Thermodynamics and Kinetics of Lithium Intercalation into Nb2 O 5 Electrodes for a 2 V Rechargeable Lithium Battery

Niobium pentoxide was synthesized by heating niobium hydroxide in the temperature range of 600‐1100°C. The crystal system of compounds depended on the heating temperatures, i.e., hexagonal, orthorhombic, and monoclinic compounds were obtained at ca. 600, 800, and >1000°C, respectively. Electrochemical lithium intercalation into the three compounds was investigated in a cell with a carbonate electrolytic solution for application as lithium battery cathodes. As a result, they displayed good charge‐discharge performance as the cathode of a 2 V lithium battery, which will play an important role in power supply for integrated circuit memory backup developed recently. The thermodynamics and kinetics of lithium intercalation into the cathode and their characteristics have been investigated. The thermodynamic parameters, such as standard free energies, lithium partial molar entropy, interaction energies between ions, crystal lattice parameters, and kinetic parameters, such as chemical and self diffusion constants, have been obtained as a function of x value in . These results were compared to those of a thin‐film electrode prepared by a radio frequency sputtering method, which has high potential for fabricating thin microbatteries. © 1999 The Electrochemical Society. All rights reserved.