Here is a section form wikipedia
Full document here ->
http://en.wikipedia.org/wiki/Lithium_ion_battery
I have three Li-ion batteries (Nikon EN-EL4) that are in their third year. Two are now showing 1/4 for their life. Using Extrapolation I expect their life to be 12 years!
Guidelines for prolonging Li-ion battery life
- Unlike Ni-Cd batteries, lithium-ion batteries should be charged early and often. However, if they are not used for a longer time, they should be brought to a charge level of around 40%. Lithium-ion batteries should never be "deep-cycled" like Ni-Cd batteries.[7]
- Lithium-ion batteries should never be depleted to below their minimum voltage, 2.4v to 3.0v.
- Li-ion batteries should be kept cool. Ideally they are stored in a refrigerator. Aging will take its toll much faster at high temperatures. The high temperatures found in cars cause lithium-ion batteries to degrade rapidly.
- According to one book,[12] lithium-ion batteries should not be frozen (should not be stored below -40 °C), because most lithium-ion battery electrolytes freeze at approximately −40 °C (this is much colder than the lowest temperature reached by household freezers, however).
- Li-ion batteries should be bought only when needed, because the aging process begins as soon as the battery is manufactured.[7]
- When using a notebook computer running from fixed line power over extended periods, the battery should be removed and stored in a cool place so that it is not affected by the heat produced by the computer.[7]