Email Post: Phase Transitions in the “Spinel-Layered” Li<sub>1+x</sub>Ni<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub> (x = 0, 0.5, 1) Cathodes upon (De)lithiation Studied with Operando Synchrotron X-ray Powder Diffraction