Battery powered cars are not the problem here. The source of energy is not the energy that is stored in the battery, but the salt-water composition, which would be a denser source of energy.
It’s just a question as to whether salt-water has the potential to store the amount of energy that the car claims to perform at. I don’t think it does, but my knowledge of chemistry is insufficient to say for sure.
This is likely crap.
Look to graphene for true battery advances.