The design of Tesla's 4680 modular battery

　　On Twitter, ALEX made some design assumptions and deductions based on Tesla’s Battery Day, Berlin Factory Open Day and Tesla’s patents, which are very helpful for understanding Tesla’s 4680 module and system design.

　　These issues can be listed as follows:

　　(1) In the state of high-nickel materials, is there any advantage to cylinders than square shells?

　　In the absence of large-surface contact, the overall design of thermal runaway should be better done. The same CTC square shell is difficult to make.

　　(2) Can the 4680 large cylinder cell be made of iron-lithium version?

　　Yes, that's what a leading OEM in the world thinks, to make an ultra-low-cost solution.

　　(3) Why does BMW, which knows the square-shell batteries best, switch to a cylinder on the sixth-generation battery?

　　BMW actually has a square shell and a cylindrical style, the core differences of which are different for each technician. iNext and i4 do not make large square-shell batteries but small square-shell batteries 4P and 5P, which is not as convenient as cylindrical in nature.

　　(4) The introduction of CTP and CTC and the differentiation of batteries?

　　From the current point of view, CTP has achieved very good results around structural innovation to break the boundaries of the previous VDA355, 390 and 590, but the essence is a structural change, which then achieved the strategic purpose of the battery cell factory to cut into Pack manufacturing and bring back the customer's entire package.

　　The strategic purpose of CTC is actually to strictly bind battery cell production to vehicle production, so it is foreseeable that CATL needs to build a battery cell factory for Tesla in Lingang to ensure the progress of CTC.

　　(5) The breakthrough of large cylindrical batteries may actually subvert the square shell era. Why?

　　1) In the 18650 era, the cylinder was a standard product and has been used in the general consumer goods industry. However, 21700 overturned the traditional concept, cylindrical batteries can be advanced in many areas. In the face of such high-quality standard products, in fact, foreign Panasonic, LG, SDI and SK can do it, and EVE Lithium Energy is also following up.

　　2) In the era of generous shells, the shells of several battery cores were optimized and turned into coil cores connected in parallel. In the CATL, this approach actually opened the gap between SDI and Panasonic, reduced the cost a lot, and placed huge cost pressure on LG Chem.

　　3) But compared with the 4680, the biggest defect of the large square shell is that fast charging can not be done under similar cost conditions-this design basically puts the bottleneck of fast charging in the cell, because the impedance is difficult to reduce. If the subsequent consumer level not only has a demand for cruising range, but also has a demand for charging experience, the original advantages will become disadvantages.

　　Lithium-ion battery (LIB) has become the main energy storage solution in modern social life. Among them, lithium iron phosphate battery is a perfect replacement for lead-acid batteries, and it is the first choice for grid-connected peak shaving, off-grid energy storage, photovoltaic energy storage, UPS, data center and other industries.