1. Field of the Invention
The present invention relates generally to a secondary battery and more particularly, to a folding secondary battery that has high structural stability and assures high level of safety.
2. Description of the Related Art
A conventional secondary battery 1, as shown in
The aforesaid conventional secondary battery is still not satisfactory in function. Because the positive electrode 2, the first isolation film 3, the negative electrode 4 and the second isolation film 5 are rolled up and flattened before insertion into the housing 7, the film of positive active material 8 and the film of negative active material 10 may be detached from the positive electrode 2 and the negative electrode 4 when they are folded, causing a short circuit. Further, the narrow elongated film of negative active material 10 will expand in dimension during charging. Expansion of the narrow elongated film of negative active material 10 due to charging may cause the negative electrode 4 or the housing 7 to deform.
The present invention has been accomplished in view of the above-noted circumstances. It is an objective of the present invention to provide a folding secondary battery, which has high structural stability and assures high level of safety.
To achieve this objective of the present invention, the folding secondary battery comprises a positive electrode, two negative electrodes, two isolation films, a housing, an electrolyte solution, and two conductive terminals.
The positive electrode includes an aluminum foil with opposite first and second sides, and films of positive active material spacedly and respectively mounted on the first and second sides of the aluminum foil in a pair manner. Each film of positive active material has a width smaller than the width of the aluminum foil so that the positive electrode defines a bare aluminum region at the top portion thereof. The two negative electrodes are provided at two opposite sides relative to the positive electrode, each including a copper foil and a plurality of films of negative active material spacedly mounted on one side of the copper foil that faces the positive electrode and corresponding to the films of positive active material. Each film of negative active material has a width smaller than the width of the copper foil such that the negative electrode defines a bare copper region at a bottom portion thereof. The two isolation films are respectively sandwiched between the positive electrode and the two negative electrodes to isolate the positive electrode from the negative electrodes. The housing has an accommodation space that accommodates the positive electrode, the negative electrodes and the isolation films. The electrolyte solution is filled in the accommodation space of the housing. The positive electrode, the negative electrodes and the isolation films are laminated and folded into a continuously zigzag-shaped folded body such that a layered bare aluminum contact is defined at a top side of the folded body and a layered bare copper contact is defined at a bottom side of the folded body. One conductive terminal is electrically connected with the layered bare aluminum contact and extends out of the housing. The other conductive terminal is electrically connected with the layered bare copper contact and extends out of the housing.
The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
As shown in
The positive electrode 30 comprises an aluminum foil 32 and multiple films of positive active material 35. The aluminum foil 32 has a first side 33 and a second side 34 opposite to the first side 33. The films of positive active material 35 are respectively symmetrically mounted on the first side 33 and the second side 34 of the aluminum foil 32 and equally spaced along the length of the aluminum foil 32 in a pair manner. Each film of positive active material 35 has a width w1 smaller than the width w2 of the aluminum foil 32 such that the positive electrode 30 has a bare aluminum region 36 defined at a top portion thereof. The films of positive active material 35 can be prepared from LiCoO2, LiMnO4, LiNiO2, or LiCoxNi1-xO2. In actual practice, the positive active material can be selected from, but not limited to, lithium oxide, lithium sulfide, lithium selenide, lithium telluride, lithium ferrite phosphor oxide, lithium vanadium phosphor oxide of vanadium, titanium, chrome, copper, molybdenum, niobium, ferrite, nickel, cobalt or manganese.
The negative electrodes 40 are provided at two opposite sides relative to the positive electrode 30, each comprising a copper foil 42 and multiple films of negative active material 45 arranged on one side of the copper foil 42 that faces the positive electrode 30. The films of negative active material 45 are equally spaced from one another and respectively correspond to the films of positive active material 35 of the positive electrode 30. Each film of negative active material 45 has a width w3 smaller than the width w4 of the copper foil 42 such that the negative electrode 40 has a bare copper region 46 defined at a bottom portion thereof. The films of negative active material 45 can be prepared from MCMB, VGCF (vapor growth carbon fiber), CNT (carbon nanotube), charcoal, carbon black, graphite, acetylene black, carbon fiber, vitreous carbon, or a mixture thereof.
The two isolation films 50 are respectively sandwiched between the positive electrode 30 and one of the two negative electrodes 40 to isolate the positive electrode 30 from the negative electrodes 40.
The housing 56 is prepared from aluminum foil, defining therein an enclosed accommodation space 57 that accommodates the positive electrode 30, the negative electrodes 40 and the isolation films 50. The electrolyte solution 58 is also filled in the accommodation space 57.
As shown in
After the folded body 60 is formed, the bare aluminum region 36 of the positive electrode 30 under fold forms a layered bare aluminum contact at the top side of the folded body 60 and the bare copper region 46 of the negative electrode 40 under fold forms a layered bare copper contact at the bottom side of the folded body 60. One conductive terminal 52 is soldered to the layered bare aluminum contact and the other conductive terminal 52 is soldered to the layered bare copper contact. In addition, the two conductive terminals 52 extend out of the housing 56.
Because the films of negative active material 45 of the secondary battery 20 are kept apart from one another at a distance, when the films of negative active material 45 are electrically charged to expand, the amount of deformation of the films of negative active material 45 does not cause the negative electrodes 40 or the secondary battery 20 to deform, assuring high level of safety.
Base on the spirit of the present invention, the folding secondary battery may be variously embodied.
Further, the positions of the positive and negative electrodes in the aforesaid first embodiment may be exchanged to form another embodiment.
In the aforesaid many embodiments of the present invention, the size and shape of the bare copper region and bare aluminum region may be changed subject to requirements.
Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.
Number | Date | Country | Kind |
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97211973 | Jul 2008 | TW | national |