You can buy sodium 18650 cells today - at the moment their parameters are worse across the board. That being said they're much safer. For instance you can disc

You can buy sodium 18650 cells today - at the moment their parameters are worse across the board. That being said they're much safer. For instance you can discharge them to 0V without serious consequences. I for one will be purchasing a few to power things I want to leave somewhere for weeks at a time. Unfortunately in terms of BMSes there's not much of a selection.