Even if it did wear out after 200 cycles, you could still use it as part of a hybrid battery pack. Imagine 50% lithium ion, 50% lithium sulphur. If LiS has 4x the energy capacity of LiIon, you'd have 2.5 times the maximum range of a pure LiIon pack. But most of the time, you don't drive anywhere near the full range, so you discharge the LiIon pack first, and only dischange the LiS pack on those rare days when you need the extra range (or if you only very very rarely need the extra range, dischange the LiS half occasionally to avoid the LiIon half wearing out first).
200 charge cycles at 4x the storage = 800 lithium ion charge cycles. That’s easily competitive. Put another way if your getting 300 miles of range a current EV that’s 300 x4 x200 = 240,000 miles.
Only if you change your habits to maximize the lifetime of the batteries. For example avoid charging the car every night and instead charge it for a few nights after it's completely empty.
What? No.. if you go from 80% to 60% back to 80%, that's not considered a full cycle.
You seem to carry a misconception from an older battery chemistry (I don't remember which, but it was common in early cell phones), where it was supposedly better to discharge the battery completely before charging again.
Most chemistries are not like that, as far as I know. In fact, with li-ion it's better to charge every night, if your EV battery has a good buffer, or you can configure it to charge to 80% except for days where you'll actually need 100%.
Maintaining 99% for 200 cycles seem pretty good to me. Possibly better than Li-ion? It depends on how fast the battery degrades after that. But I'm pretty sure my EV lost its first 1% way before 200 cycles.
To distill it down to a single figure: If you drain the battery down to 40% capacity between recharges, you can expect it to take ~600 charge cycles for total capacity to drop by 30%. If you only drain it down to 90% between recharges, the number of cycles increases to ~6,000.
The article doesn't specify, but I assume that's using a slow charge. I am guessing that with a fast charge, which is what is implemented in most consumer electronics, the difference would be even more stark.
Most batteries handle partial charging better than full charging.
But, assuming it’s an issue a hybrid design with say 150 miles of daily driving lithium ion and 150 x4 = 600 miles of extended range is another option.
That's actually a good idea. I was thinking supercapacitors for fast acceleration/recuperation and batteries only rated for sustained driving at cruising speed. Should last much longer.
As I understand it, this is a terrible thing to do to lithium ion batteries. NiCad batteries were like that, but li-ion shouldn't be allowed to go below 20% if you're interested in longevity.
I thought this was basically a non-issue as the battery circuitry would kill power before it got past that point. Or does that just stop it from emptying completely?
I think it depends on the application where the circuitry cuts off. Almost all applications will have circuitry that cuts power before the cell dies completely. You even have individual 18650 cells that have such a circuit built in (for flash-lights and so on)
But increased battery degradation starts way before you hit that limit. At least with cell phones, that tend to push battery cells pretty hard, you'll have pretty bad degradation when discharging to 0%. I think most EVs have a higher cut-off, and most people don't discharge EVs to near 0% anyway.
Then divide the battery pack into two (or more) packs. The battery controller then uses one pack to exhaustion, then switches over to the other pack. Normal charging will only charge fully depleted packs. This would reduce maximum range. So add in a charging override for an occasional max distance drive.