Why are there so many types of batteries?

A range of materials (it used to be just metals) can be used as the electrodes in a battery. Over the years, many different combinations have been trialled and there are a few favourites that have gone the distance. But why do we need different combinations of metals anyway? If you’ve got a pair of metals that work well together as electrodes, why bother messing around with others?

It turns out that different materials have different electrochemical properties, and so they produce different results when you put them together in a battery cell. For example, some combinations will produce a high voltage very quickly but then drop off rapidly, unable to sustain that voltage for very long. This is good if you need to produce, say, a sudden flash of light like a camera flash.

Other combinations will only produce a trickle of current, but they’ll keep that trickle going for ages. We don’t need a huge amount of current to power a smoke detector, for example, but we do want our smoke detectors to keep going for a long time.

Another reason to use different combinations of metals is that often two or more battery cells need to be stacked to obtain the required voltage, and it turns out that some electrode combinations stack together much more readily than other combinations. For example, the lithium iron phosphate batteries (a type of lithium-ion battery) used in electric cars stack together to make high voltage systems (100 or even more volts), but you wouldn't be able to do that with NiCad batteries as they get too hot.