Which is still quite a bit lower than
https://en.wikipedia.org/wiki/Lithium-ion_battery
> 900–2,490 J/cm3
And I don't see anything here about self-discharge rates, which are a big limitation for using capacitors for energy storage over any period of time. Does anyone know if the full study has that information?
I think some of the areas of a car to be potentially improved with this kind of advancement are: regen braking efficiency, size and weight, battery health.
And the same is true for DRAM and flash. There have been several moments in time when the tables have tilted where battery backed RAM PCI cards have made sense, or where sticking persistent Optane chips in high speed DRAM slots has.
I believe we are a bit farther from a true hybrid capacitor. As for true hybrid memory I believe the likeliest solution for embedded applications will be one of the different analog in-memory compute techniques currently being iterated on.
Without bypass capacitors every sudden draw of power would pull the supply voltage of the whole system down, especially if your power source (battery) can't react that quickly or has limited discharge rates.
Without having looked into the plans here, I'd expect a super-capacitor solution to look like this:
1. You charge your cars of super-capacitors super quickly at special charging spots and drive away
2. The stored charge is then partly used for driving, partly used to charge the cars actual battery and partly used to act as a bypass capacitor to smooth out the load for the battery
3. Eventually the capacitors are empty, but you had a short charging process that filled part of your batteries
Cars are unlikely to have huge supercapacitors useful for changing the charge much, too. (And there's not much point in moving power stored in a capacitor to be stored in a battery).
The main use of this is to provide short duration power, as you describe. That is, lithium batteries have great energy density but not as great power density or cycle life as capacitors. So a small amount of bulk capacitance can improve battery performance and reduce stresses on the battery.
This is more useful for short range vehicles like plug-in hybrids, because they have smaller packs. Larger vehicle packs tend to have plenty of power available, as a side effect of being designed to store tons of energy.
Even for high discharge I'm skeptical, lithium titanate batteries are probably much better, their durability and extreme charging and discharge rates make them half way to capacitors already.
You could say that. You could also be more pedantic and say that this comes at the cost of some decrease in battery life (and efficiency) due to the resistance resulting in some amount of heat in order to facilitate this high-speed charging process.
But I don’t know if the ROI on improved battery life would be worth the complexity, size, weight, and cost of a two-stage charging process. As battery tech improves, that resistance continues to come down.
What does? I said the limitation is usually getting enough electricity to charge them fast. Most of the time EVs are not being charged as fast as they could be.
The traces supplying power aren't theoretical, so they have a nonzero impedance. This means that when there is any change in power demand due to transistors switching, the trace will try to resist this change in supply current. An increased power demand leads to a very local voltage drop, a reduced power demand leads to a very local voltage spike.
Bypass capacitors are placed as close as possible to the individual chips to reduce the impedance between the capacitor and the chip. You even intentionally use smaller capacitors because the bigger ones have a higher impedance.
It might also pair well with battery chemistries that are good for energy density but poor on power density, like lithium-sulfur or LFP.
You'd play to capacitors high cycle life and fast charging/discharging capabilities rather than their density.
https://maxwell.com/wp-content/uploads/2022/07/3003348.2_3V-...
It seems like they didn't really look at leakage current, but did apply a 10 Hz sine wave to it for about a day (~1 million charge/discharge cycles) and it didn't degrade notably.
One big use would be ev road racing.
Cars on a track have high acceleration, followed by extreme braking.
If this energy could be buffered by a large capacitor, the main battery could just be slowly discharged to a capacitor to provide energy for the race. The capacitor would provide and absorb fluctuating energy to speed up and slow down.
I also imagine complex ev battery architecture could be simplified if the energy in and out doesn't have to be radically managed.
I see it somewhat like running an internal combustion engine at one efficient RPM instead of having to run at all RPMs and use a gearbox.
Who is saying that's the point of this capacitor?
> A new material structure could revolutionize energy storage by enabling the capacitors in electric vehicles or devices to store energy for much longer, scientists say.