We know we can't quickly replace all gas combustion engines on the road today with batteries because of material supply constraints alone. However if the goal is to reduce carbon emissions by vehicles by 90%, we can probably get there by replacing 95% of all gas-only vehicles with plug-in hybrids, which require a small fraction of the amount of battery material than fully electric cars require. I'm probably off with my estimates, but I believe they're in the ballpark.