In Situ X-Ray Diffraction Study of P2-Na[sub 2/3][Ni[sub 1/3]Mn[sub 2/3]]O[sub 2]

The electrochemical extraction and insertion of Na in was studied by in situ X-ray diffraction. All the original Na can be extracted from and it can be reversibly inserted again. When in the compound remains in the P2 structure. For a small amount of O2-type stacking faults are introduced into the structure. When the electrode exists as two coexisting phases. These are (with some O2-type stacking faults) and adopts the O2 structure with stacking faults. As sodium is reinserted in to make the P2 structure forms again. The evolution of the lattice parameters of with x and the lattice constants of are also reported. © 2001 The Electrochemical Society. All rights reserved.