In a significant development for the electric mobility and the larger stationary battery storage ecosystem in India, researchers at the Indian Institute of Technology, Madras, are developing mechanically-rechargeable zinc-air batteries as an alternative to lithium-ion (Li-ion) batteries.
(Image above of Dr. Aravind Kumar Chandiran (Centre), Assistant Professor, Department of Chemical Engineering, IIT Madras, and the research team with zinc air)
After filing for patents, these researchers under Dr Aravind Kumar Chandiran, assistant professor at the Department of Chemical Engineering, IIT-Madras, are collaborating with major industries to develop these zinc-air batteries. Compared to existing Li-ion batteries, the researchers at IIT-Madras claim that their zinc air counterparts have a long shelf life, are cheaper, safer and can be used in both two and three-wheeler electric vehicles (EVs).
“In our laboratory at IIT-Madras, we have invented low-cost and safe metal-air battery systems and that metal is based on zinc. These metal-air batteries are nearly three times cheaper even at the scale at which we have developed them. Also, the technology has been developed in-house. We have abundant amounts of zinc within the country, which makes it unique. India will own the technology and have the safest technology for its next-generation energy storage systems. These batteries can potentially be used in EVs for low powered applications like two-wheelers and three-wheelers and also stationary energy storage systems,” says Dr Chandiran.
“Speaking of stationary energy storage, solar energy is available during the daytime, and that energy peaks around midday and weans off towards the end of the day. To store that excess energy which is available at mid-day, we use batteries. So far we have options based on lead-acid or lithium-ion battery technologies. But India doesn’t own any of these technologies, so we will have to move to our in-house technologies with resources available domestically. Zinc is found abundantly in India and we are also one of its largest producers,” he adds.
Coming back to EVs, Li-ion batteries are currently the most popular choice. However, countries like China are dominating the global Li-ion battery manufacturing sector. Many OEMs in India import their Li-ion battery cells either from China, South Korea or Western Europe because battery-grade lithium isn’t widely available in India. Further, the diverse requirements of the Indian market cannot be fully met by lithium-ion batteries alone.
“Our research group is developing a futuristic model for zinc-air batteries for EVs. Through this research, we are also identifying shortcomings in existing technology and finding ways to address them. The research team has currently developed zinc-air cells and is working towards developing zinc-air packs for EVs. The elements involved in this battery cell are Zinc (anode), electrolyte (an aqueous system with potassium hydroxide) and a thin layer of platinum-coated gas diffusion layer (few mg /cm2). These zinc-air batteries use aqueous electrolyte and hence are inherently safe,” says Prof Chandiran in a conversation with The Better India.
Powering Zinc-Air Batteries
Akin to petrol stations for IC-engine vehicles, the researchers are mooting separate ‘Zinc Recharge Stations’. Based on ‘Battery-Swapping’ technology, EV users can swap used ‘zinc cassettes’ of the battery with fully-charged ‘zinc cassettes’ at these ‘Zinc recharge stations.’
Elaborating on this aspect, Dr Chandiran says, “This is a major advantage of the zinc-air batteries as currently the only option available with the lithium-ion batteries is that the entire used battery pack has to be removed and be swapped with a complete lithium-ion battery pack. This results in double the capital investment in the case of lithium-ion batteries.”
In other words, zinc-air batteries require only anode swapping and not the entire battery, like in the case of Li-ion.
“For a given vehicle, two Li-ion batteries have to be employed, one on the vehicle and another for charging. This adds to the capital expenditure. However, with zinc-air, it is the cheap anode that has to be replaced. These anodes have the shape of cassettes. Except for the anode, every other component is fixed with the vehicle. Only the anode cassettes are replaced. The anode is zinc, which upon discharging, converts to zinc oxide. Once the zinc oxide cassettes are pulled out, fresh zinc cassettes will be inserted into the vehicle. The spent zinc oxide cassettes would be regenerated using solar energy using electrochemical stations,” explains Dr Chandiran.
Meanwhile, Akhil Kongara, a research scholar at the institute and a research team member, said, “According to the proposed plan, an EV user will only have to spend a few minutes at the ‘zinc recharge stations’ to swap ‘zinc cassettes’.” Gunjan Kapadia, a research scholar who is also working on the operational safety of zinc-air and Li-ion batteries, added, “The indigenously developed zinc-air batteries, specifically in an Indian context, are extremely safe as it has aqueous electrolyte and it doesn’t catch fire even in a worst-case scenario of EVs accident.”
Advantages of Zinc-Air Batteries
The team at IIT Madras started researching and developing these Zinc Air batteries around three years ago. “The motivation was quite simple. It was to develop in-house technologies that offer low-cost energy storage and safe batteries,” explains Dr Chandiran.
As stated above, Zinc is widely available in India. This naturally would reduce dependence on countries like China or South Korea for Li-ion battery cells and thus lessen imports.
Also, as stated earlier, zinc is cheaper as compared to Li-ion batteries. Researchers note that while Li-ion batteries cost USD 200 to 250 a KWh, zinc-air batteries cost around USD 150 KWh. With wider usage, the price is expected to come below USD 100 KWh. These batteries are water-based, have a longer shelf life and have good turnaround efficiency, they add.
“Zinc-air batteries can offer better range. We are still testing their cycle life, but expect them to serve for a couple of thousand cycles. They don’t require a dry atmosphere to fabricate batteries like Li-ion batteries. Zinc-air batteries can also be fabricated in ambient conditions, and so there is less investment in CAPEX. They are yet to be tested on the road,” explains Dr Chandiran.
“We are working with OEMs and expect to put them on the road after a couple of tests. Optimistically, we would require two years before we see a fruitful outcome on the road, as we would like to do rigorous testing before we employ them in vehicles,” he adds.
Besides zinc-air batteries, there are other alternatives that are being considered for the Indian EV market. For example, there is sodium-ion, which experts believe is “cheaper than lithium-ion cells by about 30-40%”. Besides cheaper costs, there are other advantages associated with sodium-ion like its availability in India, battery capacity, and impact on the environment.
In developing zinc-air batteries, researchers at IIT-Madras have offered India another option for self-sufficiency in fulfilling its electric mobility and stationary battery storage requirements.
(Edited by Vinayak Hegde)
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