Researchers in the Power Sources R&D group at Sandia
National Laboratories have been driving nails into batteries,
heating them to extreme temperatures, overcharging them, and putting
them into some of the most adverse conditions possible to see how much
abuse they can take before they blow up.
Sandia researcher Peter Roth prepares to blow up a battery to see how robust it is. The work is part of the DOE-funded FredomCAR program. (Photo by Randy Montoya)
And for certain types of lithium-ion batteries the answer is a
lot.
The research is part of the DOE-funded FreedomCAR program that
is looking at lithium-ion batteries to be part of hybrid
electric-gasoline powered vehicles and eventually plug-in hybrids.
Current hybrid vehicles run on gasoline and use nickel-metal
hydride batteries as the energy storage device for the electric motor.
The intent of the battery portion of the FreedomCAR program is to
replace the older type batteries with safe lithium-ion batteries that
have six times the energy density of lead-acid batteries and two to
three times the energy density of nickel-metal hydride batteries.
“Lithium-ion batteries, generally found in laptop
computers and power tools, have greatly improved over the past few
years,” says Peter Roth, lead researcher for
Sandia’s FreedomCAR battery efforts. “In fact, they
have improved so much that we expect to see them in hybrids later this
year and possibly even in short-range plug-in hybrids within two
years.”
He notes the battery industry has made great strides in
manufacturing safe, long-lasting, and affordable batteries. Sandia has
played a role in assuring that the lithium-ion batteries are indeed
safe and can operate for long periods of time.
Sandia is a National Nuclear Security Administration (NNSA)
laboratory.
One way Sandia researchers have helped determine how safe and
long-lasting batteries are is by testing them in adverse situations to
determine when and how they can fail or leak their electrolyte.
The Sandia research group obtains batteries and battery
materials from research laboratories, like Argonne National Laboratory,
and companies that manufacture and sell batteries. They then study the
stability of the materials, their flame-retardant performance,
high-temperature integrity of separators between the cathode and anode,
and general thermophysical properties.
“We look at fundamental chemistry, wanting to
discover the kinds of gases they emit when they are heated and
explode,” Roth says. “We also build smaller
prototype batteries that once we get the chemistry right may eventually
be built full size to go into vehicles.”
Roth says that some of the newer batteries, like the new
lithium/iron phosphate ones used in handheld power tools, are extremely
resilient and less reactive when subjected to extreme conditions,
unlike other types of batteries.
These are the type of batteries the FreedomCAR program is
seeking, particularly for plug-in hybrid electric vehicles (PHEV). A
PHEV is a regular hybrid that operates both on gas and a battery but
has an extension cord. It can be filled with gas at the gas station and
also can be plugged into any 120-volt outlet for all-electric driving.
It’s almost like having a second fuel tank that is used first
— only it is filled up at home.
Industry experts predict that plug-ins that can run 10 miles
on all electric are two to three years away while plug-ins that can run
40 miles on all electric are three to four years away.
Plug-in hybrids make it essential that batteries be completely
safe since they will be sitting in people’s garages while
they recharge.
Lithium-ion batteries that will go into vehicles will be
similar to computer laptop batteries. One main difference is there will
be “a lot of them,” Roth says.
The first hybrids using lithium-ion batteries will be on the
market later this year. Mercedes-Benz has announced that it will
shortly launch the S400 BlueHybrid. After that, it will launch the S300
Bluetec Hybrid, a diesel car that is combined with a lithium-ion
battery. Also, General Motors plans to introduce a 40-mile plug-in
hybrid with lithium-ion batteries in 2010.