We have no idea how much it will cost. The same range in half the batteries might not save any money. And while performance would improve a bit, the main limiter right now in electric cars is price, not weight.
But, the study mentions unused lithium trapped in the battery, so if a solution if found to make that useful, the only costs increase would be to recover the R&D costs.
If any new new chemistry is used to solve the problem with very expensive elements, it could be a problem, but I don't think the scientists will stop at it if they find an expensive solution.
Reduced weight will also help in increase in speed.