Metal fatigue in anodes identified as key cause of solid-state lithium battery degradation

A team of materials scientists and engineers affiliated with several institutions in China has found that one of the major reasons solid-state lithium batteries fail over time is metal fatigue in the anode, which contributes to interface degradation and dendrite growth. In their paper published in the journal Science, the group describes how they studied dendrite growth in solid-state lithium batteries using scanning electron microscopy and what happened to their anodes over time.

One of the main goals of solid-state lithium battery makers is to make them competitive with standard lithium-ion batteries. Such batteries, it has been noted, would be a welcome improvement because they are much safer and have much higher energy densities than batteries currently in use. Unfortunately, such batteries do not last as long due to dendritic growth, which are needle-like structures that build up in the lithium, causing short circuits and battery death.

In this new effort, the research team sought to learn more about the reason for dendritic buildup and any other causes of solid-state lithium battery failure. To that end, they used phase-field simulations and scanning electron microscopy to take a closer look at the battery’s components during various stages of its useful life.

In so doing, they found that metal fatigue occurring in the anode (due to the expansion and contraction of lithium during charging and recharging) was the main reason for battery failure. Such fatigue, it was found, promoted the growth of dendrites.

More specifically, they found that the constant expansion and contraction led to the development of microvoids and cracks at the anode–solid-state electrolyte interface, which in turn led to dendrite growth and degradation—even at low densities.

The researchers also discovered that the fatigue they found in the batteries conforms to the Coffin-Manson law (an equation that describes the behavior of low-cycle fatigue), which they note means it is intrinsic to the nature of the battery and predictable. They suggest this offers hope of finding a way of preventing the metal fatigue and subsequent dendrite growth and eventual failure of the battery.

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