Did Sasuke know that Bijuu couldn't be killed?

[LeSauce]

Was he ever told or did he ever figure it out?

I don't quite remember everything, but I do believe he hadn't known about it. Especially since he kept saying he was going to kill them.

Or maybe he was just going to leave them in their rock cage.

 

[Exaar]

I'd assume that the rinnegan has ways to permanently kill them