Researchers Use NMR Spectroscopy to Observe Dendrite Formation on Li Metal Anodes

An international team of researchers from Stony Brook University (US); CSIRO (Australia); and University of Cambridge (UK) have developed a method to use in situ NMR spectroscopy to provide time-resolved, quantitative information about the nature of the metallic lithium deposited on lithium-metal anodes—i.e., dendrite formation. A paper on their work was published online 16 May in the journal Nature Materials.

Lithium metal has the highest volumetric and gravimetric energy density of all negative-electrode materials when used as an electrode material in a lithium rechargeable battery. However, the formation of lithium dendrites and/or ‘moss’ on the metal electrode surface can lead to short circuits following several electrochemical charge–discharge cycles, particularly at high rates, rendering this class of batteries potentially unsafe and unusable owing to the risk of fire and explosion.

Many recent investigations have focused on the development of methods to prevent moss/dendrite formation. In parallel, it is important to quantify Li-moss formation, to identify the conditions under which it forms. Although optical and electron microscopy can visually monitor the morphology of the lithium-electrode surface and hence the moss formation, such methods are not well suited for quantitative studies.

—Bhattacharyya et al.

Scientists have use theoretical models and optical and scanning electron microscopes to study dendrite formation, but finding a way of quantifying the amount of dendrites formed has proved elusive until now.

Fire safety is a major problem that must be solved before we can get to the next generation of lithium-ion batteries and before we can safely use these batteries in a wider range of transportation applications. Now that we can monirtor dendrite formation inside intact batteries, we can identify when they are formed and under what conditions. Our new method should allow researchers to identify which conditions lead to dendrite formation and to rapidly screen potential fixes to prevent the problem.

—Prof. Clare Gray

Last month Professor Grey was awarded the Royal Society of Chemistry’s John Jeyes Award in recognition of her world leadership role in using NMR methods to study structure and function in inorganic materials, particularly lithium-ion batteries.

Resources

• Rangeet Bhattacharyya, Baris Key, Hailong Chen, Adam S. Best, Anthony F. Hollenkamp & Clare P. Grey (2010) In situ NMR observation of the formation of metallic lithium microstructures in lithium batteries. Nature Materials doi: 10.1038/nmat2764