Tesla showed a new design for a larger battery cell during its Battery Day presentation. This should further increase the range and reduce costs for electric cars, so that a $ 25,000 EV can be released within three years.
The renewed battery cells are indicated with 4680, which stands for the size: a length of 80mm and a diameter of 46mm. These cells are a lot bigger than the 2170 cells from Panasonic that Tesla now uses in the Model 3 and Model Y and are also larger than the relatively older 18650 cells in the Model S. Those older 18650 cells are 65mm long. and a diameter of 18mm and for the 2170 cells it is 70 and 21mm respectively. These new 4680 cells provide five times more energy, but that is mainly due to the fact that these cells have about 5.5 times the volume of the 2170 cells. They lead to a power output that is six times higher, but most importantly, they allow a range that is 16 percent higher, according to Tesla.
Presumably this is the percentage achieved relative to the use of 2170 cells, although neither Elon Musk nor Drew Baglino elaborated on this during the presentation. That improvement is fully achieved by the new one form factor, improving the power-to-weight ratio. This seems to be mainly related to the fact that relatively less casing will be needed in relation to the energy content. The new cell also leads to a 14 percent decrease in costs per kWh. Tesla is going to manufacture the new cell itself and says it has the cells almost operational at the factory level.
The main innovation in the new 4680 cells, according to Tesla, is that it is a design without solder lips. Electric vehicle batteries typically have a thin layer of copper foil as a conductor or current collector for the anode and a layer of aluminum foil for the cathode. A solder tab is then connected to each of these two conductors, providing the connection to the external application to which the cell must supply power. However, these solder lips make production more difficult and more expensive. In addition, they reduce the efficiency of the battery cell, because the electrons have to travel the entire length of the electrode to reach the lips.
By removing those solder tabs, a larger coated area on the electrode is achieved that increases the cell’s capacitance without further altering the design, says Greg Less of the University of Michigan Battery Lab to Wired. Tesla obviates the scraping of the lips by using a foil with all kinds of connections to the materials of the electrode. This leads to a considerably shorter distance for the electrons to travel, which Musk says is also still shorter compared to smaller battery cells that still use solder lips. According to Baglino, this solution also solved the heat problems associated with the larger 4680 cell.
The cost savings that can be achieved with these new cells must, among other things, lead to an electric car that costs 25,000 dollars within three years, and thus at the same or a lower price level as a car with an internal combustion engine. Elon Musk gave little further details about this relatively affordable electric car, except that it will also be ‘fully autonomous’.