Search

We have established a novel method of inserting poly(3,4-ethylenedioxythiophene) (PEDOT) between the layers of V 2 O 5 using a soft process of intercalation. The reaction takes place with the in situ polymerization of EDOT within the framework of crystalline V 2 O 5 with different nominal EDOT/V 2 O 5 ratios. The hybrids PEDOT/V 2 O 5 exhibit a high electrical conductivity. [ABSTRACT FROM AUTHOR]

Traditional electrode materials are based on the redox potential difference of the electrode in the course of intercalation/deintercalation reactions. They are generally well-crystalline host compounds either with layered structure such as LiCoO 2 and LiNiO 2 , or with tunnel structure like LiMn 2 O 4 . Nanocrystalline materials are, however, being re-evaluated recently as 'nanoscience' advances. The electrochemistry of this kind of materials is much different from that of traditional crystalline ones because of their significant 'surface effects'. In connection with that, the nanocrystalline cathode materials are reported to have an enhanced electrochemical activity when the first significative electrochemical step is insertion of Li ions (discharge process). The "electrochemical grafting" concept will be given as a plausible explanation. As illustrative examples, electrochemical behaviors of nanocrystalline manganese oxydes are presented. [ABSTRACT FROM AUTHOR]

Abstract: Lithium intercalation hosts are a key point to the energy density of the largely used LiCoO2 (even if of high cost and toxicity) as well as of manganese oxides which have been investigated most extensively. Iron oxides are attractive electrode materials for low-voltage rechargeable lithium batteries from both cost and environmental standpoints. However, search for iron oxides of conventional crystalline structures and micrometer particle sizes as lithium intercalation cathodes, has been greeted with disappointing results. Here we report on the synthesis, characterizations, electrochemical study and electrochemical impedance spectroscopy (EIS) of a nanocrystalline γ-Fe2O3 that simultaneously exhibits high lithium insertion capacity and good capacity retention upon cycling. These properties reveal thermodynamics of the nanocrystalline material inherently different from those of its microcrystalline counterpart. Moreover, EIS showed that the intercalation process of the lithium ion occurs according to two processes involving first the reduction of the surface Fe3+ with concomitant charge neutralization by Li+ ions onto the surface defects of the nanoparticle followed by the reduction of the core Fe3+ with insertion of the Li+ deeper in the particle. [Copyright &y& Elsevier]