Automotive Engineering - October 2021 - 16

BYD's
Blade battery
exploded. Typically
liquid cooling is employed
for automotive applications and
BYD uses a special thermally-conductive
adhesive between the cooling system and the cell stack.
I
f I buy an electric vehicle, will its battery catch fire?
Statistically such considerations are almost irrelevant.
EV battery fires are no more apt to occur than
a gasoline blaze in a new combustion-engine vehicle.
Most EVs currently in use are admirably reliable and safe.
But a spate of highly-publicized Tesla fires (some the
result of impact or battery puncture) and GM's $1.8 billion
recall of every single one of the 142,000 Bolt EVs and
EUVs ever sold, due to a manufacturing defect found in
their lithium-ion batteries supplied by LG Energy
Solution, is enough for some prospective buyers to think
twice about making the jump to EVs.
" It's given my wife and me pause, " said Kevin
Whittle, a Farmington, Michigan-based industrial automation
consultant. " We were looking at various electrics,
not at Bolt specifically. But EV fires and the recall
concern us. We just don't trust the tech yet. " Whittle
mentioned that his confidence in buying a new EV was
further sapped when he saw an online video that
showed a sign in a San Francisco public parking lot. It
read: " For customer safety: CHEVROLET BOLT EVs are
STRICTLY PROHIBITED from parking at this facility.
Thank you for your compliance! "
" The batteries in those EVs use NCM, or nickel-cobaltmanganese,
cathodes, " explained Dr. Zhong (John) Chen,
project manager of vehicle engineering at BYD's northern
California headquarters. " With NCM you can easily get a
fire. Users of that chemistry have to put a lot of effort behind
thermal management and safety, adding cost. "
Enter lithium-iron-phosphate (LFP; LiFePO4), a proven
chemistry whose benefits were somewhat bypassed by
the industry's settling on lithium-ion cells dominated by
16 October 2021
COVER STORY
BLADE
RUNNER
The Chinese mobility-and-energy
giant's novel 'Blade' battery
eliminates the cell module level
to compete with NCM chemistry
at significantly lower cost - and
greater proven safety.
by Lindsay Brooke
NCM, experts note. Where LFP cells shine primarily is in their inherent
stability, typically sacrificing some energy density versus NCM for resistance
to thermal runaways. At approximately 200 Wh/kg at the cell level,
they're about 10-15% less energy-dense than most NCM cells (Tesla's
2170s are rated at over 260 Wh/kg).
" LFP batteries are probably most notable for their positive safety profiles
relative to other chemistries, " noted Guidehouse Insights research
analyst Maria Chavez in a May 2021 report. The chemistries " are generally
thermally and chemically stable-plus, the phosphate chemistry has
been shown to offer a long lifetime, " she stated.
LFP batteries have demonstrated life cycles in excess of 10,000 cycles,
or millions of highway miles. They exhibit lower internal resistance than
NCM types, enabling faster power delivery for improved vehicle acceleration.
Discharge voltage of LFP is very consistent. Strategically, their
chemistry does not include cobalt or nickel. And the lack of those metals
makes them inexpensive, with LFP costs under $100/kWh in China.
That cost advantage has prompted Tesla, Ford and Volkswagen to
announce a shift to LFP cathodes in order to move away from cobalt
and nickel. This is both for ethical/mining reasons as well as to offer
significant cost reduction for some EV models that do not require
high performance and +200-mile driving ranges (that will be covered
by high-manganese content lithium battery chemistries with higher
specific energy). Ford, however, has indicated that LFP cathodes may
also end up in the batteries of its electric F-Series.
Eliminate the modules
Prior to its emergence as a consumer electronics giant and an automaker,
China's BYD had been developing lithium- and nickel-based battery
technologies since 1995. LFP became a major R&D focus, leading to the
" Blade " battery, an innovation in lower cost, safer EV battery packs. As
Dr. Chen explains it, " The blade battery originates from a concept called
AUTOMOTIVE ENGINEERING
BYD
Automotive Engineering - October 2021

Table of Contents for the Digital Edition of Automotive Engineering - October 2021
