The most common types of batteries are lithium polymer and lithium ion. What are their features?
Facts about lithium polymer batteries
In lithium polymer batteries, a solid polymer electrolyte is used. In the very first examples of batteries of the type in question, created in the 70s, it was present mainly in the dry version. This electrolyte did not actually conduct an electric current, but it could exchange ions formed by lithium compounds. In modern devices - laptops, mobile phones, gadgets - batteries are used, which also contain a certain amount of electrolyte in the form of a gel.
Lithium polymer batteries are capable of providing a high level of power density based on their size and weight. They are characterized by a rather low self-discharge, do not have the so-called memory effect - when a charged battery during use is sometimes discharged only to a level that corresponds to the moment the battery is charged (that is, not necessarily to zero), and can also operate over a wide temperature range.
However, lithium polymer batteries are not always safe - especially if they overheat or take too long to charge. Batteries of this type have about 800-900 operating cycles, at which the level of capacity loss does not exceed 20%. The battery loses the same 20% of its performance after 2 years of operation, even if it is not used but is in storage.
Lithium polymer batteries are often very small - theoretically, it is possible to produce batteries with a thickness of the order of a millimeter. The use of a metal case in their construction is optional.
Facts about lithium-ion batteries
The design of a lithium-ion battery consists of electrodes and separators, usually impregnated with a liquid electrolyte. The former are represented by aluminum cathodes and copper anodes. The electric charge in batteries of this type is carried by a positively charged lithium ion, which has the ability to integrate into the crystal lattices of other substances and thus form new compounds. Cathodes in modern lithium-ion batteries are usually represented by lithium compounds with cobalt, nickel, manganese, and iron phosphate.
Batteries of this type are characterized, like lithium-polymer products, by low self-discharge, but slightly exceed them in energy consumption. Lithium-ion batteries do not need to be charged and discharged periodically to maintain functionality.
Older models of lithium-ion batteries are considered unsafe to operate, but those that include lithium iron phosphate cells are found to be reasonably reliable. Like lithium polymer devices, this type of battery will lose capacity over time - even if not used.
The main difference between lithium-polymer and lithium-ion batteries lies in the use of predominantly dry electrolyte in the structure of the former (with a small percentage of gel), while the latter is usually used liquid electrolyte. This predetermines the possibility, first of all, not to use a metal shell in the construction of lithium-polymer batteries and to produce a battery of small size and thickness. In lithium-ion batteries, in turn, it is necessary - otherwise the electrolyte will leak out. The importance of using a metal sheath can make it difficult to reduce the size of battery manufacturers.
Having identified the difference between a lithium polymer and a lithium-ion battery, we will reflect the conclusions in a small table.
|Lithium Polymer Batteries||Lithium Ion Batteries|
|What do they have in common?|
|They have general principles of electric charge transfer - using lithium compounds|
|They are characterized by low self-discharge|
|No memory effect|
|There is a common disadvantage in the form of capacity reduction over time|
|What difference between them?|
|Have a solid electrolyte in their structure (with the addition of a gel)||Have a liquid electrolyte in their structure|
|Do not require a metal shell and can be small in size||Require a metal shell, which predetermines their larger size in comparison with lithium polymer batteries|
|Have a slightly lower energy consumption||They have a slightly higher energy intensity|