Jeff Dahn - spend his entire career mixing up various chemicals and trying different chemical compounds & elements. You can listen to his talks. After decades it isn't simply random selection of things.
Good point about Cell Engineering - it is about more than just chemical engineering.
One of Dahn's biggest improvements was in testing. Waiting for a decade to see actual results isn't very practical. He (or his research team??) figured out how to test and get accurate predictions on battery performance in much less time.
You can find his talks on YouTube.