10.1038/s43246-025-00801-7
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