Seems you should know what the issue is, but by your advice to remove trickle charging we can see that you do not (these are not open cell lead acid batteries that constantly gas electrolyte). Current battery technologies share a common characteristic that the higher their charge, the more internal resistance they have. Similarly, they breakdown through cycling of extreme temperatures.
The most optimal charge method (the one that produces both the greatest amount of charge per cycle and allows for the greatest number of cycles) begins with checking the cell voltage, the resistance, and the temperature to determine roughly the charge level. If the cell is undercharged a higher current can be applied, but typically no higher than c/10 for a very depleted cell. As the resistance raises (or the cell temperature) the current needs to be reduced, eventually to ~ c/20 (your trickle charge). Trickle charge is not just a small amount of current, it is specifically an amount small enough that it does not raise a fully charged cell's temperature enough to cause any thermal breakdown, but still provides a charge. Increasing the bulk charge rate (even to c/5) will not do terrible damage, but it will reduce the life of the battery (maybe you get 600 charges, instead of 1000, etc.).
So what's the issue here? Speed. A charge rate of c/10 takes 10 hours to charge, c/20 takes 20 hours, and so on. So a completely drained phone might take 15 hours to charge completely safely to 100%.
Instead the phone manufacturers find a temperature that doesn't cause immediate catastrophic damage, identify a constant charge rate that shouldn't pop this limit, and charge you to ~85% or so, then back off slightly for the last 15%. All this, so you can charge your phone in a couple of hours (or minutes with SUPER DUPER FAST CHARGING), but you are doing much more damage to your battery.