Up until now, lithium-ion batteries have been the standard for EVs. No other battery type can hold enough charge in a small enough space. Indeed, the proliferation of lithium-ion batteries was a key factor in the modern-day rise of EVs. General Motors’ short-lived EV1 originally used lead-acid batteries, which effectively gave it the driving range of an ICE car perpetually running on empty.
However, lithium-ion batteries have not been good enough to supersede a full tank of gasoline. Toyota was an early proponent of solid-state batteries as a possible replacement, being one of the first companies to try to make them. It took a long time for others in the industry to take notice. But as the first promising test results and prototypes slowly emerged, the rest of the industry gradually decided to start investing in solid-state batteries.