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Lithium Ion
Lithium-Ion batteries were first proposed in the 1970s, but the technology to successfully create them wasn’t invented until the mid 1980s. The first commercial Lithium-Ion (Li-ion) battery was launched by Sony in late 1991.

Lithium Ion batteries still work on a variation of the same basic electrochemical principal as the earliest galvanic cells, but instead of two different metals forming the electrodes, they employ a combination of graphite, a manganese mineral and lithium cobalt oxide, in which lithium ions pass between the electrodes in one direction when charging and the other when discharging. One advantage with this technology is that the materials a relatively cheap and non-polluting, and can be shaped into almost any form, enabling ultra-thin Li-ion batteries to power increasingly tiny pocket electronics such as mobile phones and cameras.

Li-ion technology has several advantages over previous battery types, but is not without its disadvantages as well. One big bonus is its very high energy density, typically double that of NiMH batteries, and consequently their low weight and compact size. Li-ion batteries are not negatively affected by cold conditions, and may in fact operate more efficiently as they get colder. As well as this, Li-ion batteries are much better at storing charge over long periods. A typical fully charged Li-ion battery will lose approximately five percent of its charge per month. However a significant proportion of this is due not to charge leakage, but instead to one of the major disadvantages of Lithium Ion batteries, that of their limited lifespan.

It is not a widely advertised fact, but even if kept in perfect conditions, a Li-ion battery will permanently lose as much as 20 percent of its maximum charge capacity per year due to internal oxidation. If exposed to high temperatures, such as inside a laptop computer, or if kept at full charge for extended periods this deterioration in performance can be even faster. The deterioration starts as soon as the battery is manufactured, so even a brand-new Li-ion battery will generally only have a useful life of 2-3 years, which could be as little as 400-500 charge cycles.

Another disadvantage of Li-ion batteries, and one which occasionally gets some media attention, is their occasional tendency to catch fire or even explode. Although modern batteries contain numerous safety devices, there is still plenty of anecdotal evidence to suggest that Li-ion batteries can burst and ignite if exposed to continuous high temperatures, such as direct sunlight, and also that short-circuiting them, causing very rapid discharging, or over-charging them can cause them to explode. There have been a number of high-profile product recalls because of this problem.

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