New Cathode Material For Lithium-Ion Batteries | Chemical & Engineering News
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Web Date: October 3, 2013

New Cathode Material For Lithium-Ion Batteries

Batteries: Material made of abundant elements could increase the capacity of rechargeable batteries
Department: Science & Technology
News Channels: Materials SCENE
Keywords: batteries, lithium-ion, energy storage, rechargeable batteries, cathodes
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Pyramid Power
An iron nitridophosphate cathode material consists of Fe2O9 octahedra (brown) and P3O9N6- pyramids (green). The gray and blue dots represent sodium ions at different positions in the crystal lattice. In the cathode material for lithium batteries, all of the sodium ions are removed, and lithium ions take up residence in the blue sites.
Credit: Chem. Mater.
Illustration of iron nitridophosphate crystal structure
 
Pyramid Power
An iron nitridophosphate cathode material consists of Fe2O9 octahedra (brown) and P3O9N6- pyramids (green). The gray and blue dots represent sodium ions at different positions in the crystal lattice. In the cathode material for lithium batteries, all of the sodium ions are removed, and lithium ions take up residence in the blue sites.
Credit: Chem. Mater.

Between charges, an electric vehicle can travel only as far as its rechargeable lithium-ion battery allows it. And those batteries can only pack so much energy into a given volume. Making the batteries bigger would add weight to cars and be counterproductive. Now researchers have demonstrated a new battery cathode material that could potentially pack more charge into the same mass (Chem. Mater. 2013, DOI: 10.1021/cm402567e).

Peter G. Khalifah, a chemist at the State University of New York, Stony Brook, and Brookhaven National Laboratory, and his colleagues wanted to develop a cathode material that had good electrochemical properties and did not contain rare-earth elements, which are expensive and limited in supply. They started with an iron nitridophosphate, a compound of sodium, iron, phosphorous, oxygen, and nitrogen—all earth-abundant elements. They ground the material into a powder, mixed it with a powder of lithium bromide, and heated the mixture under a flow of nitrogen gas. During the heating, the lithium ions replaced the sodium ions. The researchers used the resulting material as a cathode in a battery and measured the material’s energy capacity as 125 mAh/g. Today’s lithium-ion batteries top out around 150 mAh/g.

Khalifah says this is just a first step in demonstrating this new material system for battery cathodes. Altering the structure of phosphorus groups in the material could produce a cathode material with a theoretical energy density upwards of 200 mAh/g, he says.

 
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