Zinc-air batteries
Why in News?
Zinc-air batteries are in the news following a major technological breakthrough by Indian scientists at SASTRA Deemed University.
About
- Supported by the Department of Science and Technology (DST), the team successfully engineered a patented "nanofluid electrolyte" and a low-cost catalyst.
- This breakthrough solves the long-standing industry problems of anode corrosion, hydrogen gas waste, and slow oxygen reactions without relying on expensive noble metals like platinum or ruthenium.
Mechanism & Working
- Anode: Uses metallic zinc powder as the negative electrode.
- Cathode: Uses a porous catalytic structure that pulls oxygen directly from the surrounding atmospheric air.
- Electrolyte: Employs a non-toxic, water-based (aqueous) alkaline solution, typically potassium hydroxide.
- Chemical Reaction: Electricity is generated via the chemical oxidation of zinc at the anode and the reduction of atmospheric oxygen at the cathode.
Major Advantages
- High Energy Density: They can store significantly more energy than traditional batteries because the cathode reactant (oxygen) does not need to be stored inside the cell, saving vast weight and space.
- Exceptional Safety: The water-based chemistry makes them inherently non-flammable, entirely eliminating the thermal runaway and fire risks associated with lithium-ion batteries.
- Cost-Effectiveness: Zinc is highly abundant and easy to source. These batteries cost roughly USD 150 per kWh, compared to USD 200–250 per kWh for lithium-ion systems.
- Sustainability Eco-Friendly: The latest Indian innovation upcycles discarded household water filters and surgical masks into battery carbon materials, making it a stellar green technology.
Technical Challenges
- Limited Rechargeability: Reversing the oxidation reaction is chemically difficult, often causing uneven zinc replating and dendrite formation that short-circuits the cell.
- Environmental Sensitivity: The cells are prone to drying out or absorbing carbon dioxide from the air, which degrades performance and limits overall battery lifespan.
- Low Efficiency: Heavy charging-to-discharging voltage gaps can lower cycle energy efficiency to around 50% in standard designs.
Primary Applications
- Small Electronics: Widely utilized in non-rechargeable button cell forms for hearing aids, medical sensors, and watches.
- Electric Mobility: Being developed for electric two-wheelers and three-wheelers via both electrically and mechanically rechargeable (swapping out zinc plates) systems.
- Grid-Scale Storage: Positioned as an ideal alternative for long-duration stationary energy backup and renewable energy integration due to their low cost and complete safety.
