Battery Technology - May 2021 - 15

Michael Wang, a U-M materials science and engineering Ph.D. candidate, uses a glovebox to inspect a lithium-metal battery cell. (University of Michigan)

ment. U-M's team has found a workaround that essentially allows the battery to " build itself. " Their approach harnesses the lithium already contained
within common cathode materials. When
the battery is charged for the first time,
the lithium ions on the cathode side of
the cell are extracted and moved to the
anode side of the cell - effectively synthesizing a lithium-metal anode.
" Because we can use electrochemistry
to make the battery 'build' its own lithiummetal anode, we can completely eliminate
that step of the manufacturing process.
Thus, we can manufacture batteries that
are initially 'anode-free,' " Sakamoto said.
In the 1980s, rechargeable lithiummetal batteries that used liquid electrolytes were considered the next big
thing, penetrating the market in early
portable phones. But their propensity to
combust when charged led engineers in
different directions. The lithium atoms that
shuttle between the electrodes tended to
build tree-like filaments called dendrites
on the electrode surfaces, eventually shorting the battery and igniting the flammable
electrolyte. The lithium-ion battery - a

more stable but less energy-dense technology - was introduced in 1991 and
quickly became the new standard.
By removing one key ingredient from
lithium-ion's three-component formula -
the anode - U-M's production method offers
a potential reduction in manufacturing cost.
And the fact that the process can be completed using current lithium-ion battery
manufacturing means electric vehicle makers could adapt U-M's technology without
having to completely retool their facilities.
" There is already a lot of capital investment that has gone into lithium-ion batteries, " Sakamoto said. " So, if one were to
think about replacing a current lithiumion battery with a new kind of battery, that
requires a completely different approach
to manufacturing and a whole lot more
investment has to go into that.
" Attempts to supplant incumbent battery technology requires dramatic improvements in performance, safety, and
cost - a trifecta, " he added. " In this study,
we focused on reducing the cost by simplifying the manufacturing process of
batteries using the holy grail anode -
lithium-metal. We hope the outcome of

Battery Technology, May 2021

this work can enable substantial reductions in battery cost to achieve EV cost
parity with internal combustion enginepowered vehicles. When this happens,
the widespread adoption of EVs will,
hopefully, be imminent. "
The potential cost savings generated
by U-M's technology could extend to
consumers and governments as well. One
of the major hurdles to more widespread
adoption of electric vehicles is the current inadequate number of charging stations across the U.S. Areas without high
volumes of car traffic are unlikely to offer
as many options for charging, making
them less welcoming for electric vehicles
and causing what the industry refers to
as " range anxiety. "
By doubling the range an electric vehicle can travel on a single charge, U-M's
battery technology could alleviate the
anxiety by reducing the number of charging stations needed, Sakamoto believes.
This article was written by James Lynch,
Research News & Feature writer at
Michigan Engineering, published by the
University of Michigan, Ann Arbor.

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Battery Technology - May 2021

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