January 11, 2016

New Stanford battery shuts down at high temperatures and restarts when it cools

(January 11, 2016)  Stanford researchers have developed the first lithium-ion battery that shuts down before overheating, then restarts immediately when the temperature cools.

The new technology could prevent the kind of fires that have prompted recalls and bans on a wide range of battery-powered devices, from recliners and computers to navigation systems and hoverboards.

"People have tried different strategies to solve the problem of accidental fires in lithium-ion batteries," said Zhenan Bao, a professor of chemical engineering at Stanford. "We've designed the first battery that can be shut down and revived over repeated heating and cooling cycles without compromising performance."

Bao and her colleagues describe the new battery in a study published in the Jan. 11 issue of the new journal Nature Energy.

A typical lithium-ion battery consists of two electrodes and a liquid or gel electrolyte that carries charged particles between them. Puncturing, shorting or overcharging the battery generates heat. If the temperature reaches about 300 degrees Fahrenheit (150 degrees Celsius), the electrolyte could catch fire and trigger an explosion.

Several techniques have been used to prevent battery fires, such as adding flame retardants to the electrolyte. In 2014, Stanford engineer Yi Cui created a "smart" battery that provides ample warning before it gets too hot.

"Unfortunately, these techniques are irreversible, so the battery is no longer functional after it overheats," said study co-author Cui, an associate professor of materials science and engineering and of photon science. "Clearly, in spite of the many efforts made thus far, battery safety remains an important concern and requires a new approach."

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