Lithium-polymer: Substance or Hype?

Find out why lithium-polymer is so popular.

The term polymer is commonly used to describe certain type of lithium-based battery that may or may not be polymer based. These typically include pouch and prismatic cells. While the word “polymer” is perceived as a plastic, polymers range from synthetic plastics to natural biopolymers and proteins that form fundamental biological structures.

Li-polymer is unique in that a micro porous electrolyte replaces the traditional porous separator. Li-polymer offers slightly higher specific energy and can be made thinner than conventional Li-ion, but the manufacturing cost is said to be higher than cylindrical design. For the purpose of discussion, pouch cells are often identified as being Li-polymer.
Li-polymer cells also come in a flexible foil-type case that resembles a food package. While a standard Li-ion needs a rigid case to press the electrodes together, Li-polymer uses laminated sheets that do not need compression. A foil-type enclosure reduces the weight by more than 20 percent over the classic hard shell. Thin film technology liberates the design as the battery can be made into any shape, fitting neatly into stylish mobile phones and tablet. Li-polymer can also be made very slim to resemble a credit card Light weight and high specific power make Li-polymer the preferred choice for hobbyists.
Charge and discharge characteristics of Li-polymer are identical to other Li-ion systems and do not require a dedicated charger. Safety issues are also similar in that protection circuits are needed. Gas buildup during charge can cause some prismatic and pouch cells to swell, and equipment manufacturers must make allowances for expansion. Li-polymer in a foil package may be less durable than Li-ion in the cylindrical package.