“Works” in what sense?
Ion drives have already been used for powering spacecraft. They work by generating a small amount of thrust for a very long time. They’re great for driving spacecraft around the solar system, useless for lifting the spacecraft into orbit. SpaceX and RocketLab are really good at putting things in orbit; no need for these guys to reinvent the launch vehicle.
Until someone invents an ‘anti-gravity’ machine, we will still be using powerful chemical rockets to get to space. Not very efficient, but it works.
Ion engines work and are very efficient, but they are not powerful enough to move an object off the Earth.
Various schemes have been envisioned to do just that, like the ‘Space Elevator’ and the ‘Rocket Plane’.
I’m sure Musk is looking for anything ‘new’ that could possibly replace the chemical rockets now in use................