Lithium ion polymer batteries, or more commonly lithium polymer batteries (abbreviated "Li-Poly" or "Li-Po") are rechargeable batteries which have technologically evolved from lithium ion batteries. Their light weight, high power output and slow rate of self-discharge have made them extremely popular in R/C, especially electric aircraft.
It should be noted that in R/C applications, special care must be taken in their use. While much more volatile than nickel cadmium or nickel metal hydride batteries, lithium polymer batteries can be safely recharged hundreds of times over if one follows the guidelines below:
Chargers designed for use with Li-Po batteries must be used. Failure to do so runs the risk of explosion and/or fire.
The leads must never be allowed to short together. Immediate damage to the Li-Po will result.
Unlike their nickel-cadmium bretheren, Li-Po batteries must never be allowed to discharge below a certain point. Therefore, low voltage cutouts (LVC) on ESCs or ESC/receiver combinations must be set so as not to overdischarge (see below).
A model involved in a severe crash should never be immediately loaded into a vehicle due to risk of fire.