China-made all-iron flow battery runs 6,000 cycles at 80 times cheaper than lithium

Researchers in China have created an all-iron flow battery electrolyte. It can handle over 6,000 charge and discharge cycles without losing power. This new material is about 80 times cheaper than lithium-based options.

How the New Battery Works

Flow batteries store energy in liquids called electrolytes. These liquids are kept in separate tanks. When power is needed, the liquid is pumped through a special cell. Unlike solid batteries, the amount of energy a flow battery can store depends on the tank size, not the electrode size. This makes them good for large-scale energy storage where cost per kilowatt-hour is more important than how much space they take up.

The team at the Chinese Academy of Sciences developed an iron-based electrolyte. This new liquid solves a big problem with older iron flow batteries. These older batteries would create hydrogen gas at the negative electrode. This gas would slowly use up the active material and shorten the battery's life. The new electrolyte stops this reaction, allowing the battery to last for 6,000 cycles. The full study has not yet been published in a widely available journal, so other scientists still need to confirm these results.

Why Cost Matters

Lithium carbonate is a key material for most lithium-ion batteries. Its price has varied greatly, from about $7,000 to $80,000 per metric ton in the last five years. Iron sulfate, used in iron flow batteries, is a cheap industrial byproduct. The researchers say their material is 80 times cheaper based on the raw material cost per unit of stored energy. This figure does not include the cost of other parts like membranes, pumps, and electronics.

This difference is important. Iron flow systems have often been expensive to build, which reduced their material cost advantage. If the new electrolyte means less need for costly ion-exchange membranes, the total cost could be much lower. If standard membranes are still needed, the real-world savings might be less.

Grid Storage and What's Next

Currently, vanadium redox flow batteries are common in the market. Many large installations exist in China, Europe, and the U.S. However, vanadium is expensive and hard to get. This has led to interest in iron-based options for over ten years. Previous iron flow designs struggled with the hydrogen problem, which the Chinese team now claims to have fixed.

Lithium iron phosphate (LFP) batteries are often used for large-scale storage because their prices have dropped. An iron flow battery that matches LFP's cycle life (3,000 to 6,000 cycles) and capital cost could be useful for storing energy for multiple days. For these uses, LFP's energy density is less important.

The Chinese Academy of Sciences has not yet announced plans for commercial use or pilot projects. The 6,000-cycle result was achieved in a lab. Battery performance can change when scaled up to larger systems. Independent checks of the electrolyte's stability will be the next step.

Scaling up from a stable lab chemistry to a commercial grid storage product takes time. However, the low cost of iron gives this approach a fundamental cost advantage that lithium-based systems cannot match.