I've seen some questions about loss of capacity due to internal resistance and oxidation of plates. I've also learned that these batteries have protection circuits.
But I'm curious about Self discharge, the phenomenon of charging a Lithium Ion battery to 100% and leaving it unused, only to return months later to find it has not preserved a full charge and requires topping up.
Is self discharge over time attributable to the chemistry of the battery? Is it the overhead of the protection circuitry? Or is it more complicated than that or some combination of the two? What is the mechanism behind self discharging Lithium ion batteries?