How to store/ conserve unused Li-ion/ Li-po batteries?

Have several unused Li-ion and Li-po cells: My laptop battery, only used when working outdoors (is in summer). Half broken MP3 players, phones, a broken RC helicopter and some larger batteries.  Some might be useful one day in a future project. As I understand these cells slowly deteriorate even when not in use.  What is the best way to keep them in shape? Perhaps dry storage in a freezer? Charge them occasionally or have them uncharged?  Are button cells Li-ion cells?

AndyGadget6 years ago
Store LIPO cells at least partially charged. They will self-discharge only very, very slowly. Discharging a cell below 3.2V can permanently damage a LIPO.
hellrider756 years ago
Lithium Ion Battery Storage: Storage temperature range is -20 to 60° C. Recommended storage voltage range is 4.1 to 2.0 volts per cell. For prolonged storage periods, store discharged [i.e. 2.0 to 3.0 volts per cell] and at -20° to 25° C.