Lithium ion batteries appeared in the early 1990s and were first marketed by Sony. These batteries now have a leading position on the accumulator market.
Their main advantage is their high energy density (two to five times higher than nickel metal hydride, for instance).
The lithium ion accumulator is based on the reversible exchange of lithium ions between the positive electrode, usually made of cobalt or manganese dioxide, and the negative electrode made of graphite.
Although cobalt has been used for a longer period of time, manganese is by nature less dangerous even when the cells are misused so the protection circuits can be simplified. In addition to improved safety, the cost of manganese as a raw material is lower than the cost of cobalt. On the other hand, it has a lower energy density, its capacity drops at temperatures higher than 40°C and it ages faster than cobalt. Take a look at the advantages and disadvantages of the two chemical compositions below.
|Energy density (Wh/kg)||140||120|
|Safety||When there is an overload, the cobalt electrode supplies excess lithium that can be transformed into metallic lithium, which leads to a potential safety risk if it is not protected by a protection circuit.||During an overload, the manganese electrode has a lower lithium content which means that only the element heats up. The protection circuits can be simplified for the small 1 and 2 cell packs.|
|Temperature||Wide range of temperatures. Best suited to work at high temperatures.||Loses capacity above 40°C. Not as resistant at higher temperatures.|
|Ageing||Short term storage is possible. The impedance increases with time. The new versions can be stored for longer.||Short term storage possibility is slightly lower than with cobalt. The impedance does not change much during the life cycle of the element. The shelf life is difficult to predict because of continuous improvements to the chemistry.|
|Life cycle||300 cycles, capacity of 50% at the 500th cycle.||Can be shorter than cobalt.|
|Cost||The cost of the raw materials is high and a protection circuit increases the cost.||Raw material is 30% cheaper than the cobalt. A simplified protection circuit is a real advantage in terms of cost.|
We have selected an extensive range of batteries in 18650, 18500 and 26650 formats. For prismatic cells, we consider the needs on a case-by-case basis. There are several formats and it is always best to check the durability before to starting new projects.
Depending on your technical specifications, we will help you choose the technology best suited to your project.