Contrary to their name, they're not related to Lions (but they do spend some of their life in the sea).
That's a pretty vague request. What does your study of sealions entail, and what do you already have. For sure you wouldn't want people to be repeating what you already know from the research you have already done, right...
Well most of the sea lions in the US are Californian sea lions. They are the most popular species of marine mammal that is kept in captivity. Successful breeding happens sometimes but it’s uncommon and some zoos get their animals as rescues.
I don't think it is true that breeding of California sealions is uncommon; for example three were born at Blackpool Zoo and two at Whipsnade this year. I am not sure what aspect of sealions in captivity interests "Kiah" but it might be of interest to note that a California sea lion was born in Brighton Aquarium back in 1877; this birth, 141 years ago, is the earliest captive birth of this species that I know.
"I don’t hear much about it in the US is what I mean not generally" is not even close to being the same thing as "Successful breeding happens sometimes but it’s uncommon"...