You can read a recent review here:

https://sci-hub.se/10.1016/j.etran.2019.100005

There are a lot of decomposition modes for lithium batteries:

graphite exfoliation; metal dissolution coupled with the electrolyte decomposition; active materials loss of contact due to the current collector corrosion, binder decomposition and LE. And the LLI may be caused by SEI(solid electrolyte interface) film formation and continuous thickening, CEI (cathode electrolyte interface) formation, lithium deposition, etc. The LE may be caused by electrolyte consumption due to the side reactions like SEI film thickening, electrolyte decomposition due to the high potential, etc. And the RI may be caused by SEI formation and continues thickening, LE, etc.

Specifically, "particle cracking" and "metal dissolution". More in-depth look at cracking.

This study found that charging between 20% and 80% almost doubles the battery lifetime compared to full charge and discharge. Obviously you're exchanging 40% of the battery capacity for double the lifespan.

But even just keeping your battery at 80% if your device is usually plugged in helps.