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Published online by Cambridge University Press: 26 February 2011
Two types of samples containing different La2/3-x Li3x TiO3 (LLT) solid electrolyte /LiCoO2 cathode interfaces were prepared by depositing LiCoO2 on polycrystalline LLT with two different surface finishes: cleaved and polished surfaces. Electrochemical properties of the samples were analyzed by cyclic voltammetry (CV). Microstructures of the LLT/LiCoO2 interfaces were investigated by scanning electron microscopy and transmission electron microscopy. Cyclic voltammograms of the cleaved sample show that the anodic and cathodic peaks respectively shift to higher and lower potential with the number of cycles, while those for the polished samples do not change much during cycles of potential sweeps, indicating the higher stability for the polished samples upon insertion and extraction of lithium ion. The LiCoO2 thin-film cathode is epitaxially deposited with the orientation relationships: {110}LLT//{1120}LiCoO2 and <001>LLT//<4401>LiCoO2 for both samples with different geometric configurations of the interfaces to the Li layers in the LiCoO2. Amorphous regions are observed to exist in places at the interface only in the polished samples. The geometric configuration of the interface and the existence of the amorphous regions are considered to have great influences on the stability of the LLT/LiCoO2 interfaces upon charge / discharge operations.