Main worry: The magic ingredient this time appears to be vanadium instead of lithium, but there's still a magic ingredient (at least, according to my cursory understanding of the tech, entirely due to the OP's link)
- How abundant is vanadium? Wikipedia says it's 'rarely found in nature' https://en.wikipedia.org/wiki/Vanadium
- What are the geopolitics of vanadium? Under what conditions is it typically mined? Within which nation-states' territories is it typically found?
- What other industrial uses does vanadium have?
- What quantity is needed?
- Can we ramp up exploitation of deposits, or are there hard reasons (scarcity, remoteness, etc) that prevent this?
- EDIT: most importantly, are there other candidate elements that can, in the case of shortage or war, also provide service?