The giga factories need to be able to produce not just the current technology dominant Li-ion, but as better batteries evolve, to seamlessly move to manufacturing the better batteries.
Whatever opinions are about the policy action taken by governments all over the world to move away from vehicles burning fossil fuel, it is a catalyst towards innovation. Even the "hybrid kings" Toyota, as well as still having a toe in the water on fuel cell innovation, also have plans to take the lead in solid state battery ev's and according to this
Toyota plans to be the first company to sell an electric vehicle equipped with a solid-state battery in the early 2020s.
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