Comments by "Peter Lund" (@peterfireflylund) on "Engineering Explained"
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Robert Thomas, no it has not peaked yet. There's still a lot that can be done with additives -- and since it was only about two years ago that good measurement equipment for test cells was developed, we should expect development of those additives (and other parts of lithium ion cells) to progress much faster now.
Additives help with temperature sensitivity, charging speed, heat losses during charging, and the number of cycles the cell can handle.
The density can be improved not only by using thinner layers in the cell (it's basically a rolled up very long and thin flat battery) but also by using finer carbon grains for one of the electrodes and by the use of additives again. It can also be improved by adding small amounts of silicon -- this is something Tesla and Panasonic have already started to do but there are good reasons to expect them to gradually raise it from a few percent to 20-30% of the carbon. There are problems with silicon but additives can probably solve some of them.
Jeff Dahn, Dalhouisie University, and his group have really pushed the limits of how well charging and discharging can be measured. It turns out that they can get information from a few charge/discharge cycles (or even just a single cycle) that previously took hundreds of cycles to get. That makes it much faster and cheaper to develop battery improvements.
The point of improving the energy density is not so much to make the batteries smaller as to make them cheaper: if you can get more bang out of the same materials you don't need as much of them, which makes same-size batteries cheaper.
Current lithium-ion batteries take a long time to produce (weeks or at the very least days), mostly due to a "maturation" period after the production proper where they are put through a special charge cycle (or several charge/discharge cycles) while their temperatures are raised in a specific way. If they can make that faster, they can make cheaper cells. Again, this seems to be something that can be handled with additives -- and it looks like something Dahn's group has looked into. They have published papers that almost say something about this but I expect the actual information to be proprietary to Tesla. Other groups have their own ultra-precise charging monitors (commercialized by people who used to be in Dahn's group) so they are very likely doing their own research into this as we speak.
So, to sum up:
- they are likely to become more energy dense, which is not particularly important by itself
- they are likely to become faster to charge
- they are likely to become both more cold tolerant and more heat tolerant
- they are likely to waste less energy in the form of heat while charging
- they are likely to be able to handle a higher number of cycles
- they are likely to become faster to produce
- they are likely to become cheaper. Much cheaper.
Your Jetta is going to remain cheaper for some time -- perhaps more than a decade -- but EV cars are going to become cheap enough that their other upsides outweigh the price in perhaps a decade for many people. Probably for almost everybody in two decades. And to get back to the original subject: this limits how much effort it is worth putting into improving small combustion engines.
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