Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
2001-10-16
2004-03-16
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S224000, C429S094000
Reexamination Certificate
active
06706446
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a non-aqueous electrolytic solution secondary battery, and in particular relates to a non-aqueous electrolytic solution secondary battery where an electrode winding group where a positive electrode formed by applying positive electrode active material including a lithium-manganese complex oxide comprising secondary particles formed of aggregated primary particles and conductive material on both surfaces of a strip-like collector by approximately even amounts to the both surfaces and a negative electrode from/in which lithium ions can be released/occluded through charging/discharging are wound through a separator is accommodated into a battery container having an internal pressure releasing mechanism which releases internal pressure at a predetermined internal pressure.
DESCRIPTION OF THE RELATED ART
Because a non-aqueous electrolytic solution secondary battery represented by a lithium-ion secondary battery has a high energy density as its merit, it is mainly used as a power source or power supply for portable equipment such as a VTR camera, a notebook type personal computer, a portable or cellar telephone or the like. The interior structure of this battery is generally of a winding type as described below. Each of a positive electrode and a negative electrode of the electrodes of the battery is formed in a strip-shape where active material is applied to a metal foil, and a winding group is spirally formed by winding the positive electrode and the negative electrode through a separator so as not to come in direct contact with each other. This winding group is accommodated in a cylindrical battery container or can, and after the battery container is filled with electrolytic solution, it is sealed.
An ordinary cylindrical lithium-ion secondary battery has an external dimension of a diameter of 18 mm and a height of 65 mm, which is called 18650 type, and it is widely spread as a small-sized non-aqueous electrolytic solution secondary battery for a civilian use. Carbon material is ordinarily used as a negative electrode active material for the 18650 type lithium-ion secondary battery. The carbon material used may include graphite system material such as natural graphite, scale-shaped, aggregated artificial graphite, mesophase pitch system graphite, and amorphous carbon material prepared by sintering such furan resin as furfuryl alcohol or the like. On the other hand, as a positive electrode active material, one of lithium transition metallic complex oxides is used. Among the lithium transition metallic complex oxides, lithium cobaltate (LiCoO
2
) is widely used in view of balance of capacity, cycle characteristic or the like. Battery capacity of the 18650 type lithium-ion battery is approximately 1.3 Ah to 1.7 Ah and battery power (output) thereof is about 10 W or so.
Meanwhile, in order to cope with the environmental problems in the automotive industry, development of electric vehicles (EVs) whose power sources are confined completely to batteries so that there is no gas exhausting and development of hybrid electric vehicles (HEVs) where both internal combustion engines and batteries are used as their power sources have been facilitated and some of them have reached a practical state.
Secondary batteries for the EVs and HEVs are required to have high power and high-energy characteristics. Attention to the lithium-ion secondary batteries is being paid as secondary batteries which can meet this requirement. In order to spread the EVs and HEVs, it is necessary to reduce the prices of the secondary batteries. Low cost battery materials are required for achieving such price reduction. For example, regarding the positive electrode active material, special attention is paid to manganese oxides which are rich as resources, and improvement of such batteries has been made for high performance thereof. However, it is not considered that the power characteristic of the lithium-ion secondary battery using lithium-manganese complex oxide as the positive electrode active material is sufficient for the EVs and HEVs. In order to solve this problem, it has been studied that the area of the electrode is enlarged to achieve high capacity of the battery. However, such enlargement causes an increase in a battery size, which results in a practical difficulty in view of a mounting space for the battery in a vehicle.
Also, as the battery for the EVs and HEVs, not only high capacity but also high power which affect acceleration performance of a vehicle, namely reduction of the internal resistance of the battery, is required. In order to increase the reaction area of the electrode, this requirement can be met by utilizing a lithium-manganese complex oxide as the positive electrode active material. In particular, in order to increase a specific surface area, it is necessary to reduce the particle diameter of the lithium-manganese complex oxide. However, in a case of the small particle diameter, there occurs such a drawback that powder material is scattered during manufacture of an electrode or it is difficult to obtain appropriate slurry for applying the lithium-manganese complex oxide on both surfaces of a collector. It is possible to solve such a problem by utilizing a lithium-manganese complex oxide formed by secondary particles obtained by aggregating primary particles having a small particle diameter.
Moreover, in a case that a non-aqueous electrolytic solution secondary battery with a high power, as a contrivance for reducing reaction resistance between the positive electrode active material and the non-aqueous electrolytic solution, there has been known such a technique that the positive and negative electrodes are made thinner for reducing diffusion distance of lithium ions between the positive and negative electrodes or they are made longer for increasing the reaction areas of the positive and negative electrodes and so on. However, because large power is required in a case of a secondary battery for an electric vehicle, particularly for the HEV, the space in the battery is mainly occupied by portions other than the positive electrode active material so that the occupation volume of the positive electrode active material in the battery is reduced in the technique where the positive and negative electrodes is made thinner and/or longer. As a result, it is necessary to reduce the filling weight of the positive electrode active material. Such reduction means an increase in load per unit positive electrode active material. Because lithium ions are temporarily concentrated on a surface of the positive electrode active material during high rate charging/discharging cycle conducted by pulse-like current, particularly during discharging cycle, it becomes difficult to occlude lithium ions to a portion corresponding to a normal reaction side and load acting on the positive electrode active material is increased. Accordingly, when the pulse charging/discharging cycle is repeated for a long term, there has been a problem that the structural destruction of the positive electrode active material is caused according to over-voltage, which results in a large reduction in power of the battery.
In addition, in the case of the lithium-ion secondary battery, as the capacity and/or power thereof is increased, the safety thereof is apt to lower. Particularly, as mentioned above, in the non-aqueous electrolytic solution secondary battery for obtaining a high power (performance), such a tendency is observed that the phenomenon becomes intense when the battery falls in an abnormal state. That is, in reaction of the lithium-ion secondary battery at a time of over-charged state thereof, all lithium ions are released from the positive electrode active material and the structure of the active material is made unstable according to the over-voltage, so that the non-aqueous electrolytic solution becomes easy to decompose. When the non-aqueous electrolytic solution is decomposed, oxygen releasing reaction occurs according to the decomposition of the non-aqueous electrolytic
Hironaka Kensuke
Koishikawa Yoshimasa
Nakai Kenji
Nakano Takeshi
Takatsuka Yuichi
Alejandro Raymond
Kalafut Stephen
Shin-Kobe Electric Machinery Co. Ltd.
LandOfFree
Non-aqueous electrolytic solution secondary battery does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Non-aqueous electrolytic solution secondary battery, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-aqueous electrolytic solution secondary battery will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3279455