An-Najah Staff

To develop new electrode materials for Li batteries, two different approaches are presented, namely: i) lamellar organic-inorganic hybrid materials synthesized by intercalation of monomeric units of a conductive polymer (intercalation approach); and ii) 3-dimensional transition-metal oxide nanoparticles coated by conductive polymer (core-shell approach).  The former intercalation approach is a straightforward method, in which poly(3,4-ethylenedioxythiophene), PEDOT, has been inserted between the layers of V2O5 using a soft process of intercalation. The process takes place through an in-situ polymerization of EDOT within the framework of crystalline V2O5. The insertion reaction results in a random layer stacking structure, leading to broadening of the energy state distribution. Electrochemical measurements indicated that the new hybrids showed reversible specific capacities up to ~330 mAh/g at C/10 in the potential range 2.0-4.4 V (vs. Li+/Li). This improvement of electrochemical performance compared with pristine V2O5 is attributed to higher electric conductivity, enhanced bi-dimensionality and increased structural disorder as well. To account for these observations, an electrochemical model, which highlights the effect of structural disorder, will be presented.  In the latter core-shell approach, a polypyrrole (PPY)/maghemite hybrid was prepared by pyrrole polymerization on the maghemite nanoparticle surfaces. Electrochemical measurements showed that, contrary to microcrystalline one, nanocrystalline maghemite exhibits a rather large electrochemical capacity, in agreement with the proposed electrochemical model. However, only a partial reversibility was found. In addition to capacity increase, the polypyrrole-surface modification also enhanced the electrochemical reversibility of maghemite nanoparticles. The hybrids delivered more than 300 mAh/g in the potential range 1.3-4.3 V (vs. Li+/Li(.