A Peek at the First Sodium-Ion Rechargeable Battery

spectrum.ieee.org

Sodium batteries are irrelevant, as they have no advantages over lithium batteries (except maybe a slight cost decrease). At the same time Japanese engineers prototyped magnesium-ion batteries, which will double capacity of Li-Ion:

http://www.japantoday.com/category/technology/view/japanese-...

Can't wait to see them entering mass production.

Sodium isn't toxic, 5 grams of lithium can kill you.

In addition to what mystikal said, the article also mentions the long-term availability of sodium.

Reply on news.ycombinator.com