Scientists show point defects in cathode crystals may speed lithium absorption

phys.org | 10/30/2017 | Staff
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Here's a case where detours speed up traffic. The result may be better batteries for transportation, electronics and solar energy storage.

Scientists at Rice University's Brown School of Engineering have discovered that placing specific defects in the crystalline lattice of lithium iron phosphate-based cathodes broadens the avenues through which lithium ions travel. Their theoretical calculations could improve performance up to two orders of magnitude and point the way to similar improvements in other types of batteries.

Defects - Antisites - Atoms - Positions - Lattice—that

These defects, known as antisites, are formed when atoms are placed at the wrong positions on the lattice—that is, when iron atoms sit on the sites that should be occupied by lithium. Antisite defects impede lithium movement inside the crystal lattice and are usually considered detrimental to battery performance.

In the case of lithium iron phosphate, however, the Rice researchers discovered they create many detours within the cathode and enable lithium ions to reach the reaction front over a wider surface, which helps improve the charge or discharge rate of the batteries.

Research - Nature - Computational - Materials

The research appears in the Nature journal Computational Materials.

Lithium iron phosphate is a widely used cathode material for lithium-ion batteries and also serves as a good model system for studying the physics underlying the battery cycling process, said Rice materials scientist Ming Tang, who carried out the research with alumnus Liang Hong, now a researcher at MathWorks, and graduate student Kaiqi Yang.

Insertion - Cathode - Changes - Phase - Tang

Upon lithium insertion, the cathode changes from a lithium-poor phase to a lithium-rich one, said Tang, an assistant professor of materials science and nanoengineering. When the surface reaction kinetics are sluggish, lithium can only be inserted into lithium iron phosphate within a narrow surface region around the...
(Excerpt) Read more at: phys.org
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