JP2013206700A - Electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical device which is free of a short-circuit problem between positive and negative electrodes and is less liable to cause a lamination deviation in a plurality of electrodes.SOLUTION: In the electrochemical device having a cathode and an anode laminated one on another in order via a separator, there are included a first and a second separator at the top and the bottom of the anode. At least the second separator is larger than the anode itself, and the second separator has its peripheral portion divided into a predetermined number of segments. The divided peripheral portions are folded alternately to the top and the bottom sides of the anode, whereby a bagged electrode is formed. The end portion folded to the top face of the anode overlaps the end portion of the first separator, whereby rugged portions are formed on the electrode. The bagged electrode is laminated in a plurality of layers, which are engaged with the rugged portions.

Description

  The present invention relates to an electrochemical device having stacked electrode pairs.

  In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook computers, electrochemical devices such as secondary batteries that are compact, lightweight, thin, and capable of continuous operation for a long time are required. In order to meet this demand, various proposals have been made on laminated nonaqueous electrolyte batteries, particularly lithium ion secondary batteries using lithium ion doping / undoping. In particular, it is effective to make a thinner and lighter secondary battery by using an aluminum laminate film for the exterior body.

  For example, in the lithium ion secondary battery, a positive electrode in which a positive electrode active material is provided on both sides of a positive electrode current collector and a negative electrode in which a negative electrode active material is provided on both sides of a negative electrode current collector are arranged to face each other with a separator interposed therebetween. The electrode group usually has a structure in which a plurality of electrode groups are laminated and sealed together with an electrolyte with an outer package.

  There are a method of winding a long electrode and a method of laminating a large number of methods as a method for producing an electrode group to be sealed in an exterior body.

  The winding method can be used as it is as an advanced type of cylindrical battery, but the shape of the battery is limited, and it is difficult to make a battery other than a cube, a rectangular parallelepiped or a column. Also, shorting between electrodes is likely to occur due to winding deviation, and when trying to make a thin battery, cracking may occur in the electrode due to winding, and it is possible to use a thick, high-density electrode, and energy cannot be used. This structure is also restricted in terms of density.

  On the other hand, the stacking method allows the battery shape to be relatively free, and it is not necessary to wind it, so that a thick and dense electrode can be used, and it is possible to make a thinner and higher energy density battery. The possibility of short-circuiting between electrodes is not a little inherent.

  For this reason, many proposals have been made to minimize the possibility of short-circuiting even in the lamination method.

  In the lamination method, a positive electrode in which a positive electrode active material is provided on both sides of a positive electrode current collector and a negative electrode in which a negative electrode active material is provided on both sides of a negative electrode current collector are arranged to face each other via a separator. It has a structure in which a plurality of layers are alternately stacked to form a stacked body.

  Among these structures, the arrangement of the separator is particularly important because it greatly affects the short circuit problem. For example, in the part where the positive electrode and the negative electrode face each other with the separator interposed between them, if the separator is sufficiently larger than both electrodes and completely covers both electrodes, lithium ions will normally pass through the separator. The battery is charged and discharged.

  However, when the positive electrode and the negative electrode protrude from the peripheral edge of the separator and face each other, an ion flow that does not pass through the separator occurs at a portion where the positive electrode and the negative electrode directly face each other, thereby causing problems such as a short circuit or a rapid rise in battery temperature.

  One technique for improving this is the bag method. As disclosed in Patent Literature 1, Patent Literature 2, Patent Literature 3, and the like, generally, an electrode is sandwiched between two separators, and then the peripheral edge is joined by means such as thermal welding, An electrode housed in a separator is produced. By doing so, the battery prevents the short circuit between the electrodes as described above.

  However, the electrode housed in the bag-shaped separator does not protrude from the bag-shaped separator during lamination, but the problem of misalignment between the positive electrode and the negative electrode that should be placed facing each other is completely eliminated. Instead, it is preferable to more reliably arrange the positive electrode and the negative electrode to face each other. For example, if the positive electrode is arranged at a position protruding from the negative electrode when projected on the negative electrode, the area facing substantially decreases, so that sufficient battery characteristics cannot be exhibited.

JP-A-6-36801 JP-A-9-213377 JP-A-10-55795

  In view of the above problems, an object of the present invention is to provide an electrochemical device that does not cause a short circuit between the positive and negative electrodes and is unlikely to cause stacking deviation of a plurality of electrodes.

  In the electrochemical device according to the present invention, a positive electrode and a negative electrode are alternately laminated, and the negative electrode is a bag produced by superimposing a first separator and a second separator on each other and joining the peripheral portions thereof. The peripheral portion of the bag-shaped separator is divided into a predetermined number, and has a plurality of folded portions in which the divided peripheral portions are alternately folded on the upper surface side and the lower surface side of the bag-shaped separator. The folded portion protrudes from the main surface of the bag-shaped separator when the bag-shaped separator is viewed from the side, and the bag-shaped separator is engaged with each other by the adjacent bag-shaped separator and the folded portion. It is characterized by being laminated.

  According to the electrochemical device of the present invention, it is possible to provide an electrochemical device in which there is no short circuit problem between the positive and negative electrodes and the stacking deviation of the plurality of electrodes hardly occurs.

  In the electrochemical device according to the present invention, preferably, the bag-shaped separator is a rectangular or square film, and the bag-shaped separator is evenly per side with respect to three sides excluding the side where the terminal lead portion is located. It is characterized by being divided into three.

  According to such an electrochemical device, it is possible to provide an electrochemical device in which there is no short circuit problem between the positive and negative electrodes, and the stacking deviation of the plurality of electrodes is less likely to occur.

  According to the present invention, it is possible to provide an electrochemical device that does not have a short circuit problem between the positive and negative electrodes and is less likely to cause misalignment of a plurality of electrodes.

FIG. 1 is a perspective view showing a configuration example of an electrochemical device according to the present invention. FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. 1. FIG. 3 is a cross-sectional view of a bag-shaped separator containing a negative electrode according to the present invention. 4 is a cross-sectional view taken along the line B-B 'of FIG. FIG. 5a is a perspective view of a bag-shaped separator containing a negative electrode according to the present invention. FIG. 5b is a side view of the bag-shaped separator containing the negative electrode according to the present invention. FIG. 6 a is a schematic view showing a laminated form of a separator and a positive electrode containing a negative electrode according to the present invention. FIG. 6B is a schematic view showing a laminated form of a separator and a positive electrode containing a negative electrode according to the present invention. FIG. 6 c is a schematic view showing a laminated form of a separator and a positive electrode containing a negative electrode according to the present invention. FIG. 7 a is an example of a cross-sectional view of a more preferable bag-like separator end form according to the present invention. FIG. 7 b is an example of a cross-sectional view of a more preferable bag-like separator end configuration according to the present invention. FIG. 7 c is an example of a cross-sectional view of a more preferable end portion of the bag-like separator according to the present invention. FIG. 7d is an example of a cross-sectional view of a more preferable end portion of the bag-like separator according to the present invention. FIG. 8 is a cross-sectional view showing a manufacturing process of a more preferable bag-like separator end form according to the present invention. FIG. 8 is a cross-sectional view of a more preferred bag-like separator end configuration according to the present invention made according to FIG. 8a. FIG. 9a is a side view of a more preferable bag-like separator end shape according to the present invention, FIG. 9B is a side view showing a laminated form of a separator and a positive electrode containing a negative electrode according to the present invention. FIG. 10 is a cross-sectional view of the positive electrode. FIG. 11 is a cross-sectional view of the negative electrode. FIG. 12 is a schematic diagram of a thermal indenter used in the second embodiment. 13 is a cross-sectional view of the embodiment of the present invention obtained in Example 1. FIG. 14 is a side view of the separator according to the embodiment of the present invention obtained in Example 2. FIG.

Hereinafter, an example of a preferred embodiment of an electrochemical device according to the present invention will be described in detail with reference to the accompanying drawings. However, the electrochemical device of the present invention is not limited to the following embodiments. In addition, the dimensional ratio of drawing is not restricted to the ratio of illustration.
In the electrochemical device of this embodiment, a positive electrode and a negative electrode are alternately stacked, and the negative electrode is a bag produced by superimposing a first separator and a second separator on each other and joining the peripheral portions thereof. The peripheral portion of the bag-shaped separator is divided into a predetermined number, and has a plurality of folded portions in which the divided peripheral portions are alternately folded on the upper surface side and the lower surface side of the bag-shaped separator. The folded portion protrudes from the main surface of the bag-shaped separator when the bag-shaped separator is viewed from the side, and the bag-shaped separator is engaged with each other by the adjacent bag-shaped separator and the folded portion. It is characterized by being laminated.

  In other words, an electrochemical device having a laminate in which a positive electrode and a negative electrode are laminated via a separator, and a separator surplus portion protruding outward from four sides of the negative electrode is divided into a plurality of portions, and the divided surplus portion is The separator bag body is formed with a convex portion so that at least one pair of upper surface convex portion and lower surface convex portion is formed between the adjacent surplus portions by alternately folding along the negative electrode edge along the negative electrode upper surface side and lower surface side. The upper and lower surfaces are simultaneously formed with concave portions formed between the convex portions. The unevenness is characterized in that a plurality of separator bag bodies are laminated to each other so as to be fitted with each other by the convex portions and the concave portions.

  The electrochemical device thus obtained does not have a short circuit problem between the positive and negative electrodes, provides an electrochemical device that is less prone to misalignment of a plurality of electrodes, and is excellent in energy density per unit volume. .

  In the electrochemical device of this embodiment, preferably, the bag-shaped separator is a rectangular or square film, and the bag-shaped separator has one side with respect to three sides excluding the side where the terminal lead portion is located. It is characterized by being equally divided into three.

  According to such an electrochemical device, there is no short circuit problem between the positive and negative electrodes, and it is possible to provide an electrochemical device in which the stacking deviation of a plurality of electrodes is less likely to occur.

  Next, the electrochemical device of the present embodiment will be described in more detail with reference to the drawings.

  1, 2, and 4 are a perspective view, a cross-sectional view taken along the line A-A ′, and a cross-sectional view taken along the line B-B ′, respectively, illustrating the schematic configuration of the electrochemical device according to the present embodiment. In each figure, the exterior body is omitted. In the figure, the laminate 2 has a structure in which positive electrodes 5 and negative electrodes 1 are alternately laminated with separators 3 interposed therebetween.

  As shown in the AA ′ sectional view of FIG. 2, the negative electrode 1 is housed in a bag-like separator 3 (3a, 3b), and the edge of the bag-like separator 3 will be described later. Folding is performed by such a method.

  As shown in the figure, the folding portion is set so that the direction of the folding processing is reversed in the B-B 'sectional view orthogonal to the A-A' sectional view.

  A laminate 2 is obtained by stacking a plurality of negative electrodes packed in this manner so as to face the positive electrode.

  Further, although not shown, the laminated body 2 is sealed together with the electrolytic solution in the exterior body to complete the electrochemical device.

  FIG. 3 is a cross-sectional view before folding the peripheral edge in a state where the negative electrode is housed in the bag-shaped separator. As shown in the figure, the bag-shaped separator 3 includes a first separator 3a and a second separator 3b, and the first separator 3a and the second separator 3b are each composed of a positive electrode 5 and a negative electrode 1. It is larger than the electrode, and is set to protrude around the electrode (positive electrode 5, negative electrode 1) when laminated. Of course, one of the first separator 3a and the second separator 3b may be large or the same size. The same size is preferable because an extra separator does not remain at the end.

  These first and second separators are formed in a bag shape so as to be joined to each other at the outer peripheral portion and wrap around the negative electrode 1. In addition, 4 on FIG. 1 shows the joining trace which is an edge part of the bag-shaped separator which shows a junction part. At this time, the bag-like separator 3 is joined at the peripheral portion thereof, that is, at the peripheral portion that does not overlap the negative electrode 1 in a plan view when stacked.

  Here, joining refers to means for physically bonding and fixing the periphery of the separator, and there are various means such as heat welding and using an adhesive. It is desirable to use an optimum joining method depending on the material and shape of the separator.

  In addition, it is preferable to trim the unnecessary portion of the joint thus obtained as appropriate.

  Here, when forming the bag-shaped separator, at least the extraction electrode portion of the negative electrode may or may not be joined. That is, the negative electrode 1 has an extraction portion 1a that is partly protruded from the outer periphery of the separator so that an external extraction terminal (extraction electrode) is attached or the external extraction terminal itself is configured.

  Up to now, the description has been given of the mode in which two separators are overlapped and joined at the periphery thereof, but as another means, after folding one separator sheet in half, the negative electrode is sandwiched between the separators and the peripheral portions are joined. It may take the form.

  Next, end formation of the bag-shaped separator will be described in detail with reference to the drawings.

  At the end of the bag-like separator, as shown in FIG. 3, the surplus portion 6 including the joint portion of the bag-like separator is formed on the side of the negative electrode. After forming a cut in the surplus portion in the direction from the edge of the separator toward the edge of the negative electrode, with the cut as a boundary, one surplus portion is formed along the edge of the negative electrode as shown in FIG. It folds to the upper surface side (6a). Further, the other adjacent surplus portion is folded along the edge of the negative electrode toward the lower surface of the separator (6b).

  The notches may be provided in advance before joining the separator.

  The bag-shaped separator upper surface side folded portion (6a) or lower surface side folded portion (6b) may use some fixing means in order to maintain its position. For example, means such as partial heat welding and fixing with an adhesive or resin can be considered.

  The bag-shaped separator 3 having the end shape formed in this way, the negative electrode 1 and the positive electrode 5 included therein are alternately stacked, and a laminate 2 as shown in FIG. 2 is formed.

  An example is shown in FIGS. 5a and 5b. In this example, the separator surplus portion is provided with two cuts per side to form a bag-like separator joint, and the separator surplus portion is folded toward the opposite separator surfaces with the cut as a boundary. However, here, it is assumed that cuts are provided in advance at the four points of the bag-shaped separator corner.

  The number of cuts is not particularly limited to two per side as shown in the example, and the number of cuts can be appropriately selected depending on the electrode shape, thickness, number of stacked layers, and the like.

  FIG. 6A is a schematic diagram of the upper surface convex portion and the lower surface convex portion of the end portion of the bag-shaped separator. As shown in this figure, the upper surface convex portion and the lower surface convex portion are formed at the end portion of the bag-like separator by folding the separator excess portion toward the upper surface side or the lower surface side of the separator at the notch. And they have a pair of at least a pair of upper surface convex portions and lower surface convex portions on opposite sides.

  FIG. 6b shows a state in which the positive electrode is superimposed on a bag-like separator having an upper surface convex portion and a lower surface convex portion formed at the end portion. The upper surface convex portion and the lower surface convex portion of the end portion of the bag-shaped separator are plan projections when viewed from the vertical direction with respect to the upper surface of the bag-shaped separator, and are positioned so as not to overlap with the positive electrode position. Is important and is arranged so as not to inhibit the overlap in all surfaces including the external lead-out terminal of the positive electrode.

  FIG. 6 c is a schematic view showing a laminate in which negative electrodes and positive electrodes included in a bag-like separator are alternately stacked. As shown in this figure, the upper surface convex portion and the lower surface convex portion of the bag-shaped separator end portion are the convex portions formed by the upper surface convex portion and the lower surface convex portion of the adjacent bag-shaped separator end portion and the concave portion between the convex portions. The laminated bodies that are fitted to each other and thus laminated are less likely to be displaced.

  In addition, by taking such a laminated body form, the electrochemical device has no short circuit problem between the positive and negative electrodes, and the separator surplus portion is not arranged to protrude to the side of the laminated body. It is difficult to cause, and has excellent energy density per unit volume.

  Regarding the formation of the convex shape at the end of the bag-like separator, several other forms are conceivable as shown in FIG.

  FIG. 7 a is an example of a basic folding form, in which the separator joining portion and the separator surplus portion joined on the negative electrode side are folded into the bag-shaped separator inside.

  As shown in FIG. 7b, the separator joint may be formed in advance on the negative electrode surface, and then the joint may be folded inward to contact the bag-like separator surface. This form is effective for improving the strength of the convex portion.

  As shown in FIG. 7c, after the joining portion is located closer to the lower portion on the side of the negative electrode, the joining portion may be folded from the side of the negative electrode to the upper surface of the bag-like separator. This form is an effective form for improving the strength against strain when a laminate is formed.

  As shown in FIG. 7d, the joining portion may be formed so as to be close to the end portion of the upper surface of the negative electrode, and the folded portion may be made as small as possible. In this case, it is an effective form that hardly impedes the penetration of the electrolytic solution.

  Thus, as shown in FIGS. 7A to 7D, the shape of the folded portion is various and can be varied within the range where the effect of the present invention occurs, and rises 90 degrees as shown in (d). From such a form, a folded form that makes a U-turn as shown in FIG.

  Further, as shown in FIG. 8, for example, a plurality of protrusions may be provided in the bag-like separator surplus portion in advance using a tool having a sharp tip such as a needle. In this case, there will be a plurality of protrusions on the convex top of the bag-like separator end formed when the surplus portion is folded into the negative electrode upper surface side and lower surface side, and adjacent bag shapes Since the anti-slip effect is produced when the separator overlaps with the separator, the prevention of positional deviation of the electrode is further improved, which is an effective form.

  In forming such protrusions, the means itself may also serve as a separator joining means. Further, the shape of the protrusion can take various shapes such as a rod shape, a bowl shape, and a triangular cone shape in addition to the dot shape given as an example.

  Further, as in the examples of FIGS. 9 and 14, the separator excess portion is not cut, and the convex shape of the upper end portion on the upper side of the bag-like separator and the convex shape of the lower end side of the bag-like separator are integrally formed. You can also. This is, for example, a step corresponding to the thickness dimension of the negative electrode in advance in the thermal indenter corresponding to each side of the bag-shaped separator as shown in FIG. After that, the upper and lower separator ends are thermally welded so as to be sandwiched from above and below by the thermal indenter, so that the joining marks are intended to be on the front side and back side of the bag separator even on the same side of the bag separator. It is formed so as to protrude.

  Such a form is a particularly good form because it can obtain a desired convex shape without increasing the cut forming process and can also be used as a separator joining process, thereby saving labor.

(Electrochemical device)
The laminate manufactured in the above-described form is stored inside the exterior body and sealed together with the non-aqueous electrolyte while only the negative electrode extraction portion 1a and the positive electrode extraction portion 5a are extracted to the outside, and is representative of a lithium ion secondary battery. It becomes an electrochemical device.

(Exterior body)
The exterior body is a bag body for housing the laminated body, and is composed of, for example, a laminate film using aluminum. The laminate film has, for example, a laminated structure in which an adhesive layer, a metal layer, and a surface protective layer are sequentially laminated. The adhesive layer is made of a polymer film that melts and fuses with heat or ultrasonic waves, and examples of the material constituting the polymer film include polypropylene (PP), polyethylene (PE), unstretched polypropylene (CPP), Examples include linear low density polyethylene (LLDPE) and low density polyethylene (LDPE). The metal layer is made of a metal foil and plays the most important role in protecting the contents by preventing the ingress of moisture, oxygen and light. As a material constituting the metal foil, for example, aluminum (Al) is used from the viewpoints of lightness, extensibility, price, ease of processing, and the like. Moreover, as a material which comprises metal foil, it is also possible to use metals other than aluminum (Al). As a material constituting the surface protective layer, for example, nylon (Ny) or polyethylene terephthalate (PET) is used because of its beautiful appearance, toughness, flexibility, and the like. The surface on the adhesive layer side is the storage surface on the side for storing the laminate.

  Such a laminate film is provided with a throttle containing portion that is convex from the adhesive layer side to the surface layer side, and the laminated body is accommodated in the restricting containing portion so that the laminate can be sealed. Can be improved.

(Nonaqueous electrolyte)
The non-aqueous electrolyte is sealed inside the outer package together with the laminate. As the non-aqueous electrolyte, an electrolyte salt and an organic solvent that are generally used in non-aqueous electrolyte batteries can be used.

  Specific examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate ( DPC), ethylpropyl carbonate (EPC), or a solvent in which hydrogen of these carbonates is substituted with halogen. One of these solvents may be used alone, or a plurality of these solvents may be mixed with a predetermined composition.

Moreover, as an electrolyte salt, it is possible to use the material used for a normal non-aqueous electrolyte. Specifically, LiCl, LiBr, LiI, LiClO ₃ , LiClO ₄ , LiBF ₄ , LiPF ₆ , LiNO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiAlCl ₄ , LiSiF _{6 and the} like can be mentioned, but LiPF ₆ and LiBF ₄ are preferable from the viewpoint of oxidation stability. These lithium salts may be used alone or in combination of two or more. There is no problem as long as the lithium salt can be dissolved in the above solvent, but the lithium ion concentration is 0.4 mol / kg or more and 2.0 mol / kg or less with respect to the non-aqueous solvent. Preferably there is.

(Laminate)
As described above, the laminate is composed of the positive electrode, the negative electrode, and the separator.

(Positive electrode)
The following is used for the positive electrode. As shown in FIG. 10, the positive electrode 5 includes a positive electrode current collector 51 and a positive electrode active material layer 52 formed on both surfaces of the positive electrode current collector 51. The positive electrode current collector 51 is a metal foil made of, for example, aluminum (Al). Further, a positive electrode terminal formed integrally with the positive electrode current collector 51 is led out from one side of the positive electrode 5.
Moreover, the positive electrode 5 is made into a desired shape using means such as punching.

  The positive electrode active material layer 52 includes, for example, a positive electrode active material, a conductive agent, and a binder.

As the positive electrode active material, a metal oxide, a metal sulfide, a specific polymer, or the like can be used depending on the type of the target battery. For example, in the case of constituting a lithium ion battery, Li _x MO ₂ (wherein M represents one or more transition metals, and x varies depending on the charge / discharge state of the battery, and is usually 0.05 or more and 1.10 or less. ) And a composite oxide of lithium and a transition metal.

Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiNi _y Co _1-y O ₂ (0 <y <1), LiNiCoMnO ₂ , and the like. A solid solution in which a part of the transition metal element is substituted with another element can also be used. Examples include LiNi _0.5 Co _0.5 O ₂ , LiNi _0.8 Co _0.2 O ₂ , Li ₂ MnO ₂ .LiMn ₂ O ₄ , and the like. Further, these lithium composite oxides such as an active material having an olivine skeleton such as LiFePO ₄ and a transition metal lithium phosphate such as LiVOPO ₄ are effective as being capable of generating a high voltage and having an excellent energy density. _{Furthermore, TiS 2, MoS 2, NbSe} 2, V 2 O no lithium metal sulfides such as ₅ or may be used an oxide as the positive electrode active material. These positive electrode active materials may be used alone or in combination of two or more.

  As the conductive agent, for example, a carbon material such as carbon black or graphite is used. As the binder, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) or the like is used.

(Negative electrode)
The following is used for the negative electrode. As shown in FIG. 11, the negative electrode 1 includes a negative electrode current collector 11 having an outer dimension several mm larger than the positive electrode current collector 51, and a negative electrode active material layer 12 formed on both surfaces of the negative electrode current collector 11. . The negative electrode current collector is a metal foil made of, for example, copper (Cu), nickel (Ni), stainless steel (SUS), or the like. Further, from one side of the negative electrode 1, a negative electrode terminal molded integrally with the negative electrode current collector 11 is led out in the same manner as the positive electrode.
In addition, the negative electrode 1 is formed into a desired shape using a means such as punching.

  The negative electrode active material layer 12 includes, for example, a negative electrode active material, a conductive agent if necessary, and a binder.

  As the negative electrode active material, a silicon compound in which lithium metal, a lithium alloy, a carbon material that can be doped / undoped with lithium, or a composite material of a metal-based material and a carbon-based material is used. Specifically, examples of the carbon material that can be doped / undoped with lithium include graphite, non-graphitizable carbon, and graphitizable carbon. More specifically, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke), graphites, glassy carbons, organic polymer compound fired bodies (phenolic resin, furan resin, etc.) at an appropriate temperature. Carbon materials such as those obtained by firing and carbonization), carbon fibers, activated carbon, and the like can be used. As a material capable of alloying lithium, various kinds of metals can be used, such as tin (Sn), cobalt (Co), indium (In), aluminum (Al), silicon (Si) and These alloys are often used. When metallic lithium is used, it is not always necessary to use powder as a coating film with a binder, and a method of pressure bonding a rolled lithium metal foil to a current collector may be used.

  As the binder, for example, polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR) or the like is used.

(Separator)
The following separators are used. The separator sheet forming the separator 3 is composed of one or two or more types of polyolefins such as polyethylene and polypropylene (in the case of two or more types, there are two or more laminated films), such as polyethylene terephthalate. Polyesters, thermoplastic fluororesins such as ethylene-tetrafluoroethylene copolymer, and celluloses. The form of the sheet includes a microporous membrane film, a woven fabric, a non-woven fabric, etc. having an air permeability measured by the method specified in JIS-P8117 of about 5 to 2000 sec / 100 cc and a thickness of about 5 to 100 μm.

  The separator 3 may be configured such that when the electrolytic solution is injected in the battery manufacturing process and the separator 3 is impregnated with the electrolytic solution, the electrolytic solution gels.

In the present embodiment, it is particularly desirable to use a so-called shutdown separator as the separator. By using the shutdown separator, as the temperature inside the electrochemical device rises, the micropores of the separator are closed, and the conduction of ions is suppressed, current is suppressed, and thermal runaway can be prevented. As such a shutdown separator, for example, a separator made of a synthetic resin film having micropores including at least one of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE), And a microporous membrane made of an ultrahigh molecular weight polyethylene having a weight average molecular weight of 7 × 10 ⁵ or more, and a polyethylene composition having a weight average molecular weight / number average molecular weight of 10 to 300. Further, a material having a thickness of 0.1 to 25 μm, a porosity of 40 to 95%, an average through hole diameter of 0.001 to 0.1 μm, and a 10 mm width breaking strength of 0.5 kg or more can be preferably used. .

(External lead terminal)
The electrochemical device of the present embodiment has a structure in which positive and negative electrodes and separators made of metal foil such as aluminum foil and copper foil are alternately laminated. External lead-out terminals (extraction electrodes) are connected to the positive and negative electrodes, respectively. The external lead-out terminal is made of a metal foil such as aluminum, copper, nickel, and stainless steel.

Hereinafter, the electrochemical device according to the present invention will be described in more detail with reference to Examples and Comparative Examples.
Example 1
The positive electrode is made of LiCoO ₂ (C-010, manufactured by Seimi Chemical), carbon black (HS-100, manufactured by Denki Kagaku Kogyo), graphite (KS-6, manufactured by TIMCAL), PVDF (KF-1300, manufactured by Kureha). The material was applied and dried on both sides of an aluminum foil by a doctor blade method.

  The applied positive electrode material was pressed and adjusted to have a total thickness of 200 μm on both sides. The total thickness of the positive electrode was 220 μm, including the aluminum foil thickness of 20 μm.

  The negative electrode is made of mesocarbon microbeads (MCMB, manufactured by Osaka Gas), carbon black (HS-100, manufactured by Denki Kagaku Kogyo), and PVDF (KF-1100, manufactured by Kureha). It was applied and dried.

  The applied negative electrode material was pressed and adjusted so that the thickness on both sides was 120 μm in total. The total thickness of the negative electrode was 135 μm, including the thickness of the copper foil of 15 μm.

  The positive and negative electrodes were punched in a predetermined size such that the negative electrode outer shape was 4 mm larger than the positive electrode outer shape in the vertical and horizontal directions.

  As the separator, a polyethylene microporous membrane film (product name: Asahi Kasei, trade name: microporous membrane Hypore N910) was prepared.

  After sandwiching the negative electrode between two separators larger than the negative electrode, and placing both separators so that they protrude outward in four directions from the negative electrode end, use scissors to reach the length of the negative electrode end from the separator end. Cuts were made in both separators.

  Next, in order to join both separators mentioned above by hot press, a polyethylene sheet piece (hereinafter referred to as PE) having a thickness of 150 μm serving as an adhesive was prepared.

  In any one side of the negative electrode sandwiched between two separators, the PE extends over the entire side so that the one side and the negative electrode end are parallel to each other and the position of the surplus part is 0.8 mm away from the negative electrode end. Set in the shape. At this time, the PE was divided in advance, and care was taken not to cover the cut portion.

  With respect to the side thus produced, the position parallel to the negative electrode end and 1.5 mm away was thermally welded by hot pressing, and the lower separator, PE, and upper separator were joined together. The total thickness of the integrated joint was 200 μm (= 25 μm + 150 μm + 25 μm) in total.

The heating temperature at the time of joining was 200 ° C., the heating time was 1.5 sec, and the pressure during pressurization was 10 kg / cm ² . At the same time, unnecessary portions generated in the joints were cut and trimmed by the action of heat at the time of heat welding so as to burn off the separator. As a result of observation with a microscope, it was confirmed that no unnecessary portion was adhered to the tip side further than the welding mark.

  It implemented similarly about the other three sides, and it was set as the bag-shaped separator whose thickness of the separator junction part which has a separator surplus length of 1.8 mm in length at four sides is 200 micrometers.

  On one side of the bag-like separator, one separator surplus portion was folded along the negative electrode edge to the upper surface side of the bag-like separator, with the cut portion as a boundary. Similarly, the other adjacent separator surplus part was folded along the negative electrode edge to the lower surface side of the bag-like separator. This operation is alternately repeated along the periphery of the negative electrode, and about 5 points of needle-shaped heating terminals are pressed against the folded separator surplus part, spot heat welding is performed together with the separator located inside, and the folded shape is formed. Held.

  This operation was similarly performed on the other three sides to obtain a bag-like separator having an end as shown in FIG.

  That is, it was confirmed by measuring using a digital micrometer that the height of any 10 points on the upper or lower convex portion was 200 μm ± 30 μm.

  Moreover, it confirmed by measuring using the length measuring microscope that the width | variety of arbitrary 10 points | pieces of an upper convex part or a lower convex part was 1.5 mm +/- 0.3mm.

  It was confirmed by measuring using a digital micrometer that the length of any 10 points of the separator surplus portion (= distance from the negative electrode end to the separator end) was 0.1 mm or less.

  Since the positive electrode is made 4 mm smaller in length and width than the negative electrode, it can overlap with the separator without interfering with the convex portion or the lower convex portion of the separator end.

  In this way, a negative electrode bag housed in the bag-shaped separator and a positive electrode not housed in the bag-shaped separator were prepared, and a total of 55 sheets of 28 bags each containing the negative electrode and 27 positive electrodes were alternately laminated. did. At this time, the upper surface convex portion and the lower surface convex portion of the adjacent bag-shaped separator end portions are fitted with the concave portions between the convex portions formed by the upper surface convex portion and the lower surface convex portion, and the form shown in FIG. 6c. Confirmed to take.

  Thereafter, all the negative electrode take-out portions and the lead wires were welded and integrated. Similarly, all positive electrode take-out portions and lead wires were welded and integrated.

  Vibration was intentionally applied to this laminate. The vibration was held by holding the lead wire of the laminated body and hanging it by hand, swinging it back and forth 10 times, and swinging it up and down 10 times.

This laminate is inserted into an outer package (aluminum laminate film), an electrolytic solution of EC / DEC = 4/6, LiPF ₆ of 1M (mol / L) is injected, sealed, precharged, and subjected to aging. A laminated non-aqueous electrolyte lithium ion secondary battery was produced.

  The battery capacity of the obtained non-aqueous electrolyte lithium ion secondary battery was 10 Ah.

  When this nonaqueous electrolyte lithium ion secondary battery was charged and discharged in an environment of 45 ° C., the capacity was about 8 Ah (80%) after about 1,000 times. The charge / discharge frequency at which the capacity value is 80% is shown in Table 1 as the evaluation value of the cycle characteristics. Therefore, the greater the number of times, the better the cycle characteristics.

  When this non-aqueous electrolyte lithium ion secondary battery was subjected to 1C discharge and 10C discharge in a room temperature environment, the discharge capacity ratio (= 10C discharge capacity / 1C discharge capacity) was 65%.

(Example 2)
Positive and negative electrodes were produced in the same manner as in Example 1, and punched out at a predetermined size.

  The same separator as in Example 1 was prepared.

  The negative electrode was sandwiched between two separators larger than the negative electrode, and both the separators were arranged so as to protrude outward from the negative electrode end.

  Next, a hot indenter having a meshing shape with a step difference in the vertical direction as shown in FIG. 12 was prepared. The step was 0.6 mm.

On one side of both separators, a position parallel to the negative electrode end and 0.4 mm away was hot-pressed using the hot indenter and heat-welded. At this time, both were arranged so that the center in the thickness direction of the negative electrode and the center height of the meshing portion of the thermal indenter coincided. At this time, the heating temperature is 200 ° C. Heating time is 1.5 sec. The pressure at the time of pressurization was 10 kg / cm ² . At the same time, unnecessary portions generated in the joints were cut and trimmed by the action of heat at the time of heat welding so that the separator was burned out. As a result of observation with a microscope, it was confirmed that no unnecessary portion was adhered to the tip side further than the welding mark.

  Since the total thickness of the two separators and the negative electrode is about 0.2 mm and the thermal indenter step is 0.6 mm, one joint protrudes 0.2 mm downward from the surface of the lower separator while having the same heat welding side The other one of the joints protruded 0.2 mm upward from the upper separator surface.

  The remaining three sides of the two separators were also subjected to the same hot press to obtain a separator-like shape as a bag-like separator as shown in FIG.

  It was confirmed by measuring using a digital micrometer that the height of any 10 points on the upper convex portion of the separator end was 0.2 mm ± 50 μm. Similarly, it was confirmed by measuring using a digital micrometer that the height of any 10 points on the lower convex portion at the end of the separator was 0.2 mm ± 50 μm.

  The length of any 10 points of the separator excess part (= distance from the negative electrode end to the separator end) was confirmed to be 0.5 ± 0.05 mm by measuring with a digital micrometer.

  In the same manner as in Example 1, a negative electrode bag housed in a bag-shaped separator and a positive electrode not housed in the bag-shaped separator were prepared, and a total of 55 sheets of 28 bag bodies housing the negative electrode and 27 positive electrodes were assembled. Alternatingly stacked.

  And all the negative electrode taking-out parts and lead wires were welded and integrated. Similarly, all positive electrode take-out portions and lead wires were welded and integrated.

Thereafter, vibration was intentionally applied to the laminate in the same manner as in Example 1.

In the same manner as in Example 1, this laminate was inserted into an outer package (aluminum laminate film), and an electrolyte solution having EC / DEC = 4/6 and LiPF ₆ of 1M was injected, sealed, precharged, and subjected to aging. Then, a multilayer non-aqueous electrolyte lithium ion secondary battery was produced.

  The battery capacity of the obtained non-aqueous electrolyte lithium ion secondary battery was 10.6 Ah.

  When this nonaqueous electrolyte lithium ion secondary battery was charged and discharged in an environment of 45 ° C., the capacity was about 8 Ah (80%) after about 1,090 times.

  When this non-aqueous electrolyte lithium ion secondary battery was subjected to 1C discharge and 10C discharge in a room temperature environment, the discharge capacity ratio (= 10C discharge capacity / 1C discharge capacity) was 70%.

(Comparative example)
Positive and negative electrodes were produced in the same manner as in Example 1, and punched out at a predetermined size.

  The same separator as in Example 1 was prepared.

After sandwiching the negative electrode between two separators larger than the negative electrode and arranging both separators so that they protrude outwardly from the negative electrode end, both sides of the separator are parallel to the negative electrode end and 1.5 mm apart by hot pressing. Heat welded.
The heating temperature at the time of joining was 200 ° C., the heating time was 1.5 sec, and the pressure during pressurization was 10 kg / cm ² . At the same time, unnecessary portions generated in the joint portion were cut and trimmed by the action of heat at the time of heat welding so that the separator was burned out. As a result of observation with a microscope, it was confirmed that no unnecessary portion was adhered to the tip side further than the welding mark.

  The separator surplus amount (= distance from the negative electrode end to the separator end) on each side was set to 1.8 mm. A general separator end shape as shown in FIG. 3 in which a joint exists on the side of the negative electrode was produced.

  In the same manner as in Example 1, a negative electrode bag housed in a bag-shaped separator and a positive electrode not housed in the bag-shaped separator were prepared, and a total of 55 sheets of 28 bag bodies housing the negative electrode and 27 positive electrodes were assembled. Alternatingly stacked.

  And all the negative electrode taking-out parts and lead wires were welded and integrated. Similarly, all positive electrode take-out portions and lead wires were welded and integrated.

  Thereafter, vibration was intentionally applied to the laminate in the same manner as in Example 1.

In the same manner as in Example 1, this laminate was inserted into an outer package (aluminum laminate film), and an electrolyte solution having EC / DEC = 4/6 and LiPF ₆ of 1M was injected, sealed, precharged, and subjected to aging. Then, a multilayer non-aqueous electrolyte lithium ion secondary battery was produced.

  The battery capacity of the obtained non-aqueous electrolyte lithium ion secondary battery was 8.9 Ah.

  When this non-aqueous electrolyte lithium ion secondary battery was charged and discharged in an environment of 45 ° C., the capacity was about 8 Ah (80%) after about 800 times.

  When this non-aqueous electrolyte lithium ion secondary battery was subjected to 1C discharge and 10C discharge in a room temperature environment, the discharge capacity ratio (= 10C discharge capacity / 1C discharge capacity) was 50%.

  The evaluation results of Examples 1 and 2 and Comparative Example 1 are shown in Table 1.

  From the results of various characteristics of the lithium ion secondary battery after the vibration test shown in Table 1, it is clear that the above example has no short circuit problem between the positive and negative electrodes and is difficult to cause stacking deviation of a plurality of electrodes. I found out.

  The present invention is widely applicable not only to lithium ion secondary batteries but also to electrochemical devices having a separator such as EDLC.

DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Laminated body 3 Bag-shaped separator 3a 1st separator 3b 2nd separator 4 Joining trace 5 Positive electrode 1a Negative electrode extraction part 5a Positive electrode extraction part 6 Separator surplus part 6a Folding part to upper surface side of separator (upper surface convex part)
6b Folding part to the lower side of the separator (lower surface convex part)
7 Hot Indenter 11 Negative Electrode Current Collector 12 Negative Electrode Active Material Layer 51 Positive Electrode Current Collector 52 Positive Electrode Active Material Layer

Claims (2)

The positive electrode and the negative electrode are alternately stacked,
The negative electrode is accommodated in a bag-shaped separator produced by superimposing the first separator and the second separator on each other and joining the peripheral edge portions thereof,
The peripheral portion of the bag-shaped separator is divided into a predetermined number, and the divided peripheral portions have a plurality of folded portions that are alternately folded on the upper surface side and the lower surface side of the bag-shaped separator,
The folded portion protrudes from the main surface of the bag-shaped separator when the bag-shaped separator is viewed from the side surface.
2. The electrochemical device according to claim 1, wherein the bag-like separator is laminated by being bitten together by adjacent bag-like separators. The bag-shaped separator is a rectangular or square film,
2. The electrochemical device according to claim 1, wherein in the bag-shaped separator, three sides are equally divided into three sides excluding the side where the terminal lead portion is located.

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