Revealing Chemical Processes Involved in Electrochemical (De)Lithiation of Al with in Situ Neutron Depth Profiling and X-ray Diffraction

Herein we report a direct measurement of Li transport in real-time during charge and discharge process within an Al matrix using neutron depth profiling (NDP). In situ NDP was used to reveal and quantify parasitic losses during the first 25 mAhr/g of lithiation, followed by the formation of LiAl protrusions from the surface of pristine Al. Evidence of Li entrapment is also reported during delithiation. Subsequent lithiation and delithiation showed electrochemical charge passed to be equivalent to the amount of lithium incorporated into the Al matrix with negligible difference, suggesting that the parasitic losses including the formation of the solid electrolyte layer may be confined to the first lithiation. Parallel in situ XRD measurements also confirm the transformation of β-LiAl from a solid solution of α-LiAl, revealing solid solution-mediated crystallization of β-LiAl.