Which company supplies batteries to Tesla motors?

There’s no single “Tesla battery”. Each Tesla vehicle contains a large battery pack.

Panasonic manufactures the custom 18650-format lithium-ion battery cells (18mm diameter x 65mm length) that are used in the Tesla Model S and Model X battery packs. These were the best lithium-ion battery cells available in 2012 when the Tesla Model S was first introduced; the version Tesla uses has a custom NCA chemistry. Tesla’s top-of-the-line 100 kWh battery pack has 16 modules, each with 516 of the 18650 battery cells for a total of 8,256 battery cells per battery pack. The original 2008-2012 Tesla Roadster Energy Storage System (ESS) contained about 6,800 of the 18650-format lithium-ion battery cells; “Roadster Version 3.0″ upgrade kits include improved battery cells manufactured by LG. Teardown of new 100 kWh Tesla battery pack reveals new cooling system and 102 kWh capacity – Electrek

Panasonic and Tesla also manufacture custom 2170-format lithium-ion battery cells (21mm diameter x 70mm length) with NCA chemistry in a joint-venture section of the Nevada Tesla Gigafactory #1 site. These battery cells are currently used in battery packs for Tesla Model 3 vehicles and (with a different chemistry) in the Tesla Powerpacks sold to commercial power utilities.