I think he wants to know exactly what he can do to make his cell phone battery last longer. And he wants proof. Naturally, wikipedia cites proof, such as : Research & Development World and Temperature dependent ageing mechanisms in Lithium-ion batteries – A Post-Mortem study - ScienceDirect
TLDR, there are 2 forms of loss : calendar loss and cycling loss.
Calendar loss happens no matter what you do. Charging the battery up more (over about 80%) greatly accelerates the rate it loses capacity. It can lose 1% a month or more. Discharging the battery below 20% also greatly accelerates the capacity loss.
Cycling loss happens every time you discharge the battery and then charge it up again. You get roughly 1500 cycles tops for the type of cell chemistry a cell phone battery uses (often less) before the battery is shot.
So you cannot win.
If you leave the phone on the charger all the time, it will keep the battery at 100%, and you are losing about 1% of the max capacity every month. So after 3 years, you are down to 2/3, and basically it’s toast. (it will degrade more and more rapidly from there)
If you take the phone off the charger before 100%, it will begin to discharge. If you use it some, it’s discharging. This is a cycle because you are going to have to recharge it now. Do this for 3-5 years, and the battery will be toast.
Look, a new battery is $30. How much does your phone plan cost? Having a cell phone with an active plan is costing you far more per month than a once in 3 years replacement of the battery will cost. Basically, every month, that future battery replacement is cost you about $1 ($36 new battery with the tiny screwdrivers you need/36 months) while the phone plan is cost you at *least *$40 a month.
The phone itself will be trash in 3-6 years. You can keep using old phones for a while, but eventually you will be unable to use any recently published apps, and the existing apps will be unusably slow. Replacing the whole phone is going to cost $150-$650, depending on how nice a new phone you want. *That’s *what costs ya.