Im not a battery expert- but these are the batteries that I bought. This is a totally non-technical explanation: I think of them like this- they have nearly the same performance as similar rated LiIon bats- but they can be charged many more times than LiIon. The bats I got are rared for something like 2000 charges, I think LiIon are half that. Also thes LiFeO4 batteries are un-protected but they are guaranteed not to blow-up with abuse whereas the LiIon will blow up under certain conditions.
here is an awesome deal and where I ordered mine:
Rechargeable Batteries & Battery Chargers - 6 RCR123A 3.0V 750mAh LiFePO4 Rechargeable Batteries with a Smart Charger -Specials
if you use: "tenergydeals" you get free shipping
Copied and pasted from the site specifications:
New Chemical LiFePO4 Li-Ion battery
* Rechargeable LiFePO4 RCR123A 3.0V 750mAhBattery
* Life cycle: 2000 times (Traditional Li-ion: 500 times)
* Never explodes or will catch on fire
* 100% Compatible with Disposable CR123A Batteries
* Working Voltage:3.2V and Peak Voltage: 3.6V
* Charging cut-off voltage: 3.6V
* Discharge cut-off voltage: 2.2V
o Please never overdischarge battery below 2.2V/cell
o Charge this battery with LiFePO4 RCR123A smart charger.
* Capacity: 750 mAh
* Maximum discharging rate:< 550 mA
* Maximum charge current: <550 mA
* Cell's dimension: 17mm Dia. x 34.5mm H.
* Weight: 0.6 oz (18 grams).