Most of your claims areincorrect. Lithium batteries have not reached their full capacity. Where did you hear that from? They continue to increase in energy density at the steady rate of about 10% per year while also falling in price. There are also other lithium based chemistries, like lithium air, with a theoretical energy density of 10 times current lithium ion batteries.
There’s a lot of room for growth remaining, and even at their current energy density the new Tesla Roadster has a 600 mile range, and the Rivian truck has a 400 mile range with the highest spec battery option. This shows batteries are already technologically up to the task, the cost just has to come down (which it is).
As for rare earth metals, check how recent your information is. EV companies have long since switched to motors and battery chemistries which dramatically reduce the usage of those metals to nearly nothing. There is also no rule that says batteries have to be made of those specific metals. If we couldn’t use them for some reason there’s a wide variety of other viable chemistries in existence already, and new ones in the pipeline.
As for decommissioning, lithium is very valuable. Do you really think it would simply be thrown in a landfill? That doesn’t happen. EV battery packs are resold as home energy storage for solar panel arrays when they have degraded enough that they are no longer useful for vehicular applications. After that, they are recycled. Batteries are, in fact, the most recycled consumer good on the planet.
All of these are fossil fuel industry talking points anyway, which would have us ignore that the types of pollution you mention are not atmospheric emissions and thus are irrelevant to climate change. If it stays out of the air and water, it is localized and much more easily managed.