JP6781074B2 - 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 recess is formed in advance on one sheet, the electrode body is stored in the recess, the sheet is folded back to form an exterior body, and the positive electrode terminal and the negative electrode terminal connected to the electrode body are formed from the exterior body. It is protruding.

Japanese Unexamined Patent Publication No. 2007-141714

However, in the case of the secondary battery of Patent Document 1, since the electrode body is arranged along the outer edge of the exterior body because it is folded back from the top of the recess, the gas generated inside is heated by overlapping the sheets. It will move to the vicinity of the sealed side and accumulate. The accumulated gas tries to peel off the heat-sealed portion. As a result, the sealing property is lowered.
An object of the present invention is to provide a secondary battery having improved sealing performance.

Secondary battery of the present invention includes a positive electrode layer, negative electrode layer, and an electrode comprising an arranged separators between the positive electrode layer and negative electrode layer, an electrolyte, a space for storing the electrode body and an electrolyte inside A secondary battery having an exterior body and an electrode terminal electrically connected to the electrode body and having at least a part protruding to the outside of the exterior body. The exterior body is a single piece sandwiching the electrode body. the folded sides overlaid by return folded sheets, by forming a heat seal sides were heat-sealed sheets between the return Shi other than the side edges folding, thickness folded edges and heat sealed sides of the electrode assembly is to form a space so as to be located substantially in the center direction, each of the two faces of the outer body extending from the folding return Shi sides across the folded edges in the thickness direction of the electrode bodies in a direction recessed space side The formed recesses are arranged symmetrically with respect to the folded surface of the sheet, and the radius of curvature of the recesses in the thickness direction of the electrode body from the vicinity of the center of the folded side is from the vicinity of the end of the folded side to the electrode body. It is characterized in that it is larger than the radius of curvature of the recess in the thickness direction .

According to the present invention, by providing a recess on the outer peripheral surface of the exterior body on the folded side, the recess can be allowed to accumulate by expanding to the outside of the exterior body, and the force in the peeling direction applied to the heat sealing portion can be reduced. And the sealing performance can be improved.

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. FIG. 1 is a sectional view taken along line DD 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.

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 7, and the manufacturing method will be described with reference to FIGS. 8 and 9. 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 5, and partially detailed structures are shown in FIGS. 6 and 7. 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 in each figure shows 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 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 heat-sealing resin layer 21 of the laminate film 2 are heat-sealed. Both ends of the folded side 20 overlap with the heat-sealed portions 27 and 28, and the heat-sealed portion of the folded side 20 is an unheat-sealed portion that is not 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. Here, 11 of FIG. 2 and 12 of FIG. 3 are recesses formed on the outer peripheral surface of the outer body of the folded side 20, and the radius of curvature of the recess 11 near the center of the folded side 20 is the end side of the folded side 20 ( It is larger than the radius of curvature of the recess 12 (near the heat-sealed portion). 13 of FIG. 2 and 14 of FIGS. 4 and 5 are recesses formed on the outer peripheral surface of the exterior body in the heat-sealed portion, and the radius of curvature of the recesses 11 and 12 of the folded side 20 faces the folded side 20. The radius of curvature is larger than the recess 13 on the outer peripheral surface of the exterior body on the side of the exterior body. The shape of the recess can be adjusted mainly by the amount of excess electrolyte described later and the amount of change in the space volume inside the exterior body before and after depressurization in the manufacturing process described later.

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 from which the terminal protrudes) and the thickness (vertical to the side of the exterior body where the terminal protrudes) are based on the direction of protrusion from the exterior body 2. It is preferably 40 mm to 100 mm, 0.1 mm to 0.5 mm, and 30 mm to 60 mm in this order of length) and length (length in the protruding direction). 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, 4, and 5. 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 collecting 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. 6, 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 made 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, compared to 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 includes, 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. 6 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, 4, and 5. 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. 6, 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. The active material of the negative electrode active material layer 72 occludes and releases lithium ions such as amorphous carbon, non-graphitized carbon, easily graphitized carbon, graphite, or graphite coated with amorphous carbon. 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. 6 is a welded portion.

Next, the separator 8 will be described. In FIGS. 2, 4 and 5, it is composed of 6 layers. As shown in FIG. 6, 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 mobility 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 external size, the space efficiency is significantly deteriorated.

When gas is generated inside the exterior body 2, the gas moves to a region between the electrode body 5 exterior body 2 and in a direction perpendicular to the stacking direction of the electrode body 5. Since the folded side 20 has recesses 11 and 12 on the outer peripheral surface of the exterior body 2, the deformation of the recess facilitates the accumulation of gas. In the heat-sealed portions formed by the heater heads 100, 120, and 130, the inner surfaces of the laminated films or the surface of the electrode terminal resin and the inner surface of the laminated film are heat-sealed, so that the force of the laminated film to spread outward. Is relatively weak compared to the folded side 20. Therefore, it is possible to suppress a decrease in sealing property caused by a force applied in the peeling direction of the heat-sealing portion.

Note that FIG. 7 is a side view seen from the positive / negative terminal terminals 3 and 4 of FIG. 1, and is formed by the sealing step of FIG. 9 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 arranged on the side near the folded side is 0.57 times the thickness of the positive electrode terminal 3 arranged at a distant position. It is possible to change the thickness of the positive and negative electrode terminal bodies 31 and 41 to make the thickness of the positive and negative electrode resin layers 32 and 42 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. 8 and 9. FIG. 8A is a preparation step of the exterior body. In this step, one sheet (laminated film 2) before folding is prepared. FIG. 8B shows a storage process. In this step, a state in which the positive and negative electrode terminals 3 and 4 and the electrode body 5 are connected in advance is prepared, and the main surface of the negative electrode layer 7 of the electrode body 5 faces the surface of the laminate film 2 while the laminate film 2 is formed. It was arranged at a predetermined position, and the positive and negative electrode terminal resin layers 32 and 42 of the positive and negative electrode terminals 3 and 4 were arranged in a region to be a 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) And, polyvinylidene fluoride as a binder and carbon black powder as a conductive auxiliary agent in a solid content mass 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-based conductive auxiliary agent 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. 8C 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. 9, the thermal sealing of the side where the positive and negative terminals 3 and 4 of FIG. 8 (c) protrude will be described. 9 (a) shows the arrangement state of each component, FIG. 9 (b) shows the 100 surfaces of the heater head in contact with the laminate film 2, and FIG. 9 (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. 9A, 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 other side of the folded laminated film 2 facing each other, the heater head 100 on the opposite side is arranged, and the heater head 100 moves in the positive and negative terminals 3 and 4 directions to form 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. 9B is a surface in contact with the positive electrode terminal 3 side, and the length in the width direction of 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 near 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 laminated 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 laminate 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. 8C can be heat-sealed by heating and pressurizing from both sides of the laminate film 2 with a flat heater head.

As described above, in the present embodiment, the electrode body 5 including the positive electrode layer 6, the negative electrode layer 7, and the separator 8 arranged between the positive electrode layer 6 and the negative electrode layer 7, the electrolyte, and the electrode body 5 A secondary battery 1 having an exterior body 2 for storing the electrolyte inside, and electrode terminals 3 and 4 electrically connected to the electrode body 5 and at least partially projecting to the outside of the exterior body 2. The exterior body 2 has a structure in which one sheet is folded across the electrode body 5, and the sides other than the folded side 20 are heat-sealed portions 26 in which the stacked sheets are heat-sealed. Since it has 27 and 28 and has a recess 11 on the outer peripheral surface of the exterior body of the folded side 20, the recess 11 can be allowed to accumulate by expanding to the outside of the exterior body, and the peeling direction applied to the heat sealing portion. The force of the electrode can be reduced. As a result, the effect that the sealing property can be improved can be obtained.

Further, the folded side and the heat-sealed portion are located substantially in the center of the electrode body 5 in the thickness direction, and the outer peripheral surface of the exterior body of the folded side has two recesses symmetrically. The pressure applied to the body 5 becomes substantially uniform, the internal resistance can be reduced, the packing density is increased, and the strength after sealing with the laminated film is further improved. Since the exterior body 2 does not have a cup-shaped molded portion at the position where the electrode body 5 is arranged, the recesses can be easily deformed by the gas, and the gas can be efficiently accumulated. Further, in the structure as in 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 arranged at the edge portion in the thickness direction of the secondary battery, that is, the top of the recess. Since there is no such material, the current collecting foil lead that electrically connects the power generation element and the electrode terminal is shorter than that of Patent Document 1. As a result, in the current collecting foil lead, the active material is intermittently applied to the current collecting foil, and the current collecting foil portion to which the active material is not applied is used as the current collecting 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.

In addition, the in fold return sides, because it has a heat sealed portions formed at both end portions of the in fold return sides, and a Minetsufutome portion between the heat sealed portions of the folded edges, the recesses by the gas Deformation can be controlled more easily, and gas can be accumulated efficiently. The electrode terminal includes a positive terminal connected to the positive electrode layer, and a negative terminal connected to the negative electrode layer, the positive and negative terminals protrude from one side adjacent to the side return Ri folding, Ri folding since one of the thickness of the terminal side to the electrode terminals disposed close to the return sides, was thinner than the thickness of the other terminal of electrode terminals arranged from in fold return side farther, further, the following effects There is. For example, when the arrangement of the positive electrode terminal 3 and the negative electrode terminal 4 is reversed as compared with FIGS. 7 and 9A, that is, at a position far from the folded side 20, the thickness of the nickel-plated copper as the main material is used. A negative electrode terminal 4 having a 0.1 mm thick negative electrode terminal resin layer 42 formed around a 0.2 μm wide negative electrode terminal body 41 is arranged, and aluminum is used as a main material at a position close to the folded side 20. The positive electrode terminal 3 having the positive electrode terminal resin layer 32 having a thickness of 0.15 mm is arranged around the positive electrode terminal body 31 having a thickness of 0.4 μm and a width of 60 mm, and the surface positions of the heater head surfaces 101 and 102 are also reversed. When heat-sealed, the heat-sealing resin layer 21 protruded inside and outside the exterior body 2 at the heat-sealed 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 electrode terminals by pressurization and heating. It is presumed that it protruded from the side. When the resin protrudes from the heat-sealed portion of the exterior body 2 to the inside and approaches the position where the electrode body 5 sandwiched between the laminate films 2 comes into contact with the positive electrode layer 6 or the negative electrode layer 7, the metal layer 22 of the laminate film 2 There is a risk that the electrical insulation between the positive electrode layer 6 and the negative electrode layer 7 will decrease. Further, when the resin protrudes to the outside of the heat-sealed portion of the exterior body 2, a plurality of lithium ion secondary batteries 1 are laminated in the thickness direction of the lithium ion secondary battery 1 and are on the side having the electrode terminals. When the electrode terminals are electrically connected to each other by a bus bar, a bus bar module or spacer for fixing the bus bar is required, but if there are protrusions on the outside from the exterior body 2, the layout avoids the protrusions. This may impair the degree of layout freedom and lead to an increase in the size of the device.

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 protruding portion to the outside is not generated, there is an effect that the size of the device can be suppressed. Further, since the protrusion to the inner side did not occur, it is possible to suppress a decrease in the electrical insulating property between the metal layer 22 of the laminated film 2 and the positive electrode layer 6 or the negative electrode layer 7.

Although the present embodiment has been described above by taking the lithium ion secondary battery 1 as an example, the present embodiment 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, the electrode terminal resin can be applied even when the sealing property between a certain electrode terminal body and the laminate film can be improved but not. Further, although the positive / negative electrode terminals are projected from one side of the exterior body 2, the positive electrode terminals and the negative electrode terminals may be projected from the sides of different heat sealing portions.

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 11, 12, 13, 14 ... Recesses 26, 27, 28 ... Heat sealing part

Claims (5)

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 having a space 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,
Prior Kigaiso bodies were thermally fused Oite the sheet between the folded sides overlaid by return folded one sheet across the electrode body, before Symbol folding return Shi other than the side edges thermosealing By forming the sides, the space is formed so that the folded side and the heat-sealed side are located substantially at the center in the thickness direction of the electrode body .
On each of the two surfaces of the exterior body extending from the folded side in the thickness direction of the electrode body across the folded side, recesses formed in the direction of recessing toward the space side form the folded surface of the sheet. Arranged plane-symmetrically as a reference,
The radius of curvature of the recess in the thickness direction of the electrode body from the vicinity of the center of the folded side is larger than the radius of curvature of the recess in the thickness direction of the electrode body from the vicinity of the end of the folded side. Secondary battery. On each of the two surfaces of the exterior body extending from the heat-sealed side in the thickness direction of the electrode body across the heat-sealed side, recesses formed in the direction of recessing toward the space side of the sheet. Arranged symmetrically with respect to the folded surface,
The radius of curvature of the recess in the thickness direction of the electrode body from the vicinity of the center of the folded side is greater than the radius of curvature of the recess in the thickness direction of the electrode body from the heat-sealed side facing the folded side. The secondary battery according to claim 1, wherein the secondary battery is large. The secondary battery according to claim 1 or claim 2 other than the vicinity of both end portions of the in fold return side is characterized by having a Minetsufutome portion. The electrode terminal, the positive terminal connected to the positive electrode layer, the and a negative terminal connected to the negative electrode layer, wherein 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, and characterized in that said the thinner than the thickness of the other terminal of electrode terminals arranged from in fold return side farther The secondary battery according to any one of claims 1 to 3 . The secondary battery according to any one of claims 1 to 4, wherein the exterior body is deformed by a gas generated inside the exterior body.

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