JP2006066311A - Lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery in which safety in overcharge can be secured. <P>SOLUTION: As for the lithium ion secondary battery, a rectangular laminate film having four sides is used for an exterior body. Side edge parts of the four sides of the laminate film are sealed by heat welding, and a cathode terminal and an anode terminal are respectively pinched between opposite two sides of the laminate film. In the laminate film, a laminated electrode group 10 is enclosed in which cathode plates 14 and anode plates 15 are alternately laminated. The cathode plates 14 and the anode plates 15 are respectively connected to the cathode terminal and the anode terminal. As for the cathode plate 14, the three sides which are not connected to the cathode terminal are inserted sheet by sheet into separators 12 made of polyethylene worked in a bag-shape by heat welding. Inner short circuits between the cathode and anode terminals and between the cathode and anode plates are suppressed at overcharge. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery in which an electrode group in which a positive electrode plate and a negative electrode plate are arranged via a separator is sealed with a laminate outer film having four sides.

  Lithium secondary batteries have been widely used in the consumer field as power sources for portable devices such as VTR cameras, laptop computers, and mobile phones. However, as portable devices have become smaller and more multifunctional, they can be used as power sources. However, there has been a demand for reduction in size and weight. For this reason, instead of metal cans and resin containers that have been used as exterior bodies for lithium secondary batteries, the base material is aluminum that is light and has good workability and is widely used in the fields of food packaging and medical packaging. The application of a laminate film as an exterior body has been studied, and is now widely used as a power source for portable devices.

  On the other hand, in the automobile industry, in order to cope with environmental problems, an electric vehicle without exhaust gas whose power source is completely a battery and a hybrid electric vehicle (HEV) whose power source is both an internal combustion engine and a battery are used. Development has been in full swing and some have been put into practical use. As a power source for a mobile object such as an electric vehicle, a lithium secondary battery having a high energy density has attracted attention. In addition, development has been actively promoted as a power source for small movable bodies such as assist bicycles and electric scooters. In the field of power sources for mobile objects, the development of batteries using containers such as metal cans has been preceded in the field of mobile bodies. However, studies on lithium secondary batteries using laminate films for the exterior bodies have also become active. Yes.

  Since a power source for a mobile body is required to have high output and high energy, the battery capacity is larger than that for consumer use, and it is used as a battery module to which several tens of lithium secondary batteries are connected. In a lithium secondary battery using a rigid container such as a metal can as an outer package, it is relatively easy to accommodate a safety mechanism such as a current interruption mechanism in the battery container in order to ensure safety. In order to ensure safety even in the event of battery abnormalities such as overcharging, multiple protection functions are incorporated.

  On the other hand, in the lithium secondary battery using a laminate film for the exterior body, the electrode group is wrapped in a substantially rectangular laminate film, and the laminated (edge) portion of the laminate film is thermally welded and sealed, It has a structure in which a positive and negative electrode terminal for energization is sandwiched between one side of the heat welded portion. At the time of heat welding, since it is common to reduce the pressure inside the battery and fix the electrode group to the exterior body at atmospheric pressure, it is difficult to accommodate the above-described safety mechanism or the like in the battery. In batteries that do not have a safety mechanism, when overcharged, the battery generates heat, the internal pressure of the battery rises due to evaporation of the electrolyte and the generation of decomposition gas, the laminate film expands, and the heat welded part of the laminate film peels off. Gas is blown out of the battery. When the separator contracts due to this heat generation and gas ejection and the positive electrode plate and the negative electrode plate are short-circuited inside the battery, a rapid heat generation occurs due to the short-circuit current, and the thermal runaway reaction of the active material (rapid exothermic reaction with a large amount of gas generation) cause. In order to suppress the expansion of the laminate film, for example, a technique of disposing an adhesive layer between the electrode group and the laminate film is disclosed (see Patent Document 1).

JP 2003-151512 A

  However, in the technique of Patent Document 1, although the expansion between the electrode group and the laminate film is suppressed by the adhesive layer, pressure is easily applied to the heat welded portion of the laminate film with the generation of gas, so that the heat welded portion is peeled off. And gas eruption cannot be suppressed. In addition, there is a problem that an internal short circuit between the positive and negative electrode plates is likely to occur in the vicinity of the edge portion of the laminate film from which the heat-welded portion has peeled off and the gas has been ejected, since the separator contracts. Furthermore, when the positive electrode terminal and the negative electrode terminal are led out from the same side of the laminate film, the positive and negative electrode terminals are likely to come into contact with the peeling of the heat-welded portion, so that an internal short circuit is likely to occur and a thermal runaway reaction is likely to occur. There is also a problem of becoming. Therefore, in order to maintain safety at the time of overcharging, it is necessary to quickly release the gas accumulated in the battery to the outside of the battery so that the battery cannot be charged without causing a thermal runaway reaction.

  In view of the above-described case, an object of the present invention is to provide a lithium secondary battery that can ensure safety during overcharge.

  In order to solve the above problems, the present invention provides a lithium secondary battery in which an electrode group in which a positive electrode plate and a negative electrode plate are arranged via a separator is sealed with a laminate outer film having four sides. A positive electrode terminal and a negative electrode terminal are led out from each of the two opposite sides of the laminate outer film, and separators located on three sides other than the one side from which the positive electrode terminal is led wrap around the positive electrode plate. It is characterized by being thermally welded.

  In the present invention, since the positive electrode terminal and the negative electrode terminal are led out from each of the two opposite sides of the laminate outer film, the gas generated during overcharge is released from the vicinity where the positive electrode terminal and the negative electrode terminal are led out. However, since the internal short circuit between the positive electrode terminal and the negative electrode terminal is suppressed and the separators located on three sides other than the side from which the positive electrode terminal is derived are thermally welded so as to wrap the positive electrode plate, the positive electrode terminal Even if gas is released from two sides other than the side from which the negative electrode terminal is derived and the separator contracts, an internal short circuit between the positive electrode plate and the negative electrode plate is suppressed, so that the transition to a thermal runaway reaction is suppressed. The safety of the lithium secondary battery can be ensured.

  In this case, if the width of the positive electrode terminal and the negative electrode terminal derived from the laminate outer film is not less than ½ of the length of the side of the derived laminate outer film, the positive electrode terminal and the negative electrode terminal during overcharge Since it becomes easy to radiate heat through, the gas generation inside the battery can be suppressed. Further, the positive electrode terminal and the negative electrode terminal may be led out from the long sides of the laminated exterior film, respectively. Furthermore, any one of the four sides of the laminate outer film other than the side from which the positive electrode terminal and the negative electrode terminal are derived may be used as a folded portion of the laminate outer film itself. Moreover, it is good also considering 2 sides other than the side where the positive electrode terminal and the negative electrode terminal were respectively derived | led-out among 4 sides of a laminate exterior film as the welding part to which the laminate exterior film itself was welded.

  According to the present invention, the internal short circuit between the positive electrode terminal and the negative electrode terminal is suppressed because the positive electrode terminal and the negative electrode terminal are led out from each of the two opposite sides of the laminate outer film even during overcharge. At the same time, since the separators located on three sides other than the side where the positive electrode terminal is derived are thermally welded so as to wrap the positive electrode plate, an internal short circuit between the positive electrode plate and the negative electrode plate is suppressed. The effect that it can suppress the transition to and can ensure the safety of the lithium secondary battery can be obtained.

  Hereinafter, with reference to the drawings, an embodiment of a lithium ion secondary battery using a laminate film to which the present invention can be applied as an exterior body will be described.

(Constitution)
As shown in FIG. 1, the lithium ion secondary battery 1 of the present embodiment uses a rectangular laminate film 2 having four sides on the exterior body. A laminated electrode group (not shown) is enclosed in the laminate film 2. The laminated film 2 on the upper side of the laminated electrode group (not shown) is formed in a convex shape, and the lower laminated film 2 is formed in a substantially flat shape. Four sides of the edge portion of the laminate film 2 are sealed by heat welding, and the lithium ion secondary battery 1 has a sealed structure. The positive electrode terminal 4 and the negative electrode terminal 5 are respectively sandwiched between the heat-welded portions of the laminate film 2 on the two opposite sides of the laminate film 2 with the tip portions protruding outward in opposite directions.

  The laminate film 2 uses an aluminum (hereinafter abbreviated as “Al”) foil having a thickness of 40 μm as a base material. The Al foil has a 25 μm-thick nylon (hereinafter abbreviated as ON) film for insulation protection on one side, and a heat-welded resin polypropylene (hereinafter abbreviated as “PP”) 80 μm thick on the other side. Films are laminated. The laminate film 2 is laminated and pressed through an adhesive in the order of an ON film, an Al foil, and a PP film, and has a three-layer structure.

  The positive electrode terminal 4 uses an Al plate having a cross-sectional thickness of 0.1 mm and a predetermined width as described later. A PP tape having a thickness of 100 μm and a width of 10 mm is attached to the outer periphery of the Al plate as a seal tape. It has been. The negative electrode terminal 5 uses a nickel (hereinafter abbreviated as Ni) plate having a cross-sectional thickness of 0.1 mm and a width that will be described later. The outer periphery of the Ni plate has a thickness of 100 μm as a seal tape, A PP tape having a width of 10 mm is attached. Around the positive electrode terminal 4 and the negative electrode terminal 5, the PP resin of the laminate film 2 softened at the time of heat welding is in close contact.

  As shown in FIG. 2, in the laminated electrode group 10, ten positive electrode plates 14 and eleven negative electrode plates 15 are alternately laminated so that the upper and lower ends of the laminated electrode group 10 are the negative electrode plates 15. . The positive plates 14 are inserted one by one into a separator 12 having a thickness of 40 μm and a rectangular polyethylene film that is processed into a bag shape by heat welding. For this reason, the separator 12 is interposed between each positive electrode plate 14 and the negative electrode plate 15. Further, the stacked electrode group 10 is laminated so that a positive electrode lead piece (not shown) is located on one of the two opposite sides of the laminated electrode group 10 and a negative electrode lead piece (not shown) is located on the other side. The positive electrode lead piece and the negative electrode lead piece are respectively assembled and connected to the positive electrode terminal 4 and the negative electrode terminal 5 by ultrasonic welding.

  The positive electrode plate 14 constituting the laminated electrode group 10 has an aluminum foil having a thickness of 20 μm as a positive electrode current collector. A positive electrode mixture containing lithium manganate as a positive electrode active material is applied to both surfaces of the aluminum foil. In the positive electrode mixture, for example, 10 parts by weight of scaly graphite as a conductive agent and 5 parts by weight of polyvinylidene fluoride (hereinafter abbreviated as PVDF) as a conductive agent with respect to 100 parts by weight of lithium manganate. It is blended. When the positive electrode mixture is applied to the aluminum foil, N-methylpyrrolidone (hereinafter abbreviated as NMP) is used as a dispersion solvent. After application of the positive electrode mixture, drying, pressing and cutting form a rectangular positive electrode plate 14 having a thickness of 90 μm. Note that, on one side of the positive electrode current collector, a strip-shaped positive electrode lead piece made of aluminum is ultrasonically welded.

  On the other hand, the negative electrode plate 15 has a rolled copper foil having a thickness of 10 μm as a negative electrode current collector. A negative electrode mixture containing amorphous carbon powder as a negative electrode active material is coated on both surfaces of the rolled copper foil. In the negative electrode mixture, for example, 10 parts by weight of PVDF as a binder is blended with 90 parts by weight of amorphous carbon powder. NMP is used as a dispersion solvent when the negative electrode mixture is applied to the rolled copper foil. After applying the negative electrode mixture, the negative electrode plate 15 having a thickness of 70 μm is formed by drying, pressing and cutting. Note that a strip-like negative electrode lead piece made of copper is ultrasonically welded to one side of the negative electrode current collector.

(Battery assembly)
The laminated film 2 and the laminated electrode group 10 were placed in this order in accordance with the concave portions of the cradle on a silicon rubber cradle having concave portions formed in accordance with the shape of the laminated electrode group 10. After injecting 15 ml of the non-aqueous electrolyte into the laminate film 2 in the recess, the other laminate film 2 was covered and the edge portions of the two laminate films 2 were overlapped. At this time, the tip portions of the positive electrode terminal 4 and the negative electrode terminal 5 were projected from the opposite edge portions of the laminate film 2 to the outside in opposite directions. A metal plate heated to the melting temperature of the PP film is pressed on the upper side of the laminated film 2 placed on the laminated electrode group 10 in a reduced-pressure atmosphere to thermally weld the edge of the laminated film 2 to a battery weight of about 80 g, The assembly of the lithium ion secondary battery 1 having a capacity of 4 Ah was completed. As the non-aqueous electrolyte, for example, a solution obtained by dissolving 1 mol / liter (1M) of lithium hexafluorophosphate (LiPF ₆ ) as a lithium salt (electrolyte) in a mixed solvent of ethylene carbonate and dimethyl carbonate is used. it can.

  Hereinafter, examples of the lithium ion secondary battery 1 manufactured according to the present embodiment will be described. In addition, it describes together about the lithium ion secondary battery of the comparative example produced for the comparison. As shown in FIG. 3 in each example and in FIG. 4 in each comparative example, the laminate film 2 has outer dimensions of a length L1 in the vertical direction and a length L2 in the horizontal direction. The width W1 along the side of the laminate film 2 will be described.

Example 1
As shown in Table 1 below, in Example 1, the outer dimensions of the laminate film 2 are 80 mm in length (L1) and 100 mm in width (L2), and the width (W1) of the positive electrode terminal 4 and the negative electrode terminal 5 are both 20 mm. It was. The positive electrode terminal 4 and the negative electrode terminal 5 were respectively sandwiched between two opposing sides of the laminate film 2, and the four sides of the laminate film 2 were thermally welded. For this reason, in the lithium ion secondary battery 1 of Example 1, two sides other than the side where the positive electrode terminal 4 and the negative electrode terminal 5 are sandwiched are also thermally welded (see FIG. 3). The heat welding part 3 of the heat-laminated laminate film 2 is set to a heat welding width of 5 mm.

(Example 2 to Example 3)
As shown in Table 1, Example 2 to Example 3 were the same as Example 1 except that the width W1 of the positive electrode terminal 4 and the negative electrode terminal 5 was changed. The width W1 was 40 mm in Example 2 and 60 mm in Example 3.

Example 4
As shown in Table 1, Example 4 was the same as Example 3 except that the outer dimensions of the laminate film 2 were 100 mm in length (L1) and 80 mm in width (L2).

(Example 5)
As shown in Table 1, Example 5 was the same as Example 3 except that a laminate film 2 having an outer dimension of 200 mm in length and 80 mm in width was used and folded in the vertical direction to thermally weld three sides. For this reason, in the lithium ion secondary battery 1 of Example 5, one side of the two sides other than the two sides sandwiched between the positive electrode terminal 4 and the negative electrode terminal 5 is a folded portion of the laminate film 2, and the outer dimension is vertical ( L1) 100 mm and horizontal (L2) 80 mm.

(Comparative Example 1)
As shown in Table 1, in Comparative Example 1, a lithium ion secondary battery was produced in the same manner as in Example 1 except that the positive electrode terminal 4 and the negative electrode terminal 5 were sandwiched between the same sides of the laminate film 2 (see FIG. 4). ).

(Comparative Example 2)
As shown in Table 1, Comparative Example 2 was the same as Comparative Example 1 except that the outer dimensions of the laminate film 2 were 100 mm in length (L1) and 80 mm in width (L2).

(test)
An overcharge test was carried out for each of the 20 batteries of the produced examples and comparative examples, and the maximum temperature at the center of the battery, the phenomenon of the battery and the firing rate were measured. In the overcharge test, the current value is 4A (equivalent to 10C), and the overcharge rate is 200% (12 minutes) until a phenomenon such as rupture and ignition occurs from the fully charged state and the current cannot be supplied. ). Table 2 below shows the results of the overcharge test.

  As shown in Table 2, in the batteries of Comparative Example 1 and Comparative Example 2 in which the positive electrode terminal 4 and the negative electrode terminal 5 are sandwiched between the same sides of the laminate film 2, the batteries of 10% and 15% respectively have intense white smoke. After erupting, ignition occurred and the maximum temperature could not be measured. On the other hand, in the batteries of Examples 1 to 5 in which the positive electrode terminal 4 and the negative electrode terminal 5 are sandwiched between two opposing sides of the laminate film 2, only white smoke is gently generated and ignition occurs. Was not recognized. Moreover, in the battery of Example 1 in which the width W1 of the positive electrode terminal 4 and the negative electrode terminal 5 is less than ½ of the length L1, the width W1 is set to the length L1 as compared with the maximum temperature of 160 ° C. It was found that in the batteries of Example 2 and Example 3 that were ½ or more, the maximum temperature could be kept low at 135 to 145 ° C. Furthermore, in the batteries of Example 4 and Example 5 in which the two sides between which the positive electrode terminal 4 and the negative electrode terminal 5 are sandwiched are the long sides of the laminate film 2 (L1> L2), the maximum temperature of 130 ° C. can be further reduced. I found out. Further, it was found that the maximum temperature can be suppressed to 130 ° C. even in the battery of Example 5 in which one of the two sides other than the side where the positive electrode terminal 4 and the negative electrode terminal 5 are sandwiched is the folded portion of the laminate film 2. It was.

(Action etc.)
Next, the operation and the like of the lithium ion secondary battery 1 of the present embodiment will be described.

  In a lithium ion secondary battery using a conventional laminate film as an outer package, when the battery generates heat during overcharge and the internal pressure of the battery rises due to vaporization of the non-aqueous electrolyte and generation of decomposition gas, the heat welded portion of the laminate film becomes Peeling occurs and the generated gas is ejected outside the battery. When the separator contracts due to this heat generation and gas ejection and the positive electrode plate and the negative electrode plate are short-circuited inside the battery, a rapid heat generation occurs due to the short-circuit current, and the active material shifts to a thermal runaway reaction, causing a severe reaction. In order to ensure the safety at the time of overcharge, the present inventors have intensively studied and found that an internal short circuit occurs between the positive electrode plate and the negative electrode plate in the vicinity of the heat-welded portion of the laminate film from which gas has been ejected. . Also, in the vicinity where the positive and negative terminals are sandwiched, heat is radiated to the outside through the positive and negative terminals, so the temperature rise when the battery generates heat is suppressed, and the peel strength of the heat-welded part of the laminate film is strong, but the positive terminal And when the negative electrode terminal is sandwiched between the same sides (the extraction direction of the positive electrode terminal and the negative electrode terminal is the same direction), it has been found that it is easy to shift from an internal short circuit between the positive electrode terminal and the negative electrode terminal to a thermal runaway reaction. . Therefore, in order to ensure safety during overcharge, it is necessary to quickly release the gas accumulated in the battery to the outside of the battery, thereby making it impossible to charge without causing a thermal runaway reaction.

  In the lithium ion secondary battery 1 of the present embodiment, the positive electrode terminal 4 and the negative electrode terminal 5 are sandwiched between each of the two opposite sides of the laminate film 2. For this reason, even if the gas generated at the time of overcharge is released from the vicinity where the positive electrode terminal 4 and the negative electrode terminal 5 are sandwiched, an internal short circuit between the positive electrode terminal and the negative electrode terminal can be prevented. The separator 12 is heat-sealed in a bag shape so as to wrap the positive electrode plate 14 at three sides other than the side connected to the positive electrode terminal 4 of the positive electrode plate 14. For this reason, even if the gas generated during overcharge is released from two sides other than the side where the positive electrode terminal 4 and the negative electrode terminal 5 are sandwiched, internal short circuit between the positive electrode plate 14 and the negative electrode plate 15 can be suppressed. . Therefore, since internal short circuit between the positive and negative electrode terminals and between the positive and negative electrode plates is suppressed, the transition to the thermal runaway reaction can be suppressed and the gas can be released gently, and the safety of the lithium ion secondary battery 1 can be improved. Can be secured.

  Further, in the lithium ion secondary battery 1 of the present embodiment, heat is radiated through the positive electrode terminal 4 and the negative electrode terminal 5 that are sandwiched in opposite directions by two opposite sides of the laminate film 2. For this reason, since the temperature rise is suppressed in the vicinity of the positive electrode terminal 4 and the negative electrode terminal 5, two sides other than the two opposite sides of the laminate film 2 in which the positive electrode terminal 4 and the negative electrode terminal 5 are sandwiched between the gas release and the internal short circuit, respectively. Can be limited to occur on the side. Furthermore, even if an internal short circuit between the positive electrode plate 14 and the negative electrode plate 15 occurs in the vicinity of the positive electrode terminal 4 and the negative electrode terminal 5, the transition to the thermal runaway reaction can be suppressed.

  Furthermore, in the lithium ion secondary battery 1 of the present embodiment, the positive electrode terminal 4 and the negative electrode terminal 5 have a width W1 sandwiched between the laminate films 2 and ½ of the side length L1 of the sandwich film 2 sandwiched. By setting it as the above, since the heat_generation | fever at the time of overcharge becomes easy to thermally radiate through the positive electrode terminal 4 and the negative electrode terminal 5, the maximum temperature of a battery center part can be restrained low (refer Example 2 and Example 3). Further, when the rectangular laminate film 2 is used, the width W1 can be set larger by sandwiching the positive electrode terminal 4 and the negative electrode terminal 5 in the long sides of the laminate film 2, respectively. Heat dissipation through the negative electrode terminal 5 is further facilitated, and the maximum temperature at the center of the battery can be further reduced (see Example 4). Furthermore, since the cross-sectional area of the positive and negative electrode terminals is increased by increasing the width W1 of the positive electrode terminal 4 and the negative electrode terminal 5, a large current can be applied.

  Furthermore, in the lithium ion secondary battery 1 according to the present embodiment, the laminate film 2 is folded in half and the laminated electrode group 10 is enclosed, so that the positive electrode terminal 4 and the negative electrode terminal 5 are disposed on two sides other than the sides sandwiched respectively. One side can be a folded portion of the laminate film 2. For this reason, since it can restrict | limit so that gas discharge | release and an internal short circuit may generate | occur | produce on the side opposite to a folding | turning part (refer Example 5), the transition to a thermal runaway reaction can be suppressed, lithium ion 2 The safety of the secondary battery 1 can be ensured.

  In this embodiment, the laminate film 2 is composed of three layers of ON film / Al foil / PP film, and the thickness of each component layer is ON = 25 μm, Al = 40 μm, PP = 80 μm. However, the present invention is not particularly limited to the material constituting the laminate film 2 and the thickness of each constituent layer. Usually, there are three layers of an insulating protective layer, a base material layer, and a heat welding layer, and other constituent layers may be provided between these layers.

  Moreover, in this embodiment, although the example in which the positive electrode terminal 4 and the negative electrode terminal 5 were each pinched | interposed into two opposite sides of the laminate film 2 was shown, this invention is not limited to this, The laminate film 2 What is necessary is just to be derived from two opposing sides. Further, in the present embodiment, the rectangular laminate film 2 is exemplified, but the present invention is not limited to this, and may be, for example, a square shape or a rhombus shape.

  Furthermore, in this embodiment, although the example which uses polyethylene for the material of the separator 12 was shown, this invention is not restrict | limited in particular to the material, thickness, etc. of a separator. For example, a film of polyolefin resin such as polypropylene may be used, or a plurality of films may be laminated and used.

  Furthermore, in the present embodiment, an example in which the laminated positive electrode plate 14 and the negative electrode plate 15 are alternately laminated to produce the laminated electrode group 10 is shown, but the present invention is not limited to this, for example, Alternatively, the positive electrode plate 14 and the negative electrode plate 15 formed in a belt shape may be wound into a flat shape.

Furthermore, in the present embodiment, an example in which lithium manganate is used as the positive electrode active material and amorphous carbon is used as the negative electrode active material is shown, but the present invention is not limited to the positive electrode active material and the negative electrode active material. Absent. You may use the active material of the positive / negative electrode normally used for a lithium ion secondary battery. In this embodiment, LiPF ₆ is used as the electrolyte for the non-aqueous electrolyte, and an example of using a mixed solvent of ethylene carbonate and dimethyl carbonate as the organic solvent is shown. However, the present invention is not limited to the electrolyte and organic solvent used. There is no particular limitation. Furthermore, although the example which uses an Al plate for the positive electrode terminal 4 and the Ni plate for the negative electrode terminal 5 is shown, the present invention is not limited to these materials, and a material generally used as a battery terminal may be used. it can.

  Since the present invention contributes to the manufacture and sale of lithium secondary batteries in order to provide a lithium secondary battery that can ensure safety during overcharging, it has industrial applicability.

It is a perspective view of the lithium ion secondary battery which uses the laminate film for the exterior body of embodiment which can apply this invention. It is sectional drawing which shows the electrode group of the lithium ion secondary battery of embodiment. It is a top view which shows the external dimension and the width | variety of a positive / negative electrode terminal about the lithium ion secondary battery of the Example produced according to embodiment. It is a top view which shows the external dimension about the lithium ion secondary battery of a comparative example, and the width | variety of a positive / negative terminal.

Explanation of symbols

1 Lithium ion secondary battery (lithium secondary battery)
2 Laminate film (laminate film)
4 Positive Terminal 5 Negative Terminal 10 Multilayer Electrode Group 12 Separator 14 Positive Plate 15 Negative Plate

Claims (5)

  In a lithium secondary battery in which an electrode group in which a positive electrode plate and a negative electrode plate are arranged via a separator is sealed with a laminate outer film having four sides, the positive electrode terminal and the negative electrode terminal from the electrode group are opposed to the laminate outer film. The lithium is derived from each of the two sides, and the separators located on three sides other than the side from which the positive electrode terminal is derived are heat-welded so as to enclose the positive electrode plate. Secondary battery.   2. The lithium according to claim 1, wherein the positive electrode terminal and the negative electrode terminal have a width derived from the laminate exterior film that is not less than ½ of a side length of the derived laminate exterior film. Secondary battery.   2. The lithium secondary battery according to claim 1, wherein the positive electrode terminal and the negative electrode terminal are respectively led out from long sides of the laminated exterior film.   The one side of the four sides of the laminate outer film other than the side from which the positive electrode terminal and the negative electrode terminal are respectively derived is a folded portion of the laminate outer film itself. Item 4. The lithium secondary battery according to any one of items 3.   The two sides other than the sides from which the positive electrode terminal and the negative electrode terminal are respectively led out of the four sides of the laminate exterior film are welded portions to which the laminate exterior film itself is welded. The lithium secondary battery according to claim 1.

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