I have seen all flavor of rechargeable batteries in the NiMh category and some in NiCa. There are regular one use AA/AAA LiIon batteries, but there do not seem to be any standard AA/AAA rechargeable LiIon batteries, nor have I seen any C's or D's. With the increased shelf life and use time of LiIon I find this disparity to be striking. Why do we not yet have a simple rechargeable LiIon replacement for the regular batteries that we use on a daily basis?
"Are Lithium Ion batteries available in standard sizes like AA , C or D cell size?
No, Lithium-ion batteries are not available in standard sizes. We believe this is because it would be too easy for users to inadvertently put them in a charger not designed for Lithium-ion batteries creating a potentially dangerous situation. (If an alkaline battery is put into the wrong charger it might leak or even burst, but a lithium-ion battery put into a NiCd or NiMH charger not designed for lithium-ion, might ignite. Also, because Li-ion batteries operate at much higher voltage (typically 3.7V per cell) than the 1.2 to 1.5V of most cell batteries, designing a 1.5V lithium-ion cell would be expensive."
Besides the voltage issue, the other problem is connecting Li-batteries in series. You need to have the right electronic controls to put them in series for safety reasons.
these ones here: http://www.batteryjunction.com/li18322mahre.html, they have the pcb built right into the battery... seems you could make a smaller capacity, in aa, c and d sizes at least that can begin the movement away from short life nimh batteries.