I think the text of this post should expand on the question.

For example, are you referring to the change of internal resistance of a battery over years of storage, or during use?

A graph showing the increase of resistance over time would help describe the question.

Here is such a graph (for an inactive battery):

Credit: Electropaedia

The question could then be answered in a separate post.
In that post, you could remind the casual reader on the basic design of a conventional battery.
What is a cell? What is electrolyte? Etc.

Then you could describe the chemical changes during the lifetime of the battery.

Hope it helps.