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)