[tooltalk]

That's not exactly how it happened. Sony of Japan was the first to successfully commercialize lithium ion batteries, most commonly used in EVs, in the early 1990's; quickly followed by South Korea -- most or 3/4 of all active lithium ion battery patents come from either Japan or South Korea.

China was very late to the EV battery game and LFP was more or less their only choice, which was deemed inferior for EVs due to its low energy density, but whose core patents were all about to expire -- ie, great for exports. They are effectively patent-free now.

In short, the Chinese gov't essentially forced all key EV battery industry leaders to waive their IPR to access China's local market; then effectively banned them and forced their customers, EV OEMs, to switch to local Chinese battery suppliers, who were still learning to make batteries under MIIT's Regulation on Power Standard since 2015/2016 (announced/enforced). That's essentially how China came to corner the battery supply-chain and scale up/commoditize their production at the expensive of everyone else past 10 years.