A team of researchers has developed an all-solid-state sodium battery that operates at room temperature and even below freezing.
If the batteries lithium-ion are today omnipresent and generally efficient, they are far from being impeccable. Their extraction has a significant environmental impact, their cost remains high and the fire risks linked to thermal runaway persist.
For a long time, the manufacture of sodium batteries, and more precisely of batteries all-solid sodiumwas considered as an alternative. However, a major problem remained for this type of battery: the poor ionic conductivity of their electrolytes at room temperature made their use unrealistic for sectors such as electric automobiles. And in the cold, their performance is very limited. But a team of researchers from the University of California (San Diego) has managed to develop an all-solid sodium battery that works at room temperature, and even below zero degrees.
How did they achieve this?
The team of researchers used sodium borohydride, an unstable compound, by subjecting it to a thermal cycle: heating to the crystallization threshold followed by sudden cooling. This thermal shock made it possible to stabilize a so-called metastable crystal structure, endowed with an unprecedented ionic conduction capacity, even in the cold.
Thanks to this structure, it becomes possible to design thicker cathodes, which boosts energy density (storage capacity for the same volume). This advance allows sodium batteries to finally display electrochemical performances comparable to those of lithium batteries.
The advantages of the all-solid sodium battery
First of all, sodium is much more abundant on Earth than lithium. Therefore, its cost is significantly lower. Added to this, simpler extraction, and above all more ecological. Lithium extraction causes significant soil pollution and requires an astronomical quantity of water, which aggravates water shortages in mining regions. L’extraction sodium is not without consequences either, but its abundance makes it easier.
Then, all-solid sodium batteries present a serious advantage in terms of security. As its name suggests, this type of battery does not contain flammable liquid, which eliminates the risk of fire due to thermal runaway. This is a notable difference from lithium batteries. Unfortunately, fires caused by overheated lithium batteries are not uncommon. Finally, we can also mention the fact that sodium batteries are more durable, supporting more charge cycles without losing capacity.
A new alternative
The researchers point out, however, that sodium batteries will not replace lithium batteries. Rather, it is a new alternative that could meet specific demands. Regardless, advances in this area continue. For its part, MG unveiled the first car equipped with a semi-solid battery.
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Source :
Cell.com
