This investment by Hyundai indicates a ramping up of its efforts to produce solid-state batteries. Last year, the Korea Herald reported that the company was working on the technology in-house. It is interesting that the company would partner with a smaller company based in America rather than a large battery developer from Hyundai's home country such as LG.
Hyundai is also one of several companies working hard to bring solid-state batteries to the masses' cars. Toyota says it will have them in cars by 2022. Fisker is also aiming for early 2020s for its own solid-state batteries. Honda, Nissan, BMW and VW are all reportedly working on solid-state batteries, too. Perhaps what's most surprising is that there aren't more companies openly developing the technology, since solid-state batteries eliminate flammable liquid electrolytes, and they promise the potential of more capacity and faster charging times.