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Stable Electrolytes Will Move Next-Gen EVs

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.