Seiko produces li-ion protection “IC” controller chips, widely regarded as top quality. The battery protection circuit also contains a few other components (power mosfet/switch, capacitors, resistors) but the controller chip is the brain. Anatomy of a Protected LiIon Battery (by HKJ)
Evva vs keeppower protection visual comparison
The protected batteries you often on chinese sites (fasttech,banggood,etc) with clear wrap over a big brand name cell (pana,sanyo,etc) have a protection circuit added by an un-named mystery company. All the teardowns I’ve seen seem to use the same chip. I suspect it’s a questionable quality chip at best. I have no failure statistics to back it up though.