Mining metals for the batteries has an environmental impact and I imagine that later disposal of them will as well.
These batteries are almost never disposed of in their complete form. They are harvested for materials that can be recycled and the hazardous materials are separated and properly disposed of. This recycling diminishes the need for mining. You don’t throw your normal car batteries away with the weekly garbage pick-up, do you? I hope you recycle them. These Lithium Ion batteries are similarly recycled.
As to your global warming comment, I happily admit that back in the 1980s and 1990s, there was a lot of disagreement in the scientific community, but that has changed. There is now a consensus in the scientific community, with a few scientists who don’t agree with the consensus. I get the feeling you will never accept this consensus as compelling, so I won’t try to convince you. Instead, I will regard you the same way I regard people who refuse to accept Darwin’s theory of evolution.
The real problem is that, for many people, their stance on the “global warming” issue has become a belief (on both sides of the issue). Very few people are open minded enough to reconsider the validity of their beliefs. The other thing about beliefs is that they don’t require compelling evidence. When something is a theory, an opinion, or a supposition, it can evolve as people learn more about the issue. Beliefs are much more rigid.