New water battery could last until the 24th century — and it can be safely discarded in the environment

Researchers in China have pioneered a formula for a nontoxic "aqueous battery" that they say could last 10 times longer than today's best devices. What's more, the water battery achieves this epic lifespan without degrading and can be disposed of safely in the environment, the team reported in a new study.

For the new method, researchers used synthesized covalent organic polymers (COPs). These tough, organic molecules, such as nitrogen and carbon, are bound together in a tight structure with clear openings and are used as an anode for magnesium and calcium ions.

Organic polymers like this have little use because they are generally short-lived in aqueous batteries; they break down quickly in water-based electrolytes found inside this variant of battery, which can be either extremely acidic or extremely alkaline. The electrolyte is essential to moving ions between the anode and the cathode, which is why aqueous batteries are a nonflammable and more affordable alternative to traditional batteries.

In the study, published Feb. 18 in the journal Nature Communications, the researchers found a specific compound (hexaketone-tetraaminodibenzo-p-dioxin) that combines high-density carbonyl — which is ideal for attracting positive ions — with a rigid tetraaminodibenzo-p-dioxin molecule that keeps the hexaketone in its flat, honeycomb-like structure.

The neutral electrolytes used in the research, with a pH of 7.0, conduct the ions to a high efficiency. Combined with the carefully-tuned structure, without corroding this COP.

The researchers said the polymers could last 120,000 charge cycles — more than 10 times the life of a typical lithium-ion battery (Li-ion) used for grid storage, according to data by Energy Sustainability Directory. Grid batteries completed an average of 1.1 cycles per day in 2024. At this rate, the aqueous battery could last approximately 300 years before needing to be replaced.

The researchers also said the electrolytes used in the new battery are so safe that they can be used as tofu brine, i.e. non-toxic and easy to dispose of directly into the environment.

Benefits of aqueous batteries

Aqueous batteries are particularly favored for grid-scale energy storage such as large battery energy-storage systems due to their nonflammable properties and low up-front cost.

But they also come with downsides. Aqueous batteries do not store as much energy as conventional Li-ion batteries or sodium-ion (Na-ion) devices do because water-based electrodes limit the maximum voltage.

Aqueous batteries also break down over time, as the extreme pH of the electrolyte forms hydrogen and oxygen gas, corroding the metal elements of the battery. This effect, known as electrolyte decomposition, can also cause explosions in extreme cases. This limitation — a trade-off between safety and energy capacity — is usually overcome by building larger aqueous battery storage systems.

Additionally, the aqueous solution used in the batteries tends to be toxic and must be disposed of with care. This presents a potential environmental risk in the case of an accident that could expose the batteries to the open elements, and it increases the costs associated with the safe upkeep of aqueous battery energy-storage systems.

In a 2023 study published in the journal Nature, scientists cited high cost, depletion and environmental toxicity as particular downsides of aqueous batteries.

Depletion in this context refers to the gradual reduction in battery capacity and efficiency over time –- a familiar irritation for anyone who's held onto the same smartphone for more than a few years.

The latest breakthrough aims to address these shortcomings with a chemical composition that is both nontoxic and highly efficient in the long term, resulting in a much longer battery life and fewer complications associated with battery disposal.