Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1998-03-03
2001-02-06
Nuzzolillo, Maria (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S231100, C423S618000
Reexamination Certificate
active
06183908
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a negative electrode material for a lithium ion nonaqueous electrolyte secondary battery having a high capacity and an improved charge-discharge characteristics and a lithium ion nonaqueous secondary battery using the negative electrode material.
BACKGROUND OF THE INVENTION
In recent years, the demand for the capacity increase and size reduction of the secondary batteries has been growing with the spread of portable personal computers and portable telephones. To this end, the development of lithium ion secondary batteries having a high capacity has been widely made.
As positive electrode materials for a lithium ion secondary battery there have been widely used LiCoO
2
, LiCo
1−x
Ni
x
O
2
, LiNiO
2
, and LiMn
2
O
4
which are positive electrode materials for the secondary battery having a high potential. On the other hand, as negative electrode materials there have been normally used carbonaceous materials. Such the carbonaceous material acts as an electrode active material which reversibly intercalate and deintercalate lithium ion during charging and discharging and thus constitutes a so-called rocking chair type secondary battery electrochemically connected with a nonaqueous electrolytic solution or solid electrolyte.
Examples of carbonaceous materials to be commonly used as negative electrode materials include graphite-based carbon material, pitch coke, fibrous carbon, and high capacity type soft carbon calcined at a low temperature. However, carbonaceous materials are disadvantageous in that they have a low specific gravity of 2.26 (graphite). Therefore, if they are used in an amount such that lithium intercalating capacity reaches the stoichiometric limit (372 mAh/g), it is difficult to design the battery capacity as high as desirable. As negative electrode active materials having a high capacity density surpassing the carbonaceous materials there have been disclosed negative electrode active materials made of a composite oxide mainly composed of tin oxide in JP-A-6-60867, JP-A-7-220721, JP-A-7-122274, and JP-A-7-288123 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). Processes for preparing these negative electrode active materials are also disclosed in the above cited patents.
These composite oxide negative electrode materials are synthesized by calcining at a high temperature of 1,000° C. or more.
However, the foregoing synthesis process has a handling problem in production due to corrosion on the synthesis container. Further, the contamination by impurities eluted from the container causes variation of the physical properties of the electrodes. The material prepared by a melting method is ground to adjust its particle diameter before use as an active material for the battery. However, the material thus ground is liable to wide distribution of particle diameter that can be-a factor for instabilizing the battery performance. Further, since the group of particles having such the wide diameter distribution has a relatively small surface area, the effective surface area taking place in the intercalating reaction of lithium ion decreases, reducing the high current charge-discharge (high rate) efficiency and capacity of the battery. Moreover, in the melting method, various starting material powders, i.e., metal oxide powders are each melted, and then mixed in the form of dispersion. Therefore, it is difficult to uniform the metal elements on a molecular basis, making it difficult to uniformilize the composition distribution in the particle. There have been an apprehension that such a uniformity problem can affect the stability of charge-discharge characteristics of negative electrode materials.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a lithium ion nonaqueous electrolyte secondary battery which comprises a negative electrode material having a uniform particle size and intraparticle composition distribution to exhibit improved charge-discharge characteristics.
Another object of the present invention is to provide a secondary battery which is excellent in performance stability and high rate efficiency.
A further object of the present invention is to provide a secondary battery favorable for production cost as well.
These and other objects of the present invention will become more apparent from the following detailed description and examples.
The foregoing objects of the present invention are accomplished by providing a negative electrode material for a lithium ion nonaqueous secondary battery comprising a composite metal oxide containing an amorphous structure synthesized by a sol-gel method.
In accordance with a representative preparation process of the present invention, a negative electrode material for a lithium ion nonaqueous secondary battery having improved properties can be prepared, comprising a composite oxide containing an amorphous structure which comprises tin as a main component and at least one element selected from the group consisting of elements belonging to the groups I, II, XIII, XIV and XV in the periodic table, transition metal elements and halogen elements, at least a part of the composite oxide having been synthesized from a tin-containing compound as a starting material by a sol-gel method. dr
BRIEF DESCRIPTION OF THE DRAWINGS
By way of example and to make the description more clear, reference is made to the accompanying drawings in which:
FIG. 1
is a sectional view of a coin nonaqueous secondary battery (i.e., a nonaqueous secondary battery having a coin shape) prepared according to an example of the present invention; and
FIG. 2
is a sectional view of a cylindrical nonaqueous secondary battery prepared according to an example of the present invention, wherein the reference numeral
1
indicates a negative electrode sealing plate, the reference numeral
2
indicates a pelletized negative electrode material mixture, the reference numeral
3
indicates a separator, the reference numeral
4
indicates a pelletized positive electrode material mixture, the reference numeral
5
indicates a current collector, the reference numeral
6
indicates a positive electrode case, the reference numeral
8
indicates a positive electrode sheet, the reference numeral
9
indicates a negative electrode sheet, the reference numeral
10
indicates a separator, the reference numeral
11
indicates a battery can, the reference numeral
12
indicates a battery lid, the reference numeral
13
indicates a gasket, and the reference numeral
14
indicates an explosion-proof valve.
REFERENCES:
patent: 5284721 (1994-02-01), Beard
patent: 5472810 (1995-12-01), Takeuchi et al.
patent: 5567539 (1996-10-01), Takahashi et al.
patent: 5601952 (1997-02-01), Dasgupta et al.
patent: 5604057 (1997-02-01), Nazri
patent: 5820790 (1998-10-01), Amine et al.
patent: 5958624 (1999-09-01), Frech et al.
Miyasaka Tsutomu
Nakamura Shigeru
Dove Tracy
Fuji Photo Film Co. , Ltd.
Nuzzolillo Maria
Sughrue Mion Zinn Macpeak & Seas, PLLC
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