Chemists have unlocked a secret that could transform zinc-air batteries into the ultimate rechargeable powerhouse.
Researchers at TU Darmstadt have developed a multifunctional composite material for enable rechargeable zinc-air batteries.
Making these batteries rechargeable has proved exceptionally difficult because controlling the complex chemical reactions within the cell presents a major technical barrier. To address this challenge, a research team led by Professor Jörg J. Schneider has shown that a novel composite material made of iron, nickel, and carbon can stabilize these internal processes.
Interestingly, the development enables rechargeable zinc-air batteries to achieve up to 300 hours of continuous operating time.
“The assembled secondary ZAB can be cycled for more than 300 h in a galvanostatic charge–discharge test,” the team stated.
Efficient hybrid catalyst
Zinc-air batteries have remained low-profile, disposable powerhouses used mostly in hearing aids. These batteries are known to store up to five times more energy than lithium-ion batteries. But remained single-use because controlling their complex internal chemistry during charging proved nearly impossible.
The team solved this by firmly attaching nano-sized spinel particles made of iron, nickel, and oxygen onto a carbon material enriched with nitrogen and phosphorus.
Spinels are already widely used across materials science and electrical engineering for their unique characteristics. The novel material leverages these specialized electrochemical properties to act as a long-lasting internal catalyst.
Earlier, nickel ferrites served as the foundational building block for the catalyst designed to drive the oxygen reactions inside the rechargeable zinc-air battery.
But these catalysts face challenges with low chemical activity and poor stability, which limits their use in rechargeable zinc-air batteries. To address this, researchers created a hybrid catalyst by wrapping tiny nickel ferrite cubes in nitrogen- and phosphorus-doped carbon nanohorns.
This carbon casing provides fast electron and mass transport while creating numerous active reaction sites. The structure also protects the ferrite particles from clumping or dissolving, resulting in a more durable and effective catalyst.
Move over, lithium
This catalyst displays impressive electrochemical performance, featuring a high half-wave potential of 0.79 V, a low Tafel slope of 56.5 mV/dec, and an efficient four-electron pathway for oxygen reduction.
When tested in a full zinc-air battery cell, it achieved a maximum power density of 54 mW/cm², nearly doubling the 28 mW/cm² benchmark set by standard platinum and ruthenium catalysts.
In laboratory tests, the catalyst enabled up to 300 hours of continuous operation by stabilizing the “triple junction,” the interface where the solid catalyst, liquid electrolyte, and ambient oxygen interact. As a result, the material maintains the steady chemical conditions needed for reliable, long-term battery function.
Zinc-air technology offers compelling advantages over lithium-ion systems in cost, safety, and scalable application. Lithium, cobalt, and nickel face severe supply chain issues, but materials like zinc, iron, and carbon are globally abundant and economical to source. Furthermore, zinc-air cells use non-flammable water-based electrolytes, eliminating the risk of dangerous thermal runaway fires associated with lithium-ion batteries.
While moderate power density makes them less suitable for fast-charging consumer electronics, their high energy density positions them well for stationary grid energy storage to support solar and wind power. Eventually, scaled zinc-air batteries could also act as efficient long-range power packs for heavy transport and electric vehicles.