Sodium-ion rechargeables in 18650 cell size

November 29, 2017 | 02:26
Sodium-ion cells in 18650 cell size. Source: Tiamat
Sodium-ion cells in 18650 cell size. Source: Tiamat
It looks like Lithium-ion batteries will finally be getting some serious competition. Two years ago, researchers working at several French universities developed the first sodium-ion battery in the industry-standard 18650 cell size used commonly for Li-ion cells. Batteries based on sodium-ion are less problematic and more durable than lithium-based batteries. A startup called Tiamat has been formed to exploit this technology and produce these cells in the 18650 format.

As the uptake of electric vehicles gathers pace and large capacity batteries are employed to store energy from solar farms it’s likely that lithium will become scarce and therefore even more expensive. Only about 0.06% of the Earth's crust is made up of lithium and its reserves are found mainly in South America (Argentina, Chile and Bolivia). Two years ago, a French team of researchers developed the technology for the practical use of sodium in batteries. About 2.6% of the earth's crust is made up of sodium so it’s a very cheap mineral and found everywhere in the form of common salt (NaCl).

Sodium not only offers a price advantage compared to lithium, but has a number of other beneficial properties. The most important one is probably the lifespan of over ten years compared to only about four years for lithium and the cells are good for around 5,000 charge/discharge cycles. In addition to this, sodium-ion cells can supply higher charge and discharge current which is a clear advantage for electric vehicle applications. Last but not least, sodium is more stable, in principle you can subject a sodium-ion battery to deep discharge without damaging it significantly. Another important property is that, unlike lithium, it is not a fire hazard.

In its current state of development the cells offer only about half the energy density of lithium cells. It is reported that Tiamat have already produced at least ten functional prototypes of the sodium-based cells in the 18650 format. The aim of this startup is to build a facility to mass produce the cells by 2020.
These are early days and as you might expect the exact technical specification of the new cells and the setup of Tiamat is still a bit sketchy but that should all be clarified in the near future.

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