LG has applied for a patent with the United States Patent and Trademark Office (USPTO) and the World Intellectual Property Organization (WIPO) for what is innocuously titled "electronic device." The drawings included in the files show a foldable device that utilizes a spring-loaded hinge to turn a regular-sized smartphone into something that more resembles a tablet.
https://www.notebookcheck.net/Patent-seems-to-show-LG-moving-ahead-with-foldable-smartphone-ideas.391521.0.html