Synthetic fuels are fuels made from water and carbon dioxide from the air. You split the water into hydrogen and oxygen, and combine the oxygen with CO2 to create hydrocarbons. Basically what burning fuel does but in reverse. If the energy used to do this comes from a sustainable source (i.e. wind or solar) you will have net zero emissions, and none of the environmental impact of mining the metals used in batteries. This could effectively make ICE engines better for the environment than EVs.