A lot of the batteries are being provided by LG, Samsung or Panasonic, Samsung even provides LFPs now. So it isn't completely dominated by China yet, although they have a huge lead.
> ... has about 70% of the world’s production capacity of cathodes (the part of the cell that receives electrons) and more than 80% of anodes (the part that releases electrons on discharge), and well over half of electrolyte and separator output. Those parts come together to make a lithium-ion battery, more than three quarters of which are made in China and mostly by just two firms — Contemporary Amperex Technology Co. Ltd. and BYD Co.
Tesla using CATL batteries in their entry level Model 3 is a huge breakthrough for Chinese battery manufacturers.