Deep Dive Into Tesla Tabless Electrode Patent Before Battery Day

In November 2019, Tesla filed a patent 'Cell with a tabless electrode', which Tesmanian described earlier. All Tesla’s inventions aimed at developing batteries are incredibly important, as the company strives to develop a battery that will be cheaper to manufacture and have higher performance than those currently on the market. But this patent is very important, which was emphasized by Tesla CEO Elon Musk.

Way more important than it sounds

— Elon Musk (@elonmusk) May 7, 2020

Yutuber The Limiting Factor, also drew particular attention to this patent and helped to look more deeply at it, in order to understand the importance of this invention.

In the 'Cell with a tabless electrode' patent, we can see the basic diagram of a cylindrical battery cell. As can be seen from the figure below, there is a cathode and anode, and between them there is an inner separator that prevents them from touching. If they touch, and there will be a fully charged battery, then they will explode.

 

Source: The Limiting Factor/YouTube

On the outside of the roll there is also a separator called the outer separator, it performs the same security function as the inner separator. When all these sheets are folded, they form a spiral called jelly roll. An external separator prevents the cathode and anode from touching.

Although the cathode and anode are considered as a single layer, each of them has an active layer of material that stores energy. Active material sticks to the collector foil, which conducts electricity to and from the battery cell. Tesla’s patent basically refers to these layers, so The Limiting Factor made a separate drawing to make it easier to understand how it works.

 

Source: The Limiting Factor/YouTube

The foil of cathodes and anodes is usually called an electrode. Tesla invented a new way to connect these electrodes to a battery cell, which has huge implications for the performance of a battery cell.

The image below shows a typical connection point, which is a tab, and Tesla's connection point, which is the offset of the active material, to expose the bare metal for the connection.

To better understand the benefits of the Tesla method, The Limiting Factor made a parallel comparison. A typical tab design (on top of figure below), and Tesla's tabless design (on the bottom of figure). Tesla's patent illustrates a tabbed cathode and a tabless anode. In the patent, they mention several times that the actual implementation may have tabless on both the covers or the ends of the battery cell.

 

A typical design of battery has several disadvantages:

1. tab is welded to the foil, which you can see sticking out from above. The electrode foil is about the same thickness as ordinary kitchen aluminum foil, which makes welding the tongue with the electrode foil uncertain and error prone. This increases the risk of defective items;
2. such a production process becomes more complicated and adds cost;
3. electrons must go from the entire sheet to the tab to exit the cell and vice versa. This is a bottleneck, as the electrons move along the length of the sheet into which they cut and the temperature rises;
4. since electrons find the path of least resistance through the foil sheet, hot spots of electrical activity, called current deflection, are created, which also lead to hot spots of chemical activity, where the current is the strongest;
5. only a thin piece of metal is connected from the electrode to the cap of the cell. The temperature of a typical cell is more difficult to control due to the smaller amount of conductive mosetial connected to the cell.

The tabless design has several advantages:

1. it is without tabs for welding and this eliminates the step in the production process and the number of defective cells;
2. the absence of bottlenecks means less resistance and heat dissipation and even the speed of a chemical reaction through the active material;
3. around the entire edge, the electrode becomes a radiator, which perfectly cools the entire surface.

Source: The Limiting Factor/YouTube

In fact, removing the tab not only simplifies the manufacturing process, but also reduces the ohmic resistance in the negative electrode during electrochemical cycling by 5 to 20 times.

So, according to patent, an electrochemical cell may also experience significantly less current deviation, the phenomena where some electrode regions pass more or less current than other regions over its cycle lifetime. Current will preferentially travel along paths where resistance is lowest, which in the absence of other factors will typically be along paths closer to the tab where the ohmic resistance is smallest.

Current deviation is extremely undesirable in electrochemical cells because it can lead to local electrode hotspots where large overpotentials are generated, leading to unwanted chemical reactions that reduce the cell's lifetime.

Maxwell's dry electrode technology generated with a tabless design, with a lower resistance, would be a leap for Tesla's cellular physics. This would allow Tesla to increase the size of their batteries and improve the temperature control of larger battery cells. Thus, Tesla could use fewer cells, which would reduce the cost and time for production.

Tesla Next-Gen Battery With Maxwell Tech & Patents https://t.co/MeRE7CCwP4 pic.twitter.com/MKOEOs8cTS

— Tesmanian.com (@Tesmanian_com) February 8, 2020

Tesmanian previously reported that according to information received from a person familiar with the case, the new Tesla battery will have at least 30% more capacity and will be several times cheaper to manufacture. The production process will be extremely efficient and will significantly save on capital costs for equipment. In this scenario, a 130kWh pack seems possible. It also became known that the new cell will have a diameter of approximately 1.57 inches. The new battery will have a different form factor, so most likely it will be used for Semi and/or Cybertruck. Having the data obtained from the latest patents, it seems that this information is true. 

 

Featured image: @CybertruckOC

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