The iron ion battery is cost-effective and can store a high amount of energy
Viable alternative? Iron ion battery has 55-60% of the lithium ion battery’s performance, says Ramaprabhu Sundara (right).
Indian Institute of Technology (IIT) Madras researchers have for the first time fabricated a rechargeable iron ion battery using mild steel as the anode. The iron ion battery is cost-effective and the amount of energy that can be stored in the battery is also high.
While lithium ions are the charge carriers in lithium ion battery, the Fe2+ ions perform that function in the case of iron ion battery.
With the world turning its attention to electric vehicles, the focus is on developing batteries that are cheaper. With no lithium reserves in India and shortage of lithium reserves in the world, the stress is on developing rechargeable batteries of comparable performance using materials other than lithium. And this is where the work of IIT Madras gains importance.
The team led by Ramaprabhu Sundara from the institute’s Department of Physics demonstrated the performance of an iron ion battery for up to 150 cycles of charging and discharging. With 54% capacity retention at the end of 50 cycles of charging and discharging, the battery display good stability. The results were published in the journal Chemical Communications.
When fabricated under controlled conditions, the amount of energy that can be drawn from the iron ion battery is 220 Wh per kg, which is 55-60% of lithium ion battery’s performance. The energy density of lithium ion battery is around 350 Wh per kg.
“We can fabricate the battery under ambient conditions too. Under such conditions, we get nearly 40% of lithium ion battery’s performance,” says Prof. Ramaprabhu. “The battery can also be cycled at high current densities so that energy can be drawn at a faster rate from the battery.”
“Iron has favourable physico-chemical properties like lithium,” he says. 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. “These two favourable properties of iron have been overlooked for so many years. And that’s the reason why we don’t have iron ion rechargeable batteries,” Prof. Ramaprabhu says.
In pure iron, the easy removal of iron ions from the anode and their reinsertion, which is an essential mechanism in battery operation, is not possible. However, small amount of carbon present in mild steel facilitates this process.
“Iron is more stable during the charging process and therefore prevents short-circuiting of the batteries. Thus, when compared with the popular lithium metal-based batteries, we are able to cut down the cost and make it safer to handle,” says Sai Smruti Samantaray a co-author of the paper and a PhD student at IIT Madras.
In iron ion battery, vanadium pentoxide is used as the cathode. Vanadium pentoxide was chosen as it has a layered structure with very large spacing between the layers.
“The large inter-layer spacing in vanadium pentoxide allows iron ions to easily move in and bind to the interlayers of the cathode and also easily get detached and move back to the anode,” says Ajay Piriya who is a PhD student at IIT Madras and the first author of the paper. “Vanadium pentoxide is already in use as a cathode in multivalent ion batteries.”
Finally, a different electrolyte was used — ether-based electrolyte containing dissolved iron perchlorate. “We tried different electrolytes including conventional ones and also a combination of different electrolytes. But we got the best result with ether-based solvent containing dissolved iron perchlorate. The iron perchlorate behaves like an ion-conducting medium between the anode and cathode,” says Ms. Samantaray.
The team is now focused on further improving the performance of the iron ion battery. Since the electrolyte cannot be changed, the researchers are trying out different cathode materials.
“We are trying out different metal oxides to increase the amount of iron ions that can bind to the cathode. When more iron ions bind to the cathode, more energy can be stored in the battery leading to improved performance,” says Ms. Piriya.
“We are currently working on other kinds of battery electrochemistry using iron as one of the electrodes. We are also trying to improve the stability of the battery,” he says.
Any change in irrigation policy has the potential to shift monsoon rainfall
The shortcoming: Till now, the models used widely for land-surface modelling have not been designed for Indian conditions.File photoRITU RAJ KONWAR
For the first time, researchers from the Indian Institute of Technology (IIT) Bombay have found that even a change in irrigation policy has the potential to shift monsoon rainfall and intensify extreme rainfall in India through its feedback to atmosphere. They have further found the reason behind the shift in the summer monsoon rainfall towards northwestern India and intensification of extreme rainfall over central India during the month of September.
It became possible to understand what causes the monsoon to shift and the role of irrigation as the researchers developed a module of land-surface model that takes into account the actual soil irrigation and agriculture pattern seen in India.
During the month of September, agriculture lands are highly irrigated and the crops are matured. As a result, there is maximum evapotranspiration taking place leading to highest contribution of moisture from the land to the atmosphere. “Till now, the models that have been used widely for land-surface modelling were not designed for Indian conditions,” says Subimal Ghosh from the Department of Civil Engineering at IIT Bombay and corresponding author of a paper published in Geophysical Research Letters.
“The models used so far considered that irrigation starts only when soil moisture is very low (permanent wilting point) and stops when it reaches slightly below saturated soil moisture state (field capacity)”
But the reality is otherwise — there is uncontrolled irrigation in India. And nearly 50% of crop area is covered by paddy where the fields are kept in submerged conditions. As a result, the contribution of moisture from the land to the atmosphere is very different from what is followed in the West, which is what the models used so far took into account.
“So we collaborated with Pacific Northwest National Laboratory to develop a land-surface model that takes into account the Indian conditions,” says Prof. Ghosh.
Several studies have already shown that irrigation contributes moisture to the Indian summer monsoon. But the IIT Bombay team along with researchers from Pacific Northwest National Laboratory and Oak Ridge National Laboratory have shown that whenever there is a change in the irrigation management, there is a change in the moisture feedback to the atmosphere.
The researchers considered three scenarios — no irrigation, irrigation that is based on soil moisture deficit h, and finally uncontrolled irrigation as seen in India.
The researchers found that as a result of excess irrigation over northern India, the summer monsoon rainfall in September shifts towards the northwestern part of the country. There is also intensification of extreme rainfall over central India during September.
Land-surface processes including irrigation affect the heat fluxes — temperature related and evapotranspiration. Modified heat fluxes along with changes in atmosphere moisture content and distribution result in a shift in rainfall towards northwestern part of the country and increased extreme rainfall over central India during September.
The study has not looked at how irrigation and agriculture influence monsoon in southern India.
“Rainfall increasing the moisture content in soil is well known and can be visualised. But soil moisture contributing to the atmosphere cannot be visualised easily and is therefore neglected,” points out Prof. Ghosh.
“Our analysis underlines why the soil to atmosphere feedback cannot be neglected. Each of the component — atmosphere and hydrology — have to be coupled together to understand the system in full.”
“Any land-surface model used for India should take into account Indian irrigation and agriculture system. Otherwise, we will not add value and will come up with incorrect results,” he says.
“We need more detailed irrigation data for southern India to perform much better analysis of land-surface feedback of human-natural systems,” he says.
The study informs management of cancer because a tumour needs both blood and lymph to grow and spread
Morphing cells: Up to 20% of blood vessels in tumours were derived from cancer stem cells, says T.S. Ganesan (sitting)
The role of cancer stem cells in maintaining and spreading a tumour has remained a hypothesis until recently. Now, a group of researchers from Cancer Institute (WIA), Chennai, have shown that in a common type of ovarian cancer, cancer stem cells can morph into special cell types that build tiny bunches of blood vessel within the tumour.
Further, the team also found that cells making up lymph vessels, another essential component of the tumour which aids in spreading the tumour (metastasis), can be made by the cancer stem cells. The study also indicates that a certain factor — vascular endothelial growth factor (VEGF) — could be responsible for this morphing (trans-differentiation) of the stem cells. The study was published in the journal Angiogenesis.
Epithelial ovarian cancers are about 85% of all ovarian cancers. And the researchers studied the most common epithelial ovarian cancer subtype — high-grade serous adenocarcinoma of the ovary.
Targeting stem cells
Cancer stem cells are small in number in the tumour but are perhaps the most difficult ones to target as they resist chemotherapy and radiation. They are also responsible for the relapse of cancer. Hence, there is immense interest in studying these types of cell and how they can be targeted for management of cancer.
Blood vessels are tubes lined on their inner sides by endothelial cells and on the outer by pericytes. The walls of a lymph vessel, which transports fluids through the body, are only lined by endothelial cells.
“The origin of components of a blood vessel — endothelial cells and pericytes — in primary malignant cells from ovarian tumours has been established in our study. Up to 20% of the blood vessels in the tumours were derived from the cancer stem cells,” says Prof. T.S. Ganesan, from Cancer Institute (WIA), Chennai, who led the study. “This is the first study to make this connection between lymphatic endothelial cells and the stem cells,” he adds.
The researchers established the connection in several steps. The first indicator was the proximity of the cancer stem cells and the blood vessels. Secondly, specific genetic mutations observed in the stem cells were also present in the endothelial cells.
When cancer stem cells are grown in the lab (in vitro) in a three-dimensional matrix, they form spherical structures referred to as spheroids. The cancer stem cells when grown under specific conditions are seen to develop into endothelial cells, pericytes and lymphatic endothelial cells.
“We found that the cells grown under specific conditions showed functional features of normal blood vessels such as formation of tubes,” said S. Krishna Priya, first author of the study, in an email. “We also identified a growth factor (VEGF), which is already known to play a major role in the growth of blood vessels. This is also important for cancer stem cells becoming endothelial cells,” she explained.
The spheroids were labelled with green fluorescent protein and injected into mice. “Since the spheroids were labelled, the tumours formed by these cells would glow green and hence, the blood vessels too. We found that the blood vessels and lymphatic vessels in mouse tumours showed the green fluorescence, suggesting that they are derived from cancer stem cells,” says Ms Krishna Priya.
The study has implications for management of cancer because a tumour needs supply of both blood and lymph to grow and spread. So targeting the cancer stem cells can curtail both. The study also suggests that drugs that inhibit the growth factor may be more effective clinically.