Amidst the fanfare of a standing-room-only press conference
in Detroit
today, General Motors rolled out the T-shaped
lithium-ion battery pack for the Chevy Volt and announced its cells will
be built by Korean battery manufacturer LG
Chem.
The press
conference capped off a two-year wait in which the giant automaker auditioned
two manufacturing teams for the role of battery supplier for the
highly anticipated Chevy Volt,
widely considered to be the biggest vehicle program in GM's history.
General Motors' embattled chairman,
Rick Wagoner, told a
media audience the decision to go with LG Chem instead of
Massachusetts-based A123 Systems
"was based on performance, production readiness, efficiency, durability and LG
Chem's demonstrated track record of exceptional quality."
The
competition for the GM battery development and manufacturing contract has been
highly scrutinized in technical circles because one team (LG Chem and Compact Power, Inc.) is using a
manganese-spinel chemistry for the battery's positive electrode, while the other
(A123 and Continental Automotive) employs a nano-phosphate material. Many
experts said the choice of the chemistry would be critical so that the
battery wouldn't be plagued by so-called "thermal runaway," which had
reportedly been a problem for some lithium-ion batteries used in laptops and
cell phones.
GM,
however, said safety was only one of many reasons for the choice of LG
Chem's manganese-spinel. "Safety was definitely an important part, but
ultimately it was no more of a factor than durability, cost, performance or
manufacturability," GM spokesman Rob Peterson told Design News.
The plan
announced yesterday calls for GM to use battery cells from LG Chem's plant in Korea, then build the entire battery assembly in
a GM plant located in southeast Michigan.
The assembly includes such items as electronic controls, heating, cooling and
cabling. GM said Compact Power would initially do the integration and
assembly for Volt prototypes, but added GM would take over the assembly
process once its own plant is up and running.
"We'll
start preparing the factory in early 2009 and we will start loading the
(manufacturing) equipment into the factory at mid-year of 2009," Peterson said.
Engineers
at Compact Power cited two technical advantages inherent in their team's
battery design. The manganese-spinel chemistry combines with battery separator
technology that enhances safety, they said. Known as a Proprietary Safety
Reinforced Separator, the semi-permeable membrane is coated with a ceramic
material, which is said to make it mechanically and thermally superior to other
separators.
Also key to
the company's technology was its use of a "stack-and-fold" configuration in a
laminated package, which could provide GM with easier manufacturability. The
stack-and-fold concept is used as an alternative to the well-known cylindrical
design of conventional batteries.
"Stack-and-fold
is easier for a large electrode manufacturer," said Mohamed Alamgir, director
of research for Compact Power, Inc. "Winding them around a mandrel would be no
trivial task."
GM
representatives said yesterday its decision to go with LG Chem is part of a
strategy that has been unfolding for months. "We're really confident that we
have the right plan and the right balance of technology suppliers," Peterson
said. "Right now, we don't see any hurdles in our way for having the battery
ready by 2010."
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