LI+ EXTRACTION/INSERTION REACTIONS WITH LIZN0.5MN1.5O4 SPINEL IN THE AQUEOUS-PHASE

Spinel-type lithium-zinc-manganese oxide (Li0.5Zn0.5)[Li0.5Mn1.5]O-4 was prepared by a coprecipitation/thermal crystallization method. The Li+ extraction/insertion reactions with the spinel in the aqueous phase were investigated by X-ray diffraction, DTA-TG analyses, FT-IR spectroscopy, pH titration, and distribution coefficient (K-d) measurement. The Li+ extraction and insertion proceed by topotactic ion-exchange-type mechanisms. The Zn2+ at the tetrahedral sites caused a decrease in the extractabilities of Li+ during acid treatment. The spinel with ordered arrangement of Li+ and Zn2+ at 8a tetrahedral sites showed a markedly lower Li+ extractability than the spinel with random arrangement of Li+ and Zn2+ at the same sites. The inhibiting effect of Zn2+ on Li+ extractability was discussed in terms of the Li+ migration pathway in the spinel structure. The Li+-extracted sample showed a lithium ion-sieve property from microamount to macroamount of metal ion loading.