Simanaitis Says

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SOLID-STATE BATTERY UPDATE

TOYOTA HAS recently released data on its battery research, both for solid-state batteries expected during a 2020s’ timeframe as well as a next-generation lithium-air concept perhaps a decade beyond that.

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An overview of Toyota battery research. Image from www.toyota-global.com

This amplifies on earlier news of research offered by the company about a year ago (see http://wp.me/p2ETap-UD).

A solid-state battery replaces a conventional battery’s liquid electrolyte with a solid ceramic or polymer counterpart.

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A solid-state battery’s cells are directly connected by a solid ceramic or polymer. Image from http://www.toyota-global.com.]

Benefits are multifold: A solid-state battery is more compact than a conventional one. It can be shaped for better packaging. And its chemistry allows for higher voltages and enhanced characteristics of charging and discharging.

Toyota’s lab prototypes are still only coin-sized, but upscaled components are expected to enter production in the early 2020s. Already, power outputs of solid-state batteries are around 2000 watts/liter, on par with the best lithium-ion batteries but higher than the less-costly nickel/metal-hydride technology.

Power density measures how quickly a battery can deliver or accept its charge; loosely, how well an electric car can accelerate, how quickly its battery can be recharged.

Toyota says the energy density of its solid-state concept is around 400 watt-hours per liter. This compares with a maximum of about 300 watt-hours per liter for a production lithium-ion counterpart.

What’s more, engineers say there’s potential for much higher energy densities with solid-state technology, perhaps between 600 and 700 watt-hours per liter.

Energy density is a measure of potential electric car range, Toyota engineers claiming the first solid-state production batteries will offer EV range of 300 miles on a single charge.

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Generally, the energy densities of batteries, per weight or per volume, are inferior to corresponding values of other options.

Each generation of battery technology improves performance, though conventional liquid fuels continue to be imposing targets.

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An overview of battery options. Nickel/metal-hydride data from Wikipedia; others from www.Toyota-global.com.

Toyota is also exploring lithium-air technology, seen as a next step beyond solid-state batteries. Its lithium-air batteries have energy densities around 1000 watt-hours per liter. Power outputs are still being optimized.

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Using oxygen for the cathode and lithium for the anode give a smaller, lighter package. Image from www.toyota-global.com.

Lithium-air chemistry replaces the lithium cathode with one interacting with oxygen. One benefit is less material—and hence lighter packaging and better weight-specific performance. Toyota says lithium-air technology may come to fruition after 2030. ds

© Dennis Simanaitis, SimanaitisSays.com, 2014

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