On Wed, 14 Nov 2007 06:02:33 -0000, Andrew Sarangan
wrote in
. com:

It is not unfeasible in the near
future to have a lithium-oxygen battery to power a light GA aircraft
with the same endurance as gasoline with comparable fuel+engine
weights.


Thank you for the information.

From the research below, it does indeed seem that the lithium-oxygen
battery offers the highest energy density that the laws of physics
permit.



http://www.polyplus.com/technology/laircell.htm
The high specific energy of the Li-Air couple is close to that of
liquid hydrocarbons such as gasoline, and much higher than that of
methanol.



http://www.excellatron.com/technology.htm
The performance of conventional lithium battery systems is limited
by the fundamental capacities of both the cathode and anode used
in these batteries. The best cathode materials in lithium ion
batteries have a specific capacity of less than 200mAh/g. The
most widely used anode material, graphitic or soft carbon, has a
specific capacity of 372mAh/g. Metal/air batteries have a much
larger specific energy than most of the available primary and
rechargeable batteries. These batteries are unique in that the
active cathode material (oxygen) is not stored in the battery.
Oxygen from the environment is reduced at a catalytic air
electrode surface forming either an oxide or peroxide ion that
then reacts with cationic species in the electrolyte.Among various
metal/oxygen batteries, Li/O2 couple is especially attractive
because it has the potential of the highest specific energy
(5,200Wh/kg) among all the known electrochemical couples. The
specific energy of lithium air batteries is expected to be an
order of magnitude larger than that achievable using conventional
lithium or lithium ion batteries. Excellatron has expanded its
technology base to lithium air batteries. Until now,
commercialization of these batteries has been hindered by several
problems such as corrosion and low capacity. The unique
technology developed by Excellatron has overcome these problems
and pushed Li/Air batteries closer to practical applications.
Recently, we have successfully demonstrated the feasibility of a
rechargeable lithium/oxygen battery, and Li/Air demonstration
samples have been successfully delivered to a customer.



http://www.batteriesdigest.com/lithium_air.htm
Although practical Lithium-air batteries are not yet available
from which to obtain data, the estimated value shown above, of
25% of the theoretical value, was selected. With technological
improvements, one wonders if practical densities over 1000 Wh/kg
are unreasonable to expect.

using a lithium anode with an air cathode to supply the oxygen (as
is commonly done with the very popular Zinc-air hearing aid
batteries) may result in the highest practical energy density
possible in a metal-based battery which has an abundant air
supply, environmental friendliness, and reasonable safety. Since
the anode is lithium metal which reacts aggressively with water,
a nonaqueous electrolyte is used with an organic polymer film
separator to facilitate the supply of oxygen from the air. The
cathode consists of a metal current collector surrounded by a
layer of carbon which provides the platform for combining the
oxygen with the lithium ion which moves from the electrolyte to
form lithium peroxide or lithium oxide. Electrolytes can either be
non-aqueous liquid or polymer electrolyte.

Reversability of the reaction to allow electrical recharge of
Lithium-air is possible. Despite classifying the Lithium-air cell
as a primary battery, the literature does include data on the
performance of a rechargeable form, researched by Abraham, et. al.

As noted in the Zinc-air experience, a virtually unlimited amount
of ambient air can be used to supply the oxygen, but as a result,
it also adds the limitation of convenience limiting the operating
life of about two weeks after exposing the cathode material to the
air. Unlike Alkalines, which just ‘sit there’ when not used for
days weeks or years, the Lithium-air battery cannot be put into a
standby mode conveniently. The solution here is to choose the
application which properly suits the continuous period after
activation.


Very low power density is another constraint of the Lithium-air
battery. Unlike the high power providers of chemistries such as
Lead-acid, current densities of Lithium-air can be as much as
1,000 times lower in order to extract the maximum amount of
energy. Low current may not be a problem if the application is
tailored to the capability, but one does not look upon Lithium-air
as a replacement car starting battery.

The problem of temperature range must be considered again because
the performance of Lithium-air varies by a factor of 5 over the
-20 0C to +40 0C range. It is important to note that the battery
must be tuned to the application because Lithium-air batteries are
not going to start Minnesota autos in January.

But the Army realizes that major obstacles exist for Lithium-air,
especially in the area of temperature range. The present study
looks at liquid electrolyte and the carbon black coated anode
current collector. Over temperature ranges from -30 0C to +40 0C,
the cells were discharged at constant currents from 0.05 to 0.5
mA/cm2. Cells operated at +40 0C gave nominally 10 times more
specific capacity than those at -30 0C.



http://www.freshpatents.com/x1429144000psbc.php
patent applications listed are from June 2005 to current and
include Date, Patent Application Number, Patent Title, Patent
Abstract summary and are linked to the corresponding patent
application page.




http://micro.magnet.fsu.edu/electrom.../metalair.html
Figure 1 shows a rope battery, which is a type of aluminum/air
battery. At its tip is the aluminum anode, followed by the
separator, oxygen cathode, and protective outer layer.



http://www.batteriesdigest.com/metal_air.htm
High Energy density Lithium-Air... with No Self-Discharge (Session
8.2) Polyplus has approached the challenge of the Lithium metal
electrode with a coating of a glass-ceramic membrane, sealing the
Lithium from an aqueous catholyte. The resultant structure
exhibits very small self discharge, ordinarily a large contributor
to cell failure. Test cells have produced 0.5 mAh/cm2 for 230
hours exhibiting approximately 100% Coulombic efficiency.


A production oriented cell construction with double sided lithium
anode, solid electrolyte and double sided air/cathode is
anticipated to have 600 to 1000 Wh/kg energy density.


To reduce fears of mechanical safety hazards, the cells have been
subjected to crush tests which have fractured the glass-ceramic
membrane with only a 2-30 C temperature rise, followed by a
gradual decline in open circuit potential over several hours. An
operational sample of the water-activated cell was shown at the
conference.




http://www.michigansmalltech.com/Pre...E-1741B7A8EC46
Oxazogen obtains $100,000 grant for lithium air battery research
May 9, 2007

“The lithium air battery is seen by many in the field as the
ultimate battery, so improving it is something that could affect
our very way of life,” Sarkar said.

“Lithium air batteries show great promise in terms of energy and
power density,” he said. “Their market potential is in the
billions of dollars. If our approach is successful, the membrane
that we’re developing could help make the lithium air battery a
marketable success.”