NiMH has been common in consumer batteries for around 15 years (in my experience, although Wikipedia shows the chemistry is way older) but you can still buy the other chemistry (NiCd), and there may be newer lithium rechargables but I haven’t seen them in standard sizes (AA etc)

Eneloops set the standard for good quality NiMH batteries for a while, but IKEA Ladda batteries are also NiMH, and probably plenty of others now