Japan Inc, page-5

I would imagine it is from making cars. Last year Toyota's total revenue was over USD260 billion(!). The size of the lithium carbonate market is forecast to be north of 1Mt per year by 2025 (maybe more, maybe less, depending on who you talk to). If LiCO3 is worth about USD12k/t, that's a global market of USD12bn per year by 2025 or less than 5% of Toyota's 2018 sales. Low cost lithium producers will do quite well if those prices turn out, but in the grand scheme of things, it's a small market.