Thermodynamics and kinetics of lithium intercalation into Nb{sub 2}O{sub 5} electrodes for a 2 V rechargeable lithium battery
The operating voltage for integrated circuits (ICs) in cellular phones, camcorders, and laptop computers is being reduced from about 3 to 2.5 V, with the advance of IC microfabrication technology, and it will be 1.9 V in the near future. Hence, rechargeable microbatteries which can be charged fully in the same voltage range, i.e., around 2.5--1.9 V, would be required for power supply of the IC memory backup. If such rechargeable lithium batteries are used, there is a substantial weight savings because of their high energy density and no requirement of a voltage adjuster in the devices body. On this basis, niobium pentoxide is one of few cathode candidates for 2 V rechargeable lithium batteries, as described. Niobium pentoxide was synthesized by heating niobium hydroxide in the temperature range of 600--1,100 C. The crystal system of Nb{sub 2}O{sub 5} compounds depended on the heating temperatures, i.e., hexagonal, orthorhombic, and monoclinic Nb{sub 2}O{sub 5} compounds were obtained at ca. 600, 800, and {gt} 1,000 C, respectively. Electrochemical lithium intercalation into the three Nb{sub 2}O{sub 5} compounds was investigated in a cell with a LiClO{sub 4}-propylene 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 Nb{sub 2}O{sub 5} 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 Li{sub x}Nb{sub 2}O{sub 5}. These results were compared to those of a Nb{sub 2}O{sub 5} thin-film electrode prepared by a radio frequency sputtering method, which has high potential for fabricating thin microbatteries.
- Research Organization:
- Iwate Univ., Morioka (JP)
- OSTI ID:
- 20003171
- Journal Information:
- Journal of the Electrochemical Society, Vol. 146, Issue 9; Other Information: PBD: Sep 1999
- Country of Publication:
- United States
- Language:
- English
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