sounds good, no obvious critical materials but also first facilities are just in single MW range and came online like two months ago. needs like four orders of magnitude more. already matches lead acid on durability, still less than li-ion. maybe it's solvable, but in case it's not you can just burn it down because there's nothing worthwhile to recycle and it's nontoxic

this happens a lot. lithium anything has this problem obviously, but so do flow batteries (vanadium or zinc bromide - bromine is commercially sourced just from either dead sea or some american underground brines). some lithium batteries also use cobalt. hydrogen generation or fuel cells use a lot of platinum, (some of) new power electronics are made from GaN. etc etc