Panasonic makes the battery cells. Tesla makes the battery packs, which is the product that counts in the end. This happens under the same roof. Tesla was also

Panasonic makes the battery cells. Tesla makes the battery packs, which is the product that counts in the end. This happens under the same roof. Tesla was also heavily involved in developing the battery cell chemistry and design. AFAICT, the value of Tesla’s battery packs is that they’re cheaper, have better longevity and charge rate than the competition, and that this is due to the vertical integration of the whole design & manufacturing process. So, many small details slightly better than the competition, at lower cost. Also, Tesla’s drivetrain & pack integration is more efficient than competition due to many tiny improvements, leading to fewer kWh & hence dollars of cost per mile of range.