Salt of the earth (and sea) for renewable energy storage

Global energy use is soaring. A modernizing world is spurring economic development, and with it the alleviation of poverty and more human well-being. The advance depends on energy — from fossil fuels (oil, coal and natural gas); nuclear power; and solar, hydro and wind systems. The scale of the energy requirement, measured in terawatt-hours per year (a terawatt is a unit of power equal to 1 trillion watts), is massive — estimated at 157,063.77 TWh/year in 2018.

Today, the world’s primary energy source is fossil fuel. This has environmental impacts — emitting toxic gases like SO₂, SO₃, CO and CO₂— and a resultant effect on climate change. That’s why the world is striving to meet the challenge of combining global development with a sustainable environment through the use of such renewable energy sources as the sun and wind.

The global grid infrastructure has to store this energy so it can be available for transmission on demand. Lithium-ion batteries have emerged as a vital storage medium due to their high energy/power density, long cycle life and lightweight portability. But lithium is scarce and expensive — this makes it particularly difficult to scale up storage for high-power applications.

Our work at the Purdue ViPER (Vilas Pol Energy Research) lab is focused on using sodium-ion batteries as an alternative, taking advantage of sodium’s low cost and natural abundance. The use of sodium-ion batteries as an electrochemical storage device stands out for its cost advantage over lithium due to the widespread geographical distribution of sodium in the Earth’s crust and seawater.

The trick is making sodium-ion batteries more efficient. We’ve developed a new powder version of the sodium material that addresses the problem of loss during initial battery charging. Sodium-ion batteries have encountered obstacles due to the loss of some sodium ions that stick on the surface during migration into the hard carbon anode; our sodium-powdered version fixes that problem. We also synthesized our anodes via an upcycling process from waste materials like used packing peanuts, plastics, and tires, mitigating the need to dispose of these goods.

Our lab is developing novel carbon and carbon-alloy materials with microstructure changes that increase anode capacity and reduce anode weight. We’re using advanced microscopy and spectroscopy techniques (such as transmission electron, atomic force and light microscopy and Raman spectroscopy) to investigate things like phase transformation — transitions between different states of matter — to improve the efficiency of sodium-ion anodes and batteries.

Overall, our use of sodium powder as an electrode additive has shown promising enhancement of battery performance. We have filed several U.S. patents and published numerous articles for our additive and carbon particles and sheets. Our research team is collaborating with Faradion Ltd. in England, and our work is funded by Purdue’s Trask Innovation Fund.

As the world keeps providing progressively higher levels of technology and well-being to inhabitants across the globe, new technologies like sodium-ion batteries will help to sustainably address the growing energy storage needs for the continuous betterment of the global population.

How fitting it would be if a material like sodium, so prevalent on the Earth’s crust and in its seawater, would be vital to a sustainable future of renewable energy storage that helps to preserve our Earth and seas.

Vilas G. Pol, PhD

Associate Professor

Davidson School of Chemical Engineering

Head of the ViPER (Vilas Pol Energy Research) Group and Laboratory

College of Engineering, Purdue University

Manikandan Palanisamy, PhD

Postdoctoral Research Associate

ViPER Group and Lab

Davidson School of Chemical Engineering

College of Engineering, Purdue University

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