Energy Technology have a lot of lithium-polymer cells for all sizes and all aims. Now we will try to expose the historical origins of this type of chemestry and why we make so especially many cells with all kinds of sizes and capacity.
The polymer hype of the early 2000s is still going strong, but most users cannot distinguish between a regular Li-ion and one with polymer architecture. While many people identify the term “polymer” as a “plastic,” polymers range from synthetic plastics to natural biopolymers and proteins that are from a fundamental biological structure.
Lithium-polymer differs from other battery systems in the type of electrolyte used. The original polymer design dating back to the 1970s used a solid (dry) polymer electrolyte that resembles a plastic-like film. This insulator allows the exchange of ions (electrically charged atoms) and replaces the traditional porous separator that is soaked with electrolyte. A solid polymer has a poor conductivity at room temperature and the battery must be heated to 60C (140F) and higher to enable current flow. The much anticipated “true plastic battery” promised in the early 2000s did not materialize as the conductivity could not be attained at ambient temperature.
To make the modern Li-polymer battery conductive at room temperature, gelled electrolyte has been added. All Li-ion polymer cells today incorporate a micro porous separator with some moisture. Li-polymer can be built on many systems, such as Li-cobalt, NMC, Li-phosphate and Li-manganese, and is not considered unique battery chemistry. Most Li-polymer batteries are for the consumer market and are based on Li-cobalt.
Li-polymer cells also come in a flexible foil-type case (polymer laminate or pouch cell) 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 design as the battery can be made into any shape, fitting neatly into stylish mobile phones and laptops. Li-polymer can also be made very slim to resemble a credit card.
Charge and discharge characteristics of Li-polymer are identical to other Li-ion systems and do not require a special 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.