Putting on the cap of the person working for the car manufacturer assigned to 'go out and get the lithium' what happens when you are met with a market that approaches you with a long term deal?
What if you report back to your manager "they said $xxxx/T for guaranteed 10 years." What would management do? Would they say in this environment "tell 'em they're dreamin'. We can hang out until the supply catches up." Or would they be thinking "we have to get the supply from somewhere. The other 190 companies on our list we don't think really have a chance of getting it done and we could miss out on X×sales ourselves."
In conclusion it's worth considering the offer. That's business.