Indian Scientists Develop Low-Cost Electrolyte for Zinc-Air Batteries

Researchers say the approach is directly relevant to zinc-air battery manufacturing and may be useful in grid-scale storage systems.

Scientists at SASTRA Deemed University in Thanjavur have developed a nanofluid electrolyte that could make rechargeable zinc-air batteries safer, cheaper and more efficient for renewable energy storage and electric mobility. Supported by the Department of Science and Technology's Nano and Advanced Materials Division, the technology is protected by Indian patent IN570691 and has remained stable for more than three months, making it suitable for possible industrial use.

One electrolyte tackles two battery problems

Rechargeable zinc-air batteries are attracting interest because they use water-based chemistry, offer high theoretical energy density and could provide a lower-cost alternative to lithium-ion batteries. Their wider use has been limited by two major challenges. Zinc electrodes can corrode and produce unwanted hydrogen gas, wasting charge, while oxygen reactions at the air cathode are slow and often require costly platinum or ruthenium catalysts.

The team led by Dr S. Devaraj addressed the problem by adding small quantities of inexpensive silica and zinc oxide nanoparticles to a standard electrolyte. This created a nanofluid electrolyte that suppresses hydrogen production and zinc corrosion while improving oxygen reaction performance at the cathode.

Better performance without costly inhibitors

Conventional zinc-air batteries use expensive corrosion inhibitors to protect zinc. These chemicals can slow the oxygen reaction at the cathode, creating a trade-off between protection and performance.

The new electrolyte avoids that compromise by improving both sides of the battery through one lower-cost intervention. Researchers say the approach is directly relevant to zinc-air battery manufacturing and may be useful in grid-scale storage systems.

Reliable large-scale storage is increasingly important for renewable energy because it can retain electricity generated by solar and wind projects for use when supply falls.

Copper-doped catalyst beats commercial standards

The research team also developed affordable catalysts from readily available materials to improve oxygen reduction and oxygen evolution reactions.

Alpha manganese dioxide, or α-MnO2, delivered the strongest performance because of its open tunnel-like structure. Adding only 2% copper improved its activity beyond commercial benchmarks, outperforming platinum- and ruthenium-based standards in the tests described by the researchers. This could reduce dependence on precious metals, which remain one of the biggest cost barriers in advanced battery technologies.

Waste materials turned into battery components

Researchers also explored ways to turn waste into useful electrode materials. Spent activated carbon collected from household water filters was converted into manganese dioxide-carbon nanocomposites for battery catalysts and supercapacitor electrodes. This work is covered by a separate patent application.

Used surgical face masks were also chemically converted into activated carbon with a very high surface area and oxygen-reduction activity reported to rival platinum.

The researchers said these waste-derived materials could be adapted for other clean-energy technologies, while the nanofluid electrolyte concept may also be extended to other water-based battery systems.