Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Include electrolyte chemically specified and method
Patent
1991-09-11
1993-11-09
Skapars, Anthony
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Include electrolyte chemically specified and method
429218, 296235, H01M 436
Patent
active
052601471
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a novel electrode material for a lithium electrochemical generator. More specifically, it relates to a novel positive electrode material based on vanadium oxide, optionally substituted by another element such as niobium or molybdenum, which also contain lithium.
For several years development has taken place of lithium electrochemical generators due to their very high potential mass energy. These electrochemical generators comprise a positive electrode constituted by a lithium intercalation compound, a liquid or solid electrolyte and a negative electrode constituted by lithium, a lithium alloy or an intercalation compound having a low potential compared with lithium.
Among the presently known reversible systems, considerable research has been carried out on intercalation in V.sub.2 O.sub.5 and it is known that the first discharge curve of this material has several plateau regions located respectively at approximately 3.4, 3.2 and 2.4 volts with respect to the lithium.
The operating principle of all these systems is based on the retention, during the intercalation of the lithium, of the structural skeleton of the host material used for the intercalation of the lithium. As the network of strong bonds of this reception structure is retained, it is possible for the system to be deintercalated or disintercalated, which leads to the reversibility of the generator.
Numerous authors have studied the performance characteristics of V.sub.2 O.sub.5 positive electrodes in lithium rechargeable batteries. These studies have led to the following publications: Wiesener et al in Journal of Power Sources, 20, 1987, pp. 157-164; Tranchant et al in Journal of Power Sources, 24, 1988, pp. 85-93, and Pereira-Ramos et al in Journal of Power Sources, 20, 1987, pp. 221-230.
In these publications, it is stated that batteries using such positive electrodes are cyclable when the discharge is limited to a potential so as to include, during the discharge, less than 2.35 lithium atoms per V.sub.2 O.sub.5 molecule. Therefore the mass capacity of lithium generators using electrodes of this type is limited.
Other authors have also studied the behaviour of V.sub.2 O.sub.5 electrodes when discharge takes place at lower potentials, as described by N. Kumagai et al in Electrochimica Acta, vol. 28, no. 1, 1983, pp. 17-22, by M. Sugawara et al in Proceedings of the Electrochemical Society, vol. 88-6, 1988, pp. 503-510 and by M. Pasquali et al in Journal of Power Sources, vol. 7, no. 2, 1982, pp. 145-152.
Under the discharge conditions given by these authors, less than 2.5 Li atoms are always included and there is no irreversible structural change leading to an improvement in the properties of the electrode.
The present invention specifically relates to a novel electrode material for an electrochemical generator of this type, which makes it possible to obtain a mass energy higher than that of V.sub.2 O.sub.5, a very good reversibility, a fast intercalation or deintercalation kinetics, a very broad range of use because the material is insensitive to supercharging or superdischarging of the generator and reduced costs in obtaining the said material.
According to the invention, this electrode material is in accordance with the formula: lines, which in the particular case z=t=0 are at an angular distance 2.theta. of approximately 64 and 44.degree. for the wavelength K.alpha..sub.1 of copper (1.54 .ANG.), which respectively correspond to interplanar spacings of approximately 2.0 and 1.45 .ANG..
In this material, M represents one or more elements which can be substituted for vanadium in V.sub.2 O.sub.5 used as the starting product prior to lithium intercalation. The structural interconnection characteristic of V.sub.2 O.sub.5 is retained in the substituted phase. Such a substitution has been obtained in the case of molybdenum by L. KIHLBORG (Acta Chemica Scandinavica, vol. 21, p. 2495, 1967). The phase of composition (Mo.sub.0.3 V.sub.0.7).sub.2 O.sub.5 was obtained. This author notes the structural analogy with the vari
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Electrochimica Acta, vol. 28, No. 1, Jan. 1983, Pergamon Press Ltd, N. Kumagai et al.: "Structural changes of Nb.sub.2 O.sub.5 and V.sub.2 O.sub.5 as rechargeable cathodes for lithium battery", pp. 17-22.
Proceedings of the Electrochemical Society, vol. 88-6, 1988, M. Sugawara et al.: "Electrochemical behavior of vanadium(V) oxide in propylene carbonate-LiCl0.sub.4 ", pp. 503-510.
Journal of Power Sources, vol. 7, No. 2, Jan. 1982, M. Pasquali, et al.: "(Mo.sub.0.3 V.sub.0.7).sub.2 O.sub.5 as a solid solution cathode for li cells. Part II. Structural characteristics and secondary cells", pp. 145-152.
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Electrochimica Acta, vol. 33, No. 7, Jul. 1988, Pergamon Press plc., S. Hub et al.: "X-ray investigations on electroformed Li.sub.x V.sub.2 O.sub.5 bronzes", pp. 997-1002.
Journal of Power Sources, vol. 16, No. 3, Nov. 1985, Elsevier Sequoia, J.-P. Pereira-Ramos et al.: "Sulfone-based electrolytes for lithium intercalation batteries", pp. 193-204.
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Journal of Power Sources, vol. 20, 1987, Elsevier Sequoia, J.-P. Pereira-Ramos et al.: "Investigation of lithium intercalation materials with organic solvents and molten salts as electrolytes at temperatures between 60.degree. and 175.degree. C.", pp. 221-230.
Journal of the Electrochemical Society, vol. 132, No. 2, Feb. 1985, G. Pistoia et al.: "Li/Li.sub.1+x V.sub.3 O.sub.8 secondary batteries", pp. 281-284.
Brethes Sabine
Delmas Claude
Levasseur Alain
Menetrier Michel
Centre National de la Recherche Scientifique
Skapars Anthony
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