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Researchers believe they have taken steps towards utilizing water in a more efficient and quicker way to store and deliver energy.

A team from North Carolina State University compared a crystalline tungsten oxide with a layered, crystalline tungsten oxide hydrate—consisting of crystalline tungsten oxide layers separated by atomically thin layers of water.

They discovered that the tungsten oxide stored more energy than that the hydrate when charged for 10 minutes but when charged for only 12 seconds, the hydrate stored more energy.

 “The goal for many energy-storage researchers is to create technologies that have the high energy density of batteries and the high power of capacitors,” James Mitchell, a Ph.D. student at NC State and lead author of the paper, said in a statement. “Pseudocapacitors like the one we discuss in the paper may allow us to develop technologies that bridge that gap.”

The researchers said that the hydrate wasted less energy as heat, storing energy more efficiently.

“Incorporating these solvent layers could be a new strategy for high-powered energy-storage devices that make use of layered materials,” Veronica Augustyn, an assistant professor of materials science and engineering at NC State and corresponding author of the study, said in a statement. “We think the water layer acts as a pathway that facilitates the transfer of ions through the material.

“We are now moving forward with National Science Foundation-funded work on how to fine-tune this so-called 'interlayer,' which will hopefully advance our understanding of these materials and get us closer to next-generation energy-storage devices.”

According to the study, the kinetics of energy storage in transition metal oxides are usually limited by solid-state diffusion and the strategy most often utilized to improve their rate capability is to reduce ion diffusion distances by utilizing nanostructured materials. However, the researchers proposed to improve the kinetics of layered transition metal oxides by the presence of structural water.    

Augustyn said the discovery is a first step and more research is needed.

“This is a proof of concept but the idea of using water or other solvents to 'tune' the transport of ions in a layered material is very exciting,” she said.  

“The fundamental idea is that this could allow an increased amount of energy to be stored per unit of volume, faster diffusion of ions through the material, and faster charge transfer,” she added. “Again, this is only a first step, but this line of investigation could ultimately lead to things like thinner batteries, faster storage for renewable-based power grids, or faster acceleration in electric vehicles.”

The study was published in Chemistry of Materials.

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