Engineering 101

Battery Breakdown—What Causes Charge Decay?

Battery recharging is problematic. With each subsequent charge, batteries decay.

An international, multi-agency/university study published in Science looks at what drives a battery’s lifespan and how those factors change over time in fast charging conditions. Battery decay seems driven by the properties of individual electrode particles, but after several dozen charging cycles, how those particles are put together matters more.

Researchers used computer vision techniques to study how the individual particles of a rechargeable battery electrode break apart over time. They used X-ray tomography to reconstruct 3D pictures of the cathodes of batteries after going through different charging cycles, cut those 3D pictures into a series of 2D slices, and used computer vision methods to identify particles. They identified more than 2,000 individual particles. They calculated features such as size, shape, and surface roughness and traits such as how often particles came into direct contact with each other and how varied the particles’ shapes were.

After ten charging cycles, the most prominent factors were individual particles’ properties, including how spherical the particles were and the ratio of particle volume to surface area. After 50 cycles, however, pair and group attributes — such as how far apart two particles were, how varied their shapes were, and whether more elongated, football-shaped particles were oriented similarly — drove particle breakdown.

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