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What used to be the combustion engine is now the battery pack: the most important part of an electric car. Manufacturers worldwide are doing a lot of research to increase the range, make charging faster and lower prices. An overview of the situation.
So it is with the lithium-ion battery
In current EV models, there are only two cell chemistries: NMC and LFP. These two types do not have the same properties, and certainly not the same price. NMC stands for nickel, manganese and cobalt. A mixture of these metals (together with lithium, from the designation lithium-ion) forms the cathode in the battery cell. NMC cells are powerful and have a good energy density, which gives more range. They can deliver a lot of power to the electric motor, for example when accelerating, and absorb a lot of energy, enabling fast charging. But they only work optimally at pleasant temperatures. Therefore, the cells need cooling and heating. This comes with a price tag, which is why NMC cells are relatively expensive. This is different with LFP cells, and that is due to the metals: the abbreviation stands for lithium iron phosphate. These cells do not contain expensive nickel or cobalt, which workers sometimes have to mine under terrible conditions. In addition, LFP cells are robust. Their durability is high, and the risk of so-called thermal breakdown – i.e. ignition followed by a very difficult to extinguish fire – is very low compared to NMC cells. A problem is charging in frost. The charging current must first heat the cells before they really get going. Moreover, because the energy density is poorer than with NMC technology and the range of action is smaller, LFP cells are practically only used in basic models. If you buy a Tesla Model 3 or Model Y with rear-wheel drive, you get LFP technology. This is also the case with the MG4 and from 2025 with the Volkswagen ID 2.
What is the Potential of Sodium Ion Cells?
Sodium can replace lithium in battery cells. This has many advantages. The main one is the price. Electric cars are now often too expensive for the general public, and that is because of the battery. Good NMC cells currently cost USD 164 per kilowatt hour of energy content, says Professor Markus Hölzle of the Zentrum für Sonnenenergie und Wasserstoff-Forschung (ZSW) in Ulm. For LFP cells it is $133, for sodium-ion cells $90. Plus: Sodium is readily available. The first electric cars with sodium-ion batteries will be launched in China this year. But the even lower energy density of these cells does limit the range. On the other hand, the expected lifespan is long, which makes buyers on a budget particularly happy. How widespread this cell chemistry becomes depends on how it performs in practice in EVs. The question is: can those batteries live up to what they promise?
How will lithium-ion batteries continue to develop?
NMC and LFP cells will continue to dominate the market. In NMC cells the mixing ratio changes: it contains more and more nickel and less and less cobalt. The actual step forward with regard to battery cells does not concern the cathode, but the other terminal, the anode. Almost all manufacturers use graphite for this. Graphite has proven its worth, but it makes the battery heavy and reduces the charging performance. To prevent this, manufacturers can add silicon to the graphite. The Porsche Taycan was the first EV where a manufacturer opted for such an approach. The share of silicon is currently in the single digits, but will gradually increase over the course of the decade. The effect: much faster charging and an increasing energy density.
Lithium price has risen sharply
The price of lithium will rise sharply in 2022, to €80 per kilo. But since last autumn, the price has fallen just as much and is heading for three tens per kilo. According to Reuters, leading lithium producers in China have agreed on a price floor of the equivalent of €33 per kg to counteract the slump.
Current state of affairs: solid state battery
For years they received praise for the great leap forward in battery development: in solid state batteries, the electrolyte is solid instead of liquid. A solid electrolyte is not flammable. The special feature of these batteries is the anode made of pure lithium metal. This creates a cell with an optimal energy density. We have to wait and see if and when solid-state batteries will be used on a large scale, because conventional cells with a high silicon content on the graphite anode promise solid-state-like properties. Many manufacturers say they will soon be installing solid state batteries, but often these are just ‘semi-solid’ electrolytes without pure lithium. Such cells do not have the extremely high energy density of true solid state cells.
How important is the battery system?
Regardless of chemistry and size, manufacturers combine the individual cells into a battery system. This determines the actual range and performance of an electric car. Software management controls the cells. Heating and cooling are also important for day-to-day performance. In addition, the protection must be in order in the event of a collision. The best-known battery systems currently come from the world market leader CATL and BYD, both Chinese manufacturers. CATL markets the ‘Qilin’ battery. This system is suitable for both NMC and LFP cells. The cooling is so good that the charge time from 10 to 80 percent is reportedly just ten minutes. In comparison: Hyundai produces the fastest charging series models today and they take about eighteen minutes. BYD’s Blade battery, on the other hand, takes a basic principle to the extreme: little packaging, lots of so-called active material. In this approach, the cells are not only placed directly in the housing. This is called cell-to-pack. The top lid doubles as an inner bottom. This is called cell-to-body. The BYD Seal gets this blade battery with cell-to-pack and cell-to-body technology on board as standard. The model will probably be on the Dutch market by the end of the year.
Which battery shape is the best?
Battery cells can be round (‘cylindrical’), flat like a box (‘prismatic’), or surrounded by a flexible bag (‘pouch’). It is impossible to say which cell shape is the best, because so far no cell has clearly predominated. The best known is the round cell, which we have all replaced in an electrical device. For Tesla, they once contributed to the manufacturer’s breakthrough. Today, no car manufacturer is strict in this area. BMW will use round cells from the supplier EVE in its Neue Klasse models (from 2025). The properties of these cells could be superior to those of Tesla. Yet today’s electric cars usually contain prismatic cells or pouch cells. Thanks to their box shape, prismatic cells can be integrated into the housing between the shafts in a particularly space-saving manner. Volkswagen chose this format for the upcoming unit cell the manufacturer is working on. Prismatic cells are also found in BYD’s blade battery. The Chinese are both battery and car manufacturers. BYD uses long, flat and narrow cells with LFP chemistry. In general, the form has nothing to do with the content; everything can go together in that regard.
– Thanks for information from Autoweek.nl