Tab-less battery was introduced by Tesla at the battery day Musk agrees. “It’s really a huge pain in the ass to have tabs,” Musk said during the event. In the conventional cylindrical battery the tabs are attached to the intermittent part of the electrode generally in the jelly roll assemble process, which made it non continuous and also might cause some manufacturing defects like loose welding of the tabs causing the tabs to ultimately leading to short circuits.
The other disadvantage of using the singular tabs is that the Electrons have one path and also it needs to travel a lot of distance from a point in the electrode to the tab while charge/discharge which also leads to generation of heat at the tabs, hence there is energy loss.
By eliminating the tabs, the manufacturing process becomes more straightforward and streamlined. The need for precise tab alignment and welding is removed, reducing the complexity of the assembly line. This simplification can lead to increased manufacturing efficiency, faster production rates, and potentially lower costs. Additionally, with fewer components involved in the assembly, there is also a reduced risk of defects or failures related to the tab welding process.
Case study,2021: General Motors is voluntarily expanding the current Chevrolet Bolt EV recall to cover the remaining 2019 and all 2020-2022 model year vehicles, including the Bolt EUV. In rare circumstances, the batteries supplied to GM for these vehicles may have two manufacturing defects – a torn anode tab and folded separator – present in the same battery cell, which increases the risk of fire. Out of an abundance of caution, GM will replace defective battery modules in Chevrolet Bolt EVs and EUVs with new modules, with an expected additional cost of approximately $1 billion.
In my intuition the tabs are laser cut at the edges as shown in the picture, before the winding of the jelly rolls for both cathode and the anode, and after the winding they are made in the form of something called as Rosetta pad. Now the electrons can move easily to the closest and nearest tab which eliminates heat generation and also can deliver more power at the same time as compared to the traditional single tab.
Next the Rosetta pad is covered with flower like part which is laser welded on the surface of the Rosetta pad and to the caps of the battery on the positive and negative terminals through ultrasonic welding. We can see a hole at the copper part which is useful for the welding of the aluminium foils to the positive cap through ultrasonic welding and also it is useful for the electrolyte filling process.
Pic credits: Munro Live
The cap is now sealed on the negative side of the cell and then the electrolyte is filled through the hole under vacuum atmosphere so that the separator and the cell is wet after the filling process, as we can see in the video released by tesla that 12 cells per tray are filled in a single time. The hole of the cap is now sealed with a rivet like component after the end of electrolyte filling process.
Let us know your inputs on how the Tabless design can add value to the manufacturing line.