As lithiation continues, into the lower voltage sloping region below ca. 1.5 V, a second phase transition was observed that was not expected from the electrochemical profile and not recognized in other Wadsley-Roth phases. This second discontinuous phase transition corresponds to another c-axis expansion and minor ab-plane contraction. Unlike the first phase transition, the second phase transition has a 2.6% volume expansion and the new Phase III expands continuously.