New polymer cathode makes organic batteries practical

A new polymer makes organic batteries practical

Researchers have developed a new organic battery material that overcomes the major hurdles preventing these sustainable batteries from being practical. The key is a conducting polymer cathode called poly(benzodifurandione) (PBFDO), which is stable, highly conductive, and doesn't easily dissolve.

This breakthrough could finally make organic batteries a viable alternative to today's lithium-ion batteries. Commercial lithium-ion cells rely on scarce metals like cobalt and nickel, while organic batteries use abundant, recyclable carbon-based materials.

The problem with organic electrodes

Until now, organic battery materials have faced two deal-breaking flaws. They are typically poor electrical insulators, requiring large amounts of conductive additives. They also tend to dissolve into the battery's electrolyte, destroying the cell after just a few charge cycles.

The new PBFDO polymer solves both problems. It is an n-type conducting polymer, meaning it is inherently conductive for both electrons and ions. This eliminates the need for extra conductive carbon, allowing for much denser, more powerful electrodes.

Critically, the material also shows "low solubility," meaning it stays put in the electrode instead of dissolving away. This is the foundation for long battery life.

Record-breaking battery performance

The team built ultra-thick cathodes with the polymer to demonstrate its potential. They achieved a mass loading of 206 mg cm−2, which is exceptionally high. A standard lithium-ion cathode is typically below 30 mg cm−2.

This dense electrode delivered an areal capacity of 42 mAh cm−2. For context, commercial cells aim for about 4 mAh cm−2. The high capacity comes from packing so much active material into the electrode without sacrificing performance.

The researchers then scaled up, building a practical pouch cell battery similar to those in electronics. The 2.5 Ah pouch cell achieved an energy density of 255 Wh kg−1. This is competitive with some commercial lithium-ion batteries used today.

Extreme performance from cold to flexible

Beyond basic metrics, the organic battery showed extraordinary versatility. It operated efficiently across a massive temperature range, from -70 °C to 80 °C. Most lithium-ion batteries fail below -20 °C and risk fire above 60 °C.

The cells also demonstrated excellent flexibility and safety, pointing to potential uses in wearable electronics. The organic materials are inherently less prone to the thermal runaway reactions that can cause lithium-ion batteries to catch fire.

The key advantages of the PBFDO cathode include:

• Inherent conductivity without additives
• Stable, reversible redox reactions for long life
• High lithium-ion diffusion rates for power
• Robust cycling stability in thick electrodes

The path to sustainable energy storage

This research, published in Nature, marks a significant leap from lab curiosity toward a practical device. For decades, the promise of cheap, recyclable, and non-toxic organic batteries has been stalled by the insulation and dissolution of the materials.

By solving these core issues with a single polymer, the work opens a new pathway for sustainable battery technology. The next steps will involve scaling production of the PBFDO material and integrating it into full battery systems for real-world testing.

If successful, it could lead to batteries that are not only powerful and safe but also made from some of the most common elements on Earth.