Eli5: Given their location on the periodic table and the abundance of sodium compared to lithium, why aren’t we using sodium-ion batteries?

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Eli5: Given their location on the periodic table and the abundance of sodium compared to lithium, why aren’t we using sodium-ion batteries?

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We are currently researching them. The problem is that metallic sodium needs high temperatures to be a usefull battery.

There exist sodium-in-watery-solution batteries, also just called salt-watery-battery. These have very low energy density though, wich means they would be larger and heavier than an old lead-acid type.

Research tries to find a room temperature alternative using some organic electrolyte

Sodium is more reactive than lithium **per atom**, but a sodium atom weighs 3 times as much and is much bigger than a lithium atom.

As such the energy *density* of a sodium-ion battery (whether in kWh/kg or in kWh/L) turns out to actually be less than half that of a lithium-ion battery.

When you’re designing something small like a phone battery, that difference in energy density is a very big deal.

For purposes where the size of the battery isn’t such a concern, sodium-ion batteries actually are in use already – for the reasons you posited they’re significantly cheaper per kWh of energy storage.

So there are two big reasons that sodium-ion batteries aren’t used.

The first one is that the energy density is much lower. Both energy stored per volume, and energy stored per weight are about half of that of lithium-ion batteries. When it comes to batteries that is basically one of the most important factors. And there was no reason to invest in tech that was simply going to be worse at that.

Second, they can survive way fewer charge cycles. Usually around a few 100 to a 1000 for Sodium. Where as Lithium Ion is good for over 3000.

These few disadvantages meant that a lot of the investments went into Li-ion batteries instead of Sodium. Although interest in sodium is growing because sodium is significantly more abundant than Lithium, so it *might* have a place in grid-scale storage where weight isn’t really a big deal.

Sodium batteries are sometimes used on large ships, and stationary applications, especially those in hard to service locations. Their real benefit comes in lifetime and ease of service. They don’t deteriorate like other batteries and can be serviced on-site extremely easily.