French researchers have announced a prototype of an 18650 sodium-ion battery. If you’ve bought a powerful LED flashlight, a rechargeable battery pack, or a–ahem–stronger than usual LASER pointer, you’ve probably run into 18650 batteries. You often find these inside laptop batteries and –famously– the Tesla electric vehicle runs on a few thousand of these cells. The number might seem like a strange choice, but it maps to the cell size (18 mm in diameter and 65 mm long).
The batteries usually use lithium-ion technology. However, lithium isn’t the only possible choice for rechargeable cells. Lithium has a lot of advantages. It has a high working voltage, and it is lightweight. It does, however, have one major disadvantage: it is a relatively rare element. It is possible to make sodium-ion batteries, although there are some design tradeoffs. But sodium is much more abundant than lithium, which makes up about 0.06% of the Earth’s crust compared to sodium’s 2.6%). Better still, sea water is full of sodium chloride (which we call salt) that you can use to create sodium.
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