These Batteries Could Store Five Times More Energy by Mimicking Human Intestines

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Researchers with University of Cambridge created a new type of battery promising longer storage thanks to its intestine-inspired design.

The prototype uses a lithium-sulphur battery cell rather than the traditional lithium-ion type. This would make the batteries energy-dense enough to last for extensive use.

villi[Image Courtesy of Teng Zhao/University of Cambridge]

Today, lithium-ion is the fastest growing and most promising battery chemistry. But a type of Lithium-ion rechargeable battery has taken precedence in recent years. They are Lithium–Sulphur (Sulfur) battery.

However, the lithium-sulphur batteries tend to degrade rapidly. To overcome this snag, researchers designed the next generation lithium-sulphur battery with as much as five times the energy density of a Lithium-ion by mimicking the structure of the cells which absorb nutrients.

The Cambridge Department of Material Science and Metallurgy researchers under the guidance of Dr. Vasant Kumar, partnering with Beijing Institute of Technology, developed and tested a lightweight nanostructured material which resembles villi. In the human body, intestinal villus is a numerous threadlike projection covering the surface of the mucous membrane lining the small intestine. Villi absorb the fluids and nutrients during digestion.

Lithium–Sulfur batteries dissolute and diffuse polysulfides in liquid organic electrolytes which hinder the energy storage. To trap and re-utilize the polysulfides without restraining Lithium ion conductivity, a bio-inspired, brush-like layer consisting of zinc oxide (ZnO) nanowires and interconnected conductive frameworks resembling the structure of villi, is placed on the surface of one of the battery’s electrodes.

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Basic structure of Lithium-ion battery:

It is made up of three components: an anode (negative electrode), a cathode (positive electrode) and an electrolyte in the middle. The general layered structured materials for the anode are graphite and lithium cobalt oxide for the cathode. Through the electrolyte, positively-charged lithium ions move back and forth from the cathode into the anode. However, the crystal structure of the electrode materials determines how much energy can be squeezed into the battery.

The design:

The villi layers are comprised of one-dimensional tiny zinc oxide nanowires. These form a very strong chemical bond with polysulphides. This allows for the active material to be used for a longer time, thus increasing the battery's lifespan. The high surface area fixes the active material to a conductive framework that makes it reusable.

The team ran trials on commercially available macroporous nickel foam as a conductive backbone. Later for practical applications, the foam was replaced by an ultra-light micro/mesoporous carbon (C) nanofiber mat to reduce the battery’s overall weight.

Though charging and discharging of battery has been improved, it is still not able to go through as many charge cycles as a Lithium-ion battery. In addition, a Lithium-Sulphur battery does not need to be charged as often as a Lithium-ion battery due to which the increase in energy density cancels out the lower total number of charge-discharge cycles. The batteries were designed for research purpose. However, commercially-available Lithium-Sulphur batteries are still years away.

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“It’s a tiny thing, this layer, but it’s important. This gets us a long way through the bottleneck which is preventing the development of better batteries,” said study co-author Dr. Paul Coxon from Cambridge’s Department of Materials Science and Meta.

To know more details refer Advanced Functional Materials.

Via University of Cambridge

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