My Webster's New world Dictionary does not contain the word "loaned" at all, but my Thesaurus does, and the word "lent" is the first synonym listed. My wife, who learned English as a second language and therefore often speaks it better than I do, insists "lent" is more correct than "loaned" as the past tense verb form. Which is more correct?
They are two different verbs: "to lend" is conjugated "lend, lent, have lent", and "to loan" is conjugated "loan, loaned, have loaned".
According to Merriam-Webster, the verb to loan has died out in the U.K. This is corroborated by Google Ngrams, although it now appears to have been reintroduced from AmE. Thus, for BrE, your wife is correct. For AmE, both lent and loaned are fine.
There is a difference in usage: a book is lent by a friend but loaned by a library, even if it is a lending library. I think loaned is preferred in the more formal contractual setting.
During the 1950s and 1960s when I was a student in a private, Catholic school, "lent" would have been only used for the weeks before Easter, not in place of "loaned" in common English usage. If you did use lent, it had better be for the former reason and not the latter. Fortunately, since it was a grade school, this did not come up as a problem for us students because we couldn't yet write as well as high school and college students, but, of course, we were taught the "correct" usage of terms and there was no room for the evolution of the language.