They are Li-ion batteries and not Li-iron batteries is my understanding. Here is the picture of the batteries that I have taken out from the UPS router. One battery is missing in the pic as I am using it for a radio now.Would be interested to know... it is interesting router UPS contains 18650 LiFePO4 batteries.
On a side note, most of the laptop's use 18650 Li-ion batteries inside their battery packs. When you say 6 cell battery, those are 3 pairs connected in series.