Do sperm whales use sonar to stun giant squid? In a word: maybe. I delved quite enthusiastically into the topic last year, and came out tantalized and frustrated by limited evidence.

So I was very excited to see an article in the Smithsonian called The Sperm Whale's Deadly Call. Is this new research, finally showing once and for all that sperm whales knock out their prey by very loud shouting?

No. It is a lovely piece about sperm whales and all the noises they make, but Eric Wagner doesn't even mention squid until the end of page 2:
But most of a sperm whale’s clicking, if not most of its life, is devoted to one thing: finding food. And in the Sea of Cortez, the focus of its attention is Dosidicus gigas, the jumbo squid.
Then, on page 3, you can find the most hilarious portrait I've ever read of my PhD advisor:
One afternoon, i’m sitting on the deck of the BIP XII reading Moby-Dick when Bill Gilly happens by. “Have you reached the squid chapter?” he asks. I tell him I have not. Gilly waves his hands in mock dismissal—“Gaaah!”—and continues on his way. Apparently, I am not worth talking to until I have read it. I flip ahead to “Squid,” which is only two pages long. My edition of Moby-Dick has 457 pages, but for Gilly, the rest of the book might as well not exist.
Hee. But there's no new information about stunning squid with sonar; in fact, Wagner doesn't even mention the possibility. He's just talking about how sperm whales hunt with their noses--not by smelling, but by bouncing sound out of that big schnoz and using it to echolocate squid.

Which is very cool. So do go read the whole thing.