Lithium Insertion into Anatase Inverse Opal

Anatase inverse opal was prepared either in the form of powder or thin layers via templating with polystyrene latex spheres. The four different methods employed for the TiO 2 deposition were anodic oxidative hydrolysis of TiCl 3 , liquid-phase deposition from ( NH 4 ) 2 TiF 6 solution, and deposition from titanium(IV) isopropoxide either in the vapor phase or in propanolic solution. Electrochemical preparation from TiCl 3 gave the best results. The pores were narrower by ca. 30% compared to the nominal size of latex spheres, as documented by scanning electron microscopy and by the position of the stop band in the optical spectrum. The anatase inverse opals exhibit sluggish electrochemical performance for Li-insertion compared to nontemplated anatase with more dense packing of nanocrystals. This is due to poor electrical contacts between the particles in the nanocrystalline network. The limited number of necking points for charge transport is documented by transmission electron microscopy images. Cyclic voltammograms of Li-insertion showed two pair of extra peaks (S peaks) with formal potentials of 1.5 and 1.6 V, respectively, for both templated and nontemplated electrodeposits. The S peaks were absent in the opals prepared by the remaining three synthetic methods.