Volkswagen Explains Roles Of Cathodes And Anodes In EV Adoption
Check out how each chemistry fares on Volkswagen’s scale.
Mar 17, 2021 at 10:20am ET
Gustavo Henrique Ruffo
Electric car owners and InsideEVs readers normally know what an anode and a cathode are. At the Volkswagen Power Day, the German automaker wanted to take the definitions of the negative and positive electrodes in a battery a little further. Volkswagen clarified which role each of them performs in EV adoption.
Frank Blome, Volkswagen Group Component’s head of battery cell and system, was the man in charge of the explanation. He started by saying that the negative electrode is responsible for charging times. In other words, a better anode leads to faster charging, making the use of an electric car easier for those who fear spending too much time waiting for a charge.
The positive electrode has to do with costs and range. That puts on the cathode’s shoulders the responsibility to make electric cars affordable and without compromise compared to combustion-engined vehicles.
Blome also stressed that the cathodes are the control levers for a sustainable supply chain. Lithium-ion batteries of all sorts use lithium in their anodes. It is a metal that does not pose as many concerns as cobalt or nickel in its mining, even if there are some.
Considering most electric vehicles currently use NMC cells, this is the parameter Blome uses to make comparisons with the other chemistries Volkswagen plans to use: LFP (lithium iron phosphate), and high-manganese.
According to the Volkswagen executive, the NMC cathode defines the cost of the cell by 40 percent. The range would also depend on that positive electrode by 90 percent.
Compared to an NMC cell, a lithium iron phosphate battery has about 80 percent of the cost – which is a good thing. On the other hand, it offers only around 80 percent of the range. Blome stresses that its advantages are not only in cost but also in cycling stability and safety.
Contrary to what most companies say, Blome said Volkswagen would pursue high-manganese cells, not high-nickel batteries. Manganese is a cheaper metal than nickel, and it can provide the same range of NMC cells for about 80 percent of the cost, just like LFP. This is the chemistry Volkswagen wants to adopt for volume EVs.
Regarding the anodes, they have an impact of only 10 percent in range, while charging time depends 100 percent on them, according to Blome. Most anodes are currently made of synthetic graphite.
The Volkswagen executive presented their structure compared to that of an NMC cell. The difference in size is remarkable and makes a good example of how much lighter solid-state batteries have the potential to be. According to Blome, the ID.3 with the biggest battery pack has 100 kilograms (220.5 pounds) in anodes alone.
Blome also compared solid-state batteries to NMC cells when it relates to charging times and range. A solid-state battery would be able to charge in a little less than half the time an NMC cell demands. It would also offer 30 percent more range.
Using an ID.4 Pro with a 77 kWh as the reference, solid-state batteries would imply you would have to charge the car for only 12 minutes to go from Los Angeles to Las Vegas, from Leipzig to Munich, or from Beijing to Dongying. Today, that high-speed charging takes 25 minutes. Volkswagen plans to lower that with current technology to 17 minutes by 2025.