Negative muon spin rotation and relaxation on Li metal

In order to study the effect of muonic-Li on the mu-SR spectrum for Li battery materials, the transverse field (TF) mu-SR spectra have been measured for natural Li metal and Li-6 metal samples in the temperature range between 5 and 300 K. Here, TF denotes the magnetic field perpendicular to the initial mu(-) spin polarization. For both samples, the TF-mu SR spectrum showed a clear oscillation without relaxation down to the lowest temperature measured: i.e., about 5 K. This clearly excludes the scenario that the muonic-Li starts to diffuse at a certain temperature between 5 and 300 K. Although the mechanism on such a zero TF relaxation rate is not fully understood, we could ignore the contribution from the muonic Li on the asymmetry spectrum for the Li-ion battery materials at temperatures above 5 K.