Zinc-air batteries have spent years as one of clean energy’s most tantalising “almost” technologies — cheap, safe, water-based, and built from abundant materials, but held back by two stubborn chemistry problems that kept them from being genuinely rechargeable at scale. A team at SASTRA Deemed University in Thanjavur has just published a low-cost fix for both, using materials as unglamorous as silica, zinc oxide nanoparticles, and recovered carbon from spent household water filters.
The Department of Science and Technology (DST) announced the findings on 24 July 2026. The core innovation, developed under DST’s Nano and Advanced Materials Division and led by Dr. S. Devaraj, is what the researchers call a “nanofluid electrolyte” — an otherwise standard battery electrolyte with a very small amount of inexpensive silica and zinc oxide nanoparticles dispersed into it. The technology has already been granted an Indian patent (IN570691) and is described as ready for use.
Why Zinc-Air Batteries Matter, and Why They’ve Stalled
An electrically rechargeable zinc-air battery works by drawing oxygen from the surrounding air to react with zinc at one electrode, generating electricity — and, crucially, reversing that reaction to recharge, rather than requiring the battery to be physically swapped out. On paper, zinc-air chemistry offers a high theoretical energy density, low material cost, and — because it uses water-based electrolytes rather than the flammable organic solvents in lithium-ion cells — a fundamentally safer battery. For a country like India trying to scale up battery storage without importing scarce lithium, cobalt, and nickel, that combination is exactly what a “next-generation green battery” needs to look like.
The catch has always been two linked engineering problems. At the zinc electrode, unwanted hydrogen gas evolves during operation, wasting charge and corroding the zinc itself. At the air-cathode, the oxygen reactions needed to both discharge and recharge the battery are sluggish, and historically only expensive catalysts made from platinum or ruthenium have been able to speed them up enough to be practical. Fixing one problem in isolation is well understood; fixing both at once, cheaply, is what has kept zinc-air rechargeables largely in the research stage rather than the market.
One Intervention, Two Problems Solved
The SASTRA team’s nanofluid electrolyte tackles both issues simultaneously. The dispersed silica and zinc oxide nanoparticles suppress the hydrogen evolution reaction and inhibit zinc corrosion at the anode, while also enhancing the oxygen reaction performance at the cathode — solving what had been treated as two separate electrode problems with a single, low-cost formulation. The electrolyte has demonstrated stability over three months, and the researchers say it’s directly applicable to the zinc-air battery industry, relevant both to grid-scale storage and to supporting electric mobility.
The team didn’t stop at the electrolyte. On the catalyst side — the other historically expensive piece of the zinc-air puzzle — the researchers identified α-MnO₂ (a manganese oxide) as a strong-performing, non-precious-metal catalyst for driving both the oxygen reduction and oxygen evolution reactions the battery needs to charge and discharge. Doping that catalyst with a small amount of copper — just 2 weight percent — pushed its performance beyond commercial platinum- and ruthenium-based benchmarks, according to the DST release.
Perhaps the most quietly striking detail is where some of the electrode material came from: the team recovered spent activated carbon from exhausted household water filters and hydrothermally converted it into manganese-oxide-carbon nanocomposites, turning what would otherwise be discarded filter waste into functional battery electrode material.
From Lab Result to Grid and Road
Grid-scale battery storage is one of the biggest remaining bottlenecks in renewable energy deployment worldwide — solar and wind generate power intermittently, and without affordable, safe storage to smooth that out, grids either need backup fossil generation or accept curtailment of clean power that has nowhere to go. Zinc-air batteries, with their lower cost and inherent safety compared to lithium-ion, have long been seen as a promising candidate for exactly this kind of stationary storage, where energy density matters less than cost and safety.
The relevance to electric mobility is a longer-term proposition — zinc-air’s lower energy density compared to lithium-ion makes it a less obvious fit for passenger vehicles in the near term, but a more plausible one for applications like e-rickshaws, backup power, or fixed installations where weight and volume are less constrained. What this research demonstrates is that a working, patented, published solution to zinc-air’s core engineering problems can come out of an Indian university lab — not just an import from an established EV or storage giant.
As with any lab-stage battery breakthrough, the road to commercial deployment involves scaling manufacturing, validating performance across far more demanding real-world conditions, and building a supply chain around it — a process that typically takes years even for the most promising chemistries. But a granted patent and a “ready for usage” designation from the researchers themselves suggest this one has moved further along that path than most.
For India’s sustainable energy transition — which increasingly depends on storage as much as generation — a safer, cheaper zinc-air battery chemistry that solves its own scaling problem with silica, zinc oxide, and recycled filter carbon is precisely the kind of unglamorous materials science that determines whether renewable power actually reaches the grid when it’s needed, not just when the sun is shining or the wind is blowing.
Source: Press Information Bureau, Government of India — Slew of technologies developed to enable electrically rechargeable Zinc-air batteries