JP5125438B2 - Lithium ion secondary battery and battery pack using the same - Google Patents

Description

  The present invention relates to a stacked lithium ion secondary battery and an assembled battery using the same.

  Since the lithium ion secondary battery was released, its energy density is higher than other secondary batteries such as nickel cadmium battery and nickel metal hydride battery, so it has been installed in mobile phones, notebook computers, video cameras, etc. It has spread as a power source for mobile devices.

The lithium ion secondary battery is composed of a material that can be doped / undoped with lithium ions such as carbon for the negative electrode, and a lithium-containing transition metal oxide such as lithium cobaltate, lithium nickelate, or lithium manganate for the positive electrode. An organic solvent in which a lithium salt such as LiPF ₆ is dissolved is used for the electrolytic solution.

  The electrode structure of the lithium ion secondary battery includes a winding type in which a strip-shaped electrode is wound and a laminated type in which strip-shaped electrodes are stacked. As a stacked type, for example, there is a non-aqueous electrolyte secondary battery disclosed in Patent Document 1.

  A conventional stacked lithium ion secondary battery will be further described with reference to the drawings. 7 shows a stacked state of battery elements of a conventional example, FIG. 7 (a) is an internal perspective view, and FIG. 7 (b) is a schematic sectional view. In addition, the dotted line in FIG. 7 (a) and the diagonal line of a broken line show a specific material, and the hatching in FIG.7 (b) represents a cross section.

  The two separators 4 are joined in a bag shape, the positive electrode 3 is put in the bag, and the battery element of the laminated body is configured so that the negative electrode 2 faces the separator 4 therebetween. FIG. 8 shows constituent members of the battery element. 8A is a schematic diagram of the negative electrode 2, FIG. 8B is a schematic diagram of the positive electrode 3, and FIG. 8C is a schematic diagram of the separator 4. 8A, reference numeral 21 denotes a negative electrode active material application part, 22 denotes a negative electrode current collector lead-out part, FIG. 8B shows 31 a positive electrode active material application part, and 32 a positive electrode current collector lead part. Indicates. In the separator 4 of FIG. 8C, three sides of two porous plastic sheets are joined at a fixed interval by the fusion part 5, and the upper side is left as a separator opening 16 and is formed in a bag shape. .

  9 shows a manufacturing method by punching and cutting the current collector lead portion, FIG. 9A is a schematic diagram before cutting the lead portion of the negative electrode current collector, and FIG. 9B is a positive current collector. It is a schematic diagram before the cutting | disconnection of the drawer part of a body. After the negative electrode active material application part 25 is formed, the negative electrode current collector lead part 22 is formed by punching and cutting along a cutting line 29 so as to leave a part of the negative electrode active material non-application part 26 in a rectangular shape. Similarly, after the positive electrode active material application part 35 is formed, the positive electrode current collector lead-out part 32 is formed by punching and cutting along the cutting line 39 so as to leave a part of the positive electrode active material non-application part 36 in a rectangular shape. The

JP-A-9-129211

  As described above, in the conventional stacked lithium ion secondary battery, a part of the current collector of the electrode active material uncoated portion is taken out as a tab, and after stacking the electrodes, the tabs are stacked and joined to take out battery power. As a part. In addition, in order to draw out a part of the current collector of the electrode active material uncoated part as a tab, after applying the electrode active material to the current collector, the electrode active material uncoated part is formed into a desired tab shape using a mold. Punched out.

  Since the current collector is usually made of thin-film metal of several microns to several tens of microns, there is a problem that it is not easy to generate burrs or to adjust the mold when punching out the tab with the mold.

  Accordingly, an object of the present invention is to provide a lithium ion secondary battery having an electrode lead shape suitable for manufacturing a laminate and an assembled battery using the lithium ion secondary battery.

  As a result of various studies to achieve the above object, the present inventors have found an electrode lead shape that can easily realize a laminated structure in the manufacturing process, and have completed the present invention.

  In order to solve the above problems, a negative electrode made of a negative electrode active material capable of inserting / extracting lithium ions, a positive electrode made of a positive electrode active material capable of inserting / extracting lithium ions, and a positive electrode for insulating these electrodes In a laminated lithium ion secondary battery in which a porous plastic sheet disposed between a negative electrode and a negative electrode is laminated, the porous plastic sheet covers the entire electrode active material coating portion of the positive electrode, and the negative electrode The entire overlapping portion of the electrode active material uncoated portion and the positive electrode active material uncoated portion was covered.

That is, the lithium ion secondary battery of the present invention includes a negative electrode made of a negative electrode active material capable of inserting and removing lithium ions, a positive electrode made of a positive electrode active material capable of inserting and removing lithium ions, and these electrodes. In a laminated type lithium ion secondary battery in which a porous plastic sheet disposed between the negative electrode and the positive electrode for insulation is laminated and impregnated with an electrolyte, the negative electrode and the positive electrode are electrodes on a current collector. An active material application part and an electrode active material non-application part, and the electrode active material non-application part in the negative electrode and the positive electrode overlap each other cut by at least one or two linear cutting lines And the non-overlapping parts that do not overlap each other, and the porous plastic sheet covers the electrode active material application portions of both the negative electrode and the positive electrode. Also characterized in that interposed between the overlapping portions of the electrode active material uncoated portion together with intervening.

In the lithium ion secondary battery, the cutting line is inclined with respect to the lead-out direction of the electrode lead.
Further, the porous plastic sheet has a part of a non-overlapping portion between the negative electrode active material uncoated portion and the positive electrode active material uncoated portion, and the negative electrode active material uncoated portion; It is good to intervene in the overlap part with the electrode active material non-application part of the above-mentioned positive electrode.

The shape of the electrode active material application part in the negative electrode and the positive electrode is preferably rectangular , and the shape of the electrode active material uncoated part in the negative electrode and the positive electrode is preferably triangular .

  The main component of the positive electrode active material is preferably a manganese-based transition metal oxide.

  The assembled battery of the present invention is characterized by combining the lithium ion secondary battery.

  A negative electrode made of a negative electrode active material capable of inserting / extracting lithium ions, a positive electrode made of a positive electrode active material capable of inserting / extracting lithium ions, and arranged between the positive electrode and the negative electrode to insulate these electrodes In the lithium ion secondary battery in which the porous plastic sheet is laminated, the porous plastic sheet covers the entire electrode active material application portion of the positive electrode, and the negative electrode active material uncoated portion and the positive electrode By covering the entire overlapping part with the electrode active material uncoated part, the shape of the lead part of the current collector can be made simple, and as a result, the current collector lead part can be easily manufactured and laminated. Can provide a lithium ion secondary battery having excellent resistance and an assembled battery using the same.

  Hereinafter, although embodiment of this invention is described, this invention is not limited to these.

(Embodiment 1)
1A and 1B are diagrams for explaining battery elements of a lithium ion secondary battery according to Embodiment 1 of the present invention. FIG. 1A is an internal perspective view of the battery element 1, and FIG. 1B is a battery element. 1 is a schematic cross-sectional view of FIG. In addition, the dotted line of FIG. 1 (a) and the diagonal line of a broken line show a specific material, and the hatching of FIG.1 (b) represents a cross section.

  The battery element 1 has a configuration in which a positive electrode 3 and a negative electrode 2 are each insulated and laminated by a separator 4 made of a porous plastic sheet. The separator 4 that covers the positive electrode 3 is joined to the periphery of the positive electrode 3 at the fusion part 5 at intervals to form a bag shape. The uncoated portion 7 where the electrode active material of the positive electrode 3 is not coated and the uncoated portion 6 where the electrode active material of the negative electrode 2 is not coated are stacked alternately, and the separator 4 is uncoated with the electrode active material of the negative electrode 2. It is interposed between the substantially triangular overlapping portions 8 by the portions 6 and the uncoated portions 7 of the electrode active material of the positive electrode 3. Therefore, there is no electrical short circuit in this substantially triangular region.

  2A and 2B show constituent members of the battery element. FIG. 2A is a schematic view showing the shape of the negative electrode 2, FIG. 2B is the positive electrode 3, FIG. A negative electrode active material application part 31 is a positive electrode active material application part. 3 shows the electrode before cutting, FIG. 3 (a) is a schematic diagram showing the negative electrode 2 before cutting together with the cutting line 9, and FIG. 3 (b) shows the positive electrode 3 before cutting together with the cutting line 10. It is a schematic diagram shown.

  The negative electrode 2 and the positive electrode 3 are produced by cutting the uncoated portions 6 and 7 of the electrode active material along the cutting lines 9 and 10, but can be easily cut with a mold or the like. Moreover, since it is cut in a straight line, burrs, which have been a problem in the past, do not occur, the mold can be easily adjusted, and the productivity of the negative electrode 2 and the positive electrode 3 is improved.

  Further, as shown in FIG. 2C, the separator 4 is joined by overlapping two rectangular sheets and forming the fusion part 5 at a constant interval. 16 is prepared in a bag shape.

  FIG. 4 is an internal perspective view showing the lithium ion secondary battery in the present embodiment. The negative electrode current collector 11 and the positive electrode current collector 12 in the region not covered by the separator 4 are connected to each other, and the lead 14 drawn out of the battery outer container 13 and welding such as an ultrasonic welding machine are used. The lithium ion secondary battery (battery cell) 15 of the present invention is obtained by electrically joining using a machine and impregnating the separator and the electrode active material with an electrolytic solution and storing it in the battery outer casing 13.

Next, an example produced based on this embodiment will be described. A 10 μm copper foil was used for the negative electrode current collector, and a 20 μm aluminum foil was used for the positive electrode current collector. The negative electrode active material was prepared in a paste form by adding graphite as a main component and adding a binder. LiMn ₂ O ₄ is used as the main component for the positive electrode active material, but manganese-based transition metal oxides such as LiMnO ₂ may also be used. When the electrode active material non-coated portion is punched and cut in a straight line in order to form an electrode lead-out portion in these current collectors, cutting failure due to the generation of burrs or the like can be reduced as compared with the conventional example. Next, 4 positive electrodes and 5 negative electrodes were laminated to produce a lithium ion secondary battery (battery cell) having an outer dimension of 82 × 150 × 4 mm.

(Embodiment 2)
The second embodiment of the present invention is the same as the first embodiment except for the electrode active material uncoated portion and the separator opening. FIG. 5 shows constituent elements of the battery element according to Embodiment 2 of the present invention, FIG. 5 (a) is a schematic diagram showing the shape of the negative electrode active material uncoated portion, and FIG. 5 (b) is a diagram of the positive electrode. FIG. 5C is a schematic diagram showing the shape of the opening of the separator, and FIG. 5C is a schematic diagram showing the shape of the separator opening.

  The separator 4 is not coated with the electrode active material 6 so as to be interposed between the triangular overlapping portions of the electrode active material uncoated portions of the negative electrode 2 in FIG. 5A and the positive electrode 3 in FIG. 5B. 7, the shape of the separator opening 16 is a mountain shape slightly larger than the triangular shape of the overlapping portion as shown in FIG. Moreover, the electrode active material non-application part which was not covered with the separator 4 is used as a collector drawer part, and the connection between electrodes or the connection outside a battery exterior container is performed.

(Embodiment 3)
FIG. 6 is a schematic diagram showing the shape of the active material uncoated portion of the electrode in Embodiment 3 of the present invention, and FIG. 6 (a) is a schematic diagram showing the shape of the negative electrode active material uncoated portion, FIG. 6B is a schematic diagram showing the shape of the positive electrode active material uncoated portion, and FIG. 6C is a schematic diagram showing the shape of the separator.

 The present embodiment is the same as the first embodiment except for the shapes of the uncoated portions 6 and 7 of the electrode active material. As shown in FIG. 6, the uncoated portions 6 and 7 of the electrode active material have such a substantially triangular shape and the cut portion is formed by two straight lines. The shape is easy to suppress the occurrence of burrs.

  As described above, the lithium ion secondary battery of the present invention has a shape in which the electrode active material uncoated portion of the positive and negative electrode current collectors is cut along a simple line and can be easily cut with a mold or the like. . In addition, since cutting is performed along a simple line, burrs and the like are hardly generated, and the mold can be easily adjusted, and the productivity of the battery cell of the lithium ion secondary battery is improved.

  By connecting the lithium ion secondary battery produced as described above as one battery cell in series and / or in parallel according to the voltage and current used, and adding a protection circuit, an overall control circuit, etc., the present invention The assembled battery is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the battery element of the lithium ion secondary battery in Embodiment 1 of this invention, Fig.1 (a) is an internal perspective view of a battery element, FIG.1 (b) is typical sectional drawing of a battery element. . The structural member of the battery element in Embodiment 1 is shown, respectively, Fig.2 (a) is a negative electrode, FIG.2 (b) is a positive electrode, FIG.2 (c) is a schematic diagram which shows the shape of a separator. FIG. 3A is a schematic diagram showing an electrode before cutting in Embodiment 1, FIG. 3A is a schematic diagram showing a negative electrode before cutting together with a cutting line, and FIG. 3B is a schematic diagram showing a positive electrode before cutting together with a cutting line. FIG. 3 is an internal perspective view showing the lithium ion secondary battery according to Embodiment 1. FIG. 5 (a) is a schematic diagram showing the shape of the negative electrode active material uncoated portion, and FIG. 5 (b) is the shape of the positive electrode active material uncoated portion. FIG. 5C is a schematic diagram showing the shape of the separator opening. 6 shows the shape of the electrode active material uncoated portion in Embodiment 3, FIG. 6 (a) is a schematic diagram showing the shape of the negative electrode active material uncoated portion, and FIG. 6 (b) is the positive electrode active material uncoated portion. FIG. 6C is a schematic diagram showing the shape of the separator. FIG. 7A is an internal perspective view, and FIG. 7B is a schematic cross-sectional view showing a stacked state of conventional battery elements. The structural member of the conventional battery element is shown, FIG. 8 (a) is a negative electrode, FIG.8 (b) is a positive electrode, FIG.8 (c) is a schematic diagram of a separator, respectively. 9A and 9B show a conventional method for producing a current collector lead portion by punching and cutting. FIG. 9A is a schematic diagram before cutting the lead portion of the negative electrode current collector, and FIG. Schematic diagram before cutting.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery element 2 Negative electrode 3 Positive electrode 4 Separator 5 Fusing part 6, 7 Uncoated part 8 Overlapping part 9, 10 Cutting line 11, 12 Current collector 13 Battery outer container 14 Lead 15 Lithium ion secondary battery (battery cell)
16 Separator openings 21, 31 Application part

Claims (6)

A negative electrode made of a negative electrode active material capable of inserting and removing lithium ions, a positive electrode made of a positive electrode active material capable of inserting and removing lithium ions, and disposed between the negative electrode and the positive electrode to insulate these electrodes In a laminated lithium ion secondary battery in which a porous plastic sheet is laminated and impregnated with an electrolytic solution,
The negative electrode and the positive electrode consist of an electrode active material application part and an electrode active material non-application part on the current collector,
The electrode active material non-applied portion at the negative electrode and the positive electrode is composed of at least one or two linear cutting lines that overlap each other and non-overlapping portions that do not overlap each other,
The porous plastic sheet is interposed between the negative electrode and the positive electrode so as to cover both of the negative electrode and positive electrode electrode active material coated portions, and is also interposed between the overlapping portions of the electrode active material uncoated portions. A lithium ion secondary battery characterized by the above. 2. The lithium ion secondary battery according to claim 1, wherein the cutting line is inclined with respect to the lead-out direction of the electrode lead. The porous plastic sheet leaves a part of the non-overlapping portion between the negative electrode active material uncoated portion and the positive electrode active material uncoated portion, and the negative electrode active material uncoated portion and the positive electrode. 3. The lithium ion secondary battery according to claim 1 , wherein the lithium ion secondary battery is interposed in an overlapping portion with the electrode active material uncoated portion. The shape of the electrode active material application part in the negative electrode and the positive electrode is both rectangular ,
3. The lithium ion secondary battery according to claim 1 , wherein the electrode active material uncoated portions of the negative electrode and the positive electrode each have a triangular shape. 4. The lithium ion secondary battery according to any one of claims 1 to 4 , wherein a main component of the positive electrode active material is a manganese-based transition metal oxide. An assembled battery comprising a combination of the lithium ion secondary battery according to any one of claims 1 to 5 .

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