JP2013191388A - Lamination structure cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lamination structure cell including a resin layer between an electrode and a separator, which can prevent uneven melting of the resin layer inward (internal) and outward (external) in a lamination direction, and reduce a difference in ion permeability for each resin layer.SOLUTION: A lamination structure cell comprises a cathode, an anode, and an electrolyte layer including a separator, and has three or more laminated electric cell layers with the cathode facing the anode through the electrolyte layer. A resin layer is further provided between at least one of the cathode and the anode and the separator to bond at least one of the cathode and the anode and the separator. At least one of a melting temperature, a softening point, a heat distortion temperature, and a load bending temperature of the resin layer is less on a center side than on an end side in a lamination direction.

Description

  The present invention relates to a laminated battery, which is a kind of electric device that performs work on the outside by the action of electrons and ions electrochemically. More specifically, the present invention relates to a laminated battery represented by a laminated (laminated structure) lithium ion secondary battery.

  In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide has been strongly desired. In the automobile industry, there is a great expectation for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV), and the development of secondary batteries for motor drive that holds the key to commercialization of these is thriving. Has been done.

  As a secondary battery for driving a motor, it is required to have extremely high output characteristics and high energy as compared with a consumer lithium ion secondary battery used in a mobile phone, a notebook personal computer or the like. Therefore, lithium ion secondary batteries having the highest theoretical energy among all the batteries are attracting attention, and are currently being developed rapidly.

  Generally, a lithium ion secondary battery includes a positive electrode in which a positive electrode active material or the like is applied to both surfaces of a positive electrode current collector using a binder, and a negative electrode in which a negative electrode active material or the like is applied to both surfaces of a negative electrode current collector using a binder. However, it has the structure connected through an electrolyte layer and accommodated in a battery exterior material. For example, in Patent Document 1, a battery group (power generation element) in which a positive electrode and a negative electrode are alternately stacked via a separator is accommodated in an outer case of a laminate sheet, and an electrolyte is poured, and an outer edge of the laminate sheet is added. A lithium ion secondary battery (laminated structure battery) characterized by sealing under a pressure environment is described.

JP 2009-2111937 A

  However, in a lithium ion secondary battery (laminated structure battery) having an existing laminated structure such as Patent Document 1, in order to prevent a short circuit due to thermal contraction of the separator, the outer edge of the laminate sheet as an exterior material as described above is used. It was insufficient to simply seal under a certain pressure environment.

  Therefore, in order to prevent a short circuit due to thermal contraction of the separator in the laminated battery, the present inventors provided a resin layer between the electrode and the separator, and applied a load between the electrodes by hot pressing, and the resin layer A construction method (structure) was devised in which a part was melted to connect the electrode and the separator.

  However, in a stacked structure battery, it is necessary to heat and press (hot press) the stacked power generation element (battery group) from above and below. For this reason, in a laminated battery, especially a large laminated battery such as an in-vehicle battery, there is a difference in the amount of heat received between the end side and the center side of the laminated battery, and the resin layer has a difference between the center and the end in the stacking direction. It was found that there was variation in melting (see FIG. 2). As a result, it was found that there is a problem in that deterioration is promoted because there is a difference in ion permeability in the resin layer between the central portion and the end portion in the stacking direction (compared with the examples in Table 1). See example).

  Therefore, an object of the present invention is to prevent uneven melting of the inner (inner) and outer (outer) resin layers in the stacking direction in a laminated battery having a resin layer between an electrode and a separator, and to prevent the ion for each resin layer. It is an object of the present invention to provide a laminated battery that can reduce the difference in permeability.

  The laminated battery of the present invention is a laminated battery having a resin layer between an electrode and a separator, wherein at least one of the melting point, softening point, thermal deformation temperature, and deflection temperature under load of the resin layer is the stacking direction (battery thickness). It is characterized in that the center side <the end side in the vertical direction).

  According to the present invention, a resin layer having a high melting point (hard to melt) is used on the end side of the laminated battery, and a resin layer having a low melting point (easy to melt) is used along the middle side in the stacking direction. Uneven melting can be prevented, and the resistance between the electrodes can be kept uniform. This prevents uneven reaction distribution for each single cell layer (single cell) and improves the durability of the entire laminated battery.

1 is a schematic cross-sectional view showing a basic configuration of a laminated (flat) nonaqueous electrolyte lithium ion secondary battery, which is a typical embodiment of a laminated battery. FIG. 2 is a partial cross-sectional view of the power generation element of the laminated battery of FIG. 1, schematically showing how heat is transmitted when hot pressing (hot pressing) is performed from above and below the power generation element of the laminated battery. is there. FIG. 3A is a plan view illustrating a state in which a stripe-shaped resin portion is provided on the electrode surface. 3B and 3C are plan views showing a state in which a dot-shaped resin portion is provided on the electrode surface. It is a perspective view showing the appearance of a flat lithium ion secondary battery which is a typical embodiment of a secondary battery. It is the schematic sectional drawing which represented typically a mode that the laminated battery produced in the Example was hot-pressed (hot-pressed) using the holding jig which has a hot-press function.

  The laminated battery of this embodiment further includes a resin layer that adheres between at least one of the positive and negative electrodes and the separator, and has a melting point, a softening point, a heat denaturation temperature, a heat distortion temperature, and a load deflection of the resin layer. One or more of the temperatures are characterized in that the center side is less than the end side in the stacking direction. Here, the laminated structure battery is a laminated structure in which at least a positive electrode, a negative electrode, and an electrolyte layer including a separator are included, and three or more single battery layers are stacked with the positive electrode and the negative electrode facing each other through the electrolyte layer. Battery. With such a configuration, the above-described effects of the invention can be achieved.

  As a preferred embodiment of the laminated battery, a laminated (laminated structure) non-aqueous electrolyte lithium ion secondary battery will be described, but the invention is not limited to the following embodiments. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  The laminated (laminated structure) lithium ion secondary battery of this embodiment is preferably applied to a large battery such as a vehicle-mounted battery, but is not limited to the size or use of the battery. The present invention can be applied to a lithium ion secondary battery having a laminated structure used for any conventionally known size and application.

  Even when the laminated (laminated structure) lithium ion secondary battery of the present embodiment is distinguished in the form of an electrolyte, there is no particular limitation. For example, the present invention can be applied to any of a liquid electrolyte type battery in which a separator is impregnated with a nonaqueous electrolytic solution, a polymer gel electrolyte type battery also called a polymer battery, and a solid polymer electrolyte (all solid electrolyte) type battery. In the present embodiment, the polymer gel electrolyte and the solid polymer electrolyte that are impregnated with the polymer gel electrolyte or the solid polymer electrolyte are used.

  In the following description, a non-bipolar (internal parallel connection type) layered (stacked structure) lithium ion secondary battery will be described with reference to the drawings, but should not be limited to these.

  FIG. 1 is a schematic diagram showing a basic configuration of an embodiment of a laminated (flat) nonaqueous electrolyte lithium ion secondary battery (hereinafter also simply referred to as “laminated structure battery”). As shown in FIG. 1, the laminated battery 10 of this embodiment has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a battery exterior material 29 that is an exterior body. Have. Here, the power generation element 21 has a configuration in which a positive electrode, a separator (electrolyte layer) 17 containing an electrolyte, and a negative electrode are stacked. The positive electrode has a structure in which the positive electrode active material layer 13 is disposed on both surfaces of the positive electrode current collector 11. The negative electrode has a structure in which the negative electrode active material layers 15 are disposed on both surfaces of the negative electrode current collector 12. Furthermore, in this embodiment, a resin layer 18 is further disposed between the separator (electrolyte layer) 17 and the negative electrode (active material layer 15). Further, by reversing the arrangement of the resin layer 18 from FIG. 1, a resin layer 18 formed by bonding the separator (electrolyte layer) 17 and the positive electrode (active material layer 13) is further arranged. You may be allowed to. Further, the separator (electrolyte layer) 17 and the negative electrode (active material layer 15) and the separator (electrolyte layer) 17 and the positive electrode (active material layer 13) are both bonded to each other. Each of the resin layers 18 may be disposed.

  Specifically, the negative electrode, the resin layer, the electrolyte layer, and the positive electrode are formed such that one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto face each other with the electrolyte layer 17 and the resin layer 18 therebetween. Are stacked in this order. Thus, the adjacent positive electrode, electrolyte layer, resin layer, and negative electrode constitute one single battery layer (single cell) 19. Therefore, it can be said that the stacked structure battery 10 of the present embodiment has a configuration in which a plurality of single battery layers (single cells) 19 are stacked to be electrically connected in parallel. Note that a bipolar (internal series connection type) lithium-ion secondary battery (stacked structure) has a configuration in which a plurality of single battery layers (single cells) are stacked to be electrically connected in series. It can be said that it has.

  In addition, although the positive electrode active material layer 13 is arrange | positioned only at one side in the outermost layer positive electrode collector located in both outermost layers of the electric power generation element 21, an active material layer may be provided in both surfaces. That is, instead of using a current collector dedicated to the outermost layer provided with an active material layer only on one side, a current collector having an active material layer on both sides may be used as it is as an outermost current collector. In addition, the arrangement of the positive electrode and the negative electrode is reversed from that in FIG. 1, so that the outermost layer negative electrode current collector is positioned on both outermost layers of the power generation element 21, and the outermost layer negative electrode current collector is disposed on one or both surfaces. A negative electrode active material layer may be disposed.

  In the present embodiment, the electrode (positive electrode or negative electrode) includes a self-supporting electrode. A self-supporting electrode secures the shape without a metal foil (current collector). In other words, the self-supporting electrode (self-supporting structure) can be structurally (or strength) secured with only the active material layer without the metal foil (current collector). However, even if it is a self-supporting electrode (self-supporting structure), the electrode element is a current collector (however, other than the metal foil, the mechanical strength is lower than that of the metal foil, and the metal deposited film or plated thin film that cannot secure the shape. In addition, a metal wiring or the like may be required) and an active material layer. The self-supporting electrode defined above includes an active material layer (positive electrode active material layer, negative electrode active material layer) and a current collector (positive electrode current collector, negative electrode current collector) formed directly on one side of the active material layer. And have. The active material layer includes a porous skeleton and an active material (positive electrode active material, negative electrode active material) held in the pores of the porous skeleton.

  In this specification, when it is described as “current collector”, it may refer to both a positive electrode current collector and a negative electrode current collector, or may refer to only one, or for a bipolar electrode of a bipolar battery. Sometimes refers to a current collector. Similarly, when describing as “active material layer”, both the positive electrode active material layer and the negative electrode active material layer may be referred to, or only one of them may be referred to. Similarly, when describing as "active material", both a positive electrode active material and a negative electrode active material may be pointed out, and only one side may be pointed out. Similarly, when describing as “electrode”, both the positive electrode and the negative electrode may be indicated, or only one of them may be indicated.

  The positive electrode current collector 11 and the negative electrode current collector 12 include one of a positive electrode current collector tab (positive electrode current collector plate) 25 and a negative electrode current collector tab (negative electrode current collector plate) 27 that are electrically connected to each electrode (positive electrode and negative electrode). The tip of each is attached. Further, the other end portions of the positive electrode current collecting tab 25 and the negative electrode current collecting tab 27 have a structure of being led out of the battery outer packaging material 29 so as to be sandwiched between the end portions of the battery outer packaging material 29. The positive electrode current collecting tab 25 and the negative electrode current collecting tab 27 are respectively connected to the positive electrode current collector 11 and the negative electrode current collector 11 of each electrode via electrode terminal leads (positive electrode terminal lead and negative electrode terminal lead) (not shown) as necessary. The electric body 12 may be attached by ultrasonic welding, resistance welding, or the like.

  Furthermore, as a characteristic configuration of the laminated battery 10 of the present embodiment, at least one of the melting point, the softening point, the thermal deformation temperature, and the deflection temperature under load of the resin layer 18 is the center side <the end side in the stacking direction. It is characterized by. Preferably, the melting point of the resin layer is such that the center side is less than the end side in the stacking direction. This is because the softening point, thermal deformation temperature, and deflection temperature under load generally have the same tendency as the melting point, and therefore, using only the melting point for which measurement data are already available for many resins, the center side < This is because it may be configured to be on the end side. Therefore, unless otherwise specified, including the above description of the effect of the present invention, the description will be made using the melting point of the resin layer.

  FIG. 2 is a partial cross-sectional view of the power generation element of the laminated battery, and schematically shows how heat is transferred when hot pressing is performed from above and below the power generation element of the laminated battery. It is. In addition, the arrow in a figure represents typically a mode that heat | fever transfers. As shown in FIG. 2, heat is propagated from the top and bottom (end) to the center (center side) of the power generation element 21 by hot pressing the power generation element 21 from above and below. Therefore, at the end side in the stacking direction, heat is transferred from the apparatus 20 quickly and becomes high temperature in a short time = easy to melt. On the other hand, in the central part in the stacking direction, it takes time to transfer heat from the apparatus 20, and within the time for the hot press process, the hot press is finished in a state in which it is not as hot as the end side and is not easily melted. Is done.

  Therefore, when the melting point of the resin layer is the center side = end side (all the same resin material) in the laminating direction, melting unevenness occurs in the laminating direction, and the resin layer is insufficiently melted and bonded in the central part in the laminating direction. There is a risk. As a result, the separator contracts in the event of abnormal heat generation and the ends of the opposing electrodes come into contact with each other, possibly causing a short circuit.

  In addition, when the melting point of the resin layer is the center side = end side (all the same resin material) in the stacking direction, and when the time for the hot press treatment is increased until the melting and adhesion of the center portion in the stacking direction is sufficient, A long-time load is applied to the end in the stacking direction at a high temperature. For this reason, the resin layer may be melted too much to maintain the desired thickness of the resin layer, or it may be difficult to maintain a desired porosity (pore size). For this reason, the porosity (space amount = electrolyte holding amount) and the size of pores (path width through which Li ions diffuse) change at the center side and at the end, and Li ions at the center side and at the end. There is a possibility that the conductivity changes and the ionic conductivity (= interelectrode resistance) becomes uneven in the stacking direction.

  Therefore, the configuration of the above-described embodiment, that is, the resin layer 18 having a high melting point (not easily melted (heat fusion)) is used on the end side of the laminated battery 10, and the melting point is low (melted) in the middle in the stacking direction. By using the resin layer 18 (which is easily heat-sealed), uneven melting can be prevented in the stacking direction. That is, as shown in FIG. 2, when the power generating element 21 is hot-pressed by the apparatus 20 for hot-pressing from above and below, a resin having a high melting point (not easily melted (heat-fused)) is formed on the end side of the laminated battery 10. Use layers. By doing so, a predetermined time is required for the resin layer 18 to become adhesive even at the end in the stacking direction, and the thickness of the resin layer and the pores (such as the porosity and the pore diameter) are changed. And can be appropriately melted and bonded within the hot press time. On the other hand, when the power generation element 21 is hot-pressed by the apparatus 20 for hot pressing from above and below, a resin layer having a low melting point (easily melted (heat-bonded)) is used on the center side of the laminated battery 10. By doing this, a predetermined time is sufficient until the resin layer 18 becomes adhesive on the center side in the laminating direction, and the thickness of the resin layer and the pores (such as the porosity and the pore diameter) are changed. And can be appropriately melted and bonded within the hot press time. As a result, it is possible to prevent melting unevenness in the stacking direction, and further, resin layer thickness and hole unevenness. Thereby, the resistance between electrodes can be kept uniform. Eventually, uneven reaction distribution for each single battery layer (single cell) 19 can be prevented, and the durability of the entire laminated battery 10 can be improved.

  Note that even the resin layer 18 on the center side, which is easily melted (heat-sealed), has a melting point higher than the temperature (usually about 95 ° C .; refer to the example) of the apparatus (jig) 20 for hot pressing the power generating element 21 from above and below. Resin having is used. This is because the softening start is lower than the temperature lower than the melting point of the resin layer 18. This is because the resins used for the resin layer 18 (including copolymers and polymer alloys) are not all the same (uniform) in molecular weight, molecular structure, resin shape, etc., and have a constant distribution. The surface of the resin layer is sufficiently softened (heat melted) at a temperature actually lower than the melting point obtained. For this reason, the adhesiveness can be obtained at a lower temperature, and can be sufficiently bonded to the electrode and the separator. However, since the temperature at which softening begins (temperature at which bonding is possible) is proportional to the melting point of the resin layer 18, the melting point of the resin layer 18 is melted in the stacking direction by setting the melting point of the resin layer 18 to the center side <the end side. Unevenness can be prevented and the above-described effects can be achieved.

  Here, as a preferable range of the difference in resistance between the center side (inner side: center portion) and the end side (outside: end portion) in the lamination direction, the melting point of the resin layer 18 achieves the object of the present embodiment and is desired. It is sufficient if the effects of can be achieved. That is, by increasing the melting point of the resin layer on the end side to make it difficult to melt (heat fusion) and lowering the melting point on the center side to facilitate melting (thermal fusion), Can be prevented. Thereby, the resistance between electrodes can be kept uniform. Thereby, the reaction distribution nonuniformity for every single battery layer (single cell) 19 can be prevented, and the durability of the laminated battery 10 as a whole can be improved.

  Specifically, although depending on the number of stacked single cells of the battery and the size of the electrode, the melting point of the resin layer on the end side in the stacking direction should be higher than the melting point of the central resin layer, preferably It is preferably 3 to 15 ° C higher, more preferably 5 to 10 ° C higher. If the melting point of the resin layer on the end side in the laminating direction is higher than the melting point of the resin layer in the central part by 3 ° C., preferably 5 ° C. or higher, the resin in the central part can be obtained by hot pressing, depending on the number of laminations. The layers can also be sufficiently bonded, and the occurrence of uneven melting in the stacking direction can be prevented. As a result, the above-described objects and effects can be achieved sufficiently. On the other hand, if the melting point of the resin layer on the end side in the laminating direction is higher than the melting point of the resin layer at the center by 15 ° C., preferably 10 ° C. or less, the outer side will be melted too much by hot pressing and crushed ( The desired resin layer thickness cannot be maintained, and adhesion can be performed while maintaining an appropriate porosity. Thereby, a favorable Li ion diffusion path can be secured, the inter-electrode resistance can be kept uniform, and the occurrence of uneven melting in the stacking direction can be prevented. As a result, the above-described objects and effects can be achieved sufficiently.

  The melting point, softening point, heat distortion temperature, and deflection temperature under load of the resin layer 18 can be measured by the following method.

(1) Melting point The melting point is determined from an endothermic peak when the temperature is raised at 20 ° C./min by a differential scanning calorimeter (DSC).

  Specifically, for example, using a differential scanning calorimeter manufactured by Seiko Electronics Co., Ltd., measurement is performed under the following conditions.

-Sample amount: about 5mg
・ Atmospheric gas: Nitrogen (flow rate 20ml / min)
Temperature condition: After maintaining at 230 ° C. for 10 minutes, the temperature is decreased to 30 ° C. at 10 ° C./min, and then the endothermic behavior of melting is measured when the temperature is increased at a rate of temperature increase of 10 ° C./min.

(2) Softening point The softening point temperature is a Vicat softening temperature (Vicat Softening Temperature, VST) and is measured according to JIS K7206. Explaining the outline of JIS K7206, a test piece of a prescribed size is set in a heating tub, and the temperature of the tub is adjusted with an end face of a constant cross-sectional area (1 mm ^{2 in} JIS K7206) pressed against the center. Raise. The temperature when the end surface bites into the test piece to a certain depth is the Vicat softening temperature (unit: ° C.).

(3) Thermal deformation temperature The thermal deformation temperature is based on the standard of ASTM D648. After resin pellets are molded into a thermal deformation temperature measurement specimen based on ASTM D648 with an injection molding machine and annealed at 80 ° C. for 24 hours. The temperature was measured under the condition of a low load of 4.6 kg / cm ² .

  In practice, a dumbbell test piece injection-molded under conditions of a molding temperature of 270 ° C. and a mold temperature of 80 ° C. using a Toshiba Machine IS55EPN injection molding machine was heat-treated at 120 ° C. for 5 hours, and then subjected to load according to ASTM D-648. The heat distortion temperature may be measured under the condition of 0.45 MPa.

(4) Deflection temperature under load Deflection temperature under load is measured at 1.81 MPa (18.5 kg load) using a 1/4 inch test piece by a method based on ASTM D648. Explaining the outline of ASTM-D648, the temperature of the sample is raised with the load determined by the test method standard applied, and the temperature at which the deflection becomes a constant value is defined as the deflection temperature under load. . In other words, a constant load is applied to the beam to obtain the temperature at which the displacement becomes a constant value, but the temperature at which the flexural modulus becomes 2,514 kgf / cm ² = 0.25 GPa (or 10,000 kgf / cm ² = 1 GPa) is applied. Let the deflection temperature.

  From the characteristics of the temperature change of the elastic modulus of the resin, the elastic modulus rapidly decreases when the glass transition point is exceeded, so the deflection temperature under load may be a temperature value close to the glass transition point.

  If the outline | summary of JIS 7191 is demonstrated, the both ends of the test piece of the dimension prescribed | regulated in the heating bathtub will be supported and installed, and the temperature of a bathtub will be raised in the state which applied the load to the center part. The temperature at which a certain amount of deflection occurs in the test piece is taken as the deflection temperature under load (unit: ° C) and is used as a heat resistance index. Since the test result depends on the size and load of the test piece, these values are also shown. In general, the deflection temperature under load (heat deformation temperature, Heat Defect Temperature, HDT) substantially correlates with the glass transition point in the case of an amorphous resin and the melting point in the case of a crystalline resin.

  The deflection temperature under load is one of the test methods for evaluating the heat resistance of the synthetic resin, and is also referred to as a heat distortion temperature.

  Hereinafter, each component (component) of the laminated battery 10 according to the present embodiment will be described. In addition, about each component (constituent member) of the laminated battery 10, it does not restrict | limit only to the following form, A conventionally well-known form may be employ | adopted similarly.

(1) Current collector The current collector is made of a conductive material, and an active material layer is disposed on one or both surfaces thereof. There is no particular limitation on the material constituting the current collector, and for example, a conductive resin in which a conductive filler is added to a metal or a conductive polymer material or a non-conductive polymer material may be employed.

  Examples of the metal include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil by which aluminum is coat | covered on the metal surface may be sufficient. Of these, aluminum, stainless steel, and copper are preferable from the viewpoint of conductivity and battery operating potential.

  As a form of the current collector using metal, a metal vapor deposition layer, a metal plating layer, a conductive primer layer, and a metal wiring may be used in addition to the metal foil. The metal vapor deposition layer and the metal plating layer can form (arrange) an extremely thin metal vapor deposition layer or metal plating layer on one surface of the active material layer by a vacuum vapor deposition method or various plating methods. As for the metal wiring, an extremely thin metal wiring can be formed (arranged) on one surface of the active material layer by vacuum vapor deposition or various plating methods. Further, a metal wiring can be impregnated with a primer layer and attached by thermocompression bonding. Furthermore, when a punching metal sheet or an expanded metal sheet is used as the metal wiring, an electrode slurry is applied to both sides of the punching metal sheet or the expanded metal sheet and dried, so that the metal wiring sandwiched between the active material layers (current collector) ) Can be arranged. Even when the metal foil is used, the metal foil (current collector) can be disposed on one side of the active material layer by applying and drying the electrode slurry on the metal foil (one side or both sides). The conductive primer layer is basically prepared by mixing a resin with carbon (chain, fiber) or metal filler (aluminum, copper, stainless steel, nickel powder, etc. used for the current collector material). be able to. The formulation varies. It can be formed (arranged) by applying and drying this on one side of the active material layer.

  The conductive primer layer includes a current collecting resin layer having conductivity. Preferably, the conductive primer layer is made of a current collecting resin layer having conductivity. In order for the conductive primer layer to have conductivity, specific modes are as follows: 1) the polymer material constituting the resin is a conductive polymer, 2) the current collecting resin layer is a resin and a conductive filler (conductive Material).

  The conductive polymer is selected from materials that are conductive and have no conductivity with respect to ions used as charge transfer media. These conductive polymers are considered to be conductive because the conjugated polyene system forms an energy band. As a typical example, a polyene-based conductive polymer that has been put into practical use in an electrolytic capacitor or the like can be used. Specifically, polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, polyoxadiazole, or a mixture thereof is preferable. Polyaniline, polypyrrole, polythiophene, and polyacetylene are more preferable from the viewpoint of electronic conductivity and stable use in the battery.

  The conductive filler (conductive material) used in the form 2) is selected from materials having conductivity. Preferably, from the viewpoint of suppressing ion permeation in the current collecting resin layer having conductivity, it is desirable to use a material that does not have conductivity with respect to ions used as the charge transfer medium.

  Specific examples include, but are not limited to, aluminum materials, stainless steel (SUS) materials, carbon materials, silver materials, gold materials, copper materials, and titanium materials. These conductive fillers may be used alone or in combination of two or more. Moreover, these alloy materials may be used. Silver material, gold material, aluminum material, stainless steel material, carbon material is preferable, and carbon material is more preferable. Further, these conductive fillers (conductive materials) may be those obtained by coating a conductive material (the above-mentioned conductive material) around the particle ceramic material or resin material with plating or the like.

  Examples of the carbon material include at least one selected from the group consisting of acetylene black, vulcan, black pearl, carbon nanofiber, ketjen black, carbon nanotube, carbon nanohorn, carbon nanoballoon, hard carbon, and fullerene. Can be mentioned. These carbon materials have a very wide potential window, are stable in a wide range with respect to both the positive electrode potential and the negative electrode potential, and are excellent in conductivity. Also, since the carbon material is very lightweight, the increase in mass is minimized. Furthermore, since carbon materials are often used as conductive aids for electrodes, even if they come into contact with these conductive aids, the contact resistance is very low because of the same material. When carbon materials are used as conductive particles, it is possible to reduce the compatibility of the electrolyte by applying a hydrophobic treatment to the surface of the carbon, making it difficult for the electrolyte to penetrate into the current collector holes. is there.

  The shape of the conductive filler (conductive material) is not particularly limited, and a known shape such as a particle shape, a powder shape, a fiber shape, a plate shape, a lump shape, a cloth shape, or a mesh shape can be appropriately selected. For example, when it is desired to impart conductivity to a resin over a wide range, it is preferable to use a particulate conductive material. On the other hand, when it is desired to further improve the conductivity in a specific direction in the resin, it is preferable to use a conductive material having a certain direction in the shape of a fiber or the like.

  Although the average particle diameter of a conductive filler is not specifically limited, It is desirable that it is about 0.01-10 micrometers. In the present specification, “particle diameter” means the maximum distance L among the distances between any two points on the contour line of the conductive filler. As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted. Particle diameters and average particle diameters of active material particles to be described later can be defined similarly.

  In the case where the current collecting resin layer includes a conductive filler, the resin forming the current collecting resin layer is made of a non-conductive polymer material that binds the conductive filler in addition to the conductive filler. May be included. By using a non-conductive polymer material as the constituent material of the current collecting resin layer, the binding property of the conductive filler can be increased and the reliability of the battery can be increased. The polymer material is selected from materials that can withstand the applied positive electrode potential and negative electrode potential.

  Examples of polymer materials having no electrical conductivity are preferably polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyethernitrile (PEN), polyimide (PI), polyamide ( PA), polyamideimide (PAI), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC) ), Polyvinylidene fluoride (PVdF), polyvinylidene chloride (PVDC), or mixtures thereof. These materials have a very wide potential window and are stable to both positive and negative electrode potentials. In addition, since it is lightweight, it is possible to increase the output density of the battery.

  The content of the conductive filler is not particularly limited. In particular, when the resin includes a conductive polymer material and sufficient conductivity can be secured, it is not always necessary to add a conductive filler. However, when the resin is made of only a nonconductive polymer material, it is essential to add a conductive filler in order to impart conductivity. The content of the conductive filler at this time is preferably 5 to 90% by mass, more preferably 30 to 85% by mass, and still more preferably 50 to 90% by mass with respect to the total mass of the nonconductive polymer material. 80% by mass. By adding such an amount of conductive filler to the resin, sufficient conductivity can be imparted to the non-conductive polymer material while suppressing an increase in the mass of the resin.

  The conductive primer layer may contain other additives in addition to the conductive filler and the resin, but preferably includes the conductive filler and the resin.

  Among the materials constituting the current collector, examples of the conductive polymer material include polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, and polyoxadiazole. . Since such a conductive polymer material has sufficient conductivity without adding a conductive filler, it is advantageous in terms of facilitating the manufacturing process or reducing the weight of the current collector.

  Examples of non-conductive polymer materials include polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE)), polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), polyimide ( PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), Examples include polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), and polystyrene (PS). Such a non-conductive polymer material may have excellent potential resistance or solvent resistance.

  A conductive filler may be added to the conductive polymer material or the non-conductive polymer material as necessary. In particular, when the resin used as the base material of the current collector is made of only a non-conductive polymer, a conductive filler is inevitably necessary to impart conductivity to the resin. The conductive filler can be used without particular limitation as long as it is a substance having conductivity. For example, metals, conductive carbon, etc. are mentioned as a material excellent in electroconductivity, electric potential resistance, or lithium ion barrier | blocking property. The metal is not particularly limited, but at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, Sb, and K, or these metals. It is preferable to include an alloy or metal oxide. Further, the conductive carbon is not particularly limited, but is at least one selected from the group consisting of acetylene black, vulcan, black pearl, carbon nanofiber, ketjen black, carbon nanotube, carbon nanohorn, carbon nanoballoon, and fullerene. Preferably it contains seeds. The amount of the conductive filler added is not particularly limited as long as it is an amount capable of imparting sufficient conductivity to the current collector, and is generally about 5 to 35% by mass.

  The size of the current collector is determined according to the intended use of the battery. For example, if it is used for a large battery that requires a high energy density, a current collector having a large area is used.

  The thickness of the current collector is preferably 1 to 100 μm, more preferably 3 to 80 μm, and still more preferably 5 to 40 μm. The self-standing electrode described later can be made thin, and is preferably 1 to 18 μm, more preferably 2 to 15 μm, and still more preferably 3 to 13 μm. This can be produced without going through a conventional coating / drying process when producing a free-standing electrode. Therefore, when a current collector is used for a metal vapor deposition layer, metal plating layer, conductive primer layer or metal wiring that does not need to undergo the conventional coating / drying process, the tension required in the coating / drying process is required. There is no need to have strength. Accordingly, the thickness of the current collector can be reduced as necessary, and the degree of freedom in designing the current collector is improved, which contributes to the weight reduction of the electrodes, and hence the battery.

  When using a punching metal sheet or an expanded metal sheet having a plurality of through holes as a current collector, the through holes have a quadrilateral shape, a rhombus shape, a turtle shell shape, a hexagonal shape, a round shape, a square shape, a star shape, and a cross shape. Examples include shapes. A so-called punching metal sheet or the like is formed by pressing a large number of holes having such a predetermined shape, for example, in a staggered arrangement or a parallel arrangement. A so-called expanded metal sheet or the like is formed by stretching a sheet with staggered cuts to form a large number of substantially diamond-shaped through holes.

  When the current collector having the plurality of through holes described above is used for the current collector, the aperture ratio of the through holes of the current collector is not particularly limited. However, the lower limit of the aperture ratio of the current collector is preferably 10 area% or more, more preferably 30 area% or more, further preferably 50 area% or more, more preferably 70 area% or more, and further preferably 90 area. % Or more. Thus, in the electrode of this embodiment, a current collector having an aperture ratio of 90 area% or more can also be used. Moreover, as an upper limit, it is 99 area% or less, or 97 area% or less, for example. As described above, the stacked structure battery 10 including the electrodes formed with the current collector having a significantly large aperture ratio can significantly reduce the weight, and thus can increase the capacity. The density can be increased.

  When the current collector having the plurality of through holes is used as the current collector, the diameter (opening diameter) of the through holes of the current collector is not particularly limited as well. However, the lower limit of the opening diameter of the current collector is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 50 μm or more, and particularly preferably 150 μm or more. As an upper limit, it is 300 micrometers or less, for example, Preferably, it is about 200 micrometers or less. In addition, the opening diameter here is the diameter of the circumscribed circle of the through hole = opening. The diameter of the circumscribed circle is obtained by observing the surface of the current collector with a laser microscope or a tool microscope, fitting the circumscribed circle to the opening, and averaging the results.

(2) Electrode (Positive Electrode and Negative Electrode) and Electrode Active Material Layer The positive electrode and the negative electrode have a function of generating electric energy by transferring lithium ions. The positive electrode essentially includes a positive electrode active material, and the negative electrode active essentially includes a negative electrode active material.

  In the case of a laminated battery, these electrode structures are structures in which an active material layer containing an active material is formed on the surface of the current collector as shown in FIG. On the other hand, in the case of a bipolar secondary battery (bipolar electrode), a positive electrode active material layer containing a positive electrode active material is formed on one surface of a current collector, and a negative electrode active material containing a negative electrode active material on the other surface. It has a structure in which a material layer is formed. That is, the positive electrode (positive electrode active material layer) and the negative electrode (negative electrode active material layer) are integrated with each other through the current collector. In addition to the active material, the active material layer may contain a conductive additive, a binder, and an additive such as an electrolyte salt (lithium salt) or an ion conductive polymer as an electrolyte as necessary.

(2a) Positive electrode active material As a positive electrode active material, a conventionally well-known thing can be used.

Examples of the positive electrode active material include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni, Co, Mn) O ₂ , Li ₂ MnO ₃ , Li ₂ MnO ₃ —LiMO ₂ (M = Co, Ni, etc.) ) Lithium-transition metal composite oxides such as solid solutions and those in which some of these transition metals are substituted with other elements, lithium-transition metal phosphate compounds, lithium-transition metal sulfate compounds, and the like. In some cases, two or more positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material from the viewpoint of capacity and output characteristics. Of course, positive electrode active materials other than those described above may be used. In addition, a positive electrode active material having a high energy density such as LiNiO ₂ , Li (Ni, Co, Mn) O ₂ , or Li ₂ MnO ₃ is easy to increase the capacity of the battery. It is also advantageous in that the travel distance can be extended.

  The average particle size of the positive electrode active material is not particularly limited, but is preferably 1 to 25 μm from the viewpoint of increasing the output.

  The amount of the positive electrode active material is not particularly limited, but is preferably 50 to 99% by mass, more preferably 70 to 97% by mass, and still more preferably 80 to 96% by mass with respect to the total amount of the raw material for forming the positive electrode active material layer. Range.

(2b) Negative electrode active material A negative electrode active material has a composition which can discharge | release lithium ion at the time of discharge and can occlude lithium ion at the time of charge. The negative electrode active material is not particularly limited as long as it can reversibly occlude and release lithium. Examples of the negative electrode active material include metals such as Si and Sn, TiO, Ti ₂ O ₃ , TiO ₂ , or Metal oxides such as SiO ₂ , SiO, SnO ₂ , complex oxides of lithium and transition metals such as Li _4/3 Ti _5/3 O ₄ or Li ₇ MnN, Li—Pb alloys, Li—Al alloys , Li, or carbon materials such as natural graphite, artificial graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, or hard carbon. Among these, by using an element that forms an alloy with lithium, it becomes possible to obtain a battery having a high capacity and an excellent output characteristic having a higher energy density than that of a conventional carbon-based material. The negative electrode active material may be used alone or in the form of a mixture of two or more. The element alloying with lithium is not limited to the following, but specifically, Si, Ge, Sn, Pb, Al, In, Zn, H, Ca, Sr, Ba, Ru, Rh, Ir, Pd, Pt, Ag, Au, Cd, Hg, Ga, Tl, C, N, Sb, Bi, O, S, Se, Te, Cl, and the like.

  Among the active materials, it preferably contains a carbon material and / or at least one element selected from the group consisting of Si, Ge, Sn, Pb, Al, In, and Zn. Or it is more preferable that the element of Sn is included. Of the carbon materials, it is more preferable to use graphite having a low lithium relative discharge potential.

  When the negative electrode active material is used as a negative electrode, the negative electrode active material layer containing the negative electrode active material may be formed into a plate shape and used as it is, or the negative electrode active material containing the negative electrode active material particles on the surface of the current collector. A material layer may be formed to form a negative electrode. The average particle diameter of the negative electrode active material particles in the latter form is not particularly limited, but is preferably 1 to 100 μm from the viewpoint of high capacity, reactivity, and cycle durability of the negative electrode active material, and further increase the output. From the viewpoint, the thickness is more preferably 1 to 25 μm. Within such a range, the secondary battery can suppress an increase in the internal resistance of the battery during charging and discharging under high output conditions, and can extract a sufficient current. In addition, when the negative electrode active material is secondary particles, it can be said that the average particle diameter of primary particles constituting the secondary particles is desirably in the range of 10 nm to 1 μm. It is not limited to. However, it goes without saying that, depending on the manufacturing method, the negative electrode active material may not be a secondary particle formed by aggregation, lump or the like. As the particle size of the negative electrode active material and the particle size of the primary particles, the median diameter obtained using a laser diffraction method can be used. The shape of the negative electrode active material particles varies depending on the type and manufacturing method, and examples thereof include a spherical shape (powdered shape), a plate shape, a needle shape, a column shape, and a square shape, but are not limited thereto. Any shape can be used without any problem. Preferably, an optimal shape that can improve battery characteristics such as charge / discharge characteristics is appropriately selected.

  The amount of the negative electrode active material is not particularly limited, but is preferably 50 to 99% by mass, more preferably 70 to 97% by mass, and still more preferably 80 to 96% by mass with respect to the total amount of the negative electrode active material layer forming raw material. Range.

(2b) Conductive aid The conductive aid refers to an additive blended to improve the conductivity of the active material layer. Examples of the conductive aid include carbon powders such as acetylene black, carbon black, ketjen black, and graphite, various carbon fibers such as vapor grown carbon fiber (VGCF; registered trademark), expanded graphite, and the like. However, it goes without saying that the conductive aid is not limited to these. When the active material layer contains a conductive additive, an electronic network inside the active material layer is effectively formed, which can contribute to improvement of the output characteristics of the battery.

  The content of the conductive additive mixed in the positive electrode active material layer is 1% by mass or more, more preferably 3% by mass or more, and further preferably 5% by mass or more, with respect to the total amount of the positive electrode active material layer forming raw material. Range. In addition, the content of the conductive additive mixed in the positive electrode active material layer is 15% by mass or less, more preferably 10% by mass or less, and further preferably 7% by mass with respect to the total amount of the positive electrode active material layer forming raw material. % Or less. By defining the compounding ratio (content) of the conductive auxiliary agent in the positive electrode active material layer within the above range, the electronic conductivity of the active material itself is low and the electrode resistance can be reduced by the amount of the conductive auxiliary agent. Is done. That is, the effect of this embodiment can be expressed without inhibiting the electrode reaction. In addition, the electronic conductivity can be sufficiently secured, the decrease in energy density due to the decrease in electrode density can be suppressed, and as a result, the energy density can be improved due to the increase in electrode density.

The content of the conductive additive mixed into the negative electrode active material layer cannot be uniquely defined because it varies depending on the negative electrode active material. That is, when a carbon material such as graphite (graphite), soft carbon, hard carbon, or a metal material is used, in which the negative electrode active material itself has excellent electronic conductivity, the inclusion of the conductive assistant in the negative electrode active material layer is There is no particular need. Even if it contains a conductive additive, a range of 0.1 to 1% by mass at most is sufficient with respect to the total amount of the electrode constituting material on the negative electrode side. On the other hand, like the positive electrode active material, the electronic conductivity is low, and the electrode resistance can be reduced by the amount of the conductive auxiliary. In the case of using a negative electrode active material such as a lithium alloy negative electrode material or a lithium-transition metal composite oxide (for example, Li ₄ Ti ₅ O ₁₂ ), the content of the conductive additive mixed in the positive electrode active material layer and It is desirable to have the same content. That is, the content of the conductive additive mixed in the negative electrode active material layer is also preferably 1 to 10% by mass, more preferably 2 to 8% by mass, particularly preferably relative to the total amount of the electrode constituent material on the negative electrode side. Is preferably in the range of 3 to 7% by mass.

(2c) Binder (binder)
The binder is added for the purpose of maintaining the electrode structure by binding the constituent members in the active material layer or the active material layer and the current collector. The binder is not particularly limited as long as it is an insulating material that can achieve the above-described purpose and does not cause a side reaction (oxidation-reduction reaction) at the time of charge / discharge, and examples thereof include the following materials. Polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), isoprene Rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and its hydrogenated product, styrene / isoprene / styrene block copolymer and its hydrogenated product, etc. Thermoplastic polymer, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Tet Fluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyfluorinated Fluorine resin such as vinyl (PVF), vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-TFE-based fluorine) Rubber), vinylidene fluoride-pentafluoropropylene-based fluoro rubber (VDF-PFP-based fluoro rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluoro rubber (VDF-PFP-TFE fluoro rubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluoro rubber (VDF-PFMVE-TFE fluoro rubber), vinylidene fluoride-chlorotrifluoroethylene fluoro rubber (VDF) Vinylidene fluoride fluororubbers such as (-CTFE fluororubber) and epoxy resins. Among these, polyvinylidene fluoride, polyimide, styrene / butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable. These suitable binders are excellent in heat resistance, have a very wide potential window, are stable at both the positive electrode potential and the negative electrode potential, and can be used for the active material layer. These binders may be used independently and may use 2 or more types together. However, it goes without saying that the binder is not limited to these.

  The amount of the binder is not particularly limited as long as it is an amount capable of binding the active material or the like, but preferably 0.5 to 15% by mass with respect to the total amount of the electrode active material layer forming raw material. More preferably, it is 1-10 mass%.

(2d) Electrolyte salt (lithium salt)
Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like. Furthermore, an electrolyte salt (lithium salt) used for an electrolyte layer described later can be appropriately used.

(2e) Ion conductive polymer Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers. Furthermore, an electrolyte salt (lithium salt) used for an electrolyte layer described later can be appropriately used.

(2f) Porous skeleton used for self-supporting electrode As the porous skeleton, nonwoven fabric, woven fabric, metal foam (or porous metal), carbon paper, and the like are desirable. Among these, the nonwoven fabric used for the porous skeleton is formed by overlapping fibers in different directions. A resin material is used for the nonwoven fabric, and fibers such as polypropylene, polyethylene, polyethylene terephthalate, cellulose, nylon, EVA resin (ethylene-vinyl acetate copolymer resin), and the like can be applied. Examples of the porous skeleton body other than the nonwoven fabric include resin woven fabric (regular resin porous body), metal foam or metal porous body, and carbon paper. Here, examples of the resin used for the woven fabric made of resin include polypropylene, polyethylene, polyethylene terephthalate, EVA resin, and the like, but are not limited thereto. Preferred examples of the metal foam or metal porous body include, but are not limited to, at least one metal foam or metal porous body of Cu, Ni, Al, and Ti. Preferably, it is a nonwoven fabric made of at least one metal porous body of Cu and Al, carbon paper, polypropylene, polyethylene, and EVA resin.

  The proportion of the porous skeleton in the skeleton part in the active material layer is in the range of 2% by volume or more, preferably 7% by volume or more. On the other hand, the proportion of the porous skeleton in the skeleton part in the active material layer is 28% by volume or less, preferably 12% by volume or less. If the ratio of the porous skeleton in the active material layer is within the above range, the electrode reaction is not hindered.

  The porosity (porosity) of the porous skeleton is preferably 70% to 98%, more preferably 90 to 95%. If it is in the said range, it is excellent in the point from which the effect of invention is acquired effectively.

  The pore size of the porous skeleton is preferably about 50 to 100 μm that can be sufficiently filled with active materials used in the world. If it is in the said range, it is excellent in the point from which the effect of invention is acquired effectively. That is, if the pore size of the porous skeleton is 100 μm or less, the effect of the present embodiment can be obtained effectively. If the pore size is 50 μm or more, the particle size of the active material to be used can be used without any restrictions. Accordingly, it is excellent in that an appropriate active material can be appropriately selected.

  The thickness of the porous skeleton need only be smaller than the thickness of the active material layer, and is usually about 1 to 120 μm, preferably about 1 to 20 μm.

  Although there is no restriction | limiting in particular also about the thickness of each active material layer, From a viewpoint of suppressing electronic resistance, it is preferable that the thickness (one side) of each active material layer is about 1-120 micrometers.

  With respect to the porosity of each active material layer, the porosity of each active material layer is 10 from the viewpoint of increasing the conductivity (diffusibility) of Li ions by impregnating and holding the electrolytic solution and suppressing the electronic resistance. It is preferably about ˜40%.

(3) Electrolyte layer The electrolyte layer of this embodiment consists of an electrolyte and a separator formed by impregnating or holding the electrolyte in pores. The electrolyte layer having a separator functions as a spatial partition (spacer) between the positive electrode and the negative electrode. In addition, it also has a function of holding an electrolyte that is a lithium ion transfer medium between the positive and negative electrodes during charging and discharging. Furthermore, in this embodiment, the short circuit due to the thermal contraction of the separator can be prevented by bonding the separator and the electrode using the resin layer 18 as described above.

  There is no restriction | limiting in particular in the electrolyte which comprises an electrolyte layer, Polymer electrolytes, such as a liquid electrolyte and a polymer gel electrolyte and a polymer solid electrolyte, can be used suitably.

(3a) Liquid electrolyte The liquid electrolyte is obtained by dissolving a lithium salt as a supporting salt in a solvent. Examples of the solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propionate (MP), methyl acetate (MA), and methyl formate (MF). 4-methyldioxolane (4MeDOL), dioxolane (DOL), 2-methyltetrahydrofuran (2MeTHF), tetrahydrofuran (THF), dimethoxyethane (DME), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) , And γ-butyrolactone (GBL). These solvents may be used alone or as a mixture of two or more. As the supporting salt (lithium salt) is not particularly _{limited, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiSbF 6, LiAlCl 4, Li 2 B 10 Cl 10, LiI, LiBr, LiCl Inorganic acid anion salts such as LiAlCl, LiHF ₂ , LiSCN, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiBOB (lithium bisoxide borate), LiBETI (lithium bis (perfluoroethylenesulfonylimide); And organic acid anion salts such as Li (C ₂ F ₅ SO ₂ ) ₂ N). These electrolyte salts may be used alone or in the form of a mixture of two or more.

  On the other hand, the polymer electrolyte is classified into a gel electrolyte containing an electrolytic solution and a polymer solid electrolyte containing no electrolytic solution.

(3b) Gel electrolyte The gel electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer having lithium ion conductivity. Examples of the matrix polymer having lithium ion conductivity include a polymer having polyethylene oxide in the main chain or side chain (PEO), a polymer having polypropylene oxide in the main chain or side chain (PPO), polyethylene glycol (PEG), poly Acrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), polyacrylonitrile (PAN), poly (methyl acrylate) (PMA), poly (Methyl methacrylate) (PMMA) etc. are mentioned. In addition, mixtures of the above-described polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, and the like can also be used. Among these, it is desirable to use PEO, PPO and their copolymers, PVdF, PVdF-HFP. In such a matrix polymer, an electrolyte salt such as a lithium salt can be well dissolved.

(3c) Polymer solid electrolyte The polymer solid electrolyte has a structure in which a supporting salt (lithium salt) is dissolved in the above matrix polymer, and does not contain an organic solvent. Therefore, when the electrolyte layer is composed of a polymer solid electrolyte, there is no fear of liquid leakage from the battery, and the battery reliability can be improved.

  A matrix polymer of a polymer gel electrolyte or a polymer solid electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. are performed on a polymerizable polymer (for example, PEO or PPO) for forming a polymer electrolyte, using an appropriate polymerization initiator. A polymerization treatment may be performed. In addition, the said electrolyte may be contained in the active material layer of an electrode.

(3d) Separator The separator is not particularly limited, and conventionally known separators can be appropriately used. For example, a porous sheet separator or nonwoven fabric separator made of a polymer or fiber that absorbs and holds the electrolyte can be used.

  As the separator of the porous sheet made of the polymer or fiber, for example, a microporous (microporous film) can be used. Specific examples of the porous sheet made of the polymer or fiber include polyolefins such as polyethylene (PE) and polypropylene (PP); a laminate in which a plurality of these are laminated (for example, three layers of PP / PE / PP) And a microporous (microporous membrane) separator made of a hydrocarbon resin such as polyimide, aramid, polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), glass fiber, and the like.

  The thickness of the microporous (microporous membrane) separator cannot be uniquely defined because it varies depending on the intended use. For example, in applications such as secondary batteries for driving motors such as electric vehicles (EV), hybrid electric vehicles (HEV), and fuel cell vehicles (FCV), it is 4 to 60 μm in a single layer or multiple layers. Is desirable. The microporous (microporous membrane) separator preferably has a fine pore diameter of 1 μm or less (usually a pore diameter of about several tens of nanometers) and a porosity (porosity) of 20 to 80%. .

  As the nonwoven fabric separator, cotton, rayon, acetate, nylon, polyester; polyolefins such as PP and PE; conventionally known ones such as polyimide and aramid are used alone or in combination. The bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte.

  The nonwoven fabric separator preferably has a porosity (porosity) of 45 to 90%. Furthermore, the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer, preferably 5 to 200 μm, particularly preferably 10 to 100 μm. When the thickness is less than 5 μm, the electrolyte retention deteriorates, and when it exceeds 200 μm, the resistance increases.

(4) Resin layer The resin layer may be any one that is provided for the purpose of adhering to both the electrode (positive electrode or negative electrode) and the separator and preventing a short circuit due to thermal contraction of the separator.

  The material used for the resin layer is not particularly limited as long as it is an insulating material that can achieve the above-described purpose and does not cause a side reaction (oxidation-reduction reaction) at the time of charge and discharge. Is mentioned. Olefin resins such as polyethylene (PE) and polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), ethylene-vinyl acetate copolymer, polychlorinated Vinyl, styrene / butadiene rubber (SBR), isoprene rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and hydrogenated products thereof, styrene / isoprene / styrene Thermoplastic polymers such as block copolymers and hydrogenated products thereof, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), Lafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychloro Fluoropolymers such as trifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), Vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluorine rubber (VDF-HFP-TFE fluorine rubber), vinylidene fluoride-pentafluoropropylene fluorine rubber (VDF) PFP-based fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride-perfluoromethylvinylether-tetrafluoroethylene-based fluororubber (VDF-PFMVE) -TFE fluorine rubber), vinylidene fluoride-chlorotrifluoroethylene fluorine rubber (VDF-CTFE fluorine rubber) and other vinylidene fluoride fluorine rubber, epoxy resin, (meth) acrylic resin, aramid, etc. . Among these, polyvinylidene fluoride, polyimide, styrene / butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable. The materials used for these suitable resin layers are excellent in heat resistance, have a very wide potential window, are stable at both the positive electrode potential and the negative electrode potential, and can be used for the resin layer. The material used for these resin layers may be used independently and may use 2 or more types together. However, it goes without saying that the material used for the resin layer is not limited thereto. Among these, for example, polyvinylidene fluoride (PVdF), (meth) acrylic resin, olefinic resin, and the like are applicable to any of them because they have high potential on either the positive electrode side or the negative electrode side. SBR or the like is preferably used on the negative electrode side because it is strong against the negative electrode potential. Furthermore, PTFE is preferably used on the positive electrode side because it is resistant to the positive electrode potential.

  In the present embodiment, it is desirable that at least one resin layer in the stacking direction, preferably all the resin layers 18 include polyvinylidene fluoride (PVDF). By constituting the resin layer 18 of each single battery layer (single cell) 19 with a material containing PVDF or PVDF, the bonding temperature (temperature at which the surface of the resin layer begins to soften and has adhesiveness; softening point temperature) is a separator. It can be set at a temperature lower than the deformation temperature range (softening point temperature). Therefore, since the battery reaction is not inhibited as much as possible, there is a further effect on the output characteristics. Furthermore, PVDF and PVDF-containing materials have a large amount of modification from the softening start temperature, and can be bonded immediately, so that the hot press time can be shortened or the hot press temperature can be set low.

Moreover, as a material containing PVDF, a homopolymer of PVDF, a material in which a substituent (for example, a carboxyl group) is introduced into a part of PVDF (for example, a side chain of a repeating unit), PVDF and one or more other materials Random, block, alternating, graft copolymer (binary copolymer, ternary copolymer, quaternary copolymer, etc.) with polymer, PVDF and one or more other (co) polymers Examples thereof include polymer alloys. Among them, PVDF mixed with a carboxyl group (for example, a structure having a carboxyl group partially in the side chain; — (CH (COOH) —CF ₂ ) _n —, or — (CH ₂ —CF (COOH) ) _n -, or _{- (CH 2 -CF 2 -)} n - (CH (COOH) -CF 2) m -, or _{- (CH 2 -CF 2 -)} n - (CH 2 -CF (COOH)) m -Etc.) is desirable. Melting point can be lowered (adjusted) by 1 to 10 ° C. by mixing carboxyl groups into PVDF, and melting point deviation (= resin layer on end side and center side) by adjusting the amount of carboxyl groups mixed in ) Is excellent in that it can be made easily. However, in order to exert the effect of the present invention, it is sufficient to lower the temperature by about 10 ° C., and preferably a material having a melting point lower by about 2 to 3 ° C.

  In the present embodiment, the resin layer 18 preferably contains styrene-butadiene rubber (SBR). In the case of SBR, since it is a copolymer of styrene and butadiene, increasing the proportion of styrene can raise the melting point by about 1 to 10 ° C. Therefore, the deviation in melting point (= resin layer on the end side and the center side) It is excellent in that it can be easily made.

  It is desirable that the thickness of the resin layer be as thin as possible within the range in which the above-described object can be achieved, because it is possible to suppress an increase in the diffusion distance of Li ions and contribute to the weight reduction of the battery. Particularly in the present embodiment, the melting point is changed without changing the thickness of the resin layer between the end side and the center side in the stacking direction (= without changing the thickness of the resin layer of each single cell layer). The purpose and effect of the period can be realized. As a result, there is no need to change production facilities (particularly thickness adjustment), and the production efficiency is excellent. From this point of view, the thickness of the resin layer depends on the form of the resin layer, but is 0.1 to 5 μm, preferably 1 to 2 μm when the resin layer is present on the entire surface of the separator and electrode (entire surface). Range. If the thickness of the resin layer is 0.1 μm or more, it is preferable because production is easy, and if the thickness of the resin layer is 5 μm or less, it is preferable because there is little possibility of adversely affecting the load characteristics of the battery.

  Moreover, when the resin part (resin layer) exists in stripes or dots on the entire surface of the separator and the electrode, the thickness of the resin layer is in the range of 0.1 to 5 μm, preferably in the range of 1 to 2 μm. It is. If the thickness of the resin layer is 0.1 μm or more, it is preferable because production is easy, and if the thickness of the resin layer is 5 μm or less, it is preferable because there is little possibility of adversely affecting the load characteristics of the battery.

  The thickness of the resin layer can be measured from a cross-sectional image of an SEM (scanning electron microscope) by disassembling the battery, taking out a cross-section because the resin layer is brittle and cannot be peeled off.

  The porosity of the resin layer (also referred to as the porosity) depends on the separator porosity and the form of the resin layer, but when the resin layer is present on the entire surface of the separator and the electrode (entire surface), stripes or dots When the resin part exists in the shape, it is 60% or more, preferably 60 to 90%. By setting it to 60% or more, it is excellent in that it does not hinder the diffusion of Li ions. In addition, the porosity of the resin layer mentioned above is an example when the separator porosity is about 45 to 55%, and when the porosity of the separator increases or decreases, the porosity of the resin layer May be increased or decreased in proportion to this. Thus, the porosity of the resin layer is slightly higher than the porosity of the separator (see Examples) so that the diffusion of Li ions is not inhibited by the presence of the resin layer formed on the electrode surface. It is to do. In this embodiment, the melting point is changed between the end side and the center side in the stacking direction without changing the porosity of the resin layer (= without changing the porosity of the resin layer of each single cell layer). By doing so, the intended purpose and effect can be realized. This eliminates the need to change production equipment and raw materials (adjustment of porosity by adjusting the viscosity of the slurry for resin layer formation), and is excellent in production efficiency.

  On the other hand, when the resin part is provided in the form of dots and the ratio of the resin part is very small, the porosity of the resin part (resin layer) should be rather small, preferably 10% or less, preferably 0 %. This is because the non-resin part having a large ratio functions effectively as a new electrolyte solution holding part. The proportion of the resin portion when the proportion of the resin portion is very small may be appropriately determined in consideration of adhesiveness and battery performance. However, as described above, there is no particular problem even if the porosity of the resin portion (resin layer) is 60% or more, preferably 60 to 90%.

  The porosity existing in the resin layer can be measured using a mercury intrusion method or the like after disassembling the battery, taking out each resin layer, washing and removing the electrolyte, and drying. However, if the resin layer is brittle and cannot be peeled off well, disassemble the battery, take out the cross section, and count (measure) the space part of the resin layer from the cross-sectional image of the SEM (scanning electron microscope) by mapping. You can also.

  Moreover, the ratio of the resin part (or non-resin part) present on the separator and the electrode surface is obtained by disassembling the battery, taking out a cross section, and counting (measuring) the adhesion part (dot) from the cross-sectional image of the SEM by mapping. It can be calculated by

  The form of the resin layer is not particularly limited as long as the above object can be achieved. For example, (i) the resin layer may exist on the entire surface (entire surface) of the separator and the electrode. In this case, the resin portion needs to be a porous layer so as to have a liquid retaining space (see the porosity). Alternatively, (ii) the resin layer may be present on the separator and the electrode surface at intervals so that a resin part where the resin layer exists and a non-resin part where the resin layer does not exist are formed. It is desirable that the resin portion be disposed so that uniformity is maintained on the separator and the electrode surface. In the case of (ii) above, since the non-resin portion functions effectively as a liquid retention space, the resin portion (resin layer) may be a porous layer having a liquid retention space. Alternatively, it may be nonporous (= porosity (porosity) 0%) in which no liquid retention space exists. In particular, when the resin part is provided in a dot shape (= the ratio of the resin part is very small), the resin part is made nonporous (= porosity (porosity) 0%) in which no liquid retention space exists. It is good.

  FIG. 3A is a plan view illustrating a state in which a stripe-shaped resin portion is provided on the electrode surface. 3B and 3C are plan views showing a state in which a dot-shaped resin portion is provided on the electrode surface.

  Specifically, (iii) As shown in FIG. 3A, a non-resin portion 35 is formed on the separator and electrode surface 31 between the stripe-shaped resin portion 33a and the stripe (33a) stripe (33a). The resin layer (33a) may exist at intervals. (Iib) As shown in FIGS. 3B and 3C, the resin layer is formed so that the non-resin portion 35 is formed between the dot-shaped resin portion 33 b and the dots (33 b) and dots (33 b) on the separator and electrode surface 31. (33b) may be present at intervals. As an example of (iib), (b1) The dot-shaped resin part 33b exists only in the four corners of the separator and the electrode surface 31, and the non-resin part 35 is formed on the separator and the electrode surface 31 other than the four corner dots (resin part 33b). The resin layers may be present at intervals so as to form (FIG. 3B). Alternatively, (b2) dot-like resin portions 33b are scattered on the separator and electrode surface 31 so as to maintain uniformity, and the non-resin portion 35 is formed on the separator and electrode surface 31 between the dots (33b) and (33b). The resin layers may be present at intervals so as to be formed. For example, on the separator and electrode surface 31, a total of 12 dot-like resin portions 33b with 3 horizontal points × 4 vertical points are scattered at equal intervals, and the separator and electrode surfaces other than 12 dot (resin portion 33b) A resin layer may be present at a distance so that a non-resin portion 35 is formed on 31 (FIG. 3C). However, it is not limited to these forms at all, such as a lattice shape, a rhombus lattice shape, a strip shape, a ring shape such as a continuous or discontinuous circle or ellipse, a polygonal shape, a wave shape, a semicircular shape, an indefinite shape, etc. Any other form may be used as long as the above object can be achieved.

  Moreover, in this embodiment, it is preferable that the softening point of the resin layer is lower than the softening point of the separator. This is because it is excellent in that the electrode-separator can be sufficiently adhered by softening the surface of the resin layer and maintaining adhesion while maintaining the shape of the separator. From this viewpoint, it is desirable that the softening point of the resin layer on the center side in the stacking direction having the lowest softening point is lower than the softening point of the separator. Specifically, it is preferable that the softening point of the resin layer on the center side in the stacking direction having the lowest softening point is 5 to 10 ° C. lower than the softening point of the separator. Note that it is desirable to use the same separator for each single cell in the stacking direction from the viewpoint of production efficiency and component management.

Here, the softening point temperature of the resin layer and the softening point temperature of the separator are both set to the Vicat softening temperature (Vicat Softening Temperature, VST) and can be measured according to JIS K7206. Explaining the outline of JIS K7206, a test piece of a prescribed size is set in a heating tub, and the temperature of the tub is adjusted with an end face of a constant cross-sectional area (1 mm ^{2 in} JIS K7206) pressed against the center. Raise. The temperature when the end surface bites into the test piece to a certain depth is the Vicat softening temperature (unit: ° C.).

  As shown in the examples, the resin layer is formed in advance by a resin slurry in which a resin material for forming the resin layer is dissolved in an appropriate solvent on the separator surface (the porosity of the resin layer can be adjusted by changing the concentration). Is applied to a desired thickness and shape (entire surface, stripe shape, dot shape, etc.) and dried. Thereby, a separator and a resin layer can be integrated (it is called a resin separator). In addition, when providing a resin layer in either one of positive and negative electrodes, the effect of this embodiment is the same in any case. However, when the electrode sizes are different, the separator of the same size as the larger electrode is heat-shrinked and smaller than the smaller electrode when the electrode is provided on the larger electrode side (usually the negative electrode side). Up to this point, it can be said that the opposing electrodes do not contact each other, which is advantageous. The power generation element 21 is formed by sandwiching the resin separator between the positive electrode and the negative electrode in the same manner as a normal separator. Thereafter, the surface of the resin layer 18 (resin portion) of the resin separator is softened by hot pressing from the vertical direction of the power generation element 21 with a hot press device (see FIGS. 2 and 5) 20 to cause adhesion. Adhesive with electrodes. Thereby, the resin layer 18 formed by bonding between the electrode and the separator can be formed. In addition, the resin electrode (one in which the electrode and the resin layer are integrated) may be prepared by previously applying a resin slurry to the electrode (positive electrode or negative electrode) side. Thereafter, the power generation element 21 is formed in the same manner, and the resin layer 18 formed by bonding between the electrode and the separator can be formed by hot pressing.

(5) Current collector (current collector tab; external lead)
In the lithium ion secondary battery (laminated structure battery) 10, current collecting plates (current collecting tabs) 25 and 27 may be used for the purpose of taking out current outside the battery. The current collector plates (current collector tabs) 25 and 26 are electrically connected to the current collectors 11 and 12 and are taken out to the outside such as a laminate film as an exterior material.

  The material constituting the current collecting plates 25 and 27 is not particularly limited, and a known highly conductive material conventionally used as a current collecting plate for a lithium ion secondary battery can be used. As a constituent material of the current collector plate, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. In addition, the same material may be used for the positive electrode current collecting plate (positive electrode tab) 25 and the negative electrode current collecting plate (negative electrode tab) 27, and different materials may be used.

(5a) Electrode (positive electrode and negative electrode) terminal lead (internal lead)
In the laminated battery 10 shown in FIG. 1, the current collectors 11 and 12 are electrically connected to current collector plates (current collecting tabs) 25 and 27 through a negative terminal lead and a positive terminal lead (not shown), respectively. It may be connected. However. A part of the current collectors 11 and 12 can be extended like electrode terminal leads (internal leads) and directly connected to current collector plates (current collection tabs) 25 and 27. Therefore, the electrode terminal lead (not shown) can be said to be an optional component that may be used as needed.

  As a material for the negative electrode and the positive electrode terminal lead, a lead used in a known laminated secondary battery can be used. In addition, the parts removed from the battery exterior material should be heat-insulating so that they do not affect products (for example, automobile parts, especially electronic devices) by touching peripheral devices or wiring and causing leakage. It is preferable to coat with a heat shrinkable tube or the like.

(6) Battery exterior material As a battery exterior material, a conventionally well-known metal can case can be used. In addition, the power generation element 21 may be packed using a laminate film 29 as shown in FIG. The laminate film can be configured as a three-layer structure in which, for example, polypropylene, aluminum, and nylon are laminated in this order. By using such a laminate film, it is possible to easily open the exterior material, add the capacity recovery material, and reseal the exterior material. In addition, a laminate film exterior material is also desirable from the viewpoint that it is excellent in high output and cooling performance and can be suitably used for a battery for large equipment for EV and HEV.

  The lithium ion secondary battery 10 having the above laminated structure can be manufactured by a conventionally known manufacturing method.

[Appearance structure of lithium ion secondary battery]
FIG. 4 is a perspective view showing the appearance of a flat laminated (laminated structure) lithium ion secondary battery which is a typical embodiment of a laminated battery.

  As shown in FIG. 4, the flat laminated lithium ion secondary battery 30 has a rectangular flat shape, and a positive electrode tab 38 and a negative electrode tab 39 for taking out electric power from both sides thereof. Has been pulled out. The power generation element 37 is wrapped by the battery outer packaging material 32 of the lithium ion secondary battery 30 and the periphery thereof is heat-sealed. The power generation element 37 is sealed in a state where the positive electrode tab 38 and the negative electrode tab 39 are pulled out to the outside. Has been. Here, the power generation element 37 corresponds to the power generation element 21 of the stacked lithium ion secondary battery (stacked structure battery) 10 shown in FIG. 1 described above. The power generation element 37 is formed by laminating a plurality of single battery layers (single cells) 19 composed of a positive electrode, an electrolyte layer, and a negative electrode.

  Further, the removal of the tabs 38 and 39 shown in FIG. 4 is not particularly limited. The positive electrode tab 38 and the negative electrode tab 39 may be drawn out from the same side, or the positive electrode tab 38 and the negative electrode tab 39 may be divided into a plurality of parts and taken out from each side, as shown in FIG. It is not limited to.

  The lithium ion secondary battery (stacked structure battery) 10 is a vehicle drive that requires a high volume energy density and a high volume output density as a large-capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, and a hybrid fuel cell vehicle. It can be suitably used as a power source or auxiliary power source.

  In addition, although the said embodiment illustrated the laminated-type lithium ion secondary battery as a laminated structure battery, it is not necessarily restricted to this, It applies also to other types of secondary batteries, and also a primary battery. it can.

  The laminated structure battery of the present embodiment described above has the following effects.

  In the battery 10 of the present embodiment, by setting the melting point of the resin layer to the center side <the end side in the stacking direction, uneven melting can be prevented in the stacking direction, and the interelectrode resistance can be kept uniform.

  As a result, uneven reaction distribution for each single cell layer (single cell) is prevented, and the durability of the entire laminated battery is improved. A uniform output can be obtained for each stacked single cell, and the durability of the battery can be improved.

  Since the resin layer contains polyvinylidene fluoride (PVDF), the bonding temperature (temperature at which the surface of the resin layer begins to soften and has adhesiveness; softening point temperature) is lower than the separator deformation temperature range (softening point temperature). It can be set with. Therefore, since the battery reaction is not inhibited as much as possible, a further effect can be exerted on the output characteristics.

  By making the softening point of the resin layer lower than the softening point of the separator, the surface of the resin layer is softened while maintaining the shape of the separator, thereby providing sufficient adhesion between the electrode and the separator. be able to. Therefore, since the battery reaction is not inhibited as much as possible, a further effect can be exerted on the output characteristics.

  The present invention will be described in more detail with reference to the following examples and comparative examples, but is not limited to the following examples.

1. Production of positive electrode LiMn ₂ O ₄ (average particle diameter 20 μm) as a positive electrode active material, acetylene black as a conductive auxiliary agent and polyvinylidene fluoride (PVDF) as a binder, positive active material: conductive auxiliary agent: binder = 90: 5: 5 The positive electrode slurry was obtained by mixing at a mass ratio of

While the viscosity of the slurry was adjusted using NMP (N-methyl-2-pyrrolidone), the active material amount per unit area was applied to both sides of an Al foil (thickness: 20 μm) to 20 mg / cm ^{2 on} one side. . After sufficiently drying, it was processed using a roll press so that the thickness of the positive electrode (the total thickness of the positive electrode current collector + the positive electrode active material layer (both surfaces)) was 159 μm. The porosity of the positive electrode active material layer was 23%.

2. Production of Negative Electrode Natural graphite (average particle size 20 μm) as a negative electrode active material and polyvinylidene fluoride (PVDF) as a binder were mixed at a mass ratio of negative electrode active material: binder = 95: 5 to obtain a negative electrode slurry.

While the viscosity of the slurry was adjusted using NMP (N-methyl-2-pyrrolidone), the active material amount per unit area was applied to both sides of a Cu foil (thickness: 10 μm) to be 6 mg / cm ^{2 on} one side. . After sufficiently drying, it was processed using a roll press so that the thickness of the negative electrode (the total thickness of the negative electrode current collector + the negative electrode active material layer (both surfaces)) was 90 μm. The porosity of the negative electrode active material layer was 30%.

3. Preparation of separator + resin layer A (hereinafter also simply referred to as resin separator A) Low-layer resin layer on the entire surface of a laminated microporous film of polyethylene and polypropylene (thickness 20 μm, porosity 50%, softening point temperature 105 ° C.) A density polyethylene layer (melting point 105 ° C., softening point temperature 90 ° C.) was applied to a thickness of 2 μm. The porosity of the low density polyethylene layer (resin layer) was 65%.

4). Production of separator + resin layer B (hereinafter also simply referred to as “resin separator B”) A resin layer is formed on the entire surface of a laminated microporous film of polyethylene and polypropylene (thickness 20 μm, porosity 50%, softening point temperature 105 ° C.). A density polyethylene layer (melting point: 108 ° C., softening point temperature: 85 ° C.) was applied to a thickness of 2 μm. The porosity of the high density polyethylene layer (resin layer) was 65%.

5. Preparation of separator + resin layer C (hereinafter also simply referred to as “resin separator C”) Polyvinylidene fluoride as a resin layer on a laminated microporous film of polyethylene and polypropylene (thickness 20 μm, porosity 50%, softening point temperature 120 ° C.) The layer (melting point: 175 ° C., softening point temperature: 110 ° C.) was applied to a thickness of 2 μm. The porosity of the polyvinylidene fluoride layer (resin layer) was 70%.

6). Preparation of separator + resin layer D (hereinafter also simply referred to as resin separator D) Polyethylene-polypropylene laminated microporous membrane (thickness 20 μm, porosity 50%, softening point temperature 120 ° C.) as resin layer polyvinylidene fluoride A layer (having a carboxyl group partially in the side chain) (melting point: 165 ° C., softening point temperature: 105 ° C.) was applied to a thickness of 2 μm. The porosity of the polyvinylidene fluoride layer (resin layer) was 70%. (As can be seen from comparison with the resin separator C, in the case of polyvinylidene fluoride used for the resin layer, the melting point can be easily lowered by mixing in carboxyl groups.)
7). Description of Examples A laminated battery (cell stack) in which five single battery layers (single cells) were stacked was produced by combining the constituent parts (members) of the single battery layers (single cells) 1 to 6 described above.

  The member produced by said 1 and 2 was used for the positive electrode and negative electrode of each single battery layer (single cell) of all the Examples.

  In addition, the lamination | stacking number of each single cell of the laminated structure battery which laminated | stacked the single battery layer (single cell) five layers shall be 1-5 in an order from the lower stage.

Example 1
Adhesive separator B was used in the first, second, fourth, and fifth stages, and adhesive separator A was used in the third stage.

Example 2
Adhesive separator C was used for the first, second, fourth, and fifth stages, and adhesive separator D was used for the third stage.

Example 3
In the first stage, the adhesive separator A was used in the fifth stage, the adhesive separator C was used in the second stage and the fourth stage, and the adhesive separator D was used in the third stage.

Comparative Example 1
Adhesive separator A was used for all layers (first to fifth steps).

Comparative Example 2
Adhesive separator B was used for all layers (first to fifth steps).

Comparative Example 3
Adhesive separator C was used for all layers (first to fifth steps).

Comparative Example 4
Adhesive separator D was used for all layers (first to fifth stages).

8). Production of laminated structure battery The positive electrode, the negative electrode, and the adhesive separators A to D were cut so as to be □ 20 cm (vertical, horizontal 20 cm square) in this procedure (the tab was left without being cut). Five layers (single cells) were laminated. At this time, the adhesive separators A to D were arranged so that the resin layer side was adhered to the surface of the negative electrode (active material layer) in all the single battery layers (single cells). Then, connect the tabs of each stacked single battery layer (single cell) (current collector tab provided by extending a part of the current collector; the thickness of the current collector tab is the same as the current collector) A power generation element (laminated body) (see FIGS. 1 and 5) of a stacked battery of a parallel type (internal parallel connection type) was stacked (assembled). In order to bond (heat-seal) the resin layers of the adhesive separators A to D, a constant pressure load is applied while heating from the vertical direction of the power generation element 21 using the hot press device (pressing jig) 20 shown in FIG. Applied (hot pressed). The load at this time is 10 MPa. In the hot press condition 1 (Comparative Examples 1 and 2 and Example 1), the jig temperature is 95 ° C., the press time is 5 minutes, and the hot press condition 2 (Comparative Examples 3 and 4). In Examples 2 and 3, the temperature of the jig was 110 ° C., and the pressing time was 6 minutes. Table 1 below shows the results of measuring the temperature (maximum temperature) by attaching a temperature sensor to each resin layer (in-plane center) in the batteries of each Example and Comparative Example during hot pressing.

  The numbers in the table represent the maximum temperature (unit: ° C.) of the resin layer. In addition, each single battery layer (single cell) of the laminated body which laminated | stacked five layers was made into 1 layer (uppermost layer), 2 layers, 3 layers (center layer), 4 layers, 5 layers (lowermost layer) in order from the top. .

Each power generation element 21 (laminated body) was put in an aluminum laminate outer package, and a desired electrolyte solution (see the composition of the reference value above) was injected, followed by vacuum sealing to produce a laminated structure battery. As the electrolytic solution at this time, a mixed solution of EC and DEC (5: 5 molar ratio) containing 1M LiPF ₆ was used.

9. Evaluation Method A cycle test (endurance test) was performed under the condition of storage at 50 ° C. using the laminated structure battery produced by the above procedure. Cycle conditions were 400 cycles between 4.2V and 3.0V at 1C rate.

10. Results The capacity retention ratio (%) before and after the durability test is shown in Table 2 below.

  Capacity retention rate (%) = (discharge capacity at the 400th cycle (Ah)) ÷ (discharge capacity at the first cycle (Ah)) × 100.

  A to D in the table are the abbreviations of the adhesive separators A to D used for each layer (first to fifth stages) of each example.

  From the results shown in Table 2, it is possible to secure a capacity maintenance rate of 75 to 77% by gradationizing the melting point of the resin layer for each single battery layer (single cell) laminated as in Examples 1 to 3. did it. Moreover, compared with the capacity maintenance rate (67-70%) of the laminated structure battery which is not gradation-ized the melting point of the resin layer for every single battery layer (single cell) laminated | stacked like Comparative Examples 1-4, an Example It was confirmed that durability was improved in the laminated structure batteries 1 to 3.

  Further, as can be seen from Table 2, in the present invention, any melting point of the resin layer for each unit cell from the center side to the end side may be used. It may be graded stepwise so that the melting point of the resin layer changes for every several single cells. For example, when the single cell layer (single cell) is laminated as in the example, if the melting point of the resin layer is in the order of A> B> C> D, the melting point of the resin layer is in order from the end side. The form which changes as follows is included. A> B> C <B <A, A> B> D <B <A, A> C> D <C <A, B> C> D <C so that the melting point of the resin layer changes for each single cell. <B may be a gradient. Furthermore, A = A> B <A = A, A = A> C <A = A, A = A> D <A = A, B = B so that the melting point of the resin layer changes every several single cells. > C <B = B, B = B> D <B = B, C = C> D <C = C, A> B = B = B <A, A> C = C = C <A, A> D = D = D <A, B> C = C = C <B, B> D = D = D <B, C> D = D = D <C. . However, as long as the melting point of the resin layer of the single cell satisfies the center side <the end side, it is not limited thereto.

10, 30 Stacked lithium ion secondary battery,
11 positive electrode current collector,
12 negative electrode current collector,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 electrolyte layer (separator),
18 resin layer,
19 Single battery layer (single cell),
20 heat press device (pressing jig),
21, 37 Power generation element,
25 positive current collector,
27 negative current collector,
29, 32 Battery exterior material,
31, electrode (separator) surface,
33a Striped resin part,
33b Dot-shaped resin part 35 non-resin part,
38 positive electrode tab,
39 Negative electrode tab.

Claims (4)

In a laminated structure battery having a positive electrode, a negative electrode, and an electrolyte layer including a separator, and laminating three or more unit cell layers in which the positive electrode and the negative electrode are opposed to each other through the electrolyte layer.
Between at least one of the positive and negative electrodes and the separator, there is further a resin layer formed by bonding between at least one of the positive and negative electrodes and the separator,
At least one of a melting point, a softening point, a heat distortion temperature, and a deflection temperature under load of the resin layer is a laminated structure battery characterized in that the center side is less than the end side in the lamination direction.   2. The laminated battery according to claim 1, wherein a melting point of the resin layer is a center side <an end side in a lamination direction.   3. The stacked structure battery according to claim 1, wherein the at least one resin layer in the stacking direction contains polyvinylidene fluoride (PVDF). 4.   The laminated structure battery according to claim 1, wherein a softening point of the resin layer is lower than a softening point of the separator.