Secondary battery or cell with a non-aqueous electrolyte

Details Secondary battery or cell with a non-aqueous electrolyte Secondary battery or cell with a non-aqueous electrolyte

1992-04-03

2001-09-25

Chaney, Carol (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Electrode

C429S324000, C429S232000

Reexamination Certificate

active

06294291

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a secondary battery or cell (hereafter merely referred to as battery) with a non-aqueous electrolyte, particularly to a small-sized, light-weight, new secondary battery.
BACKGROUND OF THE INVENTION
Recently portable and cordless tendency in electronic appliances for general use have been rapidly progressing. Accordingly, a demand for a small-sized, light-weight secondary battery having a high energy density, used for charge and discharge power supply for driving a motor, has been increasing. From this point of view, non-aqueous batteries, and particularly secondary lithium batteries are anticipated as batteries having high voltage and energy densities and the development of these batteries is urged. Conventionally, manganese dioxide, vanadium pentaoxide, titanium disulfide and the like have been used as a cathode active material of the secondary lithium batteries. Such a battery comprises a cathode of these materials, a lithium anode and an organic electrolyte and charge and discharge of electricity are repeated. However, in a secondary battery employing a lithium metal anode, the problems of internal short circuit caused by dendritic lithium generated upon charging or side reactions between an active material and an electrolyte are a barrier to developing useful secondary batteries. Further, there has not yet been found a secondary battery which satisfies the high rate charge and discharge property and the over discharge property.
The safety of the lithium batteries has been also severely pointed out and in battery systems employing a lithium metal or a lithium alloy therein as an anode, the safety is very difficult to ensure. On the other hand, a new type of negative electrode has attracted interest, in which the intercalating reaction of layered compounds is utilized for solving the above problems. Particularly graphite compound incorporating anions such as ClO
4
-ion, PF
6
-ion, BF
4
-ion and the like is used as a cathode or positive electrode; and graphite compound incorporating cations such as Li+, Na+ and the like is supposed to be used as an anode or negative electrode.
However, intercalated graphite incorporating cations therein is very unstable, so that in the case of using natural or artificial graphite as an anode, the battery lacks stability and the capacity thereof is low. Further, since decomposition of the electrolyte takes place, intercalated graphite cannot be used in place of a lithium anode.
Lately, it has been found that lithium doped materials of pseudo graphite materials obtained by carbonization of a variety of hydrocarbon or polymeric materials are effective as an anode material and can exhibit a high efficiency and further have excellent stability in a battery. Accordingly, many researches on small-sized, light-weight batteries with the use of these materials have been made.
On the other hand, accompanied with use of carbon materials as an anode, it is proposed that such Li-contained compounds having higher voltage as LiCoO
2
or LiMn
20
O
4
or composite oxide in which a part of Co and Mn is displaced by other elements such as, for example, Fe, Co, Ni, Mn and so on, are to be used as a cathode active material.
The amount of lithium occluded and released upon using the afore-mentioned pseudo graphite materials having more or less turbostratic structures as an anode material was measured to obtain the capacity of only 100-150 mAh/g carbon and also polarization of carbon electrode, accompanied with the electric charge and discharge, is intensified. Therefore, when these carbon anode materials are used in combination with a cathode of, for example, LiCoO
2
and so on, it is difficult to obtain a satisfactory capacity and voltage.
On the other hand, it has been reported that in the case of using a high crystalline graphite material as an anode, intercalation reaction of lithium is difficult to proceed due to the gas generated upon charging on the surface of the graphite electrode surface by the decomposition of an electrolyte. It is found that in spite of generating the gases, coke and the like heat-treated at a high temperature gives relatively high capacity (200-250 mAh/g). However, due to the large expansion and contraction of the graphite in the C axis direction, accompanied with the charge and discharge, the anode body is swollen, by which the original shape cannot be kept. Therefore, there is a serious problem in the cycle property.
Thus, an object of the present invention is to provide a secondary battery with non-aqueous electrolyte, having high voltage, high capacity and an excellent cycle property, by which the above-mentioned conventional problems can be solved.
SUMMARY OF THE INVENTION
For the purpose of overcoming these problems, according to the present invention, by using a composite carbon material comprising carbon fibers and graphite spherical particles as an anode, particularly by using a composite carbon material comprising carbon fibers and spherical graphite particles having a lattice spacing (d002) of 3.36 to 3.42 Å, measured by a wide angle X-ray diffraction method, satisfactory high stiffness and charge and discharge conductivity of the anode can be obtained and thus the swelling and decomposition of the body made thereof can be prevented.
Generally, it is reported that the uppermost limit of content of lithium intercalated chemically between the graphite layers is corresponding to that of intercalated graphite C
6
Li of the first stage wherein there is intercalated one lithium atom per 6 carbon atoms. In this case, the active material has a capacity of 372 mAh/g. When a pseudo graphite material as the abovementioned is used, the intercalation content of lithium is only a few due to the undeveloped layered structure and the charge-discharge reactions are progressing in a noble potential (about +1.0 V ) versus the lithium potential, and therefore pseudo graphite materials are not suitable for an anode material.
As a result of the research for the shapes of the carbon materials, it has been also found that graphite spherical particles provided with an optically anisotropic and single phase are preferred for an anodic graphite material and such graphite spherical particles may be meso-carbon microbeads produced by subjecting mesophase spherules, produced during the carbonization process of pitch, as a raw material to heat treatment for graphitization. In any of these materials, the graphitization step is an important factor and the lattice spacing (d002) at 002 plane is preferably from 3.36 to 3.42 Å and more preferably 3.40 Å or less. In the state of pseudo graphite having a d002 of about 3.43 Å or more, the capacity is low and the polarization of the carbon electrode is intensified in the same manner as in the other pseudo graphite materials.
As stated above, however, in the case of using the graphite spherical particles as an anode, the swelling and decomposition of the anode body may be observed and thus the capacity deterioration becomes large, accompanied with charge-discharge cycle, despite the high initial capacity of 200-250 mAh/g carbon.
According to the present invention, therefore, the above-mentioned problems can be solved by using a composite carbon material comprising the graphite spherical particles material mixed with carbon fibers to intensify the stiffness of the anode and thus prevent the anode body from swelling and decomposing.
As one of example of the carbon fiber used in the invention, there is exemplified a vapor grown carbon fiber. The carbon fiber may be prepared by subjecting hydrocarbons such as benzene, methane, propane and so on to vapor phase heat-decomposition under the presence of catalyst base plate made of Fe, Ni, Co and so on in order to make carbon fibers deposit and grow on the base plate. Other examples are pitch carbon fibers, made from petroleum or coal pitch as a raw material through a spinning and carbonating treatment, and PAN(polyacrylonitrile) carbon fibers made from polyacrylonitrile as a raw

Affiliated with

Also associated with

Rating

Secondary battery or cell with a non-aqueous electrolyte does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Secondary battery or cell with a non-aqueous electrolyte, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Secondary battery or cell with a non-aqueous electrolyte will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2476929