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Helping batteries to fail gracefully

Researchers at the US government-owned Sandia National Laboratories are working on a project to investigate how lithium-ion batteries fail – with the aim of making sure that batteries provided for future electric vehicles will not damage other systems when they run out of power.

“We want to develop a battery that has a graceful failure,” said Dan Doughty, manager of Sandia’s Advanced Power Sources R&D department.

The technical goal is to comprehend mechanisms that lead to poor abuse tolerance, including heat and gas generating reactions. Understanding the chemical response to abuse can point the way to better battery materials but, Doughty warned, there is no “magic bullet” for completely stable lithium-ion batteries.

The answer, he says, “will come from informed choices on improved cell materials, additives, and cell design as well as good engineering practices”.

In other work, Sandia is undertaking accelerated life tests to come up with a way of prolonging battery life.

Doughty said: “We have two approaches: the empirical model generates life prediction from accelerated degradation test data, while the mechanistic model relates life prediction to changes in battery materials. Our approach provides an independent measure of battery life so we don’t have to rely on what battery manufacturers tell us.”

The Sandia projects are part of the so-called “Freedom Car” electric vehicle project which was announced by President George W Bush in 2002.