Thermodynamics and kinetics of lithium intercalation into Nb2O5 electrodesfor a 2 V rechargeable lithium battery

Niobium pentoxide was synthesized by heating niobium hydroxide in the tempe rature range of 600-1100 degrees C. The crystal system of Nb2O5 compounds d epended on the heating temperatures, i.e., hexagonal, orthorhombic, and mon oclinic Nb2O5 compounds were obtained at ca. 600, 800, and >1000 degrees C, respectively. Electrochemical lithium intercalation into the three Nb2O5 c ompounds was investigated in a cell with a LiClO4-propylene carbonate elect rolytic solution for application as lithium battery cathodes. As a result, they displayed good charge-discharge performance as the cathode of a 2 V li thium battery, which will play an important role in power supply for integr ated circuit memory backup developed recently. The thermodynamics and kinet ics of lithium intercalation into the Nb2O5 cathode and their characteristi cs have been investigated. The thermodynamic parameters, such as standard f ree energies, lithium partial molar entropy, interaction energies between i ons, crystal lattice parameters, and kinetic parameters, such as chemical a nd self diffusion constants, have been obtained as a function of x value in LixNb2O5. These results were compared to those of a Nb2O5 thin-film electr ode prepared by a radio frequency sputtering method, which has high potenti al for fabricating thin microbatteries. (C) 1999 The Electrochemical Societ y. S0013-4651(99)01-034-4. All rights reserved.