“Are we (as a society) better off using batteries in stationary storage or vehicles ?” We would be far better off to prioritize battery production capacity to grid storage and integrate as much renewable energy as possible which would provide greater CO2 reductions from all in-use plug-in electric vehicles. Should there be battery capacity production shortages then better to offset using hybrid electric vehicles (HEV's) which provide half the CO2 reduction of BEV's but less than 1/30th of the battery capacity. Think of it this way, if you only have 50 kWhr of battery available are you better to use it in one 50 kWhr BEV or 50 HEV's with 1 kWhr batteries. If all the vehicles do the same annual mileage, the 50 HEV's will yield at least 25 times as much CO2 reduction as the single BEV.