Lithium Poly Vs. Lithium Ion Batteries
Lithium ion batteries began appearing in the early 1990's. They have the highest energy density of all rechargeable batteries. But due to safety concerns, developers had to incorporate special features into the design to prevent explosion under certain conditions. These concerns, along with market demands to produce thinner batteries, led scientists to investigate lithium polymer technology.
Lithium Ion Technology
Lithium ion batteries, made with "lithiated" metal oxide, were originally built with inherent safety features to prevent them from bursting or exploding under abusive conditions such as overcharging, overheating or shorting. These features included active electronic circuits to keep the voltage within certain levels, and mechanical devices to reduce internal pressures or disconnect the cells when the abuse occurred. But developers remained wary of potential dangers and continued looking for ways to reduce risks and make the batteries safer.
The Lithium Polymer Solution
Early lithium polymer seemed to solve the problem. They had the same electrochemistry as lithium ion, but with a highly porous polymer separator and a laminated aluminum bag system in a sealed metal can, reducing the risk of explosion. However this was very expensive, so scientists could not justify the additional cost just for the safety features alone. But with the shrinking size of electronic devices, the demand to produce lithium polymer batteries increased because of size and shape considerations.
Size and Shape
The original lithium ion technology used thin plates spread with the electrolyte and then rolled up like a jelly roll. They needed to be made in round form to include the safety devices. Lithium polymer technology used die cut plates stacked on top of each other like a deck or cards, with the plates connected in parallel. They could be made in a variety of shapes and sizes, and could be made very thin, which made them attractive to cell phone manufacturers
Modern Lithium Batteries
Further development of both lithium ion and lithium polymer batteries included more enhanced safety devices, and lithium ion batteries also became available in flat form. But the polymer batteries can be made thinner, and are still more expensive. So the choice between the two becomes more of a manufacturing decision than a consumer decision. If a product design demands a battery of less than four to five millimeters in thickness, the additional cost of polymer needs measured. But other than that, they have equal performance.
Safety
Incorporating proper safety features into lithium batteries makes them safe, be they ion or polymer. But some unscrupulous manufacturers have produced them at lower cost with minimized or excluded safety features, increasing the risk of explosion from overcharging, overheating or shorting the outputs. One particular series of counterfeit batteries has been recalled by the U.S. Consumer Product Safety Commission. But there is no way of telling how well a lithium battery is made by looking at the outside
Tags: safety features, lithium polymer, polymer batteries, additional cost, batteries made
