15% and 2.3% didn't really mean much to me without seeing the total composition (chart on page 3). Turns out operation is dominant source of electric vehicles' environmental impact. I guess the operational impact is primarily from electricity generation, which is always going to be cleaner than refining crude oil unless every power plant switches to coal. Compared to internal combustion engine vehicles, the battery impact is much less than the total improvement in operational impact in all 4 impact assessments.

But if the ease of installing these batteries makes home solar panels more attractive, that may offset their impact outside of EV use.