Investigation of yttrium and polyvalent ion intercalation into nanocrystalline vanadium oxide

The electrochemical reactivity of cations such as Ca2+, Mg2+, and Y3+ into crystalline V2O5 materials was investigated. The ionic diffusion constant of Li+ and Y3+ into microcrystalline and nanocrystalline V2O5 was measured by the galvanostatic intermittent titration technique. The Y3+ ion diffusion constant into a 500 nm crystalline V2O5 was found to be approximately two orders of magnitude lower than for the Li+ ion. In order to enable practical intercalation of Y3+, a nanocrystalline V2O5 was fabricated through a combustion flame synthesis technique. For the first time, reversible electrochemical intercalation of Y3+ into a host structure was shown to be feasible. An asymmetric hybrid cell configuration was utilized in order to provide a reversible counter electrode during intercalation. Preliminary data indicates Y3+ can be reversibly intercalated into V2O5 with apparent gravimetric capacities exceeding that of Ca2+, Mg2+, or Li+ over the limited voltage range of 2.5 to 4.2 V (Li/Li+). The concept of polyvalent intercalation is discussed relative to intercalation, pseudocapacitance, apparent specific capacity, and practical energy storage systems. (C) 2001 Telcordia Technologies.