My understanding is that ecological impacts were more of a problem with older battery chemistries (lead-acid, nickel-cadmium), whereas lithium-ion packs are relatively benign. For instance, the batteries used by Tesla are mostly composed of nickel, cobalt, aluminum, and lithium, and none of these things are especially toxic.
Mining these different metals may have some negative impact, but it's pretty easy to recycle li-ion packs, so in the long term it's a much more sustainable solution compared to gasoline, where you have to keep drilling for more and more of it forever.
Mining these different metals may have some negative impact, but it's pretty easy to recycle li-ion packs, so in the long term it's a much more sustainable solution compared to gasoline, where you have to keep drilling for more and more of it forever.