Asked what they most want from an electric car, many motorists would list three things: a long driving range, a short charging time and a price competitive with a similarly equipped vehicle that has an internal-combustion engine. To help with those goals, carmakers have been looking for ways to replace the traditional lithium-ion (Li-ion) batteries that power most modern electric vehicles (EVs) with more advanced “solid-state" versions. These new types of superbatteries have long promised faster charging and much greater driving range. Finally, after years of technical problems, efforts to make them are coming to fruition, with the first solid-state...