Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Patent
1995-06-30
1997-03-25
Kalafut, Stephen
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
429218, 4271263, 4273885, H01M 452, H01M 462
Patent
active
056143346
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a material, in a sheet form, for a lithium battery positive electrode, which is advantageously used for forming a cylindrical secondary battery having a high electromotive force, and the production of such long sheet.
BACKGROUND ART
There have been known, as positive electrodes capable of forming a lithium battery having a high electromotive force, positive electrodes using LiCoO.sub.2 as an active material. The group of the present inventors has found an active material comprising at least one member selected from the group of lithium phosphates, lithium-cobalt phosphates, cobalt oxides and lithium-cobalt oxides, wherein lithium, cobalt and phosphorus are contained in a proportion of more than 0.1 mole of cobalt and more than 0.2 mole of phosphorus both per mole of lithium.
The novel active material having the composition as mentioned above is characterized in that it also comprises phosphorus besides lithium, cobalt and oxygen. The addition of phosphorus leads to a less mass and increases lithium ion incorporation per unit weight, which ultimately results in increased capacities. By using said active material for a positive electrode, primary or secondary lithium batteries superior in electromotive force, discharge voltage, discharge capacity and energy density, and having a still higher electromotive force than the conventional batteries using LiCoO.sub.2, can be obtained.
DISCLOSURE OF THE INVENTION
In general terms, batteries have greatly diverse properties depending on the combination of starting materials, which is possibly due to microelectric chemical reactions they undergo. Accordingly, practical batteries are made to exhibit the specific properties they have by deliberately balancing the respective materials. When the main components are changed, therefore, new materials should be developed, so that a battery capable of exhibiting the properties based on the new main components can be fabricated.
The present invention aims at providing a material for a positive electrode of a lithium battery, which is superior in practical use and production efficiency, without impairing the high electromotive force afforded by the aforementioned novel active material.
The present invention provides a material for lithium battery positive electrodes, characterized in that a powder of an active material comprising at least one member selected from the group consisting of lithium phosphates, lithium-cobalt phosphates, cobalt oxides and lithium-cobalt oxides, wherein lithium, cobalt and phosphorus are contained in a proportion of more than 0.1 mole of cobalt and more than 0.2 mole of phosphorus both per mole of lithium, is formed into a sheet using a binder comprising an organic polymer, and a method for producing a material for a lithium battery positive electrode, which is characterized by extending a binder solution comprising a powder of the above-mentioned active material, on a long support sheet, and drying.
By using the positive electrode material of the construction as mentioned above, a material, in a sheet form, for lithium battery positive electrodes, which is superior in practical use and production efficiency, can be provided without impairing the high electromotive force of a novel active material having the above-mentioned composition. According to the production method mentioned above, a long sheet for lithium battery positive electrodes can be stably and efficiently obtained by a continuous process.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of an embodiment of a positive electrode material.
FIG. 2 is a sectional view of another embodiment of a positive electrode material.
FIG. 3 is a schematic sectional view showing a production of a positive electrode material.
FIG. 4 is a sectional view showing one example of the structure of a battery.
FIG. 5 is a schematic sectional view showing another production of a positive electrode material.
FIG. 6 is a schematic sectional view showing a still another production of a positive el
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Supplementary European Search Report for Application No. EP 94 90 0277 (Sep. 1995).
Journal of Power Sources, vol. 40, No. 3, Dec. 15, 1992, pp. 347-353 "Synthesis of LiCoO.sub.2 from cobalt-organic acid complexes and its electrode behavior in a lithium secondary battery".
European Search Report for Application Number EP 93 10 8004 (Aug. 1993).
Kamauchi Masahiro
Takada Yoshinori
Kalafut Stephen
Mitsubishi Cable Industries Ltd.
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