What's Causing The Voltage Fade In Lithium-rich NMC Cathode Materials?

Researchers led by a University of California San Diego team have published work in the journal Nature Energy that explains what's causing the performance-reducing "voltage fade" that currently plagues a promising class of cathode materials called Lithium-rich NMC (nickel magnesium cobalt) layered oxides.

The dislocations are extra atomic layers that don't fit into the otherwise perfectly periodic crystal structure," said Andrej Singer, the lead author who performed this work as a postdoctoral researcher at UC San Diego. "Discovering these dislocations was a big surprise: if anything, we expected the extra atomic layers to occur in a completely different orientation," said Singer, who is now on the faculty at Cornell University. By combining experimental evidence with theory, the research team concluded that the nucleation of this specific type of dislocation results in voltage fade.

The research described in the Nature Energy paper could eventually lead to new cathode materials for solid state batteries. Many researchers, including Meng, consider solid state batteries to be one of the most promising future battery approaches. Lithium-rich NMC cathodes, for example, operate at high voltage and therefore could eventually be paired with solid state electrolytes, which also operate at high voltage. Much of the interest in solid state batteries comes from the fact that solid state electrolytes are believed to be safer than the traditional liquid electrolytes used in Lithium-ion rechargeable batteries.

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