*3.2. TBAC Solvent-Mixtures with LiBF*<sup>4</sup>

A total of1 M LiBF4 was investigated in TBAC:EC:EMC (80:15:5 wt). However, LiBF4 did not dissolve. It was not possible to cycle the electrolyte formulation in a graphite/NCM cell. We assume that TBAC is incompatible with LiBF4.

#### *3.3. TBAC Solvent-Mixtures with LiFSI*

The results for the electrolytes with LiFSI as conducting salt are comparable to LiTFSI. Graphite/NCM cells with 1 M LiFSI dissolved in F2 showed a coloumbic efficiency of about *ηcoul* = 98%. The results of the cycling tests are shown in Figure 5 with three formation cycles at *C*/10 and 100 cycles at *C*/4.

**Figure 5.** Cycling performance of a graphite/NCM cell with 1 M LiFSI in TBAC:EC:EMC (80:15:5 wt) electrolyte at *T* = 25 ◦C. The cell was charged and discharged at C−rate *C*/4.

However, it was not possible to achieve a durable coulombic efficiency above *ηcoul* = 99%. Therefore TBAC-LiFSI electrolytes were not further investigated.
