By Gopal R. Rao
Lithium ion batteries (LIBs) are widely used in various
consumer electronic devices because of their large energy storage densities.
There is an even larger demand for more energy from LIBs that can be met by
using Li metal-containing negative electrodes instead of graphite anodes
currently used. One of the current problems with Li electrodes is that after
several charge/discharge cycles in non-aqueous electrolytes, dendritic Li
metal, sometimes called Li “moss,” forms on the Li-metal anode. Some of these
dendrites can fall off into the electrolyte. These floating Li fibers, along
with those on the electrode itself, cause various problems, including short
circuits and subsequent overheating. This issue needs to be resolved if
Li-metal anodes are to replace current graphite anodes. Various optical and
electron microscopy methods have been used to qualitatively study the formation
of the Li moss to better understand the mechanisms involved, but they have
proven to be unsatisfactory. A new study by Clare P. Grey, R. Bhattacharya and
others of Stony Brook University, University of Cambridge, and CSIRO,
Australia, now reports, in Nature
Materials, the use of in situ nuclear
magnetic resonance (NMR) for investigating the Li dendrite formation
during electrochemical cycling.
Credit: Nature Materials
The study showed that in situ NMR can dynamically
monitor the growth and stripping of these Li microstructures. Using simple
calculations based on the skin depth of the metallic structures, the amount of the
Li dendrites formed can be quantified using the change in the Li metal signal.
Two different ionic liquids were tested for their ability to prevent dendrite
formation. The results clearly showed that this technique can sensitively
monitor, with accuracy, the early stages of dendrite formation in Li batteries.
The method can be used to judge the efficacy of current strategies to prevent
the Li “moss” formation.
In situ NMR observation of the formation of metallic lithium microstructures in lithium batteries
Nature Materials Volume: 9, Pages: 504–510 (2010). DOI: 10.1038/nmat2764
_________________________________
Gopal R. Rao, Ph.D.
Web Science
Editor
Materials Research Society
(MRS)
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