Which Company Makes Iron-Air Battery?

Iron-air batteries are an emerging energy storage technology that use iron as the anode, oxygen as the cathode, and an alkaline electrolyte such as potassium hydroxide. They offer the potential for low cost, safety, sustainability, and scalability for large-scale energy storage applications like backing up renewable energy sources or providing grid-scale storage. Iron-air batteries have high energy density and the use of iron and oxygen make them inexpensive compared to lithium-ion batteries.

Interest in iron-air batteries has grown in recent years as the need for long-duration energy storage increases with greater deployment of wind and solar power generation. While still in early stages of commercialization, some companies are working to overcome challenges like improving efficiency and cycle life to make iron-air batteries a viable grid storage solution.

Major players pioneering iron-air battery technology include companies like Form Energy, ESS Inc, and Iron Air. Form Energy is notable for raising over $200 million in funding and partnering with utilities to test multi-day energy storage using their proprietary iron-air battery design.

How Iron-Air Batteries Work

Iron-air batteries work by converting iron metal to rust when discharging, and then back to iron metal when charging [1]. The chemical reaction involves combining iron, oxygen, and water to form iron oxide (rust) and heat energy. This is a reversible reaction, allowing the battery to be recharged [2].

The main components of an iron-air battery are an iron electrode (anode), air electrode (cathode), electrolyte, and separator. During discharge, the iron anode oxidizes to iron ions, releasing electrons that travel through the external circuit to the cathode. Here, oxygen from the air reacts with water in the electrolyte to form hydroxyl ions. The hydroxyl ions combine with iron ions to form iron hydroxide on the cathode, which further oxidizes into rust. This electrochemical reaction generates electricity. During charging, the reaction reverses, reducing the rust back to iron metal [1].

A key advantage of iron-air batteries is their low cost, as iron is an abundant, non-toxic material. They also offer high efficiency of 60-70%, safety since they don’t contain flammable electrolytes, and environmental benefits from relying on air rather than mined materials like lithium or cobalt [2]. Their high energy density potentially allows iron-air batteries to store large amounts of renewable energy.

[1] https://www.popularmechanics.com/science/energy/a42532492/iron-air-battery-energy-storage/

[2] https://www.pbs.org/wgbh/nova/article/iron-air-battery-renewable-grid/

Challenges Facing Iron-Air Batteries

While iron-air batteries have the potential for incredibly low cost and high energy density, there remain significant technical challenges before they can be widely implemented in grid scale storage applications.

One major challenge is the typically short lifetime of iron-air batteries. Most iron-air batteries degrade significantly within just 50-100 charge/discharge cycles due to irreversible reactions that corrode the iron anode (Fraunhofer, 2022). This is far too short for practical utility-scale deployment where batteries need to last for thousands of cycles.

Another obstacle is the relatively low power density of iron-air batteries, which refers to how much power can be delivered per unit weight or volume. While energy density is high, most iron-air chemistries have power densities well below lithium-ion batteries. This makes them ill-suited for applications requiring rapid discharge (ESS Inc, 2023).

Finally, scaling up lab-scale prototype iron-air batteries into full commercial products has proven difficult. It’s a complex challenge involving optimization of electrodes, electrolytes, separators, corrosion inhibitors, and other components. Most startups in the space are still working on scaling up small single-cell prototypes into larger multi-cell batteries (Fraunhofer, 2022).

Major Players in Iron-Air Battery Development

Several companies are making major strides in developing and commercializing iron-air battery technology, including:

companies like form energy, ess inc, and iron air are developing grid-scale iron-air batteries for long duration energy storage

Form Energy (https://formenergy.com/technology/battery-technology/) – Based in Massachusetts, Form Energy is developing ultra-low cost iron-air batteries capable of storing electricity for 100 hours, allowing renewables to provide baseload power. They have developed an innovative aqueous air electrode and electrolyte system that enables iron-air batteries to overcome previous challenges with efficiency and cyclability. Form has partnered with Great River Energy to deploy a 1MW/150MWh iron-air battery system in Minnesota in 2023.

ESS Inc. (https://www.essinc.com/) – Headquartered in Oregon, ESS specializes in long-duration energy storage systems based on iron flow battery technology. Their battery systems offer low-cost, safe, sustainable long-duration storage ideal for grid applications. ESS has deployed over 200 MWh of iron flow battery storage capacity globally. In 2021, they unveiled an 8-hour iron flow battery module targeting the long-duration energy storage market.

Iron Air (https://ironair.co/) – A Czech startup, Iron Air is developing zinc-air batteries that can store electricity for up to 48 hours per charge. They are aiming to deploy container-sized zinc-air batteries that can store megawatt-hours of renewable energy. Iron Air recently closed a $3 million seed funding round to accelerate R&D on their zinc-air battery prototypes.

Form Energy

Form Energy is an iron-air battery startup founded in 2017 and based in Somerville, Massachusetts. The company has raised over $200 million in funding to date from investors including Breakthrough Energy Ventures, Eni Next, Capricorn Investment Group, Macquarie Capital, and others. Form Energy is focused on developing multi-day discharge batteries based on iron-air chemistry to enable renewable energy sources like wind and solar to provide reliable electricity 24/7.

The iron-air batteries from Form Energy are designed to store electricity for 100 hours, providing stability to the grid for multi-day weather events. Their innovative battery architecture allows for low material costs using iron, one of the safest and cheapest materials. By pairing their long-duration energy storage with renewable generation, Form Energy aims to accelerate the transition away from fossil fuels towards a carbon-free electric grid.

In 2021, Form Energy announced a 1MW/150MWh pilot project with Minnesota utility Great River Energy scheduled to begin operation in late 2023. The company is also partnering with BMW on a demonstration project. Form Energy’s iron-air batteries could become a key grid-scale energy storage solution as increasing amounts of intermittent renewables come online in the years ahead.


Founded in 2011, ESS Inc is based in Wilsonville, Oregon and focuses on renewable energy storage [1]. The company uses an iron flow battery chemistry called the Iron Flow Battery, which utilizes iron, salt, and water for the electrolytes. This makes the batteries very safe with no risk of thermal runaway. ESS has deployed their systems in some demonstration projects to highlight the technology’s potential. In 2020, ESS partnered with Porsche to install a 27 MWh ESS Energy Warehouse system at Porsche’s new Experience Centre in Germany [2]. The system will be used to integrate onsite solar power generation and provide energy storage to reduce peak demand.

[1] https://essinc.com/

[2] https://essinc.com/porsche-and-ess-deploy-the-largest-microgrid-in-europe-for-the-porsche-experience-center-hockenheimring/

Iron Air

Iron Air is a startup founded in Australia in 2021 that promises to make safe and affordable iron-air batteries, citing the technology is “World’s largest” iron flow battery storage system unveiled in Australia. Iron Air says their batteries will be cheaper and safer than lithium-ion alternatives. The company is still in the early stages, having recently received $3 million in seed funding to continue developing their technology.

Other Notable Companies

In addition to Form Energy, ESS Inc, and Iron Air, there are several other companies working on iron-air battery technology:

NantEnergy is developing zinc-air batteries for long duration energy storage, claiming up to 72 hours of storage capacity. Their main differentiator is using zinc as the metal instead of iron, which they claim allows for lower material costs. They received investment from Patrick Soon-Shiong’s NantWorks conglomerate.

Phinergy is an Israel-based company developing aluminum-air and zinc-air battery systems. They focus on range extender applications for electric vehicles. In 2017 they demoed an electric vehicle with over 1000 km of range by using aluminum-air batteries.

E-stone Batteries is a startup spun out of the University of Illinois that is developing iron electrode chemistries for grid scale energy storage. They claim their batteries will be lower cost than lithium-ion alternatives.

While these companies have potential, most analysts agree that Form Energy is the current leader in commercializing iron-air battery technology.

Future Outlook

Iron-air batteries have the potential to greatly advance grid energy storage due to their low cost and long duration storage capacity. However, there are still challenges to address before wide scale adoption can occur. One key area for improvement is increasing the cycle life. Currently iron-air batteries only last for around 50 cycles before needing to replace the air cathode (Scientific American). Increasing cycle life to over 200 would make the batteries more commercially viable.

Some companies like Form Energy are optimistic that iron-air batteries could reach tens of gigawatts of demand in the next decade. This is based on projections for increasing renewable energy generation like wind and solar that will require multi-day energy storage. The Department of Energy has set cost and duration targets of $100/kWh and 5 day storage duration. If companies can meet these targets, iron-air batteries could play a major role in grid decarbonization.

Overall, iron-air batteries have exciting potential, but still need to overcome technical hurdles. If ongoing engineering efforts are successful, iron-air batteries could emerge as a leading long duration energy storage solution and contribute significantly to the clean energy transition.


Over the last few years, several promising companies have emerged at the forefront of iron-air battery development. Form Energy stands out with its impressive pilot projects and partnerships with utilities to deploy iron-air batteries at grid scale in the coming years. ESS Inc. is also making strides with its unique approach using iron, salt, and water. While still earlier in development, Iron Air and other startups are pushing the technology forward as well.

The innovations around iron-air batteries mark an important advancement for renewable energy storage. By providing affordable, long-duration energy storage, iron-air batteries can enable greater adoption of wind and solar power. As researchers continue to improve the performance and lifespan of iron-air batteries, they have the potential to revolutionize how we store and use electricity from renewable sources.

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