We prepared a series of 8 different samples (Figure ). The results of the ILT for four samples measured at 10°C and 30°C is given exemplary in Figure . A pink box is drawn as guide for the eye. It marks the upper and lower T1 relaxation values for the LTO in EC/DMC at 30°C as reference (Figure , first row). The use of 1 M LiPF6 (Figure , second row) and 2 M LiPF6 (Figure , third row) result in a reduction of the bulk relaxation. The use of 1 M NaTfl (Figure , last row) shows the opposite effect. It is noteworthy that the lithium containing electrolytes cause an additional liquid-state Li NMR signal with a relaxation time of about 2s. It originates from solvated Li + in the electrolyte and can easily be separated in the relaxation time dimension. However, subtraction of this feature by using the pure electrolyte is not straightforward since weak features, most probably caused by Li ion exchange between electrolyte and LTO, lead to spectrally narrow signal components at relaxation times of Li ions in the solid. This is expected if Li ions exchange between the inversion pulse and the detection pulse, hence relax during part of the recovery delay in one environment and are detected in the other. We extract from these results in the aforementioned way the maxima distribution (Figure ) and the mean distribution (Figure ) of the T1 relaxation of each sample at a given temperature. The Mean distribution stays quite constant between 70s and 85s for the same sample (Figure , c, pink circles). Such a convergence of the maximum and mean indicates that the relaxation mode becomes more symmetric at increased temperatures, which can also be observed in Figure . The contact with an organic solvent consisting of dimethylcarbonate and ethylcarbonate (1:1 by volume), henceforth called electrolyte, without salt (0M, blue triangles, Figure ) resulted at 20°C in similar relaxation behavior as the dry material. It shows a change in the slope of the temperature dependence of the maximum distribution and the mean distribution. For both distributions of the 0M sample an increase in temperature results in a decrease in relaxation time (blue line, Figure ). Yet the effect is weak and will not be further discussed. We used a 1 M LiPF6 (1M_LiPF6, green diamonds, Figure ) solution with the same organic solvent as next eluent. It resulted in a significant reduction of the T1 relaxation time of the bulk Li signal for all temperatures. The maximum of the T1 relaxation time distribution at 30°C drops from 60.8s in 0M to 16.7s in 1M_LiPF6 sample, while the mean value drops from 82.4s to 56.9s. This is a general trend for all temperatures. The effect increases when going to a 2M LiPF6 solution (2M, red stars, Figure ). The relaxation time value at 30°C is 10s for the maximum and 40s for the mean value. Such a strong relaxation effect, which affects the whole T1 distribution of Li in LTO, is only plausible if Li in the LTO bulk is affected by a changing mobility or an altered strength of interactions responsible for relaxation, such as additional paramagnetic centers in the bulk. Additional mobile electrons in the bulk material could explain it. But their origin needs to be further addressed. Wilk ening e.g. showed that the small amount of additional lithium (Li + + e -) in Li4.1Ti5O12 caused a tremendous reduction in T1 relaxation time of Li and with this an increased mobility of lithium ions, due to more mobile electrons in the bulk material . To check whether the PF6 -anion has specific properties that cause this effect, we compared the results with LiTfl and LiTpb, which are two chemically very different electrolyte salts with non-coordinating anions (Figure ). All three anions are very weakly coordinating and have only the fluorine as element in common. Still the effect on the Li relaxation time was reproducible and seems therefore to be independent of the used anion (Figure ,c black X and orange cross). To further assure this effect is not induced by an irreversible surface modification e.g. due to the introduction of fluorine, we decantively washed the 1M sample of LiPF6 four times with the salt-free organic solvent. The resulting sample (washed, brown dot, Figure ) had strongly elongated relaxation time, close to the 0M sample. It shows the effect is at least to a major part reversible and, therefore, excludes irreversible surface modifications on the LTO nano particles to be responsible. Any additional mobile negative charges must therefore be from LTO itself.