Here you go [1]. You're looking for the blue part of the bars. Compared to operating and manufacturing the rest of the vehicle it seems rather negligible, i.e. switching to EVs (and plugin hybrids) and then switching the power grid to something Carbon neutral should be your first concern, only then should we think about how to optimise the footprint of batteries.

[1] https://www.quora.com/What-is-the-carbon-foot-print-of-manuf...

Edit: As a bonus, here's a map showing how much the grey part of the bar reduces depending on the country you live in:

https://docs.google.com/spreadsheets/d/16K4gNhy_AN8Eg4Ov3z7p...