The catalog of sacred texts for the Nephites at the time of this writing consists of the brass plates, the large plates of Nephi, and the small plates of Lehi. It is unclear whether or not Lehi himself wrote down any of his experiences. Had he done so, they would likely have been on paper since the family was traveling, and more plates would have added significantly to the weight problem. Nevertheless, nothing is mentioned of texts writing by Lehi, and the best assumption we can make is that Nephi served as the chronicler for his family's history.
In this verse Nephi clarifies that what we are reading is a different "thing" from the material on the large plates. There is another set of plates upon which he has written "a full account of the history of my people" which were called the plates of Nephi. He pronounces this as though this were an official title, even though we understand that the book Joseph Smith translated from those plates was the Book of Lehi. The name would therefore be attached to the plates, not the content of the plates, and would likely signify the importance of the plates to the political/social history of the people. This is consonant with an official "dynastic" record of a political kingdom. Nephi, as the head of the political aspect of his people, would have been the one to sanctify the plates by his possession of them and the rulership.
Interestingly enough, the second set of plates is "also called the plates of Nephi." The usage in this phrase may not have the naming emphasis of the first clause, and may be related much more to being named for their author (which, of course, would contrast to the plates of Nephi where the Book of Lehi was the primary content).