Michel Jullian wrote:
They say here http://en.wikipedia.org/wiki/Lithium_ion_battery that the A123 battery
"has slightly lower energy density that other competing Lithium Ion
technologies".
Standard Li-ion (not high power): 150 to 200 Wh/kg (sez above article), so "slightly
lower" would be ~100 Wh/kg, twice ScIB's 50 Wh/kg? Unless "other competing Lithium Ion
technologies" means other high power technologies...
Wow, I didn't realize the density was that high.
In any case there seems to be a lot of promising research going on besides
these two, see
http://en.wikipedia.org/wiki/Lithium_ion_battery#Breakthrough_Research
"In December 2007, researchers at Stanford university reported creating a lithium ion battery
with ten times the energy density (amount of energy available by weight) through using silicon
nanowires deposited on stainless steel as the anode. The battery takes advantage of the fact that
silicon can hold large amounts of lithium, and helps alleviate the longstanding problem of cracking
by the small size of the wires. [4] To gain a tenfold improvement in energy density, the cathode
would need to be improved as well; however, just improving the anode as such could provide
"several" times the energy density, according to the team. The team leader, Yi Cui,
expects to be able to commercialize the technology in about five years.[5]"
Several times = at least twice, so maybe 400 Wh/kg will be the norm in five
years (EESTOR's announced 1000 Wh/kg might be beaten before they deliver!), for
a 50 kWh EV this would be 50000/400 = 125 kg, which would be perfect.
EEStor's 1000 Wh/kg also hasn't been proved to scale or be
manufactureable or anything else as yet AFAIK.
I really, really hope EESTOR can do what Zenn says they can do :-) but I
can't help wondering. In competing with batteries in the energy density
arena, it seems to me that they're up against a fundamental issue, which
is that in a capacitor the charges are mechanically separated which
implies a charge separation distance on the order of a of membrane
thickness (for some sort of membrane or membrane-like structure). Even
using nanoparticles to build the electrodes, as far as I know there's
still a mechanical separation between + and - charges in their caps. In
a battery, on the other hand, the charges may be as close together as
the two ends of one molecule. The spacial energy density depends on how
close you can get the charges to each other, so compared with a battery,
a capacitor has one foot in a bucket of cement to start with.
In an energy-density race between chemists working on batteries and
materials scientists working on supercaps, it seems like the safer bet
would be on the chemists.
In every other way caps beat batteries -- and maybe they can even beat
them in terms of energy/mass, by using less dense materials. But in
terms of spacial energy density -- kW/liter -- I will be (very happily)
surprised if they can actually manufacture caps with higher density than
batteries.
If you can't build an EV without filling the trunk with batteries then
I'll be very surprised if you can build one using supercaps and end up
with an empty trunk.
All these announcements, with rising oil price as you say, suggest that EVs are indeed
likely to replace our present "stinkers" in the near future :)
Michel
