Hey guys! Thought you might be interested in this neat video explaining some of the chemistry behind Li-ion cell degradation (@6:20): Basically in a normal Li-ion cell, there is a thin protective barrier that forms on the inside of the terminals called the "solid electrolyte interface": This layer is thin enough to be permeable to Li ions, allowing full charging. However, over time this layer builds up to a thickness that restricts ion flow, thus lowering maximum charge capacity: The main factors that cause this build up are: 1) ambient temperature during charging (heat increases the electrolyte solidification rate) 2) charging current (resistive heating effect at the electrode) 3) microscopic expansion/contraction of the electrode (surprise surprise, also related to heat ) So it seems the main takeaway is inline with conventional battery wisdom of storing batteries in a cool, dry environment and not using fast-charging where possible, instead preferring trickle charging. (I would also conjecture the density of Li-ions at the electrode attracts electron buildup at the electrolyte interface, which in turn speeds-up solidification. This explains why it's recommended to store batteries at less the maximum charge over the long term.) Happy charging folks, and keep your batteries cool.