TiO2 nano-particles in polymer electrolytes:: surface interactions

The effect of nano-sized oxide particles, especially TiO2, on the structure and dynamics of polymeric electrolytes such as LiX/PEO has previously been shown to be profound. Here a first attempt is made to investigate the local surface interactions affecting the macroscopically observed properties using a rutile TiO2-cluster via ab initio Hartree-Fock (HF) and density functional theory (DFT) (B3LYP) type calculations. As an exploratory work, we use a small Ti11O22 atomistic cluster embedded in point charges (PCs) and the (110) surface for the adsorption process. Out of lithium cations (Li+), tetrafluoroborate anions (BF4-), and dimethyl ethers (O(CH3)(2)), BF4- is found to be the preferred adsorbate. The ether has comparable energy of adsorption when adjusting for bi-dentate coordination. The present results support the creation of new diffusion pathways for the lithium ion at the nano-particle surfaces and emphasises the possible role of anion adsorption. (C) 2003 Elsevier B.V. All rights reserved.