Sodium Ion Battery Developments

By Ian Page – 2022.01.13

My understanding of sodium ion batteries is that they will be heavier, not last so long, be lower energy density, and lower cost.

Several papers have recently come out which suggest this may be wrong.

1. Bristol University have made an electrode out of an aerogel with controllable pores, by freezing an ice polyethylene oxide cellulose mixture and then sublimating off the ice to leave pores, and an aerogel containing cellulose crystals. This apparently performs well with either sodium or potassium replacing lithium. Its potentially a cheap electrode, made from sustainable materials, and strong and flexible enough to handle the large sodium ions moving in and out.
2. Uni Austin has a mechanism that layers sodium metal on a thin substrate then folds it multiple times (shades of Damascus steel!). Apparently, this achieves longevity, fast charging, and a higher energy density than lithium iron phosphate, close to lithium nickel cobalt used in Tesla performance cars. This somehow prevents the dendrite problem that occurs with metal-based batteries, while the lack of non-functional materials increases the energy density of the battery.
3. CATL is saying they have made a breakthrough in performance and stability of sodium batteries.

We can now (in due time once technology has undergone the long and tortuous journey to production) expect sodium batteries of similar energy density and volume density to Tesla/Panasonic’s best, at 60% less cost per kilowatt hour, and with minimal supply chain issues since sodium is a major constituent of salt. I'm thinking ten years, with lower performance low cost CATL batteries arriving in 2023 and a rapid learning curve.

As always, the key question is when, and how much non battery clutter will be needed to make them safe.

Sodium is much more reactive than lithium, and sodium metal is much much more reactive than lithium ions.

If water or air gets to the sodium it WILL catch fire.

It feels that they will, at least until safety is established, be best used for grid storage, where proper care can be taken, and the odd fire isn't a problem if it's anticipated.

From a pure CHON view, cellulose, salt, and water are pretty compatible. There would need to be a synthesis route to polyethylene oxide from CO2 and hydrogen. There is one from carbon monoxide which can be made from carbon dioxide, and it wouldn't be surprising to find a biological source since the molecule is pretty simple (there’s a patent from 2019 and several papers on this). This is close to the first CHON battery!