Calendering improves the energy density and optimizes the electron transport through the electrode bulk. When the electrode thickness is decreased, the contact between the electrode components is improved. Nevertheless, the ion transport decreases, and the electrode tortuosity factor increases. Symmetric cell studies provide more information on the internal pore resistance without interference from a counter electrode (lithium metal) and charge-transfer reactions (lithium intercalation). This approach reflects the ionic resistance (Rion) in the pores of the electrode bulk. To get more insight into the porous ionic resistance in the electrodes, we performed symmetric cell impedance studies using negative electrodes with the Si8%/Gr83% and Si15%/Gr76% formulation depending on the calendered percentage (see Figure and b, respectively).