The Li-polymer differs from other battery systems in the type of electrolyte used. The original design, which dates back to the 1970s, uses a polymer Lifepo4 Battery electrolyte. This electrolyte looks like a plastic-like film that does not conduct electricity but allows the exchange of ions, electrically charged atoms or groups of atoms. The polymer electrolyte replaces the traditional porous separator, which is soaked with electrolyte.

The dry polymer design offers simplifications with respect to fabrication, ruggedness, safety and thin-profile profile. There is no danger of flammability because no liquid or gelled electrolyte is used.

With a cell thickness measuring as little as one millimeter, design engineers are left to their own imagination in terms of form, shape and size. Theoretically, it is possible to create designs which form part of a protective housing, are in the shape of a mat that can be rolled up, or are even embedded into a carrying case or a piece of clothing. Such innovative batteries are still a few years away, especially for the commercial market.

Unfortunately, the dry Polymer Lithium ion Battery suffers from poor conductivity. The internal resistance is too high and cannot deliver the current bursts needed for modern communication devices and spinning up the hard drives of mobile computing equipment. Although heating the cell to 60°C and higher increases the conductivity to acceptable levels. This requirement, however, is unsuitable for portable applications.

Some dry solid Li-polymers are currently used in hot climates as standby batteries for stationary applications. One manufacturer has added heating elements in the cells that keep the battery in the conductive temperature range at all times. Such a battery performs well for the application intended because high ambient temperatures do not degrade the service life of this battery in the same way as it does with the VRLA type. Although longer lasting, the cost of the Li-polymer 18650 Battery battery is high.