Eli5: What exactly is happening, or changing, in a lithium battery when it “wears out” to cause it to have a diminished capacity?

Question

When you read about it, you’ll learn that the average lithium battery can take about 300-500 charge cycles before its considered worn out. What exactly changes inside the battery for it to reach a worn out status?

In: 217

Answer 1

Basically this happens [https://www.youtube.com/watch?v=n0jy6uVjRFQ](https://www.youtube.com/watch?v=n0jy6uVjRFQ) except much slower, with lithium and in the battery electrolyte. That that sort of dendritic growth is of course bad because it will first reduce battery capacity and eventually short the battery.

I would say the rule of thumb is more like 1000X full cycles, but it’s a bit of a line in the sand because it depends on how deep the typical charge/discharge cycle is, how high the current is and of course, at what point of degradation is the battery considered no good anymore.