0.97-2.83 = -1.86 (Pauling scale)
You can think of it like a magnetic attraction. Similar signs will repel each other (no bond), and dissimilar signs will attract in proportion to the difference, with the more electronegative element acquiring a negative charge, and the other a positive charge.
The electronegativities of Li and Cl are 0.97 and 2.83 respectively. The difference is thus 0.97-2.83, -1.86, indicating an ionic bond with the negative charge on the Cl atom.