A peer-reviewed study published in Nature Energy describes a water-based battery chemistry that achieves an energy density of up to 1200 Wh/L, a figure that dwarfs many existing aqueous storage technologies. The research centers on a hetero-halogen electrolyte composed of iodide and bromide, enabling multielectron redox reactions that could make water-based energy storage far more practical for large-scale use. Combined with the proven durability of pumped-storage hydropower, which some analyses model as lasting over 100 years, the findings raise a serious question: could water-powered storage keep grids running not just for decades, but for generations?
High-Density Chemistry Without the Fire Risk
Lithium-ion batteries dominate the energy storage conversation, but they carry well-documented drawbacks, including flammable organic electrolytes, reliance on scarce minerals, and degradation that limits useful life to roughly a decade in most grid applications. The Nature Energy paper offers a different path. Its researchers developed a reversible multielectron cathode using an iodide-to-iodate reaction in a water-based electrolyte. By introducing bromide into the system, the team created a hetero-halogen environment that stabilizes the reaction and allows multiple electrons to transfer per cycle, dramatically increasing energy storage per unit of volume.
The reported catholyte-based energy density of up to 1200 Wh/L is the headline number, and it matters because it suggests that aqueous batteries can compete with, or even exceed, the volumetric performance of some lithium-based chemistries while using water as a solvent instead of volatile organics. That distinction carries practical weight: water-based systems are inherently less prone to thermal runaway, the chain reaction behind lithium-ion battery fires. For grid operators weighing safety against capacity, a high-density aqueous option changes the calculus considerably, especially in dense urban environments or critical facilities where fire risk carries outsized economic and social costs.
Pumped Storage: The Original Water Battery
The term “water battery” covers more ground than most people realize. The U.S. energy agency uses it to describe pumped-storage hydropower, or PSH, a technology that has been storing energy at grid scale since the early 20th century. The concept is straightforward: when electricity supply exceeds demand, water is pumped uphill into an upper reservoir. When power is needed, the water flows back down through turbines to generate electricity. The agency cites typical round-trip efficiency ranges of roughly 70 to 80%, which compares favorably with many battery technologies once degradation and replacement cycles are factored in, and notes that PSH already accounts for the majority of large-scale storage capacity in the United States.
What sets PSH apart from chemical batteries is longevity. A peer-reviewed life cycle assessment published via PubMed Central models PSH with a base-case lifetime of 80 years and includes a 100-year lifetime scenario, citing sources that estimate some facilities could operate beyond a century. That kind of durability is nearly unheard of in the battery world, where even long-lived chemistries are typically modeled over a few decades. The same assessment, accessible through NCBI tools, emphasizes that the bulk of PSH’s environmental impact is front-loaded during construction, meaning that each additional year of operation effectively dilutes its life cycle footprint. For planners concerned with both reliability and sustainability, that combination of long life and declining per-year impact is hard to ignore.
New U.S. Projects Signal Growing Demand
The longevity case for PSH is not merely academic. The federal permitting map maintained by the Federal Energy Regulatory Commission shows a pipeline of proposed and advancing pumped-storage projects across multiple states. Each marker on that map represents a developer willing to navigate a complex, multi-year approval process in order to bring new long-duration storage online. The geographic spread of these permits, from mountainous regions suited to high-head projects to areas exploring off-river concepts, signals that water-based storage is being considered wherever topography and transmission constraints allow.
Preliminary permits do not guarantee construction, but they represent a formal step in the regulatory process, and their growing number suggests broad interest from utilities and private developers. Financing such capital-intensive projects has historically been a barrier, which is why federal support mechanisms matter. The government’s infrastructure exchange platform is designed to connect large energy and resilience projects with funding and technical resources, potentially smoothing the path for PSH alongside other grid assets. Each new facility that reaches completion adds storage capacity measured in decades, not the five-to-fifteen-year replacement cycles typical of lithium-ion installations, spreading upfront costs over a much longer service life.
Smaller Scale, Same Principle
Water-based battery innovation is not limited to massive hydropower installations or high-density lab cells. Researchers have also explored disposable, biodegradable batteries activated by water for use in low-power, single-use electronics. A study in Scientific Reports describes a paper battery manufactured using printing techniques that begins generating electricity when water is applied. The device, built from materials such as cellulose and benign salts, is designed for applications like environmental sensors or diagnostic test strips, where a battery needs to work once and then decompose without leaving toxic waste behind.
This sits at the opposite end of the scale spectrum from a pumped-storage dam, but the underlying philosophy is the same: use water as a safe, abundant medium for energy conversion while minimizing environmental harm. The printed paper battery will not keep anyone’s lights on for a century, yet it demonstrates the breadth of the water-battery concept. From single-use medical devices to century-spanning grid infrastructure, water is proving to be a more versatile energy storage medium than its simplicity might suggest, and the same scientific ecosystem that catalogs large hydropower assessments also maintains curated bibliographic collections of emerging electrochemical research, underscoring how diverse these water-enabled technologies have become.
What Stands Between Lab Results and Grid Reality
The 1200 Wh/L figure from the Nature Energy study is a laboratory measurement of catholyte-based energy density, not a finished product specification. Scaling any new battery chemistry from a research cell to a commercial system involves losses at every step, from electrode manufacturing to thermal management to system integration. Real-world devices must dedicate volume to separators, current collectors, housing, and safety systems, all of which reduce the effective energy density compared with a bare catholyte number. The paper does not include projections for commercial deployment timelines, and the available public materials do not spell out specific pathways to mass production, leaving open questions about cost, durability, and manufacturability.
History offers plenty of cautionary tales: many high-performance chemistries that looked transformative in the lab stalled when confronted with materials availability, side reactions, or simple economics. For the hetero-halogen aqueous system, researchers will need to demonstrate long cycle life, stable performance over wide temperature ranges, and compatibility with scalable manufacturing methods if it is to complement or displace existing grid batteries. At the same time, pumped-storage hydropower faces its own hurdles, including siting constraints, environmental permitting, and long lead times. The emerging picture is not one of a single “winner,” but of a portfolio in which durable water-based infrastructure like PSH pairs with safer, higher-density aqueous batteries and even biodegradable microdevices, collectively pushing energy storage toward a future where water plays a central, stabilizing role in how societies keep the lights on for generations.
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*This article was researched with the help of AI, with human editors creating the final content.
