Zinc-ion batteries are among the hopefuls among rechargeable power storage devices.

Because they meet the strict requirements for stationary energy storage - environmental compatibility, economy and safety - this type of battery is being discussed as a buffer for fluctuating wind and solar power.

Unlike lithium-ion batteries, zinc-ion batteries contain widely available materials and, moreover, do not contain any flammable or toxic electrolytes.

They also promise similarly high energy densities and capacities as lithium-ion cells.

Manfred Lindinger

Editor in the department "Nature and Science".

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However, the zinc battery is still a long way from being ready for the market.

One reason is the low stability and the associated limited service life.

Because of their great potential, numerous research groups have set themselves the goal of eliminating the weak points and helping the zinc-ion battery to achieve a breakthrough.

A zinc-ion battery consists of an anode made of metallic zinc and a cathode made of manganese or vanadium dioxide as well as an aqueous electrolyte, usually a saline solution.

When discharging, the anode releases zinc ions, which migrate through the electrolyte to the opposite electrode.

When loading, the process is reversed.

problem of corrosion

One of the biggest challenges is still the risk of corrosion of the zinc anode when it comes into contact with the aqueous electrolyte, write two battery researchers from the University of Bremen in "Nature Communications".

An indication of this is the evolution of hydrogen.

Because active zinc is lost during corrosion, capacity and energy density decrease over time, shortening service life.

Added to this is the formation of so-called dendrites during frequent recharging.

As a result of electrochemical processes, long, pointed zinc crystals are formed on the negative electrode.

These dendrites also reduce the active zinc of the anode and - this is the greatest danger - trigger a short circuit when they come into contact with the opposite cathode, which destroys the battery.

With protective layers on the zinc anode and a special design of the electrode, the researchers hope to reduce the risk of corrosion and dendrite formation.

Researchers at the Naval Research Laboratory in Washington recently succeeded in doing this with a porous metal foam made of zinc, which they used as an anode material.

Another parameter is the electrolyte – usually a zinc salt dissolved in water.

Chinese researchers from Tianjing University were able to suppress dendrite formation with a non-flammable organic electrolyte.

The liquid, consisting of an aqueous zinc salt and an alcohol solvent, formed a protective layer on the zinc anode, as Daliang Han and his colleagues write in "Nature Sustainability".

Their prototype has already survived around 4000 charging and discharging cycles without damage.

The capacity per active area is already in the range of the lithium battery.

The task now is to further optimize the zinc-ion battery.