Polymers for batteries
References:
LiCoO2: http://en.wikipedia.org/wiki/Lithium_cobalt_oxide
Nanomaterials: Angew. Chem. Int. Ed. 2008, 47,
2930 – 2946
Lead acid battery:
http://en.wikipedia.org/wiki/Leadacid_battery
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Zinc-Copper cells are the classic battery: copper plates
out on the zinc during use.
Volta’s cell (replica)
Crow’s foot style
These images and much more information are found at: http://w1tp.com/mbatt.htm
Used with permission
Such batteries have been know for ~200 years.
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The lead acid battery is more common than conventional.
Anode (Ox)
PbSO4 + 5H2O  PbO2 + 3H3O+ + HSO4- + 2e-
Cathode (Red) PbSO4 + H3O+ +2e-  Pb + HSO4- + H2O
+1.685V
-0.356 V
Anode & cathode are both made of Pb/PbO2 but one is “tricked” into being
brownish PbO2 (+ terminal) and the other grayish Pb (- terminal) on the surface.
Both plates contain holes which hold a paste of Pb3O4 and other stuff to prevent
crystal growth of PbSO4 and ensure high surface area.
The energy density of the lead battery is low, due to its great weight. The
power density is high, though: a lead battery can produce awesome current.
Most interesting for polymer people: the separators (green in figure above).
PVC or PE are used for separators—better than wood originally used, but why not PBZT?
http://en.wikipedia.org/wiki/Lead-acid_battery
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What gels in H2SO4?
So…separators made of PBZT/H2SO4 gel would yield a leadacid battery that would not spill. Why didn’t we hawk this
idea to the Navy for submarine use 25 years ago?
4
Here is awesome current on display.
MR2
http://www.youtube.com/watch?v=GcQ8Mr_wcTQ
Porsche 911
http://www.youtube.com/watch?v=ImWMKa8ZTq8
Lawn care, complete with plastic housing
http://neutonpower.com/
Lawn care, old school metal housing
http://www.amazon.com/Earthwise-60020-20Inch-CordlessElectric/dp/B000WEOQP4/ref=sr_1_4?ie=UTF8
&s=home-garden&qid=1273119539&sr=8-4
Change you can believe in.
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So American tinkerers—when not cleaning up oil slicks and
drilling to make new ones–play with 40-year-old German cars
and 200-year-old lead acid battery technology. What’s going on
in countries that have a plan?
Failure to plan = planning to fail.
Eliica Japanese LiIon car vs. Porsche
http://www.youtube.com/watch?v=L7zHcvDPxYU
Germany’s plan for 1 million EVs by 2020
http://www.msnbc.msn.com/id/23922063
Japanese 3-minute (half-amps) battery charger (batteries charging batteries, I think)
http://blogs.edmunds.com/greencaradvisor/2
010/05/firm-says-its-made-system-that-canrecharge-evs-batteries-halfway-in-3minutes.html
What’s interesting about this is that, even in an application
where mass is not a factor, they went with Li-ion.
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Well, Goliath did lose to David.
http://www.altairnano.com/profiles/investor/fullpage.asp?f=1&
BzID=546&to=cp&Nav=0&LangID=1&s=0&ID=10724
US has made enormous investments in nanotechnology that may help,
but will we commercialize it, or give it away like the LCD to pursue
other interests? How long are we willing to wait for profits?
Most of the countries that are nipping at our heels still experience
bone-crushing poverty for major sectors of their population.
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“The rechargeable lithium battery does not
contain lithium metal. It is a lithium-ion device,
comprising a graphite negative electrode (anode), a nonaqueous liquid electrolyte, and a positive electrode (cathode)
formed from layered LiCoO2 (Figure 1).”
Anode
Cathode
“On charging, lithium ions are
deintercalated from the layered LiCoO2
intercalation host, pass across
the electrolyte, and are intercalated
between the graphite
layers in the anode. Discharge reverses
this process.”
Bruce, Scrosati & Tarasacon,
Angew. Chem. Int. Ed. 2008, 47, 2930 – 2946
DOI: 10.1002/anie.200702505
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Enormous challenges remain.
First-generation lithium-ion battery:
*electrodes made of powders containing millimeter-sized particles
*polypropylene separator with millimeter-sized holes (…containing the
electrolyte).
*high energy density, but low-power density slow charge/discharge
*new intercalation hosts for electrodes can help, but the slow diffusivity of the
lithium ion in the solid state (ca. 108 cm2 ·s-1) limits discharge/recharge rates.
About 100 times slower than small ions in liquids.
“…an increase in the charge/discharge rate of lithium-ion batteries of more than
one order of magnitude is required to meet the future demands of hybrid
electric vehicles and clean energy storage.”
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Going to nanometer-scale solves some
problems.
Some I don’t understand: “(nanoparticles) enable…reversible
lithium intercalation into mesoporous -MnO2 without
destruction of the rutile structure.”
Some are pretty obvious:
tdiffusion
= L2/2D
Microscale to nanoscale  a million times faster!
High specific surface area goes with smaller
particle sizes.
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Nanometer scale creates new problems, too.
Worsened side reactions, due to extra surface
area.
Packing issues—nanopowders are less
dense than micropowders.
Nanoparticles may be harder to make
reliably.
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Lithium must intercalate into the
electrodes, not deposit on it.
Deposition of lithium metal on the higher
specific surface area of nanoparticles could be
catastrophic.
Lithium in water:
http://www.youtube.com/watch?v=8ypUVpwgcAA&NR=1
 Would other alkali metals be better/worse?
Other elements besides lithium (watch to end):
http://www.youtube.com/watch?v=uixxJtJPVXk
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It seems natural to wonder whether carbon
nanotubes ought to replace graphitic carbon.
The answer is no, due to lithium deposition issues.
“Carbon nanotubes do not seem to offer a major route to improved electrodes.”
Various lithium titanates and titanium dioxides are
more promising. Also other metal oxide fiber
formers. Looks like fairly serious materials science:
“Nanotubes/nanowires composed of TiO2-(B), the fifth polymorph of
titanium dioxide, retain the advantages of Li4Ti5O12 : low cost, low
toxicity, high safety, and an electrode potential that eliminates lithium
plating.”
Fibers are preferred because one long dimension ensures
good electrical connectivity, while two thin dimensions means
the intercalation involves just a few layers—no wasted mass.
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One way is to electroplate rods through, essentially, Anotop
filters. Dissolve the filter & coat with metal alloy as electrode
material.
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Problem: the electrode materials should not experience
large changes in volume on charge/discharge.
Leads to cracks or “pulverization” after many cycles.
Nanometer-scale particles seem to help with this—
probably the up side to that low density mentioned
earlier.
The Bruce, Scrosati, Tarascon article is actually organized from
“left” to “right” across a Li ion cell—e.g., Anode, Electrolyte, Cathode.
I have lumped the edges into “electrode”. The Cathode chemistry and Anode
chemistry clearly differ, but concerns about porosity, mechanical
stability, etc. must be similar.
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Enough already about the electrodes. What
about the electrolyte?
Liquid electrolytes are sometimes used (non-aqueous!).
Addition of nanometer-scale powders (Al2O3, SiO2, ZrO2) surprisingly helps in this case.
In such “soggy sands” apparently the balance between free ions and ion pairs is
favorably altered.
The future is in dry electrolyte/separators or Solid Polymer Electrolytes
And you thought SPE was Society of Plastics Engineers.
Or maybe you thought Society of Petroleum Engineers
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Poly(ethyleneoxide) is also known as
poly(ethylene glycol) or Carbowax.
Soluble in H2O, Benzene, methanol, DCM
Insoluble in diethyl ether & hexane
Toxic to kidney (due to impurities or on its own?) if applied to skin.
If you live to be 50, you’ll get to drink some!
Anyway, for SPEs you dissolve lithium salts into PEO.
Typically, one uses LiBF4.
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PEO has its problems for Li-ion batteries.
Conductivity of Li ion is only high at T > 70oC.
Al2O3, SiO2, ZrO2 again help (possibly due to
inhibition of PEO crystallization at lower
temperatures).
May we expect someone has looked into branching then?
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But maybe crystals (of the salt itself)
aren’t so bad.
PEO Chains
PEO Chains
AsF6
PF6- anion is also used;
here, AsF6- is used; astatine
belongs to the same
group as phosphorous.
You have to wonder:
How would a PEG-ylated
polypeptide LC perform?
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Lithium doesn’t grow on trees.
The lithium battery craze carries its own environmental risks:
http://www.dailymail.co.uk/home/moslive/article-1166387/In-search-Lithium-The-battle-3rd-element.html +
http://en.wikipedia.org/wiki/Salar_de_Uyuni
And speaking
of craze…check
out the pattern
on the floor of
Boliva’s Salar de
Unuye; Bolivia
is resisting
development to
avoid the damage
caused in Chile.
The Salar de Unuye is one of the largest mirrors
on earth when water coats the desert floor.
Salar de Unuye and Salar Coipasa
from space. The former is 25x
bigger than the Bonneville salt
flats. Square kilometers are flat
to +/- centimeters.
There are alternatives to the Li-ion battery—e.g., methanol fuel cells.
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Or we could just continue to burn oil.
http://www.districtofcolumbiadispatches.blogspot.com/
http://www.deseretnews.com/article/700027439/Ro
bot-subs-key-to-oil-spill-cleanup.html
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