This is based on a video seen on Facebook, so take it with a grain of salt.

AFAIK, BYD batteries are based on "bad" materials, with fabrication method perfected until they are competitive [enough(?)] with batteries made with the "good" materials.

The good stuff is patented, locked by the West. China workarounds it. It's not that it is "bad", is just copying West's strategy doesn't work for them.

This seems like a garbled retelling of the shift from NMC batteries to LFP.

The latter are worse on some dimensions, so much so they weren't considered viable for cars in the West. But incremental improvement saw them take over the Chinese market. A classic "low end disruption" story.

They bought up the patents from A123, and American firm with a Taiwanese American MIT researcher founder. The firm floundered in the global financial crisis, a time that is a big inflection point for China's global domination of green tech.

https://en.wikipedia.org/wiki/A123_Systems

The problem with that theory is that BYD and a few other Chinese companies already for some years have had batteries that are better than anything made in the West, from the point of view of energy density, charging rate, temperature range, cost, so if there is some stuff that is patented and locked by the West, that is the bad stuff.

Living in the EU, I find it concerning that China has advanced so much in battery technology and in the West there are very few positive signs of attempting to keep up with them.

Closing your eyes and imagining that others are not really better, when they are, is not the right strategy to avoid remaining behind.

Which good (EV, I presume) battery provider is from "the West"?

From what I’ve heard from owners (anecdotal) those batteries are still utter garbage.