Transitioning to renewable energy across society will require many changes, including more batteries. Energy storage is crucial for making sure that inconsistent renewable sources, like wind or solar, can stay humming even when the weather isn't going their way. But batteries have their own problem in the form of the commonly used lithium. Researchers at the Indian Institute of Technology (IIT) Madras have come up with what could be a possible replacement: a rechargeable iron ion battery that uses mild steel as the anode.

“The major limitations of lithium-ion batteries are the unavailability of lithium in conjunction with the safety issues," said M.V. Sangaranarayanan, a chemistry professor at IIT Madras, in a recent talk. "It is hence imperative to look for new and abundantly available electrode materials in order to make the energy storage devices commercially viable, devoid of safety limitations."

Lithium, in many ways, is the dirty secret of many environmental efforts. Analysts have called electric car company's demand for lithium "increasingly ravenous," and the mineral is used in everything from smartphones to glass ceramics to airbag ignitions.

But while lithium mining is relatively cheap, it comes with huge downsides. When brine mining, miners need to let the water surrounding lithium evaporate in order to reach it, which means using 500,000 gallons of water per tonne of lithium. And when digging the mineral out of rock, it requires toxic chemicals, which can lead to disastrous results.

So the need for an alternative is a pressing one, and iron could be a strong option.

“Iron has favorable physico-chemical properties like lithium,” Ramaprabhu Sundara, an IIT Madras physics professor, told The Hindu. "The redox potential of iron ion is higher than lithium ion and the radius of the Fe2+ ion is nearly the same as that of the lithium ion."

Redox refers to "reduction potential," or the tendency for a chemical substance to lose or gain electrons and have their effectiveness lowered.

"These two favorable properties of iron have been overlooked for so many years. And that’s the reason why we don’t have iron ion rechargeable batteries,” Ramaprabhu says.



The team's iron battery successfully withstood 150 cycles of charging and discharging under controlled conditions. And after 50 cycles, it still had 54 percent capacity retention, which is a sign of stability.

“Iron is more stable during the charging process and therefore prevents short-circuiting of the batteries," study coauthor Sai Smruti Samantaray, a Ph.D. student at IIT Madras, told The Hindu. "Thus, when compared with the popular lithium metal-based batteries, we are able to cut down the cost and make it safer to handle."

The next step for the team is to increase the iron battery's performance. One challenge could be cathodes, or the way currents move out of a battery. While cathodes can be replaced in some batteries, that's not the case in iron.

“We are trying out different metal oxides to increase the amount of iron ions that can bind to the cathode," said Ajay Piriya,a Ph.D. student at IIT Madras and the first author of the paper showing the team's findings. "When more iron ions bind to the cathode, more energy can be stored in the battery, leading to improved performance."

There's a global hunt for the next lithium battery. Even the creator of the original lithium battery, 97-year old John Goodenough, has developed an improvement.

Source: The Hindu

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