Many people don't know that it takes about 7.46kWh of electricity to refine one US gallon of petrol according to a study done at the Argonne National Laboratory. This means that liquid fueled cars are powered by coal too. The difference is that as grid power becomes cleaner, so does the EV. Companies such as Ecotricity are installing charging stations and putting wind power on the grid to match so using their service can be considered fossil fuel free power.
I had already read an article that stated the 400 engineers that Dyson claims are working on the project were involved with battery technology. Vertical integration isn't always a good thing and what happens is Dyson might not only be competing with EV manufacturers, but battery (cell) manufacturers as well. They could be better off minimizing battery work and spend more effort on getting a vehicle to market. Meeting safety certifications in multiple countries is a big hurdle to clear. They will also do better if they get to testing sub-systems on a longer term basis unlike Tesla that didn't spend much time vigorously testing their Model 3 before declaring a production candidate and going full steam into production. Most traditional manufacturers spend around 18 months beta testing hand built versions to work out emergent problems when they are coming out with a new model. This is in addition to stuffing new power trains into "mule" cars. Mules are often another car body from the manufacturer that is used to disguise that they are working on a new model.