ELECTROCHEMICAL LITHIUM INTERCALATION INTO VANADIUM PENTOXIDE XEROGELFILM ELECTRODE

The lithium-ion transport in vanadium pentoxide xerogel film electrode s has been investigated by using cyclic voltammetry and electrochemica l impedance spectroscopy. The oxide xerogel film electrodes were prepa red by spin-coating a viscous gel on an indium tin oxide (ITO) substra te. The spin-coated xerogel films were dried under vacuum at 130 and 2 70 degrees C, respectively, The lithium intercalation into the xerogel film electrode dried at 270 degrees C is limited by the interfacial r eaction at the electrolyte/electrode interface rather than the lithium -ion transport in the oxide electrode. On the other hand, lithium inte rcalation into the film electrode dried at 130 degrees C is largely li mited by the lithium transport in the oxide film, and the chemical dif fusivity of the lithium ion in the oxide film was determined to decrea se from 10(-10) to 10(-12) cm(2) s(-1) as the electrode potential of t he oxide film fell from 3.0 to 2.2 VLi/Li+. The transition of the diff usion-controlled intercalation to the interfacial reaction-controlled intercalation into the oxide xerogel film with decreasing drying tempe rature was explained in terms of the modification of the oxide lattice to a more open-structured lattice by structural modification of the o xide film by water molecules incorporated into the film. (C) 1997 Else vier Science S.A.