Pretty much every source of electricity does a better job of emmisions reductions, at a lower price, than a car can.
There is no doubt that, on an operating basis, a battery-operated electric car generates less C02.
The question is whether the mining and manufacturing process for the batteries generates more C02 than the lifetime savings from operation. And when people try to answer that question “no”, they invariably count every last cost of the parts that go into the electric car, and then do nOT count the cost in C02 for mining operations to pull up coal, or the C02 costs in pumping oil, or in building dams for hydroelectric plants, or manufacturing the solar panels or collectors for solar power.
In other words, if you really want to know whether the life cycle of a battery-operated electric car is less C02-intensive than the “average” gas-powered car, or diesel car, you probably will not be able to find any study that has correctly compared them.
Money can be thought of as highly accurate data about energy use, both direct and indirect. The only study needed is the total cost of ownership. If electric cars really use less total energy they will be cheaper and customers will flock to them without any deficit spending market distortions.