It doesn't matter. One big power plant is so much more efficient than a million little ICE cars that you typically end up with lower emissions and less pollution from EVs even if 100% of your electricity is from coal.

That said, China - and most of the world - is on an exponential growth curve for renewables right now. It will take a long time for the world to switch over to EVs, so we're better off starting now, regardless of the current emission profiles for electricity generation.