# Synthesis, Phase Stability, and Electrochemically Driven Transformations in the $LiCuO_2-Li_2CuO_2$ System

Prakash, AS and Larcher, D and Morcrette, M and Hegde, MS and Leriche, JB and Masquelier, C (2005) Synthesis, Phase Stability, and Electrochemically Driven Transformations in the $LiCuO_2-Li_2CuO_2$ System. In: Chemistry Of Materials, 17 (17). pp. 4406-4415.

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## Abstract

Trivalent $LiCuO_2$ was prepared by oxidative leaching of divalent $Li_2CuO_2 in Br_2$-acetonitrile solutions at ambient temperature. Both phases were found to be thermally air unstable and the onset temperatures $(100-150^ \circ C)$ relatively low for their transformation into CuO and lithium salts. Electrochemically driven lithium insertion/ extraction into/from both $Li_2CuO_2 and LiCuO_2$ were followed by in situ X-ray diffraction that revealed, for both starting materials, that the $Li_2CuO_2 \rightleftharpoons LiCuO_2$ transitions always proceed through a succession of biphasic and monophasic processes involving three type phases: $Li_1_+_yCuO_2, "Li_1_._5CuO-2", and Li_2_-_zCuO_2$. Such a strategy can therefore be used for the preparation of stable copper mixed valence oxides. This study also revealed a very large polarization linked to the $Li_1_._5CuO_2 \to Li_2CuO_2$ transition. Although so far not explained, this fact enabled us to test the respective reversibility of the $LiCuO_2 \rightleftharpoons Li_1_._5CuO_2 and Li_1_._5CuO_2 \rightleftharpoons Li_2CuO_2$ transitions. It was found that performing cycling on both transitions comes with a continuous decrease in the cell capacity while good capacity retention can be obtained when one limits the electrochemical work to the $LiCuO_2 \rightleftharpoons Li_1_._5CuO_2$ process.

Item Type: Journal Article The copyright belongs to American Chemical Society. Division of Chemical Sciences > Solid State & Structural Chemistry Unit 16 Dec 2005 19 Sep 2010 04:20 http://eprints.iisc.ernet.in/id/eprint/3685