Let us compare the contribution of different battery components to the overall resistance in a 4680 battery. When an electrode sheet is unrolled, the footprint area is 8 cm x 6.25 m for a single electrode. Based on these values, you will understand what contribute most to the internal resistance of a battery, and why tab-less design is important.

1) Calculate the electrolyte resistance. Assume that the transport distance is 50 um. The porous is 30% and the tortuosity is 4.5. The ionic conductivity of the electrolyte at 25 degrees C is 5 mS/cm.

2) Calculate the electronic resistance of the current collector for (a) and (b). Take the current collector of the negative electrode as an example. It is Cu with a thickness of 6 um. Cu has an electronic conductivity of 6 x 10⁵ S/cm.

(a) All electronic currents accumulate to one end of the current collector. This means that there is only one tab at the short side of the sheet, and current flow in parallel to the long side. Take the location-dependent current into account.

(b) Tab-less design, which is used in Tesla 4680 cell, where current flows along the short side of the electrode sheet. Again, take the location-dependent current into account.

3) Calculate the charge transfer resistance. Let us just take a look at the negative electrode. Assume all electrode particles have a surface area of 0.1 m2/g. Their specific capacity is 360 mAh/g for the negative electrode. A 4680 cell has a capacity of 27 Ah. The exchange current density is 0.1 mA/cm2. Transfer coefficient is 0.5. Temperature is 300 K. Calculate the charge transfer resistance at a current of 15 A.