Central Glass building the chemicals that could take
lithium-air batteries 500 miles
Satoru Narizuka
Editor’s note: This article is by Senior Research
Engineer Satoru Narizuka of Central Glass.
‘Electrolyte’ isn't just a fancy word to describe sports drink
additives that help athletic performance. An electrolyte is also a vital component
in electric vehicles’ rechargeable batteries. And for IBM’s lithium-air battery
project, we at Central Glass in Japan are developing electrolytes for
rechargeable lithium-air batteries that could lead to an EV with a 500
mile-per-charge (800 km) range.
Electrolytes are an essential part of all batteries, but
those used for state-of-the-art EV lithium-ion batteries are unstable in
lithium-air batteries. Although lithium-ion batteries can power an EV for as
many as 300 miles (480 km) per charge – depending on the manufacturer – stable
electrolytes will be necessary for a next generation of EVs powered by 500
mile-per-charge lithium-air batteries.
Narizuka in the Central Glass lab.
Electrolytes in EV
Batteries
Batteries have three main components: the anode, the cathode
and the electrolyte.
In an EV lithium-ion battery, the electrolyte allows lithium
ions to shuttle back-and-forth between the anode and cathode during the
discharge and charge cycles. During discharge in lithium-air batteries, lithium
ions move through the electrolyte from the lithium metal anode to react with
oxygen at the cathode. The reverse reaction occurs during recharge, and lithium
metal is deposited on the anode – and oxygen is released back into the
air.
The challenge: improving stability of the electrolyte in the
presence of both the lithium metal anode and the lithium oxide products in the
cathode.
Going from ion to air
Tank-sized
Li-ion batteries needed to go 500 miles
For a car running on today's lithium-ion batteries to match the range provided by a tank of gasoline, car manufacturers would need several more batteries which would weigh down the car and take up too much space – making an EV the size of a tank!
To popularize electric cars, an energy density that is 10 times greater than those of today’s lithium-ion batteries is needed.
Typical electrolytes employed in lithium-ion batteries do
not work in lithium-air batteries. They quickly react with lithium oxide
products formed at the cathode, leading to a degradation of battery performance
and lifecycle. A viable electrolyte must be stable throughout both the
discharge (i.e., while driving) and the recharge (while plugged in) cycles.
We are currently testing several candidate electrolytes
using a suite of state-of-the-art analytical methods. Our final desire is to
find an electrolyte system that will provide high Li-ion conductivity (which
translates to high battery power) while not significantly degrading during
battery charge cycling, over time. We believe a combination of these two
features will be a huge advance in the quest to build a Li-air battery for
electric vehicles.
By working with IBM Research, we’re close to developing this
stable electrolyte that can achieve 500 miles per charge – within a battery
that lasts 20,000 total miles. And we’ll ultimately realize the next generation
of electric vehicles.
