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Superior batteries for laptops, smartphones in the offing

Monday, Feb 8, 2016,17:08 IST By Metrovaartha A A A

New York | Scientists, including those of Indian-origin, have developed a new way to use rechargeable lithium metal batteries at room temperature, an advance that may lead to far superior portable energy storage devices to power smartphones and laptops.

Rechargeable lithium metal batteries offer better energy storage capabilities than today’s workhorse lithium-ion technology that are used in our smartphones and laptops. However on being recharged, they spontaneously grow bumps called dendrites on the surface of the negative electrode.

This makes it difficult to use these batteries in smartphones and laptops. With the new technology developed at the Cornell University in US, creating a highly efficient lithium metal battery for a cellphone or other device could be reality in the near future. Current technology focuses on managing the dendrites by putting up a mechanically strong barrier, normally a ceramic separator, between the negative and the positive electrodes to restrict the movement of the dendrite.

The relative non-conductivity and brittleness of such barriers, however, means the battery must be operated at high temperature and are prone to failure when the barrier cracks.

Researchers, led by professor Lynden Archer and graduate student Snehashis Choudhury, found that by designing nanostructured membranes with pore dimensions below a critical value, it is possible to stop growth of dendrites in lithium batteries at room temperature.

Archer credits Choudhury with identifying the polymer polyethylene oxide (PEO) as particularly promising. The idea was to take advantage of ‘hairy’ nanoparticles, created by grafting PEO onto silica to form nanoscale organic hybrid materials (NOHMs) to create nanoporous membranes.

To screen out dendrites, the nanoparticle-tethered PEO is cross-linked with another polymer, polypropylene oxide, to yield mechanically robust membranes that are easily infiltrated with liquid electrolytes.

This produces structures with good conductivity at room temperature while still preventing dendrite growth, said researchers, including doctoral students Rahul Mangal and Akanksha Agrawal, also from Cornell. Instead of a ‘wall’ to block the dendrites’ proliferation, the membranes provided a porous media through which the ions pass, with the pore-gaps being small enough to restrict dendrite penetration, Choudhury said.

With this membrane design, we are able to suppress dendrite growth more efficiently than anything else in the field, Archer said. The membrane can be incorporated with batteries in a variety of form factors, since it’s like a paint  and we can paint the surface of electrodes of any shape, Choudhury said.

The structures can be as effective with batteries based on other metals, such as sodium and aluminium, that are more earth-abundant and less expensive than lithium and also limited by dendrites, Archer said.

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