and (ii) oxygen redox activity, provided that a high degree of Ni(3d)-O(2p) hybridization can be achieved. Li 4 NiTeO 6 was prepared by a conventional ceramic method from a stoichiometric mixture of Li 2 CO 3 (Aldrich), NiC 4 H 6 O 4 Á4H 2 O and TeO 2 (across organics) (2 : 1 : 1) annealed at about 1000 1C for 18 h, followed by heating at 1050 1C for 6 h with intermediate grinding. 10% Li 2 CO 3 was added in excess to compensate lithium loss due to high temperature heat treatment. The structure of the compound was analyzed by Rietveld refinement 7 using the Fullprof program 8 against high-resolution synchrotron powder diffraction data, collected on the 11-BM beamline at the Advanced Photon Source (APS, Argonne National Laboratory) with a wavelength of 0.4138 Å. Bragg peaks unambiguously indicate that the sample crystallizes in the C2/m space group with cell parameters a = 5.1584(1) Å, b = 8.8806(1) Å, c = 5.1366(1) Å and b = 110.241(1)1 (V = 220.777(3) Å 3 ), i.e. a cell similar to the one reported for Li 2 MnO 3 . 9 Refinements using different distributions of atoms within the layers led to a structure with Li layers alternating with honeycomb Li/Ni/Te layers (Fig. 1). In the latter, Li and Ni are statistically distributed in the same octahedral site (colored in yellow/green), surrounding TeO 6 octahedra (colored in blue). The final refinement which includes a strain analysis is shown in Fig. 1, and the deduced structural parameters are detailed in ESI † (Fig. S1, Tables S1 and S2).

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