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.
The researchers are keeping some of the construction details a trade secret, so far. There’s a lot at stake as electric vehicle, and other battery uses are expected to grow significantly in the coming years. However, they are quoting a 90 Wh/kg energy density and over 2,000 recharge cycle life span. By comparison, a typical lithium-ion battery has around 110 Wh/kg and tops out at about 1200 recharge cycles. In all fairness, though, some lithium-ion batteries (like cobalt lithium-ion) can reach over 160 Wh/kg.
What does this mean to hackers? Only a few of us will be building our own batteries (although we’ve seen it more than once). However, many of us do build with portable power, and sodium-ion may be–if not the next big thing–another choice in your battery arsenal. You can see a short video about the new technology below.
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