*3.3. Influence of Temperature*

In order to investigate the effect of temperature on the kinetics of Li deposition and consequently the stability and cyclability of *insitu* deposited lithium electrodes, experiments were performed at three different temperatures with *T*Cell = {25, 40, 60} ◦C on the Cu/Li cells using LiFSI with a concentration of *c* = 2 M in DME as the electrolyte. The Coulombic efficiency results obtained from cycling tests are shown in Figure 5. Two different Crates of *I*Cell{1, 2} C were investigated, and the corresponding results are displayed in Figure 5a,b, respectively. The cells cycled at a temperature of *T*Cell = 25 ◦C are presented in the orange color, the results at *T*Cell = 40 ◦C and *T*Cell = 60 ◦C are visualized in black and blue colors, respectively.

**Figure 5.** Cycle performance of cells with Cu/Li structure having LiFSI 2M in DME as the electrolyte. (**a**) Cells are running with the C-rate of *I*Cell = 1 C and each at the different temperatures of *T*Cell = {25, 40, 60} ◦C shown in orange, black and blue colors, respectively. (**b**) Cells are running with the C-rate of *I*Cell = 2 C and each at the different temperatures of *T*Cell = {25, 40, 60} ◦C shown with orange, black and blue colors, respectively.

In both investigated C-rates, the most stable cycling results were reached at a temperature of *T* = 25 ◦C. At this temperature, the cell cycled with *I*Cell = 1 C shows 160 smooth cycles with a high average Coulombic efficiency of *<sup>η</sup>*CE > 0.99. After 160 cycles the Coulombic efficiency drops below the threshold value of *<sup>η</sup>*CE < 0.95. The cell cycled at *T*Cell = 40 ◦C shows an instability at earlier cycles and reached a Coulombic efficiency of *<sup>η</sup>*CE < 0.95 already after 130 cycles. The worst cycling performance was obtained at a temperature of *T*Cell = 60 ◦C. The instability starts at the initial cycles and no smoothing behavior, as was found at *T*Cell = 40 ◦C, could be achieved during the 70 cycles for which the cell was running. The same trend is observable for the cells running with a C-rate of *I*Cell = 2 C. The positive influence of higher C-rates is reflected in an increase of the number of cycles reached for all three cells at the considered temperatures.
