JP6753802B2 - Rechargeable battery - Google Patents

Description

The present invention relates to a secondary battery.

As a conventional secondary battery, the configuration described in Patent Document 1 is known. In this secondary battery, one sheet is folded back, the electrode body is stored inside, and the positive electrode terminal and the negative electrode terminal connected to the electrode body are projected from one side.

Japanese Unexamined Patent Publication No. 2007-141714

However, if the secondary battery of Patent Document 1, since the thickness of the side of the terminal close to the folded edge is the same as the thickness of the far side of the terminal from the in fold return sides, edges folded to the side of the terminal close to the folded edge If the resin is brought closer to the side, the resin in the inner layer of the sheet may protrude from the sealing portion due to the heat during sealing. The battery becomes large release the side pin near the folded edges from in fold return sides.

An object of the present invention is to provide a secondary battery that suppresses protrusion from a sealed portion while suppressing size increase.

Secondary battery of the present invention includes a positive electrode layer, negative electrode layer, and an electrode body comprising separators disposed between the negative electrode layer and positive electrode layer, an electrolyte, exterior body for storing the electrode body and an electrolyte inside A secondary battery having an electrode terminal electrically connected to the electrode body and having at least a part protruding to the outside of the exterior body, the electrode terminal is a positive electrode terminal connected to the positive electrode layer and a negative electrode. It has a negative electrode terminal connected to the layer, and the exterior body has a three-layer structure of a heat-sealing resin layer, a metal layer, and a protective layer, and one sheet is folded back with the electrode body sandwiched between them. It has the structure and, on the side other than the folded edge the sheet is folded, has a heat seal portion which is heat-sealed thermally adhesive resin layers, the positive and negative terminals returns Ri folding edge projecting from one side adjacent to, the thickness of the one terminal of electrode terminals arranged closer to the in fold return side is thinner than the thickness of the other terminal of electrode terminals arranged from in fold return side farther It is characterized by that.
Electrode terminals disposed on a side closer to the in fold return side is preferably a negative terminal. It is preferable that the positive electrode terminal is mainly made of aluminum and the negative electrode terminal is mainly made of copper. The exterior body is preferably substantially symmetrical with respect to the folded surface of the sheet. The positive electrode layer has a positive electrode active material layer having a substantially rectangular shape on the main surface, and the negative electrode layer has a negative electrode active material layer having a substantially rectangular shape on the main surface, and the positive electrode active material layer and the negative electrode active material layer face each other. Of the main surfaces, the main surface of the active material layer having a small area preferably has a short side length of 110 mm or more. The thickness of the electrode terminals arranged near the folded side is preferably smaller than 0.6 times the thickness of the electrode terminals arranged at a distant position. The positive electrode terminal has a positive electrode terminal body and a positive electrode terminal resin layer that surrounds a part of the positive electrode terminal body in the protruding direction, and the negative electrode terminal is a negative electrode that surrounds the negative electrode terminal body and a part of the negative electrode terminal body in the protruding direction. It is preferable that the terminal resin layer is provided, the thickness of the negative electrode terminal body is smaller than the thickness of the positive electrode terminal body, and the thickness of the negative electrode terminal resin layer is smaller than the thickness of the positive electrode terminal resin layer.

The present invention has an effect that it is possible to suppress the protrusion from the sealed portion while suppressing the increase in size.

It is a top view of the secondary battery which concerns on embodiment of this invention. It is a cross section AA of FIG. It is a cross-sectional view of BB of FIG. FIG. 5 is a sectional view taken along the line CC of FIG. It is a top view which removed the exterior body of the secondary battery of FIG. It is the figure which looked at the secondary battery of FIG. 1 from the terminal side. It is a figure explaining the manufacturing process of the secondary battery of FIG. It is a figure explaining the heat sealing of the side where the terminal of FIG. 7C protrudes. It is a figure explaining a comparative example.

The secondary battery according to the embodiment of the present invention will be described with reference to the drawings. First, the configuration of the secondary battery will be described with reference to FIGS. 1 to 6, the manufacturing method will be described with reference to FIGS. 7 and 8, and the effect of the present embodiment will be demonstrated using the comparative example of FIG. explain. The lithium ion secondary battery 1 as the secondary battery of the present embodiment is configured to include an exterior body 2, electrode terminals 3 and 4, an electrode body 5, and an electrolyte. The external shape of the lithium ion secondary battery 1 is shown in FIG. 1, each cross-sectional structure is shown in FIGS. 2 to 4, and partially detailed structures are shown in FIGS. 5 and 6. In each figure, the same elements or the corresponding elements are designated by the same reference numerals, and duplicate description will be omitted. In addition, the dimensional ratio of each figure may differ from the actual one.

First, the exterior body will be described. Reference numeral 2 shown in the figure is an exterior body of the lithium ion secondary battery 1, which is flat and has a substantially rectangular main surface. The exterior body 2 is used by folding back one sheet. 20 and 20 of FIG. 2 in FIG. 1 shows the in fold return sides. The enlarged view of FIG. 2 shows the structure of one sheet. For example, it is a laminated film structure having a three-layer structure of a thermosetting resin layer 21, a metal layer 22, and a protective layer 23. Hereinafter, the sheet before being completed as the exterior body 2 may be referred to as a laminated film 2. As the thermosetting resin layer 21, a synthetic resin capable of thermosetting, for example, a polyolefin resin such as polypropylene (PP) can be used. The metal layer 22 can be prevented from invading moisture by using, for example, an aluminum foil. For the protective layer 23, a synthetic resin having excellent durability or heat resistance, for example, polyethylene terephthalate (PET) or nylon can be used. The protective layer 23 is not essential, and may have a configuration in which the thermosetting resin 21 is provided inside the metal layer 22. The thermosetting resin layer 21 is preferably 30 μm to 100 μm. The barrier layer 22 is preferably 12 μm to 50 μm. The protective layer 23 is preferably 6 μm to 50 μm.

Reference numeral 24 denotes a bottom portion of the cup-shaped convex portion of the exterior body 2, and reference numeral 25 denotes a top portion of the cup-shaped convex portion. Cup-shaped convex portions are formed on both sides in the direction perpendicular to the flat surface of the lithium ion secondary battery 1 (vertical direction in FIG. 2) so as to be substantially plane-symmetrical when folded back at the folded side 20. Reference numerals 26 and 27 are heat-sealing portions in which the thermosetting resin layers 21 of the laminate film 2 are heat-sealed together. Reference numeral 28 denotes a heat-sealing portion in which the positive and negative terminals 3 and 4 described later and the thermosetting resin layer 21 of the laminate film 2 are heat-sealed. The exterior body 2 is formed so that the surface connecting the folded side 20 and the heat-sealed portions 26, 27, 28 is the folded surface and is substantially symmetrical with respect to this.

Next, the electrode terminals will be described. Reference numeral 3 denotes a positive electrode terminal, and the positive electrode terminal 3 is composed of a positive electrode terminal main body 31 and a positive electrode terminal resin layer 32 formed around a part of the positive electrode terminal main body 31 in the longitudinal direction (protruding direction). The positive electrode terminal body 31 is, for example, an aluminum plate. The shape is, for example, a rectangular parallelepiped, and the width (the length of the portion parallel to the side of the exterior body on which the terminal protrudes) and the thickness (vertical to the side of the exterior body on which the terminal protrudes) are based on the direction of protrusion from the exterior body 2. 40 mm to 100 mm, 0.1 mm to 0.5 m in the order of length (length in the direction) and length (length in the protruding direction)
m, preferably 30 mm to 60 mm. As the positive electrode terminal resin layer 32, for example, a polyolefin resin such as polypropylene can be used, and since it is heat-sealed with the heat-sealing resin layer 21 of the laminate film 2, the same type as the heat-sealing resin layer 21 is preferable. The thickness of the positive / negative terminal resin layer 32 is preferably 0.1 mm to 0.2 mm.

Reference numeral 4 denotes a negative electrode terminal, and the negative electrode terminal 4 is composed of a negative electrode terminal main body 41 and a negative electrode terminal resin layer 42 formed around a part of the negative electrode terminal main body 41 in the longitudinal direction (protruding direction). The negative electrode terminal body 41 is, for example, a copper plate. Not limited to this, the copper plate can be nickel-plated, and a corrosion-resistant layer can be formed on the surface. The shape is, for example, a rectangular parallelepiped, and the width (the length of the portion parallel to the side of the exterior body on which the terminal protrudes) and the thickness (on the side of the exterior body on which the terminal protrudes) are based on the direction of protrusion from the exterior body 2. The length in the vertical direction) and the length (length in the protruding direction) are preferably 40 mm to 100 mm, 0.05 mm to 0.3 mm, and 30 mm to 60 mm in this order. For the negative electrode terminal resin layer 42, for example, a polyolefin resin such as polypropylene can be used, and since it is heat-sealed with the heat-sealing resin 21 of the laminate film 2, the same type as the heat-sealing resin 21 of the laminate film 2 is preferable. .. The thickness of the negative electrode terminal resin layer 42 is preferably 0.05 mm to 0.15 mm.

Next, the electrode body 5 will be described. In the present embodiment, the electrode body 5 is a laminated structure in which the negative electrode layer 7, the separator 8, the positive electrode layer 6, and the separator 8 are repeatedly laminated in this order, and the negative electrode layer 7 is arranged on the outermost layer in the stacking direction. There is. A so-called wound structure consisting of one positive electrode layer, one negative electrode layer, and two layers of separators arranged between the positive electrode layer and the negative electrode layer and on one side of the positive electrode layer and the negative electrode layer can also be used. is there.

The positive electrode layer 6 is composed of three layers in FIGS. 2 to 4. Reference numeral 61 denotes a positive electrode current collector foil. Reference numeral 62 denotes a positive electrode active material layer formed on both sides of the positive electrode current collector foil 61. Reference numeral 63 denotes a portion extending from the positive electrode current collecting foil 61 and not forming the positive electrode active material layer 62, and is referred to as a positive electrode current collecting foil lead portion. As shown in FIG. 5, the positive electrode active material layer 62 has a rectangular main surface. The peripheral edge of the positive electrode active material layer 62 has a size inside the peripheral edge of the negative electrode active material layer 72. The positive electrode current collecting foil lead portion 63 is formed to have a narrow width with reference to the direction extending from the positive electrode current collecting foil 61. As the positive electrode current collecting foil 61, an electrochemically stable metal foil such as an aluminum foil, an aluminum alloy foil, a copper foil, or a nickel foil can be used.

The positive electrode active material layer 62 is, for example, lithium nickel oxide (eg LiNiO ₂ ), lithium manganate (eg LiMnO ₂ ), spinel-type lithium manganate (eg LiMn 2O ₄ ), or lithium cobalt oxide (eg LiMn ₂ O ₄ ). A mixture of a positive electrode active material composed of a lithium composite oxide such as LiCoO ₂ ), a binder, and a solvent capable of dissolving the binder is applied to the main surface of the positive electrode current collector foil 61 and dried to remove the solvent. It is formed by doing. Here, a part of the transition metal (Ni, Mn, Co) of the lithium composite oxide is replaced with Li, Mg, B, Al, V, Cr, Fe, Co, Ni, Mn, W, Ti or the like. May be. It is preferable that at least a part of the lithium composite oxide used in the positive electrode active material layer 62 is a spinel type. This is because this type of material has a relatively stable crystal structure change due to the occlusion and release of lithium due to charging and discharging, and therefore the pores between the particles become narrower due to the deformation of the particles, as compared with other types of materials. This is because the decrease in Li ion mobility in the in-plane direction, which will be described later, is lessened.

Further, a conductive auxiliary agent made of a carbon material such as acetylene black, carbon black, graphite or fibrous carbon may be added to the positive electrode active material layer 62. The binder is, for example, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer rubber, carboxymethyl cellulose, polytetrafluoroethylene, polypropylene. , Polyethylene, polyimide, polyamideimide and the like are used alone or in combination. The three positive electrode current collecting foil lead portions 63 are superposed on the positive electrode terminal main body 31 on one end side thereof and are electrically connected to the positive electrode terminal main body 31. Ultrasonic welding can be used as the connection method, and 64 shown in FIG. 5 is a welded portion.

The negative electrode layer 7 is composed of four layers, one layer more than the positive electrode layer 6 in FIGS. 2 to 4. Reference numeral 71 denotes a negative electrode current collecting foil. Reference numeral 72 denotes negative electrode active material layers formed on both sides of the negative electrode current collecting foil 71. Reference numeral 73 denotes a portion extending from the negative electrode current collecting foil 71 and not forming the negative electrode active material layer 72, and is referred to as a negative electrode current collecting foil lead portion. As shown in FIG. 5, the negative electrode active material layer 72 has a rectangular main surface. The negative electrode current collecting foil 71 is made of an electrochemically stable metal foil such as a copper foil, a stainless foil, or an iron foil. As the active material of the negative electrode active material layer 72, lithium ions such as amorphous carbon, non-graphitized carbon, easily graphitized carbon, graphite, or graphite coated with amorphous carbon are stored and released. A mixture of a negative electrode active material and a binder can be used. The binder and the conductive auxiliary agent used in the positive electrode active material layer 62 can also be used in common with the negative electrode active material layer 62. The four negative electrode current collecting foil lead portions 73 are superposed on the negative electrode terminal main body 41 on one end side thereof and are electrically connected to the negative electrode terminal main body 41. Ultrasonic welding can be used as the connection method, and 74 shown in FIG. 5 is a welded portion.

Next, the separator 8 will be described. In FIGS. 2 to 4, it is composed of 6 layers. As shown in FIG. 5, the separator 8 arranged between the positive electrode layer 6 and the negative electrode layer 7 has a rectangular main surface, and the peripheral edge of the separator 8 is the peripheral edge of the negative electrode active material layer 72 and the positive electrode active material layer. The size is outside the peripheral edge of 62. The separator 8 has a function of allowing lithium ions to pass through, providing electrical insulation between the positive electrode active material layer 62 and the negative electrode active material layer 72, and holding an electrolyte, which will be described later. For example, polyethylene (PE) or A microporous single-layer film composed of polypropylene or the like such as polypropylene (PP), a three-layer structure in which a polypropylene film is sandwiched between polyethylene films, or a laminate of a polyolefin microporous film and an organic non-woven fabric is also used. be able to. Further, those in which inorganic particles such as silica, alumina, magnesia, zirconia, and titania are adhered to one side or both sides of the polyolefin microporous membrane, and those in which these inorganic particles are dispersed in the polyolefin membrane can also be used. The thickness of the separator is preferably 10 μm to 40 μm. If it is too thin, there is a concern about mechanical strength, and if it is too thick, the Li ion conductivity between the front and back surfaces of the separator, which will be described later, deteriorates.

Next, the electrolyte (not shown) will be described. As the electrolyte, an electrolyte generally used for the lithium ion secondary battery 1, for example, a non-aqueous electrolyte in which a lithium salt is dissolved in a solvent can be used. As the solvent, for example, an organic solvent in which one or more kinds of solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate can be used can be used. Further, as the lithium salt, for example, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) _{3, and the} like can be used. ..

The amount of electrolyte shall be the amount including excess electrolyte. Here, the surplus electrolyte mass is the total of the pore volume of the positive electrode layer 6, the pore volume of the negative electrode layer 7, and the pore volume of the separator 8 from the volume of the total electrolyte existing in the exterior body 2 (hereinafter, the electrode). It is the electrolytic mass obtained by subtracting the pore volume of the body 5. When this value is positive, the magnification of the electrolytic mass (volume of all electrolytes existing in the exterior body 2 / volume of pores in the electrode body 5) exceeds 1 times the volume of pores in the electrode body 5. .. The magnification of the electrolytic mass may be more than 1 times with respect to the pore volume of the electrode body 5, but it is preferable to set the electrolytic mass to be 1.1 times to 1.7 times, and the magnification is 1. It is more preferably 2 times to 1.6 times. In a state where the outer body 2 contains an amount of electrolyte containing an electrolytic mass that fills the pore volume of the electrode body 5 and a surplus electrolyte component, for example, a plurality of lithium ion secondary batteries 1 are opposed to each other on a flat surface. When the flat surface of the electrode body 5 is pressed from the outside of the exterior body 2 by a part of the case or another elastic member stacked in the thickness direction of the lithium ion secondary battery 1, the main surface side of the electrode body 5 and the exterior body are pressed. The excess electrolyte between 2 moves and is stored in the peripheral portion of the electrode body 5 in the exterior body 2, that is, in the direction perpendicular to the stacking direction of the electrodes of the electrode body 5.

In order to store this stored portion, it is preferable that the outer edge of the electrode body 5 and the inner side of the exterior body 2 are separated by about 1 mm to 5 mm. It is preferable that the separated portion for accommodating the stored portion is provided between the exterior body 2 and all four sides of the electrode body 5. This is because the surplus electrolyte serves as a supply source of Li ions for the electrode body 5, as will be described later, and therefore it is preferable that the surplus electrolyte can be supplied from four directions. Further, from the viewpoint as a Li ion supply source, if the distance between the separated portions is too small and the excess electrolyte is too small, the cycle characteristics deteriorate, and if the distance between the separated portions is too large, the battery is in the in-plane direction of the main surface. Since it leads to an increase in the outer size, the space efficiency is significantly deteriorated.

Note that FIG. 6 is a side view seen from the positive and negative terminals 3 and 4 of FIG. 1, and is formed by the sealing step of FIG. 8 described later. A negative electrode terminal having a thickness of 0.2 μm and a width of 60 mm and a negative electrode terminal resin layer 42 having a thickness of 0.1 mm formed around a negative electrode terminal body 41 made of nickel-plated copper at a position close to the folded side 20. 4 is arranged, and a positive electrode terminal resin layer 32 having a thickness of 0.15 mm is formed around a positive electrode terminal body 31 having a thickness of 0.4 μm and a width of 60 mm using aluminum as a main material at a position far from the folded side 20. The positive electrode terminal 3 is arranged. In other words, the thickness of the negative electrode terminal 4 which is disposed closer to the in fold return side (0.4 mm) is thinner than the thickness of the positive electrode terminal 3 arranged from in fold return side farther (0.7 mm) There is. The thickness of the negative electrode terminal 4 arranged near the folded side is 0.57 times the thickness of the positive electrode terminal arranged at a distant position. It is possible to change the thickness of the positive and negative electrode terminal bodies to make the thickness of the positive and negative electrode resin layers the same, but it is preferably smaller than 0.6 times.

The manufacturing process of the lithium ion secondary battery 1 will be described with reference to FIGS. 7 and 8. FIG. 7A shows a preparation step of the exterior body. In this step, cup-shaped recesses are formed at two locations that face each other when the single laminated film 2 is folded back. This concave portion is a portion that becomes a cup-shaped convex portion in appearance after being sealed as an exterior body. 29 in FIG. 7A is the bottom of the recess and corresponds to the top 25 of the convex in FIG. Reference numeral 30 denotes a top of the recess, which corresponds to the bottom 24 of the convex in FIG. FIG. 7B shows a storage process. In this step, a state in which the electrode terminals 3 and 4 and the electrode body 5 are connected in advance is prepared, the portion of the electrode body 5 is arranged on one recess, and the electrode terminal resin layer of the electrode terminals 3 and 4 is arranged. 32 and 42 were arranged in the region to be the heat sealing portion 28 of the exterior body 2. At this time, the main surface of the positive electrode active material layer 62 facing the negative electrode active material layer 72 of the electrode body 5 is 110 mm × 200 mm in size, and the main surface of the negative electrode active material layer 72 is 120 mm × 210 mm in size. Was used. The positive electrode layer 6 and the negative electrode layer 7 were created as follows.

First and _Li 1.1 _Mn 1.9 _{O 4} powder having a spinel structure as a positive electrode active material, the second cathode active material as a lithium-nickel-cobalt-lithium manganate (Ni / Li molar ratio 0.7) , Polyfluoride vinylidene as a binder, and carbon black powder as a conductive auxiliary agent in a solid content ratio of 71: 23: 2: 4 in N-methyl-2-pyrrolidone (NMP) as a solvent. A positive electrode slurry was prepared by addition. This positive electrode slurry was applied and dried on the positive electrode current collector foil 61 to form the positive electrode active material layer 62 on the positive electrode current collector foil 61. The thickness of the positive electrode active material layer per one side was 79 μm.

Spherical natural graphite powder coated with amorphous carbon as a negative electrode active material, polyvinylidene fluoride as a fluororesin-based binder, and a carbon black conductive aid in a solid content mass ratio of 96.5: 3: 0 By adding to N-methyl-2-pyrrolidone (NMP) at a ratio of .5 and stirring, these materials were uniformly dispersed in NMP to prepare a negative electrode slurry. This negative electrode slurry was applied and dried on the negative electrode current collector foil 71 to form the negative electrode active material layer 72 on the negative electrode current collector foil 71. The thickness of the negative electrode active material layer 72 per one side was 60 μm.

FIG. 7C shows a folding step, a temporary sealing step, a liquid injection step, and a final sealing step.
The laminate film 2 was folded back (folding step) with reference to the position of the folded side 20, and heat-sealed by the heater head 100 and the heater head 120 (temporary sealing step). Next, it was placed in the vacuum chamber with the remaining unheat-sealed side facing upward, and the electrolytic solution was injected from the unheat-sealed side. In this injection step, an electrolyte in which 1 M of LiPF6 was dissolved in a 3: 7 mixed solvent of ethylene carbonate and diethyl carbonate was injected to reduce the pressure inside the exterior body 2. After that, as a final sealing step, the exterior body 2 is sealed by heat fusion with the heater head 130, the inside of the vacuum chamber is returned to atmospheric pressure, then taken out from the vacuum chamber, various inspections are performed, and the lithium ion can be shipped. The secondary battery 1 was manufactured.

The separation distance (closest distance) from the side surface of the electrode body 5 to the inner boundary of the exterior body 2, that is, the inner boundary of the heat-sealed portion, is 7 mm on the side where the electrode terminal is provided, 3 mm on the folded side, and other sides. Was 2 mm. The injected electrolytic mass was 1.4 times the volume of the pores of the electrode body 5, and excess electrolyte was present around the electrode body 5.

Here, using FIG. 8, the thermal sealing of the side where the positive and negative terminals 3 and 4 of FIG. 7 (c) protrude will be described. 8 (a) shows the arrangement state of each component, FIG. 8 (b) shows the 100 surfaces of the heater head in contact with the laminate film 2, and FIG. 8 (c) shows the side surface of the heater head 100. A rod-shaped heater 104 is inserted. From the top of the figure of FIG. 8A, the heater head 100, one surface of the folded laminated film 2, and the positive and negative terminals 3 and 4 (terminal bodies 31, 41 and the resin layer) sandwiched between the folded laminated films 2. 32, 42), the opposite side of the folded laminated film 2 and the heater head 100 on the opposite side are arranged, and the heater head 100 moves in the positive and negative terminals 3 and 4 directions to move the laminated film 2 and the positive and negative terminals. It is heated while pressurizing 3 and 4.

The surface 101 of the heater head 100 in FIG. 8B is a surface in contact with the positive electrode terminal 3 side, and the length in the width direction in the figure is the length of the laminated film 2 close to the positive electrode terminal resin layer 32 and the positive electrode terminal resin layer 32. The length includes a part of the laminated film, which is between a part of the laminated film 2 and the positive electrode terminal resin layer 32 due to heat transferred from the heater 104 to the heater head 100, and a part of the laminated film close to the positive electrode terminal resin layer 32. The portion where the two overlap each other is heat-sealed. The position of the surface 101 is a position in contact with the laminated film surface earlier than the surface 102. The length of the surface 101 in the depth direction (the length in the vertical direction in the figure) is the same as that of the surfaces 102 and 103.

The surface 102 is a surface in contact with the negative electrode terminal 4 side, and the length in the width direction in the figure is a length including a part of the laminate film close to the negative electrode terminal resin layer 42 and the negative electrode terminal resin layer 42, and the heater. Due to the heat transferred from 104 to the heater head 100, a part of the laminated film and the portion where the negative electrode terminal resin layer 42 and a part of the laminated films close to the negative electrode terminal resin layer 42 overlap are heat-sealed. The position of the surface 102 is later than that of the surface 101 and earlier than that of 103 in contact with the surface of the laminated film. Therefore, the time during which heat is applied is shorter than that of the surface 101 and longer than that of the surface 103.

The surface 103 is connected between the side end portions extending vertically from the surfaces 101 and 102, and is formed so that the overlapped portion of the laminated film 2 is heat-sealed by folding back.

Then, the heater 104 waits until the temperature reaches 180 ° C., and then the heater head 100 is moved in the positive and negative terminals 3 and 4 directions. First, a part of the laminate film 2 comes into contact with the surface 101 of the heater head 100 and is heated with pressure. After that, the surface 102 and the surface 103 are heated in this order with pressurization. Ten seconds after the surfaces 103 come into contact, the heater head 100 is returned to its original position, and heat sealing is completed. The heater heads 120 and 130 of FIG. 7C can be heat-sealed by heating and pressurizing from both sides of the laminate film 2 with a flat heater head.

A comparative example will be described with reference to FIG. 9 (a) shows that the arrangement of the positive electrode terminal 3 and the negative electrode terminal 4 is reversed as compared with FIGS. 6 and 8 (a). That is, at a position far from the folded side 20, a negative electrode terminal resin layer 42 having a thickness of 0.1 mm was formed around a negative electrode terminal body 41 having a thickness of 0.2 μm and a width of 60 mm, which was mainly made of nickel-plated copper. A negative electrode terminal 4 is arranged, and a positive electrode terminal resin layer 32 having a thickness of 0.15 mm is placed around a positive electrode terminal body 31 having a thickness of 0.4 μm and a width of 60 mm, which is mainly made of aluminum, at a position close to the folded side 20. The formed positive electrode terminals 3 are arranged, and the surface positions of the surfaces 101 and 102 of the heater head are also reversed. As a result, as shown in FIG. 9B, the heat-sealing resin layer 21 protruded inside and outside the exterior body 2 at the heat-sealing portion at the end of the folded side 20. This is because, in addition to the heat from the surface 103, the heat from the surface 101 is also applied to the end of the folded side 20, and the heat-sealed resin layer 23 of the folded laminated film 2 has an electrode terminal by pressurization and heating. It is presumed that it protruded from the side.

When the inner protruding resin 91 or the outer protruding resin 92 occurs, the following problems may occur. When the inner protruding resin 91 approaches the position where it comes into contact with the positive electrode layer 6 or the negative electrode layer 7 of the electrode body 5 sandwiched between the laminated films 2, it is between the metal layer 22 of the laminated film 2 and the positive electrode layer 6 or the negative electrode layer 7. There is a risk that the electrical insulation of the Further, when a plurality of lithium ion secondary batteries 1 are laminated in the thickness direction of the lithium ion secondary battery 1 and the electrode terminals are electrically connected to each other by a bus bar on the side having the electrode terminals, the bus bar is fixed. A bus bar module and spacers are required to do this, but if there are protrusions on the outside from the exterior body 2, the layout must be avoided, which impairs the degree of layout freedom and increases the size of the device. There is a risk of connection.

In the present embodiment, the positive electrode terminal 3 and negative electrode terminal 4 has at different thicknesses thermosealing part by the outer body 2, is in a position close to the in fold return sides 20 disposed as a negative electrode terminal 4 is thinner than the positive electrode terminal 3 did. As a result, since the outer protruding portion 91 is not generated, there is an effect that the size of the device can be suppressed. Further, since the inner protruding portion 92 was not generated, it is possible to suppress a decrease in electrical insulation between the metal layer 22 of the laminated film 2 and the positive electrode layer 6 or the negative electrode layer 7.

The embodiment has been described above by taking the lithium ion secondary battery 1 as an example, but the present invention is not limited thereto. Further, the number of laminated positive electrode layers and negative electrode layers can be arbitrarily changed, and the outermost layer of the electrode body can be a positive electrode layer. The separator may have a single rectangular shape instead of a plurality of rectangular shapes, and may have a zigzag or winding structure so that a positive electrode layer or a negative electrode layer is arranged between the separators. The positive electrode active material is not limited to lithium manganate, and the negative electrode active material is not limited to graphite, and amorphous carbon or the like can also be used. Further, although the cup-shaped convex portion is formed on the exterior body so as to be plane-symmetric with respect to the folded surface, it can be made substantially plane-symmetrical by not forming the cup-shaped convex portion on both sides in advance.

The lithium ion secondary battery 1 includes an electrode body 5 including a positive electrode layer 6, a negative electrode layer 7, and a separator 8 arranged between the positive electrode layer 6 and the negative electrode layer 7, an electrolyte, and an electrode body 5. A secondary battery 1 having an exterior body 2 for storing and an electrolyte inside, and electrode terminals 3 and 4 electrically connected to the electrode body 5 and having at least a part protruding to the outside of the exterior body 2. The electrode terminal has a positive electrode terminal 3 connected to the positive electrode layer 6 and a negative electrode terminal 4 connected to the negative electrode layer 7, and the positive electrode terminal 3 and the negative electrode terminal 4 project from the same side of the exterior body 2. exterior body 2 has a sandwiched between the electrode member 5 returns in fold a single sheet of arranging the resin layer 21 and 23 on both sides of the metal layer 22, and the folded edges other than the edges Since the exterior body 2 has heat-sealed portions 26, 27, and 28 and is substantially plane-symmetrical with respect to the folded surface of the sheet, the terminal positions can be arranged substantially in the center, and a plurality of lithium ions two can be arranged. Even when used for a laminated battery of the type in which the secondary battery 1 is laminated, the distance between the electrode terminal of a certain lithium ion secondary battery 1 and the metal layer 22 of the exterior body 2 of the adjacent lithium ion secondary battery 1 should be separated. Therefore, it is not necessary to arrange an insulator or a space between them, and it is possible to suppress the increase in size.

Further, unlike Patent Document 1, a recess for storing the power generation element is formed only on one side of the sheet in which the exterior body is folded back, and the electrode terminal is not arranged at the edge portion in the thickness direction of the secondary battery. The collector foil lead that electrically connects the electrode terminals is shorter than that of Patent Document 1. As a result, in the current collector foil lead, the active material is intermittently applied to the current collector foil, and the current collector foil portion to which the active material is not applied is used as the current collector foil lead, so that the amount of active material per unit pick length is increased. Manufacturing costs can be reduced by using more and shorter current collector foil leads.

1 ... Lithium ion secondary battery 2 ... Exterior body 3 ... Positive electrode terminal 4 ... Negative electrode terminal 5 ... Electrode body 6 ... Positive electrode layer 7 ... Negative electrode layer 8 ... Separator 26, 27, 28 ... Heat sealing part

Claims (7)

An electrode comprising an arranged separators between the positive electrode layer, negative electrode layer, and the positive electrode layer and negative electrode layer,
And electrolytic quality,
An exterior body for storing the previous SL electrode body and the electrolyte therein,
A secondary battery having an electrode terminal at least partially protrude, the outside of the front SL is electrically connected to the electrode body and outer body,
Before Symbol electrode terminal has the positive terminal connected to the positive electrode layer, and a negative terminal connected to the negative electrode layer,
Before Kigaiso body is a three-layer structure of the heat-sealing resin layer and the metal layer and the protective layer has a single sheet across the electrode body is folded structure and the seat is the side of the non-folded edges folded, has a heat seal portion which is heat sealed the heat-fusible resin layers,
Before Symbol the negative terminal and the positive electrode terminal protrudes from one side adjacent to the side return Ri folding, the thickness of the one terminal of electrode terminals arranged closer to the in fold return sides, remote from the in fold return side A secondary battery characterized in that it is thinner than the thickness of the other terminal of the electrode terminal arranged in. The secondary battery of claim 1, wherein the kite placing the negative terminal on the side closer to the in fold return sides. The secondary battery according to claim 2, wherein the positive electrode terminal is made of aluminum as a main material, and the negative electrode terminal is made of copper as a main material. The secondary battery according to any one of claims 1 to 3, wherein the exterior body is substantially symmetrical with respect to the folded surface of the sheet. The positive electrode layer has a positive electrode active material layer having a rectangular main surface, and the negative electrode layer has a negative electrode active material layer having a rectangular main surface, and is composed of the positive electrode active material layer and the negative electrode active material layer. The method according to any one of claims 1 to 4, wherein the main surface of the active material layer having a small area among the opposing main surfaces is a rectangle having a short side length of 110 mm or more. Secondary battery. Any one of claims 1 to 5, wherein the thickness of the electrode terminal arranged on the side close to the folded side is smaller than 0.6 times the thickness of the electrode terminal arranged at a distant position. The secondary battery described in. The positive electrode terminal has a positive electrode terminal body and a positive electrode terminal resin layer that surrounds a part of the positive electrode terminal body in the protruding direction, and the negative electrode terminal is a negative electrode that surrounds the negative electrode terminal body and a part of the negative electrode terminal body in the protruding direction. The claim is characterized in that it has a terminal resin layer, the thickness of the negative electrode terminal body is smaller than the thickness of the positive electrode terminal body, and the thickness of the negative electrode terminal resin layer is smaller than the thickness of the positive electrode terminal resin layer. The secondary battery according to any one of claims 1 to 6.

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