How does Tesla add power to its power lithium-ion battery?

Recently, Tesla's 100kWh model passed the audit of the EU certification body RDW. This means that the S/X100D model will be available soon! Its theoretical range will reach 613 kilometers (according to NEDC standards). According to EU regulations, all models sold in EU member states must be certified by authorized agencies. RDW is a Dutch company commissioned by Tesla and is certified for sale in the European Union. In this article, we will explore how to achieve this 100kWh. Elon Musk said earlier that Tesla's battery life will increase at a rate of 5% per year. From the battery iteration at that time, this strategy is basically over. In addition to 60kWh as entry-level equipment, 70kWh and 85kWh have been upgraded to 75kWh and 90kWh. Soon, 100kWh and 120kWh batteries will be added to the optional list. For now, 60kWh is still a promotional tool for Tesla. The real story is how to add 5kWh to 70kWh and 85kWh respectively. One thing is certain, that is, the structure of the battery pack will not change during the power-on process. The number of internal battery modules has not changed. Let's take a quick look at the inside of the Tesla battery pack. There are 14 battery packs in 60kWh, each battery pack contains 384 batteries, a total of 5376 batteries. 85kWh is composed of 16 battery packs, each battery pack contains 444 batteries, a total of 7102 batteries. Later, 70kWh, actually a 75kWh battery pack, came from software constraints. The remaining 5kWh (starting) is supplied to the owner as an optional $3,000 package. After the OTA software is updated, 70D can be changed to 75D. So the question is, how did the 75kWh battery pack appear? Tesla managers did not provide technical explanations on this issue. According to the author's judgment, 75kWh is actually an 85kWh battery pack because of the reduction of 2 battery packs. In an 85 kWh battery, the capacity of each battery pack is 5.3 kWh, so the capacity of 14 such battery packs is 74.2 kWh. This is the connection between 70kWh, 75kWh and 85kWh. As for 60kWh, it is just a device to lower the barrier to entry. So how did 90kWh come about? From 85 degrees to 90 degrees, this is an extra 5 degrees. Are there extra battery packs? In the 85 kWh battery pack structure, battery packs can no longer be stacked. The only possibility is a new cell. Of course, the battery is still 18650 type, but the chemical materials have been adjusted to increase the energy density. In this process, Tesla added a small amount of silicon to the graphite anode of the battery to increase the energy density of the battery. The addition of silicon to the anode is considered a way to increase the energy density of the battery. In order to prevent the accumulation of too heavy batteries, Tesla will have to focus on the development of high energy density batteries. However, for ternary lithium batteries, it is not so simple to add energy density through silicon. The basic principle is that after adding silicon to the graphite anode, the structure of silicon atoms can hold more lithium ions than graphite, thereby enhancing the absorption of lithium ions in the anode. In a single charge-discharge cycle, the more lithium anodes, the higher the energy density. However, silicon swells by 300% after absorbing lithium ions, which is far greater than the 7% expansion rate of graphite after absorbing lithium ions. This repeated volume correction causes the solid electrode to become soft and briefly collapse. At this point, the cycle life of the battery decreases. The other layer is a silicon anode. During charge and discharge, the expansion/elasticity of the silicon anode will destroy the composition of the lithium battery electrolyte SEI film. This film is formed during the initial cycling of the lithium battery. The anode material has a protective purpose and can prevent the collapse of the material structure. For these reasons, the use of silicon as an anode has a significant increase in energy density, but it is also accompanied by side uses, which ultimately leads to a shortened battery life. Therefore, Tesla's plan is to gradually add a small amount of silicon to the graphite anode to balance the energy density and cycle life. As we all know, Tesla's 18650 battery is processed by Panasonic. As the cooperation deepens, Tesla is also developing new cylindrical batteries. When Model 3 is put into processing, the new 21700 battery will replace the 18650 as the new battery. The 21700 battery is still a ternary lithium battery with lithium nickel cobalt aluminate (NCA) cathode. This cylindrical ternary battery is currently the highest energy density power lithium-ion battery solution. Compared with prismatic batteries, although this kind of battery has high energy density, it has poor stability, so it needs better BMS (Battery Treatment System) to support it. Tesla's first sports car used Panasonic's NCR18650A battery with a rated voltage of 3.6v and a capacity of 3.1ah. The previous 85kWh battery pack was NCR18650B, rated 3.6v and 3.1ah. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete.