Panasonic (JP) designed the cells Tesla uses and produces half of them. (The rest are made by CATL, as far as I'm aware.) The "gigafactories" are mostly just Tesla providing facilities for Panasonic to use stateside to make cells, and then they do screwdriver assembly to make packs. Panasonic is also building more of their own factories in the US to serve other car companies.

Tesla doesn't have any competitive advantage in batteries.