Accumulation lasts 27 years and costs little

In a major advance in energy storage technology, researchers have developed a new electrode that effectively suppresses the harmful self-discharge phenomenon in flow-free zinc bromine (FLZBB) batteries, meaning they are able to hold a charge even when not in use.

The search for clean, sustainable energy is ongoing, and researchers are constantly innovating to improve energy storage systems. Although lithium-ion batteries are the dominant form, they face a major safety issue: flammable electrolytes.

FLZBBs offer a promising alternative due to their non-flammable properties and use of common metals. However, a nagging problem called self-discharge has hindered their widespread adoption. The research was published on Chemical Engineering Journal.

Now, a team of researchers at the Gwangju Institute of Science and Technology (GIST) in Korea has developed a revolutionary electrode that addresses this problem, paving the way for a future powered by safe and efficient FLZBBs.

Convert FLZBBs into something useful

FLZBBs have several advantages over lithium-ion batteries. They are safer, cheaper, and simpler in design. They work by using a positive electrode, a negative electrode, a separator to separate them from each other, and a gel-like electrolyte.

However, during operation, bromine ions generated at the positive electrode can migrate to the negative electrode, causing self-discharge and impairing performance. This was a major obstacle for the FLZBB.

Professor Chanho Pak and his team, including Yongin Cho, the study’s first author, have developed an innovative electrode that effectively limits self-discharge. This is a thick graphite electrode coated with nitrogen-doped mesoporous carbon (NMC/GF).

Their work paves the way for more stable and effective FLZBBs. Here’s their chemical function:

Ion Trapping: How NMC/GF Electrodes Work

The NMC/GF electrode is manufactured in a simple and economical way. The researchers coated a standard graphite wool electrode with the precursor material, followed by drying and polymerization. The magic lies in the micropores (tiny holes) created by the NMC coating.

These mesopores, together with strategically placed nitrogen sites, act as tiny cages, trapping bromine ions and their complexes within the positive electrode. This prevents them from reaching the negative electrode, stopping self-discharge.

“This coating made the original GF electrodes, which were originally hydrophobic, highly hydrophilic, which improved the interfacial contact with the electrolyte in the aqueous electrolyte and increased the electrochemical performance,” explains Professor Buck about the advantages of the NMC/GF electrode.

“In addition, it allowed for the incorporation of abundant oxygen and nitrogen species, which improved the rate of bromine reaction, increasing performance.”

Unprecedented performance and long life

The FLZBBs equipped with the NMC/GF electrode showed exceptional efficiency, with a Coulomb efficiency of 96% and an energy efficiency of 76% at a given current density. They also offer a high areal capacitance (the amount of charge stored per unit area) of 2 mA cm-2. But that’s not all.

These batteries have shown remarkable durability, lasting over 10,000 charge and discharge cycles – a testament to their long-term stability. This translates to a satisfactory life cycle of 27 years.

In addition, using thicker GF electrode can reduce battery costs.

In the press release“The development of the FLZBB positive electrode, which maintains long-term operation of more than 10,000 cycles with high efficiency, will accelerate the development of stable ESS and long-term green energy conversion,” said A. Pak, excited about the future implications. “Moreover, the NMC/GF positive electrode can also be used for other aqueous batteries.”

This discovery has the potential to revolutionize the world of energy storage. With safer, more stable, and more sustainable FLZBBs on the horizon, the path to a clean, sustainable energy future looks brighter.