Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
2000-04-13
2001-10-09
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S212000, C429S217000, C429S218100, C429S231400, C429S231600, C429S231900, C429S231950
Reexamination Certificate
active
06300013
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a material for a negative electrode composed of a mixture of a non-carbon material and carbon material and a nonaqueous-electrolyte battery incorporating the material for a negative electrode. More particularly, the present invention relates to a material for a negative electrode exhibiting excellent resistance against cycle operations realized by specifying the particle size of each of the non-carbon material and the carbon material and a nonaqueous-electrolyte battery incorporate the foregoing material.
2. Description of the Related Art
Hitherto, a multiplicity of portable electronic apparatuses, such as camcoders, portable telephones and laptop computers have made their appearance in recent years. The size and weight of the electronic apparatuses have been required. Studies have energetically been performed to improve the energy density of the secondary battery which serves as the power source for the electronic apparatus. In particular, lithium-ion secondary batteries have been expected because the lithium-ion battery permits a considerably high energy density as compared with that realized by the conventional lead batteries and the nickel-cadmium batteries.
As the material of the negative electrode of the lithium-ion battery, a carbon material, such as non-graphitizable carbon or graphite, has widely been used. The reason for this lies in that the foregoing carbon material has a relatively large capacity and capable of realizing satisfactory resistance against cycle operations.
Since the capacity has been enlarged in recent years, the foregoing carbon materials suffer from unsatisfactory capacities. Therefore, a further improvement in the performance has been required. Hence it follows that studies of materials for the negative electrode, such as silicon and tin, exhibiting larger capacities have energetically been performed so as to be substituted for the conventional carbon materials.
The non-carbon material for the negative electrode suffers from excessive change in the volume of the active material thereof occurring when lithium is doped/dedoped. Therefore, excessive deterioration in the resistance against cycle operations takes place, causing application of the foregoing carbon material to the battery to be inhibited.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a material for a negative electrode which is capable of preventing change in the volume of the active material occurring when lithium is doped/dedoped and improving the resistance against cycle operations and a nonaqueous-electrolyte battery incorporating the material for a negative electrode.
To achieve the foregoing object, according to one aspect of the invention, there is provided a material for a negative electrode comprising: a mixture of a non-carbon material and a carbon material, wherein when an assumption is made that the average particle size of the non-carbon material is R
M
and the average particle size of the carbon material is R
C
, the ratio R
M
/R
C
is not higher than one, and when an assumption is made that the weight of the non-carbon material is W
M
and the weight of the carbon is W
C
, the ratio W
M
/W
C
is not higher than one.
According to another aspect of the invention, there is provided a material for a negative electrode comprising: a mixture of a silicon compound and a carbon material, wherein when an assumption is made that the average particle size of the silicon compound is R
Si
and the average particle size of the carbon material is R
C
, the ratio R
Si
/R
C
is not higher than one.
The material for a negative electrode according to the present invention has the structure that the ratio of the particle size of the silicon compound and the carbon material is specified. Therefore, change in the volume of the silicon compound occurring when lithium is doped/dedoped can be absorbed by the carbon material. Thus, change in the overall volume of the material for a negative electrode can be prevented.
Other objects, features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.
REFERENCES:
patent: 5922491 (1999-07-01), Ikawa et al.
patent: 6007945 (1999-12-01), Jacobs et al.
patent: 6051340 (2000-04-01), Kawakami et al.
Endo Takuya
Imoto Hiroshi
Li Guohua
Tanizaki Hiroaki
Yamada Shinichiro
Chaney Carol
Sonnenschein Nath & Rosenthal
Sony Corporation
Yuan Dah-Wei D.
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