Hi,
Lithium Ion
Advantages
* High energy density - potential for yet higher capacities.
* Does not need prolonged priming when new. One regular charge is all that's needed.
* Relatively low self-discharge - self-discharge is less than half that of nickel-based batteries.
* Low Maintenance - no periodic discharge is needed; there is no memory.
* Specialty cells can provide very high current to applications such as power tools.
Limitations
* Requires protection circuit to maintain voltage and current within safe limits.
* Subject to aging, even if not in use - storage in a cool place at 40% charge reduces the aging effect.
* Transportation restrictions - shipment of larger quantities may be subject to regulatory control. This restriction does not apply to personal carry-on batteries. (See last section)
* Expensive to manufacture - about 40 percent higher in cost than nickel-cadmium.
* Not fully mature - metals and chemicals are changing on a continuing basis.
Lithium Polymer
Advantages
* Very low profile - batteries resembling the profile of a credit card are feasible.
* Flexible form factor - manufacturers are not bound by standard cell formats. With high volume, any reasonable size can be produced economically.
* Lightweight - gelled electrolytes enable simplified packaging by eliminating the metal shell.
* Improved safety - more resistant to overcharge; less chance for electrolyte leakage.
Limitations
* Lower energy density and decreased cycle count compared to lithium-ion.
* Expensive to manufacture.
* No standard sizes. Most cells are produced for high volume consumer markets.
* Higher cost-to-energy ratio than lithium-ion